Psoriasis

Inflammatory skin conditions often have a relapsing and remitting course and represent a large proportion of chronic skin diseases. Common inflammatory skin disorders include acne, psoriasis, hidradenitis suppurativa (HS), atopic dermatitis (AD), and seborrheic dermatitis (SD).¹ Although each of these conditions has a unique pathogenesis, they all are driven by a background of chronic inflammation. It has been reported that diets with high levels of refined carbohydrates and saturated or trans-fatty acids may exacerbate existing inflammation.² Consequently, dietary interventions, such as the ketogenic and low-glycemic diets, have potential anti-inflammatory and metabolic effects that are being assessed as stand-alone or adjunctive therapies for dermatologic diseases.

Diet may partially influence systemic inflammation through its effect on weight. Higher body mass index and obesity are linked to a low-grade inflammatory state and higher levels of circulating inflammatory markers. Therefore, weight loss leads to decreases in inflammatory cytokines, including C-reactive protein, tumor necrosis factor α, and IL-6.³ These cytokines and metabolic effects overlap with inflammatory skin condition pathways. It also is posited that decreased insulin release associated with weight loss results in decreased sebaceous lipogenesis and androgens, which drive keratinocyte proliferation and acne development.^4,5 For instance, in a 2015 meta-analysis of 5 randomized controlled trials on psoriasis, patients in the weight loss intervention group had more substantial reductions in psoriasis area and severity index (PASI) scores compared with controls receiving usual care (P=.004).⁶ However, in a systematic review of 35 studies on acne vulgaris, overweight and obese patients (defined by a body mass index of ≥23 kg/m²) had similar odds of having acne compared with normal-weight individuals (P=.671).⁷

Similar to weight loss, ketogenesis acts as a negative feedback mechanism to reduce insulin release, leading to decreased inflammation and androgens that often exacerbate inflammatory skin diseases.⁸ Ketogenesis ensues when daily carbohydrate intake is limited to less than 50 g, and long-term adherence to a ketogenic diet results in metabolic reliance on ketone bodies such as acetoacetate, β-hydroxybutyrate, and acetone.⁹ These metabolites may decrease free radical damage and consequently improve signs and symptoms of acne, psoriasis, and other inflammatory skin diseases.^10-12 Similarly, increased ketones also may decrease activation of the NLRP3 (NOD-, LRR-, and Pyrin domain-containing protein 3) inflammasome and therefore reduce inflammatory markers such as IL-1β and IL-1.^4,13 Several proposed mechanisms are outlined in the Table.

Collectively, low-glycemic and ketogenic diets have been proposed as potential interventions for reducing inflammatory skin conditions. These dietary approaches are hypothesized to exert their effects by facilitating weight loss, elevating ketone levels, and reducing systemic inflammation. The current review summarizes the existing evidence on ketogenic and low-glycemic diets as treatments for inflammatory skin conditions and evaluates the potential benefits of these dietary interventions in managing and improving outcomes for individuals with inflammatory skin conditions.

Methods

Using PubMed for articles indexed for MEDLINE and Google Scholar, a review of the literature was conducted with a combination of the following search terms: low-glycemic diet, inflammatory, dermatologic, ketogenic diet, inflammation, dermatology, acne, psoriasis, eczema, seborrheic dermatitis, and hidradenitis suppurativa. Reference citations in identified works also were reviewed. Interventional (experimental studies or clinical trials), survey-based, and observational studies that investigated the effects of low-glycemic or ketogenic diets for the treatment of inflammatory skin conditions were included. Inclusion criteria were studies assessing acne, psoriasis, SD, AD, and HS. Exclusion criteria were studies published before 1965; those written in languages other than English; and those analyzing other diets, such as the Mediterranean or low-fat diets. The search yielded a total of 11 observational studies and 4 controlled studies published between 1966 and January 2023. Because this analysis utilized publicly available data and did not qualify as human subject research, institutional review board approval was not required.

Results

Acne Vulgaris—Acne vulgaris is a disease of chronic pilosebaceous inflammation and follicular epithelial proliferation associated with Propionibacterium acnes. The association between acne and low-glycemic diets has been examined in several studies. Diet quality is measured and assessed using the glycemic index (GI), which is the effect of a single food on postprandial blood glucose, and the glycemic load, which is the GI adjusted for carbohydrates per serving.¹⁴ High levels of GI and glycemic load are associated with hyperinsulinemia and an increase in insulinlike growth factor 1 concentration that promotes mechanistic target of rapamycin (mTOR) complex 1–mediated follicular lipogenesis, sebum fatty acid production, and androgen synthesis.¹⁵ Propionibacterium acnes directly activates toll-like receptor 2 on monocytes through damage-associated molecular patterns and indirectly through products of triglyceride catalysis, causing release of IL-12, IL-6, tumor necrosis factor α, and other proinflammatory cytokines.¹⁶ Therefore, lifestyle modifications focused on strict glucose control have been postulated to reduce acne severity via modulation of lipogenesis, androgen concentration, and inflammation.

Six survey-based studies evaluated sugar intake in patients with acne compared to healthy matched controls (eTable). Among these studies, 5 reported higher glycemic loads or daily sugar intake in acne patients compared to individuals without acne.^{12,19,20,26,28} The remaining study was conducted in 1967 and enrolled 16 acne patients and 32 matched controls. It reported no significant difference in sugar intake between the groups (P>.05).¹⁷

Smith et al¹⁸ randomized 43 male patients aged 15 to 25 years with facial acne into 2 cohorts for 12 weeks, each consuming either a low-glycemic diet (25% protein, 45% low-glycemic food [fruits, whole grains], and 30% fat) or a carbohydrate-dense diet of foods with medium to high GI based on prior documentation of the original diet. Patients were instructed to use a noncomedogenic cleanser as their only acne treatment. At 12 weeks, patients consuming the low-glycemic diet had an average of 23.5 fewer inflammatory lesions, while those in the intervention group had 12.0 fewer lesions (P=.03).¹⁸

In another controlled study by Kwon et al,²¹ 32 male and female acne patients were randomized to a low-glycemic diet (25% protein, 45% low-glycemic food, and 30% fat) or a standard diet for 10 weeks. Patients on the low-glycemic diet experienced a 70.9% reduction in inflammatory lesions (P<.05). Hematoxylin and eosin staining and image analysis were performed to measure sebaceous gland surface area in the low-glycemic diet group, which decreased from 0.32 to 0.24 mm² (P=.03). The sebaceous gland surface area in the control group was not reported. Moreover, patients on the low-glycemic diet had reduced IL-8 immunohistochemical staining (decreasing from 2.9 to 1.7 [P=.03]) and sterol regulatory element-binding protein 1 levels (decreasing from 2.6 to 1.3 [P=.03]), suggesting suppression of ongoing inflammation. Patients on the low-glycemic diet had no significant difference in transforming growth factor β1(P=.83). In the control group, there was no difference in IL-8, sterol regulatory element binding protein 1, or transforming growth factor β1 (P>.05) on immunohistochemical staining.²¹

Psoriasis—Psoriasis is a systemic inflammatory disease characterized by hyperproliferation and aberrant keratinocyte plaque formation. The innate immune response of keratinocytes in response to epidermal damage or infection begins with neutrophil recruitment and dendritic cell activation. Dendritic cell secretion of IL-23 promotes T-cell differentiation into helper T cells (T_H1) that subsequently secrete IL-17 and IL-22, thereby stimulating keratinocyte proliferation and eventual plaque formation. The relationship between diet and psoriasis is poorly understood; however, hyperinsulinemia is associated with greater severity of psoriasis.³¹ 

Four observational studies examined sugar intake in psoriasis patients. Barrea et al²³ conducted a survey-based study of 82 male participants (41 with psoriasis and 41 healthy controls), reporting that PASI score was correlated with intake of simple carbohydrates (percentage of total kilocalorie)(r=0.564, P<.001). Another study by Yamashita et al²⁷ found higher sugar intake in psoriasis patients than controls (P=.003) based on surveys from 70 patients with psoriasis and 70 matched healthy controls.

These findings contrast with 2 survey-based studies by Johnson et al²² and Afifi et al²⁵ of sugar intake in psoriasis patients using the National Health and Nutrition Examination Survey. Johnson et al²² reported reduced sugar intake among 156 psoriasis patients compared with 6104 unmatched controls (odds ratio, 0.998; CI, 0.996-1 [P=.04]) from 2003 to 2006. Similarly, Afifi et al²⁵ reported decreased sugar intake in 1206 psoriasis patients compared with sex- and age-matched controls (P<.0001) in 2009 and 2010. When patients were asked about dietary triggers, 13.8% of psoriasis patients reported sugar as the most common trigger, which was more frequent than alcohol (13.6%), gluten (7.2%), and dairy (6%).²⁵

Castaldo et al^29,30 published 2 nonrandomized clinical intervention studies in 2020 and 2021 evaluating the impact of the ketogenic diet on psoriasis. In the first study, 37 psoriasis patients followed a 10-week diet consisting of 4 weeks on a ketogenic diet (500 kcal/d) followed by 6 weeks on a low-caloric Mediterranean diet.²⁹ At the end of the intervention, there was a 17.4% reduction in PASI score, a 33.2-point reduction in itch severity score, and a 13.4-point reduction in the dermatology life quality index score; however, this study did not include a control diet group for comparison.²⁹ The second study included 30 psoriasis patients on a ketogenic diet and 30 control patients without psoriasis on a regular diet.³⁰ The ketogenic diet consisted of 400 to 500 g of vegetables, 20 to 30 g of fat, and a proportion of protein based on body weight with at least 12 g of whey protein and various amino acids. Patients on the ketogenic diet had significant reduction in PASI scores (value relative to clinical features, 1.4916 [P=.007]). Furthermore, concentrations of cytokines IL-2 (P=.04) and IL-1β (P=.006) decreased following the ketogenic diet but were not measured in the control group.³⁰

Seborrheic Dermatitis—Seborrheic dermatitis is associated with overcolonization of Malassezia species near lipid-rich sebaceous glands. Malassezia hydrolyzes free fatty acids, yielding oleic acids and leading to T-cell release of IL-8 and IL-17.³² Literature is sparse regarding how dietary modifications may play a role in disease severity. In a survey study, Bett et al¹⁷ compared 16 SD patients to 1:2 matched controls (N=29) to investigate the relationship between sugar consumption and presence of disease. Two control cohorts were selected, 1 from clinic patients diagnosed with verruca and 1 matched by age and sex from a survey-based study at a facility in London, England. Sugar intake was measured both in total grams per day and in “beverage sugar” per day, defined as sugar taken in tea and coffee. There was higher total sugar and higher beverage sugar intake among the SD group compared with both control groups (P<.05).¹⁷

Atopic Dermatitis—Atopic dermatitis is a disease of epidermal barrier dysfunction and IgE-mediated allergic sensitization.³³ There are several mechanisms by which skin structure may be disrupted. It is well established that filaggrin mutations inhibit stratum corneum maturation and lamellar matrix deposition.³⁴ Upregulation of IL-4–, IL-13–, and IL-17–secreting T_H2 cells also is associated with disruption of tight junctions and reduction of filaggrin.^35,36 Given that a T cell–mediated inflammatory response is involved in disease pathogenesis, glycemic control is hypothesized to have therapeutic potential.

Nosrati et al²⁴ surveyed 169 AD patients about their perceived dietary triggers through a 61-question survey based on the National Health and Nutrition Examination Survey. Respondents were queried about their perceptions and dietary changes, such as removal or addition of specific food groups and trial of specific diets. Overall, 16.5% of patients reported sugar being a trigger, making it the fourth most common among those surveyed and less common than dairy (24.8%), gluten (18.3%), and alcohol (17.1%).²⁴

Hidradenitis Suppurativa—Hidradenitis suppurativa is driven by hyperkeratosis, dilatation, and occlusion of pilosebaceous follicular ducts, whose eventual rupture evokes a local acute inflammatory response.³⁷ The inciting event for both acne and HS involves mTOR complex–mediated follicular hyperproliferation andinsulinlike growth factor 1 stimulation of androgen receptors in pilosebaceous glands. Given the similarities between the pathogenesis of acne and HS, it is hypothesized that lifestyle changes, including diet modification, may have a beneficial effect on HS.^38-40

Comment

Acne—Overall, there is strong evidence supporting the efficacy of a low-glycemic diet in the treatment of acne. Notably, among the 6 observational studies identified, there was 1 conflicting study by Bett et al¹⁷ that did not find a statistically significant difference in glucose intake between acne and control patients. However, this study included only 16 acne patients, whereas the other 5 observational studies included 32 to 2255 patients.¹⁷ The strongest evidence supporting low-glycemic dietary interventions in acne treatment is from 2 rigorous randomized clinical trials by Kwon et al²¹ and Smith et al.¹⁸ These trials used intention-to-treat models and maintained consistency in gender, age, and acne treatment protocols across both control and treatment groups. To ensure compliance with dietary interventions, daily telephone calls, food logs, and 24-hour urea sampling were utilized. Acne outcomes were assessed by a dermatologist who remained blinded with well-defined outcome measures. An important limitation of these studies is the difficulty in attributing the observed results solely to reduced glucose intake, as low-glycemic diets often lead to other dietary changes, including reduced fat intake and increased nutrient consumption.^18,21

A 2022 systematic review of acne by Meixiong et al⁴¹ further reinforced the beneficial effects of low-glycemic diets in the management of acne patients. The group reviewed 6 interventional studies and 28 observational studies to investigate the relationship among acne, dairy, and glycemic content and found an association between decreased glucose and dairy on reduction of acne.⁴¹

It is likely that the ketogenic diet, which limits glucose, would be beneficial for acne patients. There may be added benefit through elevated ketone bodies and substantially reduced insulin secretion. However, because there are no observational or interventional studies, further research is needed to draw firm conclusions regarding diet for acne treatment. A randomized clinical trial investigating the effects of the ketogenic diet compared to the low-glycemic diet compared to a regular diet would be valuable.

Psoriasis—Among psoriasis studies, there was a lack of consensus regarding glucose intake and correlation with disease. Among the 4 observational studies, 2 reported increased glucose intake among psoriasis patients and 2 reported decreased glucose intake. It is plausible that the variability in studies is due to differences in sample size and diet heterogeneity among study populations. More specifically, Johnson et al²² and Afifi et al²⁵ analyzed large sample sizes of 6260 and 2412 US participants, respectively, and found decreased sugar intake among psoriasis patients compared to controls. In comparison, Barrea et al²³ and Yamashita et al²⁷ analyzed substantially smaller and more specific populations consisting of 82 Italian and 140 Japanese participants, respectively; both reported increased glucose intake among psoriasis patients compared to controls. These seemingly antithetical results may be explained by regional dietary differences, with varying proportions of meats, vegetables, antioxidants, and vitamins.

Moreover, the variation among studies may be further explained by the high prevalence of comorbidities among psoriasis patients. In the study by Barrea et al,²³ psoriasis patients had higher fasting glucose (P=.004) and insulin (P=.022) levels than healthy patients. After adjusting for body mass index and metabolic syndrome, the correlation coefficient measuring the relationship between the PASI score and intake of simple carbohydrates changed from r=0.564 (P<.001) to r=0.352 (P=.028). The confounding impact of these comorbidities was further highlighted by Yamashita et al,²⁷ who found statistically significant differences in glucose intake between psoriasis and healthy patients (P=.003). However, they reported diminished significance on additional subgroup analysis accounting for potential comorbidities (P=.994).²⁷ Johnson et al²² and Afifi et al²⁵ did not account for comorbidities; therefore, the 4 observational study results must be interpreted cautiously.

The 2 randomized clinical trials by Castaldo et al^29,30 weakly suggest that a ketogenic diet may be beneficial for psoriasis patients. The studies have several notable limitations, including insufficient sample sizes and control groups. Thus, the decreased PASI scores reported in psoriasis patients on the ketogenic diets are challenging to interpret. Additionally, both studies placed patients on highly restrictive diets of 500 kcal/d for 4 weeks. The feasibility of recommending such a diet to patients in clinical practice is questionable. Diets of less than 500 kcal/d may be dangerous for patients with underlying comorbidities and are unlikely to serve as long-term solutions.²³ To contextualize our findings, a 2022 review by Chung et al⁴² examined the impact of various diets—low-caloric, gluten-free, Mediterranean, Western, and ketogenic—on psoriasis and reported insufficient evidence to suggest a benefit to the ketogenic diet for psoriasis patients, though the Mediterranean diet may be well suited for psoriasis patients because of improved cardiovascular health and reduced mortality.

Seborrheic Dermatitis—Sanders et al⁴³ found that patients with a high-fruit diet had lower odds of having SD, while those on a Western diet had higher odds of having SD. Although the study did not measure glycemic load, it is conceivable that the high glycemic load characteristic of the Western diet contributed to these findings.⁴³ However, no studies have investigated the direct link between low-glycemic or ketogenic diets and SD, leaving this area open for further study.

Atopic Dermatitis—It has been hypothesized that mitigating T cell–mediated inflammation via glucose control may contribute to the improvement in AD.^35,36 However, in one study, 16.5% of AD patients self-identified sugar as a dietary trigger, ranking fourth among other dietary triggers.²⁴ Thus, the connection between glucose levels and AD warrants further exploration.

Hidradenitis Suppurativa—Given the role of metabolic and hormonal influence in HS as well as the overlapping pathophysiology with acne, it is possible that low-glycemic and ketogenic diets may have a role in improving HS.^38-40 However, there is a gap in observation and controlled studies investigating the link between low-glycemic or ketogenic diets and HS.

Conclusion

Our analysis focused on interventional and observational research exploring the effects of low-glycemic and ketogenic diets on associations and treatment of inflammatory skin conditions. There is sufficient evidence to counsel acne patients on the benefits of a low-glycemic diet as an adjunctive treatment for acne. Currently, there is insufficient evidence to recommend a low-glycemic or ketogenic diet as a treatment for patients with any other inflammatory skin disease. Prospective and controlled clinical trials are needed to clarify the utility of dietary interventions for treating inflammatory skin conditions.

Inflammatory skin conditions often have a relapsing and remitting course and represent a large proportion of chronic skin diseases. Common inflammatory skin disorders include acne, psoriasis, hidradenitis suppurativa (HS), atopic dermatitis (AD), and seborrheic dermatitis (SD).¹ Although each of these conditions has a unique pathogenesis, they all are driven by a background of chronic inflammation. It has been reported that diets with high levels of refined carbohydrates and saturated or trans-fatty acids may exacerbate existing inflammation.² Consequently, dietary interventions, such as the ketogenic and low-glycemic diets, have potential anti-inflammatory and metabolic effects that are being assessed as stand-alone or adjunctive therapies for dermatologic diseases.

Diet may partially influence systemic inflammation through its effect on weight. Higher body mass index and obesity are linked to a low-grade inflammatory state and higher levels of circulating inflammatory markers. Therefore, weight loss leads to decreases in inflammatory cytokines, including C-reactive protein, tumor necrosis factor α, and IL-6.³ These cytokines and metabolic effects overlap with inflammatory skin condition pathways. It also is posited that decreased insulin release associated with weight loss results in decreased sebaceous lipogenesis and androgens, which drive keratinocyte proliferation and acne development.^4,5 For instance, in a 2015 meta-analysis of 5 randomized controlled trials on psoriasis, patients in the weight loss intervention group had more substantial reductions in psoriasis area and severity index (PASI) scores compared with controls receiving usual care (P=.004).⁶ However, in a systematic review of 35 studies on acne vulgaris, overweight and obese patients (defined by a body mass index of ≥23 kg/m²) had similar odds of having acne compared with normal-weight individuals (P=.671).⁷

Similar to weight loss, ketogenesis acts as a negative feedback mechanism to reduce insulin release, leading to decreased inflammation and androgens that often exacerbate inflammatory skin diseases.⁸ Ketogenesis ensues when daily carbohydrate intake is limited to less than 50 g, and long-term adherence to a ketogenic diet results in metabolic reliance on ketone bodies such as acetoacetate, β-hydroxybutyrate, and acetone.⁹ These metabolites may decrease free radical damage and consequently improve signs and symptoms of acne, psoriasis, and other inflammatory skin diseases.^10-12 Similarly, increased ketones also may decrease activation of the NLRP3 (NOD-, LRR-, and Pyrin domain-containing protein 3) inflammasome and therefore reduce inflammatory markers such as IL-1β and IL-1.^4,13 Several proposed mechanisms are outlined in the Table.

Collectively, low-glycemic and ketogenic diets have been proposed as potential interventions for reducing inflammatory skin conditions. These dietary approaches are hypothesized to exert their effects by facilitating weight loss, elevating ketone levels, and reducing systemic inflammation. The current review summarizes the existing evidence on ketogenic and low-glycemic diets as treatments for inflammatory skin conditions and evaluates the potential benefits of these dietary interventions in managing and improving outcomes for individuals with inflammatory skin conditions.

Methods

Using PubMed for articles indexed for MEDLINE and Google Scholar, a review of the literature was conducted with a combination of the following search terms: low-glycemic diet, inflammatory, dermatologic, ketogenic diet, inflammation, dermatology, acne, psoriasis, eczema, seborrheic dermatitis, and hidradenitis suppurativa. Reference citations in identified works also were reviewed. Interventional (experimental studies or clinical trials), survey-based, and observational studies that investigated the effects of low-glycemic or ketogenic diets for the treatment of inflammatory skin conditions were included. Inclusion criteria were studies assessing acne, psoriasis, SD, AD, and HS. Exclusion criteria were studies published before 1965; those written in languages other than English; and those analyzing other diets, such as the Mediterranean or low-fat diets. The search yielded a total of 11 observational studies and 4 controlled studies published between 1966 and January 2023. Because this analysis utilized publicly available data and did not qualify as human subject research, institutional review board approval was not required.

Results

Acne Vulgaris—Acne vulgaris is a disease of chronic pilosebaceous inflammation and follicular epithelial proliferation associated with Propionibacterium acnes. The association between acne and low-glycemic diets has been examined in several studies. Diet quality is measured and assessed using the glycemic index (GI), which is the effect of a single food on postprandial blood glucose, and the glycemic load, which is the GI adjusted for carbohydrates per serving.¹⁴ High levels of GI and glycemic load are associated with hyperinsulinemia and an increase in insulinlike growth factor 1 concentration that promotes mechanistic target of rapamycin (mTOR) complex 1–mediated follicular lipogenesis, sebum fatty acid production, and androgen synthesis.¹⁵ Propionibacterium acnes directly activates toll-like receptor 2 on monocytes through damage-associated molecular patterns and indirectly through products of triglyceride catalysis, causing release of IL-12, IL-6, tumor necrosis factor α, and other proinflammatory cytokines.¹⁶ Therefore, lifestyle modifications focused on strict glucose control have been postulated to reduce acne severity via modulation of lipogenesis, androgen concentration, and inflammation.

Six survey-based studies evaluated sugar intake in patients with acne compared to healthy matched controls (eTable). Among these studies, 5 reported higher glycemic loads or daily sugar intake in acne patients compared to individuals without acne.^{12,19,20,26,28} The remaining study was conducted in 1967 and enrolled 16 acne patients and 32 matched controls. It reported no significant difference in sugar intake between the groups (P>.05).¹⁷

Smith et al¹⁸ randomized 43 male patients aged 15 to 25 years with facial acne into 2 cohorts for 12 weeks, each consuming either a low-glycemic diet (25% protein, 45% low-glycemic food [fruits, whole grains], and 30% fat) or a carbohydrate-dense diet of foods with medium to high GI based on prior documentation of the original diet. Patients were instructed to use a noncomedogenic cleanser as their only acne treatment. At 12 weeks, patients consuming the low-glycemic diet had an average of 23.5 fewer inflammatory lesions, while those in the intervention group had 12.0 fewer lesions (P=.03).¹⁸

In another controlled study by Kwon et al,²¹ 32 male and female acne patients were randomized to a low-glycemic diet (25% protein, 45% low-glycemic food, and 30% fat) or a standard diet for 10 weeks. Patients on the low-glycemic diet experienced a 70.9% reduction in inflammatory lesions (P<.05). Hematoxylin and eosin staining and image analysis were performed to measure sebaceous gland surface area in the low-glycemic diet group, which decreased from 0.32 to 0.24 mm² (P=.03). The sebaceous gland surface area in the control group was not reported. Moreover, patients on the low-glycemic diet had reduced IL-8 immunohistochemical staining (decreasing from 2.9 to 1.7 [P=.03]) and sterol regulatory element-binding protein 1 levels (decreasing from 2.6 to 1.3 [P=.03]), suggesting suppression of ongoing inflammation. Patients on the low-glycemic diet had no significant difference in transforming growth factor β1(P=.83). In the control group, there was no difference in IL-8, sterol regulatory element binding protein 1, or transforming growth factor β1 (P>.05) on immunohistochemical staining.²¹

Psoriasis—Psoriasis is a systemic inflammatory disease characterized by hyperproliferation and aberrant keratinocyte plaque formation. The innate immune response of keratinocytes in response to epidermal damage or infection begins with neutrophil recruitment and dendritic cell activation. Dendritic cell secretion of IL-23 promotes T-cell differentiation into helper T cells (T_H1) that subsequently secrete IL-17 and IL-22, thereby stimulating keratinocyte proliferation and eventual plaque formation. The relationship between diet and psoriasis is poorly understood; however, hyperinsulinemia is associated with greater severity of psoriasis.³¹ 

Four observational studies examined sugar intake in psoriasis patients. Barrea et al²³ conducted a survey-based study of 82 male participants (41 with psoriasis and 41 healthy controls), reporting that PASI score was correlated with intake of simple carbohydrates (percentage of total kilocalorie)(r=0.564, P<.001). Another study by Yamashita et al²⁷ found higher sugar intake in psoriasis patients than controls (P=.003) based on surveys from 70 patients with psoriasis and 70 matched healthy controls.

These findings contrast with 2 survey-based studies by Johnson et al²² and Afifi et al²⁵ of sugar intake in psoriasis patients using the National Health and Nutrition Examination Survey. Johnson et al²² reported reduced sugar intake among 156 psoriasis patients compared with 6104 unmatched controls (odds ratio, 0.998; CI, 0.996-1 [P=.04]) from 2003 to 2006. Similarly, Afifi et al²⁵ reported decreased sugar intake in 1206 psoriasis patients compared with sex- and age-matched controls (P<.0001) in 2009 and 2010. When patients were asked about dietary triggers, 13.8% of psoriasis patients reported sugar as the most common trigger, which was more frequent than alcohol (13.6%), gluten (7.2%), and dairy (6%).²⁵

Castaldo et al^29,30 published 2 nonrandomized clinical intervention studies in 2020 and 2021 evaluating the impact of the ketogenic diet on psoriasis. In the first study, 37 psoriasis patients followed a 10-week diet consisting of 4 weeks on a ketogenic diet (500 kcal/d) followed by 6 weeks on a low-caloric Mediterranean diet.²⁹ At the end of the intervention, there was a 17.4% reduction in PASI score, a 33.2-point reduction in itch severity score, and a 13.4-point reduction in the dermatology life quality index score; however, this study did not include a control diet group for comparison.²⁹ The second study included 30 psoriasis patients on a ketogenic diet and 30 control patients without psoriasis on a regular diet.³⁰ The ketogenic diet consisted of 400 to 500 g of vegetables, 20 to 30 g of fat, and a proportion of protein based on body weight with at least 12 g of whey protein and various amino acids. Patients on the ketogenic diet had significant reduction in PASI scores (value relative to clinical features, 1.4916 [P=.007]). Furthermore, concentrations of cytokines IL-2 (P=.04) and IL-1β (P=.006) decreased following the ketogenic diet but were not measured in the control group.³⁰

Seborrheic Dermatitis—Seborrheic dermatitis is associated with overcolonization of Malassezia species near lipid-rich sebaceous glands. Malassezia hydrolyzes free fatty acids, yielding oleic acids and leading to T-cell release of IL-8 and IL-17.³² Literature is sparse regarding how dietary modifications may play a role in disease severity. In a survey study, Bett et al¹⁷ compared 16 SD patients to 1:2 matched controls (N=29) to investigate the relationship between sugar consumption and presence of disease. Two control cohorts were selected, 1 from clinic patients diagnosed with verruca and 1 matched by age and sex from a survey-based study at a facility in London, England. Sugar intake was measured both in total grams per day and in “beverage sugar” per day, defined as sugar taken in tea and coffee. There was higher total sugar and higher beverage sugar intake among the SD group compared with both control groups (P<.05).¹⁷

Atopic Dermatitis—Atopic dermatitis is a disease of epidermal barrier dysfunction and IgE-mediated allergic sensitization.³³ There are several mechanisms by which skin structure may be disrupted. It is well established that filaggrin mutations inhibit stratum corneum maturation and lamellar matrix deposition.³⁴ Upregulation of IL-4–, IL-13–, and IL-17–secreting T_H2 cells also is associated with disruption of tight junctions and reduction of filaggrin.^35,36 Given that a T cell–mediated inflammatory response is involved in disease pathogenesis, glycemic control is hypothesized to have therapeutic potential.

Nosrati et al²⁴ surveyed 169 AD patients about their perceived dietary triggers through a 61-question survey based on the National Health and Nutrition Examination Survey. Respondents were queried about their perceptions and dietary changes, such as removal or addition of specific food groups and trial of specific diets. Overall, 16.5% of patients reported sugar being a trigger, making it the fourth most common among those surveyed and less common than dairy (24.8%), gluten (18.3%), and alcohol (17.1%).²⁴

Hidradenitis Suppurativa—Hidradenitis suppurativa is driven by hyperkeratosis, dilatation, and occlusion of pilosebaceous follicular ducts, whose eventual rupture evokes a local acute inflammatory response.³⁷ The inciting event for both acne and HS involves mTOR complex–mediated follicular hyperproliferation andinsulinlike growth factor 1 stimulation of androgen receptors in pilosebaceous glands. Given the similarities between the pathogenesis of acne and HS, it is hypothesized that lifestyle changes, including diet modification, may have a beneficial effect on HS.^38-40

Comment

Acne—Overall, there is strong evidence supporting the efficacy of a low-glycemic diet in the treatment of acne. Notably, among the 6 observational studies identified, there was 1 conflicting study by Bett et al¹⁷ that did not find a statistically significant difference in glucose intake between acne and control patients. However, this study included only 16 acne patients, whereas the other 5 observational studies included 32 to 2255 patients.¹⁷ The strongest evidence supporting low-glycemic dietary interventions in acne treatment is from 2 rigorous randomized clinical trials by Kwon et al²¹ and Smith et al.¹⁸ These trials used intention-to-treat models and maintained consistency in gender, age, and acne treatment protocols across both control and treatment groups. To ensure compliance with dietary interventions, daily telephone calls, food logs, and 24-hour urea sampling were utilized. Acne outcomes were assessed by a dermatologist who remained blinded with well-defined outcome measures. An important limitation of these studies is the difficulty in attributing the observed results solely to reduced glucose intake, as low-glycemic diets often lead to other dietary changes, including reduced fat intake and increased nutrient consumption.^18,21

A 2022 systematic review of acne by Meixiong et al⁴¹ further reinforced the beneficial effects of low-glycemic diets in the management of acne patients. The group reviewed 6 interventional studies and 28 observational studies to investigate the relationship among acne, dairy, and glycemic content and found an association between decreased glucose and dairy on reduction of acne.⁴¹

It is likely that the ketogenic diet, which limits glucose, would be beneficial for acne patients. There may be added benefit through elevated ketone bodies and substantially reduced insulin secretion. However, because there are no observational or interventional studies, further research is needed to draw firm conclusions regarding diet for acne treatment. A randomized clinical trial investigating the effects of the ketogenic diet compared to the low-glycemic diet compared to a regular diet would be valuable.

Psoriasis—Among psoriasis studies, there was a lack of consensus regarding glucose intake and correlation with disease. Among the 4 observational studies, 2 reported increased glucose intake among psoriasis patients and 2 reported decreased glucose intake. It is plausible that the variability in studies is due to differences in sample size and diet heterogeneity among study populations. More specifically, Johnson et al²² and Afifi et al²⁵ analyzed large sample sizes of 6260 and 2412 US participants, respectively, and found decreased sugar intake among psoriasis patients compared to controls. In comparison, Barrea et al²³ and Yamashita et al²⁷ analyzed substantially smaller and more specific populations consisting of 82 Italian and 140 Japanese participants, respectively; both reported increased glucose intake among psoriasis patients compared to controls. These seemingly antithetical results may be explained by regional dietary differences, with varying proportions of meats, vegetables, antioxidants, and vitamins.

Moreover, the variation among studies may be further explained by the high prevalence of comorbidities among psoriasis patients. In the study by Barrea et al,²³ psoriasis patients had higher fasting glucose (P=.004) and insulin (P=.022) levels than healthy patients. After adjusting for body mass index and metabolic syndrome, the correlation coefficient measuring the relationship between the PASI score and intake of simple carbohydrates changed from r=0.564 (P<.001) to r=0.352 (P=.028). The confounding impact of these comorbidities was further highlighted by Yamashita et al,²⁷ who found statistically significant differences in glucose intake between psoriasis and healthy patients (P=.003). However, they reported diminished significance on additional subgroup analysis accounting for potential comorbidities (P=.994).²⁷ Johnson et al²² and Afifi et al²⁵ did not account for comorbidities; therefore, the 4 observational study results must be interpreted cautiously.

The 2 randomized clinical trials by Castaldo et al^29,30 weakly suggest that a ketogenic diet may be beneficial for psoriasis patients. The studies have several notable limitations, including insufficient sample sizes and control groups. Thus, the decreased PASI scores reported in psoriasis patients on the ketogenic diets are challenging to interpret. Additionally, both studies placed patients on highly restrictive diets of 500 kcal/d for 4 weeks. The feasibility of recommending such a diet to patients in clinical practice is questionable. Diets of less than 500 kcal/d may be dangerous for patients with underlying comorbidities and are unlikely to serve as long-term solutions.²³ To contextualize our findings, a 2022 review by Chung et al⁴² examined the impact of various diets—low-caloric, gluten-free, Mediterranean, Western, and ketogenic—on psoriasis and reported insufficient evidence to suggest a benefit to the ketogenic diet for psoriasis patients, though the Mediterranean diet may be well suited for psoriasis patients because of improved cardiovascular health and reduced mortality.

Seborrheic Dermatitis—Sanders et al⁴³ found that patients with a high-fruit diet had lower odds of having SD, while those on a Western diet had higher odds of having SD. Although the study did not measure glycemic load, it is conceivable that the high glycemic load characteristic of the Western diet contributed to these findings.⁴³ However, no studies have investigated the direct link between low-glycemic or ketogenic diets and SD, leaving this area open for further study.

Atopic Dermatitis—It has been hypothesized that mitigating T cell–mediated inflammation via glucose control may contribute to the improvement in AD.^35,36 However, in one study, 16.5% of AD patients self-identified sugar as a dietary trigger, ranking fourth among other dietary triggers.²⁴ Thus, the connection between glucose levels and AD warrants further exploration.

Hidradenitis Suppurativa—Given the role of metabolic and hormonal influence in HS as well as the overlapping pathophysiology with acne, it is possible that low-glycemic and ketogenic diets may have a role in improving HS.^38-40 However, there is a gap in observation and controlled studies investigating the link between low-glycemic or ketogenic diets and HS.

Conclusion

Our analysis focused on interventional and observational research exploring the effects of low-glycemic and ketogenic diets on associations and treatment of inflammatory skin conditions. There is sufficient evidence to counsel acne patients on the benefits of a low-glycemic diet as an adjunctive treatment for acne. Currently, there is insufficient evidence to recommend a low-glycemic or ketogenic diet as a treatment for patients with any other inflammatory skin disease. Prospective and controlled clinical trials are needed to clarify the utility of dietary interventions for treating inflammatory skin conditions.

Inflammatory skin conditions often have a relapsing and remitting course and represent a large proportion of chronic skin diseases. Common inflammatory skin disorders include acne, psoriasis, hidradenitis suppurativa (HS), atopic dermatitis (AD), and seborrheic dermatitis (SD).¹ Although each of these conditions has a unique pathogenesis, they all are driven by a background of chronic inflammation. It has been reported that diets with high levels of refined carbohydrates and saturated or trans-fatty acids may exacerbate existing inflammation.² Consequently, dietary interventions, such as the ketogenic and low-glycemic diets, have potential anti-inflammatory and metabolic effects that are being assessed as stand-alone or adjunctive therapies for dermatologic diseases.

Diet may partially influence systemic inflammation through its effect on weight. Higher body mass index and obesity are linked to a low-grade inflammatory state and higher levels of circulating inflammatory markers. Therefore, weight loss leads to decreases in inflammatory cytokines, including C-reactive protein, tumor necrosis factor α, and IL-6.³ These cytokines and metabolic effects overlap with inflammatory skin condition pathways. It also is posited that decreased insulin release associated with weight loss results in decreased sebaceous lipogenesis and androgens, which drive keratinocyte proliferation and acne development.^4,5 For instance, in a 2015 meta-analysis of 5 randomized controlled trials on psoriasis, patients in the weight loss intervention group had more substantial reductions in psoriasis area and severity index (PASI) scores compared with controls receiving usual care (P=.004).⁶ However, in a systematic review of 35 studies on acne vulgaris, overweight and obese patients (defined by a body mass index of ≥23 kg/m²) had similar odds of having acne compared with normal-weight individuals (P=.671).⁷

Similar to weight loss, ketogenesis acts as a negative feedback mechanism to reduce insulin release, leading to decreased inflammation and androgens that often exacerbate inflammatory skin diseases.⁸ Ketogenesis ensues when daily carbohydrate intake is limited to less than 50 g, and long-term adherence to a ketogenic diet results in metabolic reliance on ketone bodies such as acetoacetate, β-hydroxybutyrate, and acetone.⁹ These metabolites may decrease free radical damage and consequently improve signs and symptoms of acne, psoriasis, and other inflammatory skin diseases.^10-12 Similarly, increased ketones also may decrease activation of the NLRP3 (NOD-, LRR-, and Pyrin domain-containing protein 3) inflammasome and therefore reduce inflammatory markers such as IL-1β and IL-1.^4,13 Several proposed mechanisms are outlined in the Table.

Collectively, low-glycemic and ketogenic diets have been proposed as potential interventions for reducing inflammatory skin conditions. These dietary approaches are hypothesized to exert their effects by facilitating weight loss, elevating ketone levels, and reducing systemic inflammation. The current review summarizes the existing evidence on ketogenic and low-glycemic diets as treatments for inflammatory skin conditions and evaluates the potential benefits of these dietary interventions in managing and improving outcomes for individuals with inflammatory skin conditions.

Methods

Using PubMed for articles indexed for MEDLINE and Google Scholar, a review of the literature was conducted with a combination of the following search terms: low-glycemic diet, inflammatory, dermatologic, ketogenic diet, inflammation, dermatology, acne, psoriasis, eczema, seborrheic dermatitis, and hidradenitis suppurativa. Reference citations in identified works also were reviewed. Interventional (experimental studies or clinical trials), survey-based, and observational studies that investigated the effects of low-glycemic or ketogenic diets for the treatment of inflammatory skin conditions were included. Inclusion criteria were studies assessing acne, psoriasis, SD, AD, and HS. Exclusion criteria were studies published before 1965; those written in languages other than English; and those analyzing other diets, such as the Mediterranean or low-fat diets. The search yielded a total of 11 observational studies and 4 controlled studies published between 1966 and January 2023. Because this analysis utilized publicly available data and did not qualify as human subject research, institutional review board approval was not required.

Results

Acne Vulgaris—Acne vulgaris is a disease of chronic pilosebaceous inflammation and follicular epithelial proliferation associated with Propionibacterium acnes. The association between acne and low-glycemic diets has been examined in several studies. Diet quality is measured and assessed using the glycemic index (GI), which is the effect of a single food on postprandial blood glucose, and the glycemic load, which is the GI adjusted for carbohydrates per serving.¹⁴ High levels of GI and glycemic load are associated with hyperinsulinemia and an increase in insulinlike growth factor 1 concentration that promotes mechanistic target of rapamycin (mTOR) complex 1–mediated follicular lipogenesis, sebum fatty acid production, and androgen synthesis.¹⁵ Propionibacterium acnes directly activates toll-like receptor 2 on monocytes through damage-associated molecular patterns and indirectly through products of triglyceride catalysis, causing release of IL-12, IL-6, tumor necrosis factor α, and other proinflammatory cytokines.¹⁶ Therefore, lifestyle modifications focused on strict glucose control have been postulated to reduce acne severity via modulation of lipogenesis, androgen concentration, and inflammation.

Six survey-based studies evaluated sugar intake in patients with acne compared to healthy matched controls (eTable). Among these studies, 5 reported higher glycemic loads or daily sugar intake in acne patients compared to individuals without acne.^{12,19,20,26,28} The remaining study was conducted in 1967 and enrolled 16 acne patients and 32 matched controls. It reported no significant difference in sugar intake between the groups (P>.05).¹⁷

Smith et al¹⁸ randomized 43 male patients aged 15 to 25 years with facial acne into 2 cohorts for 12 weeks, each consuming either a low-glycemic diet (25% protein, 45% low-glycemic food [fruits, whole grains], and 30% fat) or a carbohydrate-dense diet of foods with medium to high GI based on prior documentation of the original diet. Patients were instructed to use a noncomedogenic cleanser as their only acne treatment. At 12 weeks, patients consuming the low-glycemic diet had an average of 23.5 fewer inflammatory lesions, while those in the intervention group had 12.0 fewer lesions (P=.03).¹⁸

In another controlled study by Kwon et al,²¹ 32 male and female acne patients were randomized to a low-glycemic diet (25% protein, 45% low-glycemic food, and 30% fat) or a standard diet for 10 weeks. Patients on the low-glycemic diet experienced a 70.9% reduction in inflammatory lesions (P<.05). Hematoxylin and eosin staining and image analysis were performed to measure sebaceous gland surface area in the low-glycemic diet group, which decreased from 0.32 to 0.24 mm² (P=.03). The sebaceous gland surface area in the control group was not reported. Moreover, patients on the low-glycemic diet had reduced IL-8 immunohistochemical staining (decreasing from 2.9 to 1.7 [P=.03]) and sterol regulatory element-binding protein 1 levels (decreasing from 2.6 to 1.3 [P=.03]), suggesting suppression of ongoing inflammation. Patients on the low-glycemic diet had no significant difference in transforming growth factor β1(P=.83). In the control group, there was no difference in IL-8, sterol regulatory element binding protein 1, or transforming growth factor β1 (P>.05) on immunohistochemical staining.²¹

Psoriasis—Psoriasis is a systemic inflammatory disease characterized by hyperproliferation and aberrant keratinocyte plaque formation. The innate immune response of keratinocytes in response to epidermal damage or infection begins with neutrophil recruitment and dendritic cell activation. Dendritic cell secretion of IL-23 promotes T-cell differentiation into helper T cells (T_H1) that subsequently secrete IL-17 and IL-22, thereby stimulating keratinocyte proliferation and eventual plaque formation. The relationship between diet and psoriasis is poorly understood; however, hyperinsulinemia is associated with greater severity of psoriasis.³¹ 

Four observational studies examined sugar intake in psoriasis patients. Barrea et al²³ conducted a survey-based study of 82 male participants (41 with psoriasis and 41 healthy controls), reporting that PASI score was correlated with intake of simple carbohydrates (percentage of total kilocalorie)(r=0.564, P<.001). Another study by Yamashita et al²⁷ found higher sugar intake in psoriasis patients than controls (P=.003) based on surveys from 70 patients with psoriasis and 70 matched healthy controls.

These findings contrast with 2 survey-based studies by Johnson et al²² and Afifi et al²⁵ of sugar intake in psoriasis patients using the National Health and Nutrition Examination Survey. Johnson et al²² reported reduced sugar intake among 156 psoriasis patients compared with 6104 unmatched controls (odds ratio, 0.998; CI, 0.996-1 [P=.04]) from 2003 to 2006. Similarly, Afifi et al²⁵ reported decreased sugar intake in 1206 psoriasis patients compared with sex- and age-matched controls (P<.0001) in 2009 and 2010. When patients were asked about dietary triggers, 13.8% of psoriasis patients reported sugar as the most common trigger, which was more frequent than alcohol (13.6%), gluten (7.2%), and dairy (6%).²⁵

Castaldo et al^29,30 published 2 nonrandomized clinical intervention studies in 2020 and 2021 evaluating the impact of the ketogenic diet on psoriasis. In the first study, 37 psoriasis patients followed a 10-week diet consisting of 4 weeks on a ketogenic diet (500 kcal/d) followed by 6 weeks on a low-caloric Mediterranean diet.²⁹ At the end of the intervention, there was a 17.4% reduction in PASI score, a 33.2-point reduction in itch severity score, and a 13.4-point reduction in the dermatology life quality index score; however, this study did not include a control diet group for comparison.²⁹ The second study included 30 psoriasis patients on a ketogenic diet and 30 control patients without psoriasis on a regular diet.³⁰ The ketogenic diet consisted of 400 to 500 g of vegetables, 20 to 30 g of fat, and a proportion of protein based on body weight with at least 12 g of whey protein and various amino acids. Patients on the ketogenic diet had significant reduction in PASI scores (value relative to clinical features, 1.4916 [P=.007]). Furthermore, concentrations of cytokines IL-2 (P=.04) and IL-1β (P=.006) decreased following the ketogenic diet but were not measured in the control group.³⁰

Seborrheic Dermatitis—Seborrheic dermatitis is associated with overcolonization of Malassezia species near lipid-rich sebaceous glands. Malassezia hydrolyzes free fatty acids, yielding oleic acids and leading to T-cell release of IL-8 and IL-17.³² Literature is sparse regarding how dietary modifications may play a role in disease severity. In a survey study, Bett et al¹⁷ compared 16 SD patients to 1:2 matched controls (N=29) to investigate the relationship between sugar consumption and presence of disease. Two control cohorts were selected, 1 from clinic patients diagnosed with verruca and 1 matched by age and sex from a survey-based study at a facility in London, England. Sugar intake was measured both in total grams per day and in “beverage sugar” per day, defined as sugar taken in tea and coffee. There was higher total sugar and higher beverage sugar intake among the SD group compared with both control groups (P<.05).¹⁷

Atopic Dermatitis—Atopic dermatitis is a disease of epidermal barrier dysfunction and IgE-mediated allergic sensitization.³³ There are several mechanisms by which skin structure may be disrupted. It is well established that filaggrin mutations inhibit stratum corneum maturation and lamellar matrix deposition.³⁴ Upregulation of IL-4–, IL-13–, and IL-17–secreting T_H2 cells also is associated with disruption of tight junctions and reduction of filaggrin.^35,36 Given that a T cell–mediated inflammatory response is involved in disease pathogenesis, glycemic control is hypothesized to have therapeutic potential.

Nosrati et al²⁴ surveyed 169 AD patients about their perceived dietary triggers through a 61-question survey based on the National Health and Nutrition Examination Survey. Respondents were queried about their perceptions and dietary changes, such as removal or addition of specific food groups and trial of specific diets. Overall, 16.5% of patients reported sugar being a trigger, making it the fourth most common among those surveyed and less common than dairy (24.8%), gluten (18.3%), and alcohol (17.1%).²⁴

Hidradenitis Suppurativa—Hidradenitis suppurativa is driven by hyperkeratosis, dilatation, and occlusion of pilosebaceous follicular ducts, whose eventual rupture evokes a local acute inflammatory response.³⁷ The inciting event for both acne and HS involves mTOR complex–mediated follicular hyperproliferation andinsulinlike growth factor 1 stimulation of androgen receptors in pilosebaceous glands. Given the similarities between the pathogenesis of acne and HS, it is hypothesized that lifestyle changes, including diet modification, may have a beneficial effect on HS.^38-40

Comment

Acne—Overall, there is strong evidence supporting the efficacy of a low-glycemic diet in the treatment of acne. Notably, among the 6 observational studies identified, there was 1 conflicting study by Bett et al¹⁷ that did not find a statistically significant difference in glucose intake between acne and control patients. However, this study included only 16 acne patients, whereas the other 5 observational studies included 32 to 2255 patients.¹⁷ The strongest evidence supporting low-glycemic dietary interventions in acne treatment is from 2 rigorous randomized clinical trials by Kwon et al²¹ and Smith et al.¹⁸ These trials used intention-to-treat models and maintained consistency in gender, age, and acne treatment protocols across both control and treatment groups. To ensure compliance with dietary interventions, daily telephone calls, food logs, and 24-hour urea sampling were utilized. Acne outcomes were assessed by a dermatologist who remained blinded with well-defined outcome measures. An important limitation of these studies is the difficulty in attributing the observed results solely to reduced glucose intake, as low-glycemic diets often lead to other dietary changes, including reduced fat intake and increased nutrient consumption.^18,21

A 2022 systematic review of acne by Meixiong et al⁴¹ further reinforced the beneficial effects of low-glycemic diets in the management of acne patients. The group reviewed 6 interventional studies and 28 observational studies to investigate the relationship among acne, dairy, and glycemic content and found an association between decreased glucose and dairy on reduction of acne.⁴¹

It is likely that the ketogenic diet, which limits glucose, would be beneficial for acne patients. There may be added benefit through elevated ketone bodies and substantially reduced insulin secretion. However, because there are no observational or interventional studies, further research is needed to draw firm conclusions regarding diet for acne treatment. A randomized clinical trial investigating the effects of the ketogenic diet compared to the low-glycemic diet compared to a regular diet would be valuable.

Psoriasis—Among psoriasis studies, there was a lack of consensus regarding glucose intake and correlation with disease. Among the 4 observational studies, 2 reported increased glucose intake among psoriasis patients and 2 reported decreased glucose intake. It is plausible that the variability in studies is due to differences in sample size and diet heterogeneity among study populations. More specifically, Johnson et al²² and Afifi et al²⁵ analyzed large sample sizes of 6260 and 2412 US participants, respectively, and found decreased sugar intake among psoriasis patients compared to controls. In comparison, Barrea et al²³ and Yamashita et al²⁷ analyzed substantially smaller and more specific populations consisting of 82 Italian and 140 Japanese participants, respectively; both reported increased glucose intake among psoriasis patients compared to controls. These seemingly antithetical results may be explained by regional dietary differences, with varying proportions of meats, vegetables, antioxidants, and vitamins.

Moreover, the variation among studies may be further explained by the high prevalence of comorbidities among psoriasis patients. In the study by Barrea et al,²³ psoriasis patients had higher fasting glucose (P=.004) and insulin (P=.022) levels than healthy patients. After adjusting for body mass index and metabolic syndrome, the correlation coefficient measuring the relationship between the PASI score and intake of simple carbohydrates changed from r=0.564 (P<.001) to r=0.352 (P=.028). The confounding impact of these comorbidities was further highlighted by Yamashita et al,²⁷ who found statistically significant differences in glucose intake between psoriasis and healthy patients (P=.003). However, they reported diminished significance on additional subgroup analysis accounting for potential comorbidities (P=.994).²⁷ Johnson et al²² and Afifi et al²⁵ did not account for comorbidities; therefore, the 4 observational study results must be interpreted cautiously.

The 2 randomized clinical trials by Castaldo et al^29,30 weakly suggest that a ketogenic diet may be beneficial for psoriasis patients. The studies have several notable limitations, including insufficient sample sizes and control groups. Thus, the decreased PASI scores reported in psoriasis patients on the ketogenic diets are challenging to interpret. Additionally, both studies placed patients on highly restrictive diets of 500 kcal/d for 4 weeks. The feasibility of recommending such a diet to patients in clinical practice is questionable. Diets of less than 500 kcal/d may be dangerous for patients with underlying comorbidities and are unlikely to serve as long-term solutions.²³ To contextualize our findings, a 2022 review by Chung et al⁴² examined the impact of various diets—low-caloric, gluten-free, Mediterranean, Western, and ketogenic—on psoriasis and reported insufficient evidence to suggest a benefit to the ketogenic diet for psoriasis patients, though the Mediterranean diet may be well suited for psoriasis patients because of improved cardiovascular health and reduced mortality.

Seborrheic Dermatitis—Sanders et al⁴³ found that patients with a high-fruit diet had lower odds of having SD, while those on a Western diet had higher odds of having SD. Although the study did not measure glycemic load, it is conceivable that the high glycemic load characteristic of the Western diet contributed to these findings.⁴³ However, no studies have investigated the direct link between low-glycemic or ketogenic diets and SD, leaving this area open for further study.

Atopic Dermatitis—It has been hypothesized that mitigating T cell–mediated inflammation via glucose control may contribute to the improvement in AD.^35,36 However, in one study, 16.5% of AD patients self-identified sugar as a dietary trigger, ranking fourth among other dietary triggers.²⁴ Thus, the connection between glucose levels and AD warrants further exploration.

Hidradenitis Suppurativa—Given the role of metabolic and hormonal influence in HS as well as the overlapping pathophysiology with acne, it is possible that low-glycemic and ketogenic diets may have a role in improving HS.^38-40 However, there is a gap in observation and controlled studies investigating the link between low-glycemic or ketogenic diets and HS.

Conclusion

Our analysis focused on interventional and observational research exploring the effects of low-glycemic and ketogenic diets on associations and treatment of inflammatory skin conditions. There is sufficient evidence to counsel acne patients on the benefits of a low-glycemic diet as an adjunctive treatment for acne. Currently, there is insufficient evidence to recommend a low-glycemic or ketogenic diet as a treatment for patients with any other inflammatory skin disease. Prospective and controlled clinical trials are needed to clarify the utility of dietary interventions for treating inflammatory skin conditions.

Psoriasis is a chronic inflammatory disease that affects approximately 3% of the US population.¹ Plaque psoriasis comprises 80% to 90% of cases, while pustular, erythrodermic, guttate, inverse, and palmoplantar disease are less common variants (Figure 1). Psoriatic skin manifestations range from localized to widespread or generalized disease with recurrent flares. Body surface area or psoriasis area and severity index (PASI) measurements primarily focus on skin manifestations and are important for evaluating disease activity and response to treatment, but they have inherent limitations: they do not capture extracutaneous disease activity, systemic inflammation, comorbid conditions, quality of life impact, or the economic burden of psoriasis.

A common manifestation of psoriasis is psoriatic arthritis (PsA), which can involve the nails, joints, ligaments, or tendons in 30% to 41% of affected individuals (Figure 2).^2,3 A growing number of psoriasis-associated comorbidities also have been reported including metabolic syndrome⁴; hyperlipidemia⁵; cardiovascular disease⁶; stroke⁷; hypertension⁸; obesity⁹; sleep disorders¹⁰; malignancy¹¹; infections¹²; inflammatory bowel disease¹³; and mental health disorders such as depression,¹⁴ anxiety,¹⁵ and suicidal ideation.¹⁵ Psoriatic disease also interferes with daily life activities and a patient’s overall quality of life, including interpersonal relationships, intimacy, employment, and work productivity.¹⁶ Finally, the total estimated cost of psoriasis-related health care is more than $35 billion annually,¹⁷ representing a substantial economic burden to our health care system and individual patients.

The overall burden of psoriatic disease has declined markedly in the last 2 decades due to revolutionary advances in our understanding of the immunopathogenesis of psoriasis and the subsequent development of improved therapies that predominantly interrupt IL-23/IL-17 cytokine signaling; however, critical knowledge and treatment gaps persist, underscoring the importance of ongoing clinical and research efforts in psoriatic disease. We review the working immune model of psoriasis, summarize related immune discoveries, and highlight recent therapeutic innovations that are shaping psoriatic disease management.

Current Immune Model of Psoriatic Disease

Psoriasis is an autoinflammatory T cell–mediated disease with negligible contributions from the humoral immune response. Early clinical observations reported increased inflammatory infiltrates in psoriatic skin lesions primarily consisting of both CD4⁺ and CD8⁺ T-cell populations.^18,19 Additionally, patients treated with broad-acting, systemic immunosuppressive medications (eg, cyclosporine, oral corticosteroids) experienced improvement of psoriatic lesions and normalization of the immune infiltrates observed in skin biopsy specimens.^20,21 These early clinical findings led to more sophisticated experimentation in xenotransplant models of psoriasis,^22,23 which explored the clinical efficacy of several less immunosuppressive (eg, methotrexate, anti–tumor necrosis factor [TNF] biologics)²⁴ or T cell–specific agents (eg, alefacept, abatacept, efalizumab).^25-27 The results of these translational studies provided indisputable evidence for the role of the dysregulated immune response as the primary pathogenic process driving plaque formation; they also led to a paradigm shift in how the immunopathogenesis of psoriatic disease was viewed and paved the way for the identification and targeting of other specific proinflammatory signals produced by activated dendritic cell (DC) and T-lymphocyte populations. Among the psoriasis-associated cytokines subsequently identified and studied, elevated IL-23 and IL-17 cytokine levels in psoriatic skin were most closely associated with disease activity, and rapid normalization of IL-23/IL-17 signaling in response to effective oral or injectable antipsoriatic treatments was the hallmark of skin clearance.²⁸ The predominant role of IL-23/IL-17 signaling in the development and maintenance of psoriatic disease is the central feature of all working immune models for this disease (Figure 3).

Psoriasis-Associated Genetic and Environmental Risk Factors

The exact sequence of events that lead to the initiation and formation of plaque psoriasis in susceptible individuals is still poorly understood; however, several important risk factors and key immune events have been identified. First, decades of genetic research have reported more than 80 known psoriasis-associated susceptibility loci,²⁹ which explains approximately 50% of psoriasis heritability. The major genetic determinant of psoriasis, HLA-C*06:02 (formerly HLA-Cw6), resides in the major histocompatibility complex class I region on chromosome 6p21.3 (psoriasis susceptibility gene 1, PSORS1) and is most strongly associated with psoriatic disease.³⁰ Less common psoriasis-associated susceptibility genes also are known to directly or indirectly impact innate and adaptive immune functions that contribute to the pathogenesis of psoriasis.

Second, several nongenetic environmental risk factors for psoriasis have been reported across diverse patient populations, including skin trauma/injury, infections, alcohol/tobacco use, obesity, medication exposure (eg, lithium, antimalarials, beta-blockers), and stress.³¹ These genetic and/or environmental risk factors can trigger the onset of psoriatic disease at any stage of life, though most patients develop disease in early adulthood or later (age range, 50–60 years). Some patients never develop psoriasis despite exposure to environmental risk factors and/or a genetic makeup that is similar to affected first-degree relatives, which requires further study.

Prepsoriatic Skin and Initiation of Plaque Development

In response to environmental stimuli and/or other triggers of the immune system, DC and resident IL-17–producing T-cell (T17) populations become activated in predisposed individuals. Dendritic cell activation leads to the upregulation and increase of several proinflammatory cytokines, including TNF, interferon (IFN) α, IFN-γ, IL-12, and IL-23. Tumor necrosis factor and IL-23 play a vital role in psoriasis by helping to regulate the polarization and expansion of T22 and T17 cells in the skin, whereas IL-12 promotes a corresponding type 1 inflammatory response.³² Increased IL-17 and IL-22 result in alteration of the terminal differentiation and proliferative potential of epidermal keratinocytes, leading to the early clinical hallmarks of psoriatic plaques. The potential contribution of overexpressed psoriasis-related autoantigens, such as LL-37/cathelicidin, ADAMTSL5, and PLA2G4D,³³ in the initiation of psoriatic plaques has been suggested but is poorly characterized.³⁴ Whether these specific autoantigens or others presented by HLA-C variants found on antigen-presenting cells are required for the breakdown of immune tolerance and psoriatic disease initiation is highly relevant but requires further investigation and validation.

 

 

Feed-Forward Inflammation, Mature Psoriatic Plaques, and Resident Memory T Cells

In response to the upstream production of IL-23 by dermal DCs, high levels of IL-17 cytokines can be found in mature psoriatic plaques. The IL-17 family consists of 6 dimeric cytokines (IL-17A through IL-17F) that provide innate cutaneous protection against bacterial, viral, and fungal infectious agents, such as Candida albicans. Unlike other IL-17 isoforms, IL-17A and IL-17F share the same receptor complex and have the highest structural homology of any pair (approximately 50% similar).³⁵ The relative expression of IL-17F is higher than IL-17A in psoriasis,³⁶ though IL-17A has been considered as the predominant IL-17 cytokine found in psoriatic skin lesions due to its higher potency.

Binding of IL-17A/F with the IL-17 receptor (IL-17R) on keratinocytes contributes to the development of psoriatic plaques by inducing epidermal hyperplasia via activation of CCAAT/enhancer-binding proteins β and δ, nuclear factor κB, and signal transducer and activator of transcription 1 gene (STAT1).^37,38 This also increases the expression of other keratinocyte-derived proteins (eg, human β-defensins, S-100 proteins, LL-37, other antimicrobial peptides, IL-19, IL-36, IL-17C) that act as reinforcing proinflammatory signals or chemotactic factors (eg, chemokine [C-C motif] ligand 20 [CCL20], chemokine [C-C motif] ligand 1/2/3/5 [CXCL1/2/3/5], CXCL8, IL-8) that facilitate the recruitment of additional immune cells to the skin including polymorphonuclear neutrophils (PMNs), macrophages, and DCs.^39-41 Routine immunohistochemical staining for these keratinocyte-derived proteins reveals a striking epidermal gene expression gradient wherein levels of IL-17–induced proteins are most highly expressed in the uppermost layers of keratinocytes and facilitate the recruitment of immune cells into the epidermis. Activated T17 cells also stimulate the production of keratinocyte-derived chemokines (eg, CXCL9/10/11), which recruit type 1 inflammatory T-cell populations into developing psoriatic plaques.^42,43 Finally, TNF, IL-36, and IL-17C cytokines act synergistically with IL-17A/F to amplify the proinflammatory effects of IL-17 signaling and further stimulate their production from T17 cell populations.⁴⁰ This inflammatory circuit in the skin creates and supports a self-amplifying or positive feedback loop between the skin and immune system that commonly is referred to as feed-forward inflammation (Figure 3).³⁴ The feed-forward inflammatory loop in psoriasis—predominantly driven by increased IL-23/IL-17 signaling—best characterizes the mature psoriatic plaque.

Several findings suggest that the influx of persistent, long-lived resident memory T cells (Trms) may contribute to the mature psoriatic plaque. It is believed that CD8⁺CD103⁺CD49a⁻ Trm cell populations may be responsible for the sharply demarcated borders of untreated psoriasis plaques or their recurrence at specific body sites such as the scalp, buttocks, extremity extensor surfaces, umbilicus, or acral skin following specific stimuli or trauma (Koebner phenomenon or isomorphic response).^44,45 It is not known if repeated stimuli or trauma induce disease formation via the activation of Trm cell populations; further study in large patient cohorts is needed, but this remains an intriguing area of study for durable treatment responses and potential cures for psoriasis.

Recent Discoveries in Psoriatic Disease

Remarkable treatment outcomes for psoriasis have been achieved with multiple selective IL-17 and IL-23 inhibitors (eTable). As demonstrated in several pivotal phase 3 clinical trials for members of these classes of medications, the majority of treated psoriasis patients achieved PASI90 clearance.⁴⁶ Due to their more favorable dosing schedule (ie, fewer injections) and ability to induce a durable remissionlike treatment response, IL-23 inhibitors have become the preferred treatment class for cutaneous disease, while IL-17 inhibitors may be preferred when treating patients with both plaque psoriasis and PsA.^47,48 Nevertheless, the complexity of this disease is punctuated by treated patients who do not adequately respond to selective IL-23/IL-17 blockade.⁴⁹ Recent and emerging treatments may shed light on these recalcitrant cases and will add to the rapidly growing arsenal of available psoriasis therapies.

The Role of IL-17F in Psoriasis and Other Inflammatory Skin Diseases

Dysregulation of IL-17A and IL-17F is associated with several chronic inflammatory conditions, such as psoriasis and PsA.^35,50 Both cytokines, either as homodimers or heterodimers, can selectively bind to the heterodimeric IL-17R formed by the IL-17RA and IL-17RC subunits.³⁵ IL-17F and IL-17C also can synergize with TNF and other cytokines to promote and support the self-sustaining inflammatory circuits in mature psoriatic plaques, though their inflammatory effects in the skin are more limited than IL-17A.^51,52 Therefore, incomplete blockade of IL-17 signaling (ie, unopposed IL-17F and IL-17C) represents a potential mechanism to explain the persistence of psoriasis in patients treated with selective IL-17A inhibitors. This hypothesis is supported by reports of psoriasis patients who have inadequate clinical responses to selective IL-17A inhibition but subsequently improve with IL-17R blockade, which results in disruption of IL-17A as well as IL-17C/E/F cytokine signaling. This formed the basis for further study into the specific role of IL-17F in psoriatic disease and any potential therapeutic benefits associated with its inhibition.

Recently approved in the European Union, Canada, Australia, Japan, the United Kingdom, and the United States for moderate to severe psoriasis, bimekizumab is a novel humanized IgG antibody that selectively inhibits both IL-17A and IL-17F cytokines.⁵³ Specifically, bimekizumab simultaneously prevents binding of IL-17A/A, IL-17A/F, and IL-17F/F dimers with the IL-17R. Compared to other IL-17 and IL-23 biologic therapies, bimekizumab (320 mg) achieved relatively higher response rates for PASI75, PASI90, and PASI100.⁴⁹ Neutralization of IL-17A and IL-17F by bimekizumab also resulted in more complete suppression of cytokine responses and PMN chemotaxis than either cytokine alone in treated PsA patients,⁵⁴ which is notable because of the incremental benefits of recent IL-23 and IL-17 inhibitors on inflammatory arthritis symptoms in contrast to the substantial improvements observed for cutaneous disease with those same agents.

The primary disadvantage of bimekizumab and its more complete blockade of the IL-17 signaling pathway is that treated patients have a substantially increased risk for oral candidiasis (>10%).⁵⁵ However, the precise link between candidiasis and IL-17 blockade is not yet fully understood because other targeted agents that also broadly suppress IL-17 signaling (ie, IL-17R, IL-23 inhibitors) are associated with much lower rates of candidiasis.^56-58 Bimekizumab also is being investigated as a novel therapy for hidradenitis suppurativa and will provide important reference information regarding the role for bispecific biologic agents in the treatment of chronic inflammatory skin diseases.⁵⁹

 

 

IL-36 Signaling and Generalized Pustular Psoriasis

Recent genetic and clinical studies have expanded our understanding of the role of IL-36 signaling in the immunopathogenesis of pustular psoriasis variants. Generalized pustular psoriasis (GPP) is a rare distinct psoriasis subtype characterized by the recurrent development of widespread erythema, superficial sterile pustules, and desquamation. Systemic symptoms such as fever, malaise, itching, and skin pain accompany acute GPP flares.⁶⁰ Generalized pustular psoriasis is more common in female patients (in contrast with plaque psoriasis), and acute flares may be caused by multiple stimuli including infections, hypocalcemia, initiation or discontinuation of medications (eg, oral corticosteroids), pregnancy, or stress.^61,62 Flares of GPP often require emergency or in-patient care, as untreated symptoms increase the risk for severe health complications such as secondary infections, sepsis, or multisystem organ failure.⁶³ The prevalence of GPP is estimated to be approximately 1 in 10,000 individuals in the United States,^64-67 with mortality rates ranging from 0 to 3.3 deaths per 100 patient-years.⁶⁷

In contrast to plaque psoriasis, aberrant IL-36 signaling is the predominant driver of GPP. IL-36 is a member of the IL-1 cytokine family that includes three IL-36 agonists (IL-36α, IL-36β, IL-36γ) and 1 endogenous antagonist (IL-36Ra, encoded by IL36RN).⁶⁸ The immunopathogenesis of GPP involves dysregulation of the IL-36–chemokine–PMN axis, resulting in unopposed IL-36 signaling and the subsequent recruitment and influx of PMNs into the epidermis. IL36RN mutations are strongly associated with GPP and result in impaired function of the IL-36Ra protein, leading to unopposed IL-36 signaling.⁶⁹ However, approximately two-thirds of GPP patients lack identifiable gene mutations, suggesting other immune mechanisms or triggers causing upregulated IL-36 signaling.⁷⁰ In response to these triggers, increased IL-36 cytokines released by keratinocytes bind to the IL-36R, resulting in substantial keratinocyte hyperproliferation, increased IL-36 levels, and the expression of hundreds of additional inflammatory signals (eg, IL-17C, antimicrobial peptides, TNF, IL-6).⁷¹ Increased IL-36 levels also drive the production of PMN chemotactic proteins (eg, CXCL1/2/3/5/6/8 and CXCR1/2) and act synergistically with IL-17 cytokines to create an autoamplifying circuit that is analogous to the feed-forward inflammatory loop in plaque psoriasis.⁷² Biopsies of involved GPP skin reveal increased expression of IL-36 in the uppermost layers of the epidermis, which creates a gene expression gradient that acts as a strong attractant for PMNs and forms the basis for the hallmark pustular lesions observed in GPP patients.

Until recently, treatment strategies for GPP involved the off-label use of topical, oral, or biologic therapies approved for plaque psoriasis, which often was associated with variable or incomplete disease control. In September 2022, the US Food and Drug Administration (FDA) approved intravenous spesolimab as a first-in-class humanized monoclonal IgG1 antibody for the treatment of GPP flares in adults. Spesolimab binds to IL-36R and prevents its activation by its endogenous agonists. A phase 2, randomized, 12-week clinical trial (Effisayil-1) evaluated the efficacy and safety of a single 900-mg intravenous dose of spesolimab followed by an optional second dose 1 week later for inadequate treatment responses in 53 enrolled GPP patients (2:1 treatment to placebo randomization).⁷³ Remarkably, more than half (19/35 [54%]) of GPP patients experienced complete resolution of pustules (GPP physician global assessment subscore of 0 [range, 0–4]) and showed sustained efficacy out to week 12 after just 1 or 2 doses of spesolimab. Overall, the safety profile of spesolimab was good; asthenia, fatigue, nausea, vomiting, headache, pruritus, infusion-related reaction and symptoms, and mild infections (eg, urinary tract infection) were the most common adverse events reported.⁷³

Imsidolimab, a high-affinity humanized IgG4 monoclonal antibody that binds and blocks activation of IL-36R, also has completed phase 2 testing,⁷⁴ with phase 3 study results expected in early 2024. The rapid onset of action and overall safety of imsidolimab was in line with and similar to spesolimab. Future approval of imsidolimab would add to the limited treatment options available for GPP and has the additional convenience of being administered to patients subcutaneously. Overall, the development of selective IL-36R inhibitors offers a much-needed therapeutic option for GPP and illustrates the importance of translational research.

Role of Tyrosine Kinase in Psoriatic Disease

The Janus kinase (JAK) enzyme family consists of 4 enzymes—tyrosine kinase 2 (TYK2), JAK1, JAK2, and JAK3—that function as intracellular transduction signals that mediate the biologic response of most extracellular cytokines and growth factors.⁷⁵ Critical psoriasis-related cytokines are dependent on intact JAK-STAT signaling, including IL-23, IL-12, and type I IFNs. In 2010, a genome-wide association identified TYK2 as a psoriasis susceptibility locus,⁷⁶ and loss-of-function TYK2 mutations confer a reduced risk for psoriasis.⁷⁷ Unlike other JAK isoforms, TYK2 mediates biologic functions that are highly restricted to the immune responses associated with IL-23, IL-12, and type I IFN signaling.^78,79 For these reasons, blockade of TYK2 signaling is an attractive therapeutic target for the potential treatment of psoriatic disease.

In September 2022, the FDA approved deucravacitinib as a first-in-class, oral, selective TYK2 inhibitor for the treatment of adult patients with moderate to severe plaque psoriasis. It was the first FDA approval of an oral small-molecule treatment for plaque psoriasis in nearly a decade. Deucravacitinib inhibits TYK2 signaling via selective binding of its unique regulatory domain, resulting in a conformational (allosteric) change that interferes with its active domain.⁸⁰ This novel mechanism of action limits the unwanted blockade of other broad biologic processes mediated by JAK1/2/3. Of note, the FDA did not issue any boxed warnings for deucravacitinib as it did for other FDA-approved JAK inhibitors.

In a head-to-head, 52-week, double-blind, prospective, randomized, phase 3 study, deucravacitinib showed clear superiority over apremilast for PASI75 at week 16 (53.0% [271/511] vs 39.8% [101/254]) and week 24 (58.7% [296/504] vs 37.8% [96/254]).⁸¹ Clinical responses were sustained through week 52 and showed efficacy for difficult-to-treat areas such as the scalp, acral sites, and nails. Other advantages of deucravacitinib include once-daily dosing with no need for dose titration or adjustments for renal insufficiency as well as the absence of statistically significant differences in gastrointestinal tract symptoms compared to placebo. The most common adverse effects included nasopharyngitis, upper respiratory tract infections, headache, diarrhea, and herpes infections.⁸¹ The potential benefit of deucravacitinib for PsA and psoriasis comorbidities remains to be seen, but it is promising due to its simultaneous disruption of multiple psoriasis-related cytokine networks. Several other TYK2 inhibitors are being developed for psoriatic disease and related inflammatory conditions, underscoring the promise of targeting this intracellular pathway.

 

 

Aryl Hydrocarbon Receptor Agonism

Topical steroids are the mainstay treatment option for localized or limited plaque psoriasis due to their potent immunosuppressive effect on the skin and relatively low cost. Combined with vitamin D analogs, topical steroids result in marked improvements in disease severity and improved tolerability.⁸² However, chronic use of topical steroids is limited by the need for twice-daily application, resulting in poor treatment compliance; loss of efficacy over time; risk for steroid-induced skin atrophy on special body sites; and patient concerns of potential systemic effects. The discovery of novel drug targets amenable to topical inhibition is needed.

Dysregulated aryl hydrocarbon receptor (AHR) levels have been reported in atopic dermatitis and psoriasis.⁸³ Aryl hydrocarbon receptors are ubiquitously expressed in many cell types and play an integral role in immune homeostasis within the skin, skin barrier function, protection against oxidative stressors, and regulation of proliferating melanocytes and keratinocytes.^84,85 They are widely expressed in multiple immune cell types (eg, antigen-presenting cells, T lymphocytes, fibroblasts) and modulate the differentiation of T17 and T22 cells as well as their balance with regulatory T-cell populations.⁸⁶ In keratinocytes, AHR helps to regulate terminal differentiation, enhance skin barrier integrity via AHR-dependent filaggrin (FLG) expression, and prevent transepidermal water loss.^87,88 The mechanisms by which AHR ligands lead to the upregulation or downregulation of specific genes is intricate and highly context dependent, such as the specific ligand and cell type involved. In preclinical studies, AHR-deficient mice develop psoriasiform skin inflammation, increased IL-17 and IL-22 expression, and abnormal skin barrier function.⁸⁹ Keratinocytes treated with AHR ligands in vitro modulated psoriasis-associated inflammatory cytokines, such as IL-6, IL-8, and type I and II IFNs.^89,90 The use of coal tar, one of the earliest historical treatments for psoriasis, is thought to activate AHRs in the skin via organic compound mixtures containing polyaromatic hydrocarbons that help normalize the proinflammatory environment in psoriatic skin.⁹¹

In June 2022, the FDA approved tapinarof as a first-in-class, topical, nonsteroidal AHR agonist for the treatment of plaque psoriasis in adults. Although the exact mechanism of action for tapinarof has not been fully elucidated, early studies suggest that its primary function is the activation of AHR, leading to reduced T-cell expansion and T17 cell differentiation. In the imiquimod mouse model, cytokine expression of IL-17A, IL-17F, IL-19, IL-22, IL-23A, and IL-lβ in psoriasiform skin lesions were downregulated following tapinarof treatment.⁹² In humans, tapinarof treatment is associated with a remittive effect, in which the average time for tapinarof-treated psoriasis lesions to remain clear was approximately 4 months.⁹³ Preliminary research investigating the mechanism by which tapinarof induces this remittive effect is ongoing and may involve the reduced activation and influx of T17 and Trm populations into the skin.⁹⁴ However, these preclinical studies were performed on healthy dermatome-derived skin tissue cultured in T17-skewing conditions and needs to be replicated in larger samples sizes using human-derived psoriatic tissue. Alternatively, a strong inhibitory effect on IL-23 cytokine signaling may, in part, explain the remittive effect of tapinarof, as an analogous response is observed in patients who start and discontinue treatment with selective IL-23 antagonists. Regardless, the once-daily dosing of tapinarof and sustained treatment response is appealing to psoriasis patients. Tapinarof generally is well tolerated with mild folliculitis (>20% of patients) and contact dermatitis (5% of patients) reported as the most common skin-related adverse events.

New Roles for Phosphodiesterase 4 Inhibition

Phosphodiesterases (PDEs) are enzymes that hydrolyze cyclic nucleotides (eg, cyclic adenosine monophosphate) to regulate intracellular secondary messengers involved in the inflammatory response. One of several enzymes in the PDE family, PDE4, has been shown to have greater activity in psoriatic skin compared to healthy skin.⁹⁵ Phosphodiesterase inhibitors decrease the degradation of cyclic adenosine monophosphate, which triggers protein kinase A to downregulate proinflammatory (eg, TNF-α, IL-6, IL-17, IL-12, IL-23) cytokines and increased expression of anti-inflammatory signals such as IL-10.^96,97 Apremilast, the first oral PDE4 inhibitor approved by the FDA for psoriasis, offered a safe alternative to traditional oral immunosuppressive agents that had extensive risks and potential end-organ adverse effects. Unfortunately, apremilast demonstrated modest efficacy for psoriatic disease (better efficacy in the skin vs joint manifestations) and was supplanted easily by next-generation targeted biologic agents that were more efficacious and lacked the troublesome gastrointestinal tract adverse effects of PDE4 inhibition.⁹⁸

Crisaborole became the first topical PDE4 inhibitor approved in the United States in December 2016 for twice-daily treatment of atopic dermatitis. Although phase 2 trial results were reported in psoriasis, this indication was never pursued, presumably due to similar improvements in primary outcome measures at week 12, compared to placebo (ClinicalTrials.gov Identifier NCT01300052).

In July 2022, the first topical PDE4 inhibitor indicated for plaque psoriasis was approved by the FDA—­roflumilast cream 0.3% for once-daily use in individuals 12 years and older. Roflumilast was found to be clinically efficacious as early as 2 weeks after its use in an early-phase clinical trial.⁹⁹ In 2 phase 3 clinical trials (DERMIS-1 and DERMIS-2), roflumilast significantly increased the proportion of patients achieving PASI75 at week 8 compared to vehicle (39%–41.6% vs 5.3%–7.6%, respectively)(P<.001).¹⁰⁰ Overall, this nonsteroidal topical therapy was found to be well tolerated, with infrequent reports of application site pain or irritation as adverse events. Similar to tapinarof, patients can apply roflumilast on all body surface areas including the face, external genitalia, and other intertriginous areas.¹⁰⁰ Importantly, the broad immune impact of PDE4 inhibition suggests that topical roflumilast likely will be an effective treatment for several additional inflammatory conditions, including seborrheic dermatitis and atopic dermatitis, which would expand the clinical utility of this specific medication.

Conclusion

In the last 2 decades, we have witnessed a translational revolution in our understanding of the underlying genetics and immunology of psoriatic disease. Psoriasis is widely considered one of the best-managed inflammatory conditions in all of medicine due to the development and availability of highly targeted, effective topical and systemic therapies that predominantly disrupt IL-23/IL-17 cytokine signaling in affected tissues. However, future clinical studies and laboratory research are necessary to elucidate the precise cause of psoriasis as well as the underlying genetic and immune signaling pathways driving less common clinical variants and recalcitrant disease.

Psoriasis is a chronic inflammatory disease that affects approximately 3% of the US population.¹ Plaque psoriasis comprises 80% to 90% of cases, while pustular, erythrodermic, guttate, inverse, and palmoplantar disease are less common variants (Figure 1). Psoriatic skin manifestations range from localized to widespread or generalized disease with recurrent flares. Body surface area or psoriasis area and severity index (PASI) measurements primarily focus on skin manifestations and are important for evaluating disease activity and response to treatment, but they have inherent limitations: they do not capture extracutaneous disease activity, systemic inflammation, comorbid conditions, quality of life impact, or the economic burden of psoriasis.

A common manifestation of psoriasis is psoriatic arthritis (PsA), which can involve the nails, joints, ligaments, or tendons in 30% to 41% of affected individuals (Figure 2).^2,3 A growing number of psoriasis-associated comorbidities also have been reported including metabolic syndrome⁴; hyperlipidemia⁵; cardiovascular disease⁶; stroke⁷; hypertension⁸; obesity⁹; sleep disorders¹⁰; malignancy¹¹; infections¹²; inflammatory bowel disease¹³; and mental health disorders such as depression,¹⁴ anxiety,¹⁵ and suicidal ideation.¹⁵ Psoriatic disease also interferes with daily life activities and a patient’s overall quality of life, including interpersonal relationships, intimacy, employment, and work productivity.¹⁶ Finally, the total estimated cost of psoriasis-related health care is more than $35 billion annually,¹⁷ representing a substantial economic burden to our health care system and individual patients.

The overall burden of psoriatic disease has declined markedly in the last 2 decades due to revolutionary advances in our understanding of the immunopathogenesis of psoriasis and the subsequent development of improved therapies that predominantly interrupt IL-23/IL-17 cytokine signaling; however, critical knowledge and treatment gaps persist, underscoring the importance of ongoing clinical and research efforts in psoriatic disease. We review the working immune model of psoriasis, summarize related immune discoveries, and highlight recent therapeutic innovations that are shaping psoriatic disease management.

Current Immune Model of Psoriatic Disease

Psoriasis is an autoinflammatory T cell–mediated disease with negligible contributions from the humoral immune response. Early clinical observations reported increased inflammatory infiltrates in psoriatic skin lesions primarily consisting of both CD4⁺ and CD8⁺ T-cell populations.^18,19 Additionally, patients treated with broad-acting, systemic immunosuppressive medications (eg, cyclosporine, oral corticosteroids) experienced improvement of psoriatic lesions and normalization of the immune infiltrates observed in skin biopsy specimens.^20,21 These early clinical findings led to more sophisticated experimentation in xenotransplant models of psoriasis,^22,23 which explored the clinical efficacy of several less immunosuppressive (eg, methotrexate, anti–tumor necrosis factor [TNF] biologics)²⁴ or T cell–specific agents (eg, alefacept, abatacept, efalizumab).^25-27 The results of these translational studies provided indisputable evidence for the role of the dysregulated immune response as the primary pathogenic process driving plaque formation; they also led to a paradigm shift in how the immunopathogenesis of psoriatic disease was viewed and paved the way for the identification and targeting of other specific proinflammatory signals produced by activated dendritic cell (DC) and T-lymphocyte populations. Among the psoriasis-associated cytokines subsequently identified and studied, elevated IL-23 and IL-17 cytokine levels in psoriatic skin were most closely associated with disease activity, and rapid normalization of IL-23/IL-17 signaling in response to effective oral or injectable antipsoriatic treatments was the hallmark of skin clearance.²⁸ The predominant role of IL-23/IL-17 signaling in the development and maintenance of psoriatic disease is the central feature of all working immune models for this disease (Figure 3).

Psoriasis-Associated Genetic and Environmental Risk Factors

The exact sequence of events that lead to the initiation and formation of plaque psoriasis in susceptible individuals is still poorly understood; however, several important risk factors and key immune events have been identified. First, decades of genetic research have reported more than 80 known psoriasis-associated susceptibility loci,²⁹ which explains approximately 50% of psoriasis heritability. The major genetic determinant of psoriasis, HLA-C*06:02 (formerly HLA-Cw6), resides in the major histocompatibility complex class I region on chromosome 6p21.3 (psoriasis susceptibility gene 1, PSORS1) and is most strongly associated with psoriatic disease.³⁰ Less common psoriasis-associated susceptibility genes also are known to directly or indirectly impact innate and adaptive immune functions that contribute to the pathogenesis of psoriasis.

Second, several nongenetic environmental risk factors for psoriasis have been reported across diverse patient populations, including skin trauma/injury, infections, alcohol/tobacco use, obesity, medication exposure (eg, lithium, antimalarials, beta-blockers), and stress.³¹ These genetic and/or environmental risk factors can trigger the onset of psoriatic disease at any stage of life, though most patients develop disease in early adulthood or later (age range, 50–60 years). Some patients never develop psoriasis despite exposure to environmental risk factors and/or a genetic makeup that is similar to affected first-degree relatives, which requires further study.

Prepsoriatic Skin and Initiation of Plaque Development

In response to environmental stimuli and/or other triggers of the immune system, DC and resident IL-17–producing T-cell (T17) populations become activated in predisposed individuals. Dendritic cell activation leads to the upregulation and increase of several proinflammatory cytokines, including TNF, interferon (IFN) α, IFN-γ, IL-12, and IL-23. Tumor necrosis factor and IL-23 play a vital role in psoriasis by helping to regulate the polarization and expansion of T22 and T17 cells in the skin, whereas IL-12 promotes a corresponding type 1 inflammatory response.³² Increased IL-17 and IL-22 result in alteration of the terminal differentiation and proliferative potential of epidermal keratinocytes, leading to the early clinical hallmarks of psoriatic plaques. The potential contribution of overexpressed psoriasis-related autoantigens, such as LL-37/cathelicidin, ADAMTSL5, and PLA2G4D,³³ in the initiation of psoriatic plaques has been suggested but is poorly characterized.³⁴ Whether these specific autoantigens or others presented by HLA-C variants found on antigen-presenting cells are required for the breakdown of immune tolerance and psoriatic disease initiation is highly relevant but requires further investigation and validation.

 

 

Feed-Forward Inflammation, Mature Psoriatic Plaques, and Resident Memory T Cells

In response to the upstream production of IL-23 by dermal DCs, high levels of IL-17 cytokines can be found in mature psoriatic plaques. The IL-17 family consists of 6 dimeric cytokines (IL-17A through IL-17F) that provide innate cutaneous protection against bacterial, viral, and fungal infectious agents, such as Candida albicans. Unlike other IL-17 isoforms, IL-17A and IL-17F share the same receptor complex and have the highest structural homology of any pair (approximately 50% similar).³⁵ The relative expression of IL-17F is higher than IL-17A in psoriasis,³⁶ though IL-17A has been considered as the predominant IL-17 cytokine found in psoriatic skin lesions due to its higher potency.

Binding of IL-17A/F with the IL-17 receptor (IL-17R) on keratinocytes contributes to the development of psoriatic plaques by inducing epidermal hyperplasia via activation of CCAAT/enhancer-binding proteins β and δ, nuclear factor κB, and signal transducer and activator of transcription 1 gene (STAT1).^37,38 This also increases the expression of other keratinocyte-derived proteins (eg, human β-defensins, S-100 proteins, LL-37, other antimicrobial peptides, IL-19, IL-36, IL-17C) that act as reinforcing proinflammatory signals or chemotactic factors (eg, chemokine [C-C motif] ligand 20 [CCL20], chemokine [C-C motif] ligand 1/2/3/5 [CXCL1/2/3/5], CXCL8, IL-8) that facilitate the recruitment of additional immune cells to the skin including polymorphonuclear neutrophils (PMNs), macrophages, and DCs.^39-41 Routine immunohistochemical staining for these keratinocyte-derived proteins reveals a striking epidermal gene expression gradient wherein levels of IL-17–induced proteins are most highly expressed in the uppermost layers of keratinocytes and facilitate the recruitment of immune cells into the epidermis. Activated T17 cells also stimulate the production of keratinocyte-derived chemokines (eg, CXCL9/10/11), which recruit type 1 inflammatory T-cell populations into developing psoriatic plaques.^42,43 Finally, TNF, IL-36, and IL-17C cytokines act synergistically with IL-17A/F to amplify the proinflammatory effects of IL-17 signaling and further stimulate their production from T17 cell populations.⁴⁰ This inflammatory circuit in the skin creates and supports a self-amplifying or positive feedback loop between the skin and immune system that commonly is referred to as feed-forward inflammation (Figure 3).³⁴ The feed-forward inflammatory loop in psoriasis—predominantly driven by increased IL-23/IL-17 signaling—best characterizes the mature psoriatic plaque.

Several findings suggest that the influx of persistent, long-lived resident memory T cells (Trms) may contribute to the mature psoriatic plaque. It is believed that CD8⁺CD103⁺CD49a⁻ Trm cell populations may be responsible for the sharply demarcated borders of untreated psoriasis plaques or their recurrence at specific body sites such as the scalp, buttocks, extremity extensor surfaces, umbilicus, or acral skin following specific stimuli or trauma (Koebner phenomenon or isomorphic response).^44,45 It is not known if repeated stimuli or trauma induce disease formation via the activation of Trm cell populations; further study in large patient cohorts is needed, but this remains an intriguing area of study for durable treatment responses and potential cures for psoriasis.

Recent Discoveries in Psoriatic Disease

Remarkable treatment outcomes for psoriasis have been achieved with multiple selective IL-17 and IL-23 inhibitors (eTable). As demonstrated in several pivotal phase 3 clinical trials for members of these classes of medications, the majority of treated psoriasis patients achieved PASI90 clearance.⁴⁶ Due to their more favorable dosing schedule (ie, fewer injections) and ability to induce a durable remissionlike treatment response, IL-23 inhibitors have become the preferred treatment class for cutaneous disease, while IL-17 inhibitors may be preferred when treating patients with both plaque psoriasis and PsA.^47,48 Nevertheless, the complexity of this disease is punctuated by treated patients who do not adequately respond to selective IL-23/IL-17 blockade.⁴⁹ Recent and emerging treatments may shed light on these recalcitrant cases and will add to the rapidly growing arsenal of available psoriasis therapies.

The Role of IL-17F in Psoriasis and Other Inflammatory Skin Diseases

Dysregulation of IL-17A and IL-17F is associated with several chronic inflammatory conditions, such as psoriasis and PsA.^35,50 Both cytokines, either as homodimers or heterodimers, can selectively bind to the heterodimeric IL-17R formed by the IL-17RA and IL-17RC subunits.³⁵ IL-17F and IL-17C also can synergize with TNF and other cytokines to promote and support the self-sustaining inflammatory circuits in mature psoriatic plaques, though their inflammatory effects in the skin are more limited than IL-17A.^51,52 Therefore, incomplete blockade of IL-17 signaling (ie, unopposed IL-17F and IL-17C) represents a potential mechanism to explain the persistence of psoriasis in patients treated with selective IL-17A inhibitors. This hypothesis is supported by reports of psoriasis patients who have inadequate clinical responses to selective IL-17A inhibition but subsequently improve with IL-17R blockade, which results in disruption of IL-17A as well as IL-17C/E/F cytokine signaling. This formed the basis for further study into the specific role of IL-17F in psoriatic disease and any potential therapeutic benefits associated with its inhibition.

Recently approved in the European Union, Canada, Australia, Japan, the United Kingdom, and the United States for moderate to severe psoriasis, bimekizumab is a novel humanized IgG antibody that selectively inhibits both IL-17A and IL-17F cytokines.⁵³ Specifically, bimekizumab simultaneously prevents binding of IL-17A/A, IL-17A/F, and IL-17F/F dimers with the IL-17R. Compared to other IL-17 and IL-23 biologic therapies, bimekizumab (320 mg) achieved relatively higher response rates for PASI75, PASI90, and PASI100.⁴⁹ Neutralization of IL-17A and IL-17F by bimekizumab also resulted in more complete suppression of cytokine responses and PMN chemotaxis than either cytokine alone in treated PsA patients,⁵⁴ which is notable because of the incremental benefits of recent IL-23 and IL-17 inhibitors on inflammatory arthritis symptoms in contrast to the substantial improvements observed for cutaneous disease with those same agents.

The primary disadvantage of bimekizumab and its more complete blockade of the IL-17 signaling pathway is that treated patients have a substantially increased risk for oral candidiasis (>10%).⁵⁵ However, the precise link between candidiasis and IL-17 blockade is not yet fully understood because other targeted agents that also broadly suppress IL-17 signaling (ie, IL-17R, IL-23 inhibitors) are associated with much lower rates of candidiasis.^56-58 Bimekizumab also is being investigated as a novel therapy for hidradenitis suppurativa and will provide important reference information regarding the role for bispecific biologic agents in the treatment of chronic inflammatory skin diseases.⁵⁹

 

 

IL-36 Signaling and Generalized Pustular Psoriasis

Recent genetic and clinical studies have expanded our understanding of the role of IL-36 signaling in the immunopathogenesis of pustular psoriasis variants. Generalized pustular psoriasis (GPP) is a rare distinct psoriasis subtype characterized by the recurrent development of widespread erythema, superficial sterile pustules, and desquamation. Systemic symptoms such as fever, malaise, itching, and skin pain accompany acute GPP flares.⁶⁰ Generalized pustular psoriasis is more common in female patients (in contrast with plaque psoriasis), and acute flares may be caused by multiple stimuli including infections, hypocalcemia, initiation or discontinuation of medications (eg, oral corticosteroids), pregnancy, or stress.^61,62 Flares of GPP often require emergency or in-patient care, as untreated symptoms increase the risk for severe health complications such as secondary infections, sepsis, or multisystem organ failure.⁶³ The prevalence of GPP is estimated to be approximately 1 in 10,000 individuals in the United States,^64-67 with mortality rates ranging from 0 to 3.3 deaths per 100 patient-years.⁶⁷

In contrast to plaque psoriasis, aberrant IL-36 signaling is the predominant driver of GPP. IL-36 is a member of the IL-1 cytokine family that includes three IL-36 agonists (IL-36α, IL-36β, IL-36γ) and 1 endogenous antagonist (IL-36Ra, encoded by IL36RN).⁶⁸ The immunopathogenesis of GPP involves dysregulation of the IL-36–chemokine–PMN axis, resulting in unopposed IL-36 signaling and the subsequent recruitment and influx of PMNs into the epidermis. IL36RN mutations are strongly associated with GPP and result in impaired function of the IL-36Ra protein, leading to unopposed IL-36 signaling.⁶⁹ However, approximately two-thirds of GPP patients lack identifiable gene mutations, suggesting other immune mechanisms or triggers causing upregulated IL-36 signaling.⁷⁰ In response to these triggers, increased IL-36 cytokines released by keratinocytes bind to the IL-36R, resulting in substantial keratinocyte hyperproliferation, increased IL-36 levels, and the expression of hundreds of additional inflammatory signals (eg, IL-17C, antimicrobial peptides, TNF, IL-6).⁷¹ Increased IL-36 levels also drive the production of PMN chemotactic proteins (eg, CXCL1/2/3/5/6/8 and CXCR1/2) and act synergistically with IL-17 cytokines to create an autoamplifying circuit that is analogous to the feed-forward inflammatory loop in plaque psoriasis.⁷² Biopsies of involved GPP skin reveal increased expression of IL-36 in the uppermost layers of the epidermis, which creates a gene expression gradient that acts as a strong attractant for PMNs and forms the basis for the hallmark pustular lesions observed in GPP patients.

Until recently, treatment strategies for GPP involved the off-label use of topical, oral, or biologic therapies approved for plaque psoriasis, which often was associated with variable or incomplete disease control. In September 2022, the US Food and Drug Administration (FDA) approved intravenous spesolimab as a first-in-class humanized monoclonal IgG1 antibody for the treatment of GPP flares in adults. Spesolimab binds to IL-36R and prevents its activation by its endogenous agonists. A phase 2, randomized, 12-week clinical trial (Effisayil-1) evaluated the efficacy and safety of a single 900-mg intravenous dose of spesolimab followed by an optional second dose 1 week later for inadequate treatment responses in 53 enrolled GPP patients (2:1 treatment to placebo randomization).⁷³ Remarkably, more than half (19/35 [54%]) of GPP patients experienced complete resolution of pustules (GPP physician global assessment subscore of 0 [range, 0–4]) and showed sustained efficacy out to week 12 after just 1 or 2 doses of spesolimab. Overall, the safety profile of spesolimab was good; asthenia, fatigue, nausea, vomiting, headache, pruritus, infusion-related reaction and symptoms, and mild infections (eg, urinary tract infection) were the most common adverse events reported.⁷³

Imsidolimab, a high-affinity humanized IgG4 monoclonal antibody that binds and blocks activation of IL-36R, also has completed phase 2 testing,⁷⁴ with phase 3 study results expected in early 2024. The rapid onset of action and overall safety of imsidolimab was in line with and similar to spesolimab. Future approval of imsidolimab would add to the limited treatment options available for GPP and has the additional convenience of being administered to patients subcutaneously. Overall, the development of selective IL-36R inhibitors offers a much-needed therapeutic option for GPP and illustrates the importance of translational research.

Role of Tyrosine Kinase in Psoriatic Disease

The Janus kinase (JAK) enzyme family consists of 4 enzymes—tyrosine kinase 2 (TYK2), JAK1, JAK2, and JAK3—that function as intracellular transduction signals that mediate the biologic response of most extracellular cytokines and growth factors.⁷⁵ Critical psoriasis-related cytokines are dependent on intact JAK-STAT signaling, including IL-23, IL-12, and type I IFNs. In 2010, a genome-wide association identified TYK2 as a psoriasis susceptibility locus,⁷⁶ and loss-of-function TYK2 mutations confer a reduced risk for psoriasis.⁷⁷ Unlike other JAK isoforms, TYK2 mediates biologic functions that are highly restricted to the immune responses associated with IL-23, IL-12, and type I IFN signaling.^78,79 For these reasons, blockade of TYK2 signaling is an attractive therapeutic target for the potential treatment of psoriatic disease.

In September 2022, the FDA approved deucravacitinib as a first-in-class, oral, selective TYK2 inhibitor for the treatment of adult patients with moderate to severe plaque psoriasis. It was the first FDA approval of an oral small-molecule treatment for plaque psoriasis in nearly a decade. Deucravacitinib inhibits TYK2 signaling via selective binding of its unique regulatory domain, resulting in a conformational (allosteric) change that interferes with its active domain.⁸⁰ This novel mechanism of action limits the unwanted blockade of other broad biologic processes mediated by JAK1/2/3. Of note, the FDA did not issue any boxed warnings for deucravacitinib as it did for other FDA-approved JAK inhibitors.

In a head-to-head, 52-week, double-blind, prospective, randomized, phase 3 study, deucravacitinib showed clear superiority over apremilast for PASI75 at week 16 (53.0% [271/511] vs 39.8% [101/254]) and week 24 (58.7% [296/504] vs 37.8% [96/254]).⁸¹ Clinical responses were sustained through week 52 and showed efficacy for difficult-to-treat areas such as the scalp, acral sites, and nails. Other advantages of deucravacitinib include once-daily dosing with no need for dose titration or adjustments for renal insufficiency as well as the absence of statistically significant differences in gastrointestinal tract symptoms compared to placebo. The most common adverse effects included nasopharyngitis, upper respiratory tract infections, headache, diarrhea, and herpes infections.⁸¹ The potential benefit of deucravacitinib for PsA and psoriasis comorbidities remains to be seen, but it is promising due to its simultaneous disruption of multiple psoriasis-related cytokine networks. Several other TYK2 inhibitors are being developed for psoriatic disease and related inflammatory conditions, underscoring the promise of targeting this intracellular pathway.

 

 

Aryl Hydrocarbon Receptor Agonism

Topical steroids are the mainstay treatment option for localized or limited plaque psoriasis due to their potent immunosuppressive effect on the skin and relatively low cost. Combined with vitamin D analogs, topical steroids result in marked improvements in disease severity and improved tolerability.⁸² However, chronic use of topical steroids is limited by the need for twice-daily application, resulting in poor treatment compliance; loss of efficacy over time; risk for steroid-induced skin atrophy on special body sites; and patient concerns of potential systemic effects. The discovery of novel drug targets amenable to topical inhibition is needed.

Dysregulated aryl hydrocarbon receptor (AHR) levels have been reported in atopic dermatitis and psoriasis.⁸³ Aryl hydrocarbon receptors are ubiquitously expressed in many cell types and play an integral role in immune homeostasis within the skin, skin barrier function, protection against oxidative stressors, and regulation of proliferating melanocytes and keratinocytes.^84,85 They are widely expressed in multiple immune cell types (eg, antigen-presenting cells, T lymphocytes, fibroblasts) and modulate the differentiation of T17 and T22 cells as well as their balance with regulatory T-cell populations.⁸⁶ In keratinocytes, AHR helps to regulate terminal differentiation, enhance skin barrier integrity via AHR-dependent filaggrin (FLG) expression, and prevent transepidermal water loss.^87,88 The mechanisms by which AHR ligands lead to the upregulation or downregulation of specific genes is intricate and highly context dependent, such as the specific ligand and cell type involved. In preclinical studies, AHR-deficient mice develop psoriasiform skin inflammation, increased IL-17 and IL-22 expression, and abnormal skin barrier function.⁸⁹ Keratinocytes treated with AHR ligands in vitro modulated psoriasis-associated inflammatory cytokines, such as IL-6, IL-8, and type I and II IFNs.^89,90 The use of coal tar, one of the earliest historical treatments for psoriasis, is thought to activate AHRs in the skin via organic compound mixtures containing polyaromatic hydrocarbons that help normalize the proinflammatory environment in psoriatic skin.⁹¹

In June 2022, the FDA approved tapinarof as a first-in-class, topical, nonsteroidal AHR agonist for the treatment of plaque psoriasis in adults. Although the exact mechanism of action for tapinarof has not been fully elucidated, early studies suggest that its primary function is the activation of AHR, leading to reduced T-cell expansion and T17 cell differentiation. In the imiquimod mouse model, cytokine expression of IL-17A, IL-17F, IL-19, IL-22, IL-23A, and IL-lβ in psoriasiform skin lesions were downregulated following tapinarof treatment.⁹² In humans, tapinarof treatment is associated with a remittive effect, in which the average time for tapinarof-treated psoriasis lesions to remain clear was approximately 4 months.⁹³ Preliminary research investigating the mechanism by which tapinarof induces this remittive effect is ongoing and may involve the reduced activation and influx of T17 and Trm populations into the skin.⁹⁴ However, these preclinical studies were performed on healthy dermatome-derived skin tissue cultured in T17-skewing conditions and needs to be replicated in larger samples sizes using human-derived psoriatic tissue. Alternatively, a strong inhibitory effect on IL-23 cytokine signaling may, in part, explain the remittive effect of tapinarof, as an analogous response is observed in patients who start and discontinue treatment with selective IL-23 antagonists. Regardless, the once-daily dosing of tapinarof and sustained treatment response is appealing to psoriasis patients. Tapinarof generally is well tolerated with mild folliculitis (>20% of patients) and contact dermatitis (5% of patients) reported as the most common skin-related adverse events.

New Roles for Phosphodiesterase 4 Inhibition

Phosphodiesterases (PDEs) are enzymes that hydrolyze cyclic nucleotides (eg, cyclic adenosine monophosphate) to regulate intracellular secondary messengers involved in the inflammatory response. One of several enzymes in the PDE family, PDE4, has been shown to have greater activity in psoriatic skin compared to healthy skin.⁹⁵ Phosphodiesterase inhibitors decrease the degradation of cyclic adenosine monophosphate, which triggers protein kinase A to downregulate proinflammatory (eg, TNF-α, IL-6, IL-17, IL-12, IL-23) cytokines and increased expression of anti-inflammatory signals such as IL-10.^96,97 Apremilast, the first oral PDE4 inhibitor approved by the FDA for psoriasis, offered a safe alternative to traditional oral immunosuppressive agents that had extensive risks and potential end-organ adverse effects. Unfortunately, apremilast demonstrated modest efficacy for psoriatic disease (better efficacy in the skin vs joint manifestations) and was supplanted easily by next-generation targeted biologic agents that were more efficacious and lacked the troublesome gastrointestinal tract adverse effects of PDE4 inhibition.⁹⁸

Crisaborole became the first topical PDE4 inhibitor approved in the United States in December 2016 for twice-daily treatment of atopic dermatitis. Although phase 2 trial results were reported in psoriasis, this indication was never pursued, presumably due to similar improvements in primary outcome measures at week 12, compared to placebo (ClinicalTrials.gov Identifier NCT01300052).

In July 2022, the first topical PDE4 inhibitor indicated for plaque psoriasis was approved by the FDA—­roflumilast cream 0.3% for once-daily use in individuals 12 years and older. Roflumilast was found to be clinically efficacious as early as 2 weeks after its use in an early-phase clinical trial.⁹⁹ In 2 phase 3 clinical trials (DERMIS-1 and DERMIS-2), roflumilast significantly increased the proportion of patients achieving PASI75 at week 8 compared to vehicle (39%–41.6% vs 5.3%–7.6%, respectively)(P<.001).¹⁰⁰ Overall, this nonsteroidal topical therapy was found to be well tolerated, with infrequent reports of application site pain or irritation as adverse events. Similar to tapinarof, patients can apply roflumilast on all body surface areas including the face, external genitalia, and other intertriginous areas.¹⁰⁰ Importantly, the broad immune impact of PDE4 inhibition suggests that topical roflumilast likely will be an effective treatment for several additional inflammatory conditions, including seborrheic dermatitis and atopic dermatitis, which would expand the clinical utility of this specific medication.

Conclusion

In the last 2 decades, we have witnessed a translational revolution in our understanding of the underlying genetics and immunology of psoriatic disease. Psoriasis is widely considered one of the best-managed inflammatory conditions in all of medicine due to the development and availability of highly targeted, effective topical and systemic therapies that predominantly disrupt IL-23/IL-17 cytokine signaling in affected tissues. However, future clinical studies and laboratory research are necessary to elucidate the precise cause of psoriasis as well as the underlying genetic and immune signaling pathways driving less common clinical variants and recalcitrant disease.

Psoriasis is a chronic inflammatory disease that affects approximately 3% of the US population.¹ Plaque psoriasis comprises 80% to 90% of cases, while pustular, erythrodermic, guttate, inverse, and palmoplantar disease are less common variants (Figure 1). Psoriatic skin manifestations range from localized to widespread or generalized disease with recurrent flares. Body surface area or psoriasis area and severity index (PASI) measurements primarily focus on skin manifestations and are important for evaluating disease activity and response to treatment, but they have inherent limitations: they do not capture extracutaneous disease activity, systemic inflammation, comorbid conditions, quality of life impact, or the economic burden of psoriasis.

A common manifestation of psoriasis is psoriatic arthritis (PsA), which can involve the nails, joints, ligaments, or tendons in 30% to 41% of affected individuals (Figure 2).^2,3 A growing number of psoriasis-associated comorbidities also have been reported including metabolic syndrome⁴; hyperlipidemia⁵; cardiovascular disease⁶; stroke⁷; hypertension⁸; obesity⁹; sleep disorders¹⁰; malignancy¹¹; infections¹²; inflammatory bowel disease¹³; and mental health disorders such as depression,¹⁴ anxiety,¹⁵ and suicidal ideation.¹⁵ Psoriatic disease also interferes with daily life activities and a patient’s overall quality of life, including interpersonal relationships, intimacy, employment, and work productivity.¹⁶ Finally, the total estimated cost of psoriasis-related health care is more than $35 billion annually,¹⁷ representing a substantial economic burden to our health care system and individual patients.

The overall burden of psoriatic disease has declined markedly in the last 2 decades due to revolutionary advances in our understanding of the immunopathogenesis of psoriasis and the subsequent development of improved therapies that predominantly interrupt IL-23/IL-17 cytokine signaling; however, critical knowledge and treatment gaps persist, underscoring the importance of ongoing clinical and research efforts in psoriatic disease. We review the working immune model of psoriasis, summarize related immune discoveries, and highlight recent therapeutic innovations that are shaping psoriatic disease management.

Current Immune Model of Psoriatic Disease

Psoriasis is an autoinflammatory T cell–mediated disease with negligible contributions from the humoral immune response. Early clinical observations reported increased inflammatory infiltrates in psoriatic skin lesions primarily consisting of both CD4⁺ and CD8⁺ T-cell populations.^18,19 Additionally, patients treated with broad-acting, systemic immunosuppressive medications (eg, cyclosporine, oral corticosteroids) experienced improvement of psoriatic lesions and normalization of the immune infiltrates observed in skin biopsy specimens.^20,21 These early clinical findings led to more sophisticated experimentation in xenotransplant models of psoriasis,^22,23 which explored the clinical efficacy of several less immunosuppressive (eg, methotrexate, anti–tumor necrosis factor [TNF] biologics)²⁴ or T cell–specific agents (eg, alefacept, abatacept, efalizumab).^25-27 The results of these translational studies provided indisputable evidence for the role of the dysregulated immune response as the primary pathogenic process driving plaque formation; they also led to a paradigm shift in how the immunopathogenesis of psoriatic disease was viewed and paved the way for the identification and targeting of other specific proinflammatory signals produced by activated dendritic cell (DC) and T-lymphocyte populations. Among the psoriasis-associated cytokines subsequently identified and studied, elevated IL-23 and IL-17 cytokine levels in psoriatic skin were most closely associated with disease activity, and rapid normalization of IL-23/IL-17 signaling in response to effective oral or injectable antipsoriatic treatments was the hallmark of skin clearance.²⁸ The predominant role of IL-23/IL-17 signaling in the development and maintenance of psoriatic disease is the central feature of all working immune models for this disease (Figure 3).

Psoriasis-Associated Genetic and Environmental Risk Factors

The exact sequence of events that lead to the initiation and formation of plaque psoriasis in susceptible individuals is still poorly understood; however, several important risk factors and key immune events have been identified. First, decades of genetic research have reported more than 80 known psoriasis-associated susceptibility loci,²⁹ which explains approximately 50% of psoriasis heritability. The major genetic determinant of psoriasis, HLA-C*06:02 (formerly HLA-Cw6), resides in the major histocompatibility complex class I region on chromosome 6p21.3 (psoriasis susceptibility gene 1, PSORS1) and is most strongly associated with psoriatic disease.³⁰ Less common psoriasis-associated susceptibility genes also are known to directly or indirectly impact innate and adaptive immune functions that contribute to the pathogenesis of psoriasis.

Second, several nongenetic environmental risk factors for psoriasis have been reported across diverse patient populations, including skin trauma/injury, infections, alcohol/tobacco use, obesity, medication exposure (eg, lithium, antimalarials, beta-blockers), and stress.³¹ These genetic and/or environmental risk factors can trigger the onset of psoriatic disease at any stage of life, though most patients develop disease in early adulthood or later (age range, 50–60 years). Some patients never develop psoriasis despite exposure to environmental risk factors and/or a genetic makeup that is similar to affected first-degree relatives, which requires further study.

Prepsoriatic Skin and Initiation of Plaque Development

In response to environmental stimuli and/or other triggers of the immune system, DC and resident IL-17–producing T-cell (T17) populations become activated in predisposed individuals. Dendritic cell activation leads to the upregulation and increase of several proinflammatory cytokines, including TNF, interferon (IFN) α, IFN-γ, IL-12, and IL-23. Tumor necrosis factor and IL-23 play a vital role in psoriasis by helping to regulate the polarization and expansion of T22 and T17 cells in the skin, whereas IL-12 promotes a corresponding type 1 inflammatory response.³² Increased IL-17 and IL-22 result in alteration of the terminal differentiation and proliferative potential of epidermal keratinocytes, leading to the early clinical hallmarks of psoriatic plaques. The potential contribution of overexpressed psoriasis-related autoantigens, such as LL-37/cathelicidin, ADAMTSL5, and PLA2G4D,³³ in the initiation of psoriatic plaques has been suggested but is poorly characterized.³⁴ Whether these specific autoantigens or others presented by HLA-C variants found on antigen-presenting cells are required for the breakdown of immune tolerance and psoriatic disease initiation is highly relevant but requires further investigation and validation.

 

 

Feed-Forward Inflammation, Mature Psoriatic Plaques, and Resident Memory T Cells

In response to the upstream production of IL-23 by dermal DCs, high levels of IL-17 cytokines can be found in mature psoriatic plaques. The IL-17 family consists of 6 dimeric cytokines (IL-17A through IL-17F) that provide innate cutaneous protection against bacterial, viral, and fungal infectious agents, such as Candida albicans. Unlike other IL-17 isoforms, IL-17A and IL-17F share the same receptor complex and have the highest structural homology of any pair (approximately 50% similar).³⁵ The relative expression of IL-17F is higher than IL-17A in psoriasis,³⁶ though IL-17A has been considered as the predominant IL-17 cytokine found in psoriatic skin lesions due to its higher potency.

Binding of IL-17A/F with the IL-17 receptor (IL-17R) on keratinocytes contributes to the development of psoriatic plaques by inducing epidermal hyperplasia via activation of CCAAT/enhancer-binding proteins β and δ, nuclear factor κB, and signal transducer and activator of transcription 1 gene (STAT1).^37,38 This also increases the expression of other keratinocyte-derived proteins (eg, human β-defensins, S-100 proteins, LL-37, other antimicrobial peptides, IL-19, IL-36, IL-17C) that act as reinforcing proinflammatory signals or chemotactic factors (eg, chemokine [C-C motif] ligand 20 [CCL20], chemokine [C-C motif] ligand 1/2/3/5 [CXCL1/2/3/5], CXCL8, IL-8) that facilitate the recruitment of additional immune cells to the skin including polymorphonuclear neutrophils (PMNs), macrophages, and DCs.^39-41 Routine immunohistochemical staining for these keratinocyte-derived proteins reveals a striking epidermal gene expression gradient wherein levels of IL-17–induced proteins are most highly expressed in the uppermost layers of keratinocytes and facilitate the recruitment of immune cells into the epidermis. Activated T17 cells also stimulate the production of keratinocyte-derived chemokines (eg, CXCL9/10/11), which recruit type 1 inflammatory T-cell populations into developing psoriatic plaques.^42,43 Finally, TNF, IL-36, and IL-17C cytokines act synergistically with IL-17A/F to amplify the proinflammatory effects of IL-17 signaling and further stimulate their production from T17 cell populations.⁴⁰ This inflammatory circuit in the skin creates and supports a self-amplifying or positive feedback loop between the skin and immune system that commonly is referred to as feed-forward inflammation (Figure 3).³⁴ The feed-forward inflammatory loop in psoriasis—predominantly driven by increased IL-23/IL-17 signaling—best characterizes the mature psoriatic plaque.

Several findings suggest that the influx of persistent, long-lived resident memory T cells (Trms) may contribute to the mature psoriatic plaque. It is believed that CD8⁺CD103⁺CD49a⁻ Trm cell populations may be responsible for the sharply demarcated borders of untreated psoriasis plaques or their recurrence at specific body sites such as the scalp, buttocks, extremity extensor surfaces, umbilicus, or acral skin following specific stimuli or trauma (Koebner phenomenon or isomorphic response).^44,45 It is not known if repeated stimuli or trauma induce disease formation via the activation of Trm cell populations; further study in large patient cohorts is needed, but this remains an intriguing area of study for durable treatment responses and potential cures for psoriasis.

Recent Discoveries in Psoriatic Disease

Remarkable treatment outcomes for psoriasis have been achieved with multiple selective IL-17 and IL-23 inhibitors (eTable). As demonstrated in several pivotal phase 3 clinical trials for members of these classes of medications, the majority of treated psoriasis patients achieved PASI90 clearance.⁴⁶ Due to their more favorable dosing schedule (ie, fewer injections) and ability to induce a durable remissionlike treatment response, IL-23 inhibitors have become the preferred treatment class for cutaneous disease, while IL-17 inhibitors may be preferred when treating patients with both plaque psoriasis and PsA.^47,48 Nevertheless, the complexity of this disease is punctuated by treated patients who do not adequately respond to selective IL-23/IL-17 blockade.⁴⁹ Recent and emerging treatments may shed light on these recalcitrant cases and will add to the rapidly growing arsenal of available psoriasis therapies.

The Role of IL-17F in Psoriasis and Other Inflammatory Skin Diseases

Dysregulation of IL-17A and IL-17F is associated with several chronic inflammatory conditions, such as psoriasis and PsA.^35,50 Both cytokines, either as homodimers or heterodimers, can selectively bind to the heterodimeric IL-17R formed by the IL-17RA and IL-17RC subunits.³⁵ IL-17F and IL-17C also can synergize with TNF and other cytokines to promote and support the self-sustaining inflammatory circuits in mature psoriatic plaques, though their inflammatory effects in the skin are more limited than IL-17A.^51,52 Therefore, incomplete blockade of IL-17 signaling (ie, unopposed IL-17F and IL-17C) represents a potential mechanism to explain the persistence of psoriasis in patients treated with selective IL-17A inhibitors. This hypothesis is supported by reports of psoriasis patients who have inadequate clinical responses to selective IL-17A inhibition but subsequently improve with IL-17R blockade, which results in disruption of IL-17A as well as IL-17C/E/F cytokine signaling. This formed the basis for further study into the specific role of IL-17F in psoriatic disease and any potential therapeutic benefits associated with its inhibition.

Recently approved in the European Union, Canada, Australia, Japan, the United Kingdom, and the United States for moderate to severe psoriasis, bimekizumab is a novel humanized IgG antibody that selectively inhibits both IL-17A and IL-17F cytokines.⁵³ Specifically, bimekizumab simultaneously prevents binding of IL-17A/A, IL-17A/F, and IL-17F/F dimers with the IL-17R. Compared to other IL-17 and IL-23 biologic therapies, bimekizumab (320 mg) achieved relatively higher response rates for PASI75, PASI90, and PASI100.⁴⁹ Neutralization of IL-17A and IL-17F by bimekizumab also resulted in more complete suppression of cytokine responses and PMN chemotaxis than either cytokine alone in treated PsA patients,⁵⁴ which is notable because of the incremental benefits of recent IL-23 and IL-17 inhibitors on inflammatory arthritis symptoms in contrast to the substantial improvements observed for cutaneous disease with those same agents.

The primary disadvantage of bimekizumab and its more complete blockade of the IL-17 signaling pathway is that treated patients have a substantially increased risk for oral candidiasis (>10%).⁵⁵ However, the precise link between candidiasis and IL-17 blockade is not yet fully understood because other targeted agents that also broadly suppress IL-17 signaling (ie, IL-17R, IL-23 inhibitors) are associated with much lower rates of candidiasis.^56-58 Bimekizumab also is being investigated as a novel therapy for hidradenitis suppurativa and will provide important reference information regarding the role for bispecific biologic agents in the treatment of chronic inflammatory skin diseases.⁵⁹

 

 

IL-36 Signaling and Generalized Pustular Psoriasis

Recent genetic and clinical studies have expanded our understanding of the role of IL-36 signaling in the immunopathogenesis of pustular psoriasis variants. Generalized pustular psoriasis (GPP) is a rare distinct psoriasis subtype characterized by the recurrent development of widespread erythema, superficial sterile pustules, and desquamation. Systemic symptoms such as fever, malaise, itching, and skin pain accompany acute GPP flares.⁶⁰ Generalized pustular psoriasis is more common in female patients (in contrast with plaque psoriasis), and acute flares may be caused by multiple stimuli including infections, hypocalcemia, initiation or discontinuation of medications (eg, oral corticosteroids), pregnancy, or stress.^61,62 Flares of GPP often require emergency or in-patient care, as untreated symptoms increase the risk for severe health complications such as secondary infections, sepsis, or multisystem organ failure.⁶³ The prevalence of GPP is estimated to be approximately 1 in 10,000 individuals in the United States,^64-67 with mortality rates ranging from 0 to 3.3 deaths per 100 patient-years.⁶⁷

In contrast to plaque psoriasis, aberrant IL-36 signaling is the predominant driver of GPP. IL-36 is a member of the IL-1 cytokine family that includes three IL-36 agonists (IL-36α, IL-36β, IL-36γ) and 1 endogenous antagonist (IL-36Ra, encoded by IL36RN).⁶⁸ The immunopathogenesis of GPP involves dysregulation of the IL-36–chemokine–PMN axis, resulting in unopposed IL-36 signaling and the subsequent recruitment and influx of PMNs into the epidermis. IL36RN mutations are strongly associated with GPP and result in impaired function of the IL-36Ra protein, leading to unopposed IL-36 signaling.⁶⁹ However, approximately two-thirds of GPP patients lack identifiable gene mutations, suggesting other immune mechanisms or triggers causing upregulated IL-36 signaling.⁷⁰ In response to these triggers, increased IL-36 cytokines released by keratinocytes bind to the IL-36R, resulting in substantial keratinocyte hyperproliferation, increased IL-36 levels, and the expression of hundreds of additional inflammatory signals (eg, IL-17C, antimicrobial peptides, TNF, IL-6).⁷¹ Increased IL-36 levels also drive the production of PMN chemotactic proteins (eg, CXCL1/2/3/5/6/8 and CXCR1/2) and act synergistically with IL-17 cytokines to create an autoamplifying circuit that is analogous to the feed-forward inflammatory loop in plaque psoriasis.⁷² Biopsies of involved GPP skin reveal increased expression of IL-36 in the uppermost layers of the epidermis, which creates a gene expression gradient that acts as a strong attractant for PMNs and forms the basis for the hallmark pustular lesions observed in GPP patients.

Until recently, treatment strategies for GPP involved the off-label use of topical, oral, or biologic therapies approved for plaque psoriasis, which often was associated with variable or incomplete disease control. In September 2022, the US Food and Drug Administration (FDA) approved intravenous spesolimab as a first-in-class humanized monoclonal IgG1 antibody for the treatment of GPP flares in adults. Spesolimab binds to IL-36R and prevents its activation by its endogenous agonists. A phase 2, randomized, 12-week clinical trial (Effisayil-1) evaluated the efficacy and safety of a single 900-mg intravenous dose of spesolimab followed by an optional second dose 1 week later for inadequate treatment responses in 53 enrolled GPP patients (2:1 treatment to placebo randomization).⁷³ Remarkably, more than half (19/35 [54%]) of GPP patients experienced complete resolution of pustules (GPP physician global assessment subscore of 0 [range, 0–4]) and showed sustained efficacy out to week 12 after just 1 or 2 doses of spesolimab. Overall, the safety profile of spesolimab was good; asthenia, fatigue, nausea, vomiting, headache, pruritus, infusion-related reaction and symptoms, and mild infections (eg, urinary tract infection) were the most common adverse events reported.⁷³

Imsidolimab, a high-affinity humanized IgG4 monoclonal antibody that binds and blocks activation of IL-36R, also has completed phase 2 testing,⁷⁴ with phase 3 study results expected in early 2024. The rapid onset of action and overall safety of imsidolimab was in line with and similar to spesolimab. Future approval of imsidolimab would add to the limited treatment options available for GPP and has the additional convenience of being administered to patients subcutaneously. Overall, the development of selective IL-36R inhibitors offers a much-needed therapeutic option for GPP and illustrates the importance of translational research.

Role of Tyrosine Kinase in Psoriatic Disease

The Janus kinase (JAK) enzyme family consists of 4 enzymes—tyrosine kinase 2 (TYK2), JAK1, JAK2, and JAK3—that function as intracellular transduction signals that mediate the biologic response of most extracellular cytokines and growth factors.⁷⁵ Critical psoriasis-related cytokines are dependent on intact JAK-STAT signaling, including IL-23, IL-12, and type I IFNs. In 2010, a genome-wide association identified TYK2 as a psoriasis susceptibility locus,⁷⁶ and loss-of-function TYK2 mutations confer a reduced risk for psoriasis.⁷⁷ Unlike other JAK isoforms, TYK2 mediates biologic functions that are highly restricted to the immune responses associated with IL-23, IL-12, and type I IFN signaling.^78,79 For these reasons, blockade of TYK2 signaling is an attractive therapeutic target for the potential treatment of psoriatic disease.

In September 2022, the FDA approved deucravacitinib as a first-in-class, oral, selective TYK2 inhibitor for the treatment of adult patients with moderate to severe plaque psoriasis. It was the first FDA approval of an oral small-molecule treatment for plaque psoriasis in nearly a decade. Deucravacitinib inhibits TYK2 signaling via selective binding of its unique regulatory domain, resulting in a conformational (allosteric) change that interferes with its active domain.⁸⁰ This novel mechanism of action limits the unwanted blockade of other broad biologic processes mediated by JAK1/2/3. Of note, the FDA did not issue any boxed warnings for deucravacitinib as it did for other FDA-approved JAK inhibitors.

In a head-to-head, 52-week, double-blind, prospective, randomized, phase 3 study, deucravacitinib showed clear superiority over apremilast for PASI75 at week 16 (53.0% [271/511] vs 39.8% [101/254]) and week 24 (58.7% [296/504] vs 37.8% [96/254]).⁸¹ Clinical responses were sustained through week 52 and showed efficacy for difficult-to-treat areas such as the scalp, acral sites, and nails. Other advantages of deucravacitinib include once-daily dosing with no need for dose titration or adjustments for renal insufficiency as well as the absence of statistically significant differences in gastrointestinal tract symptoms compared to placebo. The most common adverse effects included nasopharyngitis, upper respiratory tract infections, headache, diarrhea, and herpes infections.⁸¹ The potential benefit of deucravacitinib for PsA and psoriasis comorbidities remains to be seen, but it is promising due to its simultaneous disruption of multiple psoriasis-related cytokine networks. Several other TYK2 inhibitors are being developed for psoriatic disease and related inflammatory conditions, underscoring the promise of targeting this intracellular pathway.

 

 

Aryl Hydrocarbon Receptor Agonism

Topical steroids are the mainstay treatment option for localized or limited plaque psoriasis due to their potent immunosuppressive effect on the skin and relatively low cost. Combined with vitamin D analogs, topical steroids result in marked improvements in disease severity and improved tolerability.⁸² However, chronic use of topical steroids is limited by the need for twice-daily application, resulting in poor treatment compliance; loss of efficacy over time; risk for steroid-induced skin atrophy on special body sites; and patient concerns of potential systemic effects. The discovery of novel drug targets amenable to topical inhibition is needed.

Dysregulated aryl hydrocarbon receptor (AHR) levels have been reported in atopic dermatitis and psoriasis.⁸³ Aryl hydrocarbon receptors are ubiquitously expressed in many cell types and play an integral role in immune homeostasis within the skin, skin barrier function, protection against oxidative stressors, and regulation of proliferating melanocytes and keratinocytes.^84,85 They are widely expressed in multiple immune cell types (eg, antigen-presenting cells, T lymphocytes, fibroblasts) and modulate the differentiation of T17 and T22 cells as well as their balance with regulatory T-cell populations.⁸⁶ In keratinocytes, AHR helps to regulate terminal differentiation, enhance skin barrier integrity via AHR-dependent filaggrin (FLG) expression, and prevent transepidermal water loss.^87,88 The mechanisms by which AHR ligands lead to the upregulation or downregulation of specific genes is intricate and highly context dependent, such as the specific ligand and cell type involved. In preclinical studies, AHR-deficient mice develop psoriasiform skin inflammation, increased IL-17 and IL-22 expression, and abnormal skin barrier function.⁸⁹ Keratinocytes treated with AHR ligands in vitro modulated psoriasis-associated inflammatory cytokines, such as IL-6, IL-8, and type I and II IFNs.^89,90 The use of coal tar, one of the earliest historical treatments for psoriasis, is thought to activate AHRs in the skin via organic compound mixtures containing polyaromatic hydrocarbons that help normalize the proinflammatory environment in psoriatic skin.⁹¹

In June 2022, the FDA approved tapinarof as a first-in-class, topical, nonsteroidal AHR agonist for the treatment of plaque psoriasis in adults. Although the exact mechanism of action for tapinarof has not been fully elucidated, early studies suggest that its primary function is the activation of AHR, leading to reduced T-cell expansion and T17 cell differentiation. In the imiquimod mouse model, cytokine expression of IL-17A, IL-17F, IL-19, IL-22, IL-23A, and IL-lβ in psoriasiform skin lesions were downregulated following tapinarof treatment.⁹² In humans, tapinarof treatment is associated with a remittive effect, in which the average time for tapinarof-treated psoriasis lesions to remain clear was approximately 4 months.⁹³ Preliminary research investigating the mechanism by which tapinarof induces this remittive effect is ongoing and may involve the reduced activation and influx of T17 and Trm populations into the skin.⁹⁴ However, these preclinical studies were performed on healthy dermatome-derived skin tissue cultured in T17-skewing conditions and needs to be replicated in larger samples sizes using human-derived psoriatic tissue. Alternatively, a strong inhibitory effect on IL-23 cytokine signaling may, in part, explain the remittive effect of tapinarof, as an analogous response is observed in patients who start and discontinue treatment with selective IL-23 antagonists. Regardless, the once-daily dosing of tapinarof and sustained treatment response is appealing to psoriasis patients. Tapinarof generally is well tolerated with mild folliculitis (>20% of patients) and contact dermatitis (5% of patients) reported as the most common skin-related adverse events.

New Roles for Phosphodiesterase 4 Inhibition

Phosphodiesterases (PDEs) are enzymes that hydrolyze cyclic nucleotides (eg, cyclic adenosine monophosphate) to regulate intracellular secondary messengers involved in the inflammatory response. One of several enzymes in the PDE family, PDE4, has been shown to have greater activity in psoriatic skin compared to healthy skin.⁹⁵ Phosphodiesterase inhibitors decrease the degradation of cyclic adenosine monophosphate, which triggers protein kinase A to downregulate proinflammatory (eg, TNF-α, IL-6, IL-17, IL-12, IL-23) cytokines and increased expression of anti-inflammatory signals such as IL-10.^96,97 Apremilast, the first oral PDE4 inhibitor approved by the FDA for psoriasis, offered a safe alternative to traditional oral immunosuppressive agents that had extensive risks and potential end-organ adverse effects. Unfortunately, apremilast demonstrated modest efficacy for psoriatic disease (better efficacy in the skin vs joint manifestations) and was supplanted easily by next-generation targeted biologic agents that were more efficacious and lacked the troublesome gastrointestinal tract adverse effects of PDE4 inhibition.⁹⁸

Crisaborole became the first topical PDE4 inhibitor approved in the United States in December 2016 for twice-daily treatment of atopic dermatitis. Although phase 2 trial results were reported in psoriasis, this indication was never pursued, presumably due to similar improvements in primary outcome measures at week 12, compared to placebo (ClinicalTrials.gov Identifier NCT01300052).

In July 2022, the first topical PDE4 inhibitor indicated for plaque psoriasis was approved by the FDA—­roflumilast cream 0.3% for once-daily use in individuals 12 years and older. Roflumilast was found to be clinically efficacious as early as 2 weeks after its use in an early-phase clinical trial.⁹⁹ In 2 phase 3 clinical trials (DERMIS-1 and DERMIS-2), roflumilast significantly increased the proportion of patients achieving PASI75 at week 8 compared to vehicle (39%–41.6% vs 5.3%–7.6%, respectively)(P<.001).¹⁰⁰ Overall, this nonsteroidal topical therapy was found to be well tolerated, with infrequent reports of application site pain or irritation as adverse events. Similar to tapinarof, patients can apply roflumilast on all body surface areas including the face, external genitalia, and other intertriginous areas.¹⁰⁰ Importantly, the broad immune impact of PDE4 inhibition suggests that topical roflumilast likely will be an effective treatment for several additional inflammatory conditions, including seborrheic dermatitis and atopic dermatitis, which would expand the clinical utility of this specific medication.

Conclusion

In the last 2 decades, we have witnessed a translational revolution in our understanding of the underlying genetics and immunology of psoriatic disease. Psoriasis is widely considered one of the best-managed inflammatory conditions in all of medicine due to the development and availability of highly targeted, effective topical and systemic therapies that predominantly disrupt IL-23/IL-17 cytokine signaling in affected tissues. However, future clinical studies and laboratory research are necessary to elucidate the precise cause of psoriasis as well as the underlying genetic and immune signaling pathways driving less common clinical variants and recalcitrant disease.

ORLANDO, FLORIDA — Amid all the hype, claims, and confusion, there is evidence linking some foods and drinks to an increased risk for acne, psoriasis, atopic dermatitis, rosacea, and other common skin conditions. So, what is the connection in each case? And how can people with any of these skin conditions potentially improve their health and quality of life with dietary changes?

Acne

One of the major areas of interest is diet and acne. “We’ve all heard sugar and dairy are bad, and the Western diet is high in sugar and dairy,” Dr. Shi said at the ODAC Dermatology, Aesthetic & Surgical Conference.
Dairy, red meat, and carbohydrates can break down into leucine, an essential amino acid found in protein. Leucine and sugar together, in turn, can produce insulin and insulin-like growth factor 1 (IGF-1), which, through different pathways, can reach the androgen receptors throughout the body, including the skin. This results in sebogenesis, lipogenesis, and keratinization, which triggers follicular inflammation and results in more of the acne-causing bacteria Cutibacterium acnes. 
Milk and other dairy products also can increase IGF-1 levels, which can alter hormonal mediators and increase acne.
Not all types of dairy milk are created equal, however, when it comes to acne. Dr. Shi wondered why 2% milk has overall color and nutritional content very similar to that of whole milk. “I looked into this.” She discovered that when milk manufacturers remove the fat, they often add whey proteins to restore some nutrients. Whey protein can increase acne, Dr. Shi added. 
“So, if you’re going to choose any milk to drink, I think from an acne perspective, it’s better to use whole milk. If you can get it organic, even better.” Skim milk is the most acnegenic, she said.

Psoriasis

A systematic review of 55 studies evaluating diet and psoriasis found obesity can be an exacerbating factor. The strongest evidence for dietary weight reduction points to a hypocaloric diet in people with overweight or obesity, according to the review. Other evidence suggests alcohol can lower response to treatment and is linked with more severe psoriasis. Furthermore, a gluten-free diet or vitamin D supplements can help some subpopulations of people with psoriasis. 
“An overwhelming majority of our psoriasis patients are vitamin D deficient,” Dr. Shi said. 
The National Psoriasis Foundation (NPF) publishes dietary modification guidelines, updated as recently as November 2023. The NPF states that “there is no diet that will cure psoriatic disease, but there are many ways in which eating healthful food may lessen the severity of symptoms and play a role in lowering the likelihood of developing comorbidities.”
Healthier choices include fruits, vegetables, whole grains, and fat-free or low-fat dairy products. Include lean meats, poultry, fish, beans, eggs, and nuts. Adherence to a Mediterranean diet has been linked to a lower severity of psoriasis.

Atopic Dermatitis

Atopic dermatitis (AD) is “one of the prototypical diseases related to diet,” Dr. Shi said. A different meta-analysis looked at randomized controlled trials of synbiotics (a combination of prebiotics and probiotics) for treatment of AD.
These researchers found that synbiotics do not prevent AD, but they can help treat it in adults and children older than 1 year. In addition, synbiotics are more beneficial than probiotics in treating the condition, although there are no head-to-head comparison studies. In addition, the meta-analysis found that prebiotics alone can lower AD severity.
However, Dr. Shi said, there are no recommendations from the American Academy of Dermatology (AAD) on prebiotics or probiotics for AD, and the AAD does not recommend any supplement or essential oil for AD.
In a 2022 review, investigators ranked the efficacy of different supplements for AD based on available evidence. They found the greatest benefit associated with vitamin D supplementation, followed by vitamin E, probiotics, hemp seed oil, histidine, and oolong tea. They also noted the ‘Six Food Elimination Diet and Autoimmune Protocol’ featured the least amount of evidence to back it up. 

Rosacea

Rosacea appears to be caused by “all the fun things in life” like sunlight, alcohol, chocolate, spicy foods, and caffeine, Dr. Shi said. In people with rosacea, they can cause facial flushing, edema, burning, and an inflammatory response.
Certain foods can activate skin receptors and sensory neurons, which can release neuropeptides that act on mast cells in blood that lead to flushing. The skin-gut axis may also be involved, evidence suggests. “And that is why food has a pretty profound impact on rosacea,” Dr. Shi said. 
Dr. Shi reported no relevant financial relationships.

A version of this article appeared on Medscape.com.

ORLANDO, FLORIDA — Amid all the hype, claims, and confusion, there is evidence linking some foods and drinks to an increased risk for acne, psoriasis, atopic dermatitis, rosacea, and other common skin conditions. So, what is the connection in each case? And how can people with any of these skin conditions potentially improve their health and quality of life with dietary changes?

Acne

One of the major areas of interest is diet and acne. “We’ve all heard sugar and dairy are bad, and the Western diet is high in sugar and dairy,” Dr. Shi said at the ODAC Dermatology, Aesthetic & Surgical Conference.
Dairy, red meat, and carbohydrates can break down into leucine, an essential amino acid found in protein. Leucine and sugar together, in turn, can produce insulin and insulin-like growth factor 1 (IGF-1), which, through different pathways, can reach the androgen receptors throughout the body, including the skin. This results in sebogenesis, lipogenesis, and keratinization, which triggers follicular inflammation and results in more of the acne-causing bacteria Cutibacterium acnes. 
Milk and other dairy products also can increase IGF-1 levels, which can alter hormonal mediators and increase acne.
Not all types of dairy milk are created equal, however, when it comes to acne. Dr. Shi wondered why 2% milk has overall color and nutritional content very similar to that of whole milk. “I looked into this.” She discovered that when milk manufacturers remove the fat, they often add whey proteins to restore some nutrients. Whey protein can increase acne, Dr. Shi added. 
“So, if you’re going to choose any milk to drink, I think from an acne perspective, it’s better to use whole milk. If you can get it organic, even better.” Skim milk is the most acnegenic, she said.

Psoriasis

A systematic review of 55 studies evaluating diet and psoriasis found obesity can be an exacerbating factor. The strongest evidence for dietary weight reduction points to a hypocaloric diet in people with overweight or obesity, according to the review. Other evidence suggests alcohol can lower response to treatment and is linked with more severe psoriasis. Furthermore, a gluten-free diet or vitamin D supplements can help some subpopulations of people with psoriasis. 
“An overwhelming majority of our psoriasis patients are vitamin D deficient,” Dr. Shi said. 
The National Psoriasis Foundation (NPF) publishes dietary modification guidelines, updated as recently as November 2023. The NPF states that “there is no diet that will cure psoriatic disease, but there are many ways in which eating healthful food may lessen the severity of symptoms and play a role in lowering the likelihood of developing comorbidities.”
Healthier choices include fruits, vegetables, whole grains, and fat-free or low-fat dairy products. Include lean meats, poultry, fish, beans, eggs, and nuts. Adherence to a Mediterranean diet has been linked to a lower severity of psoriasis.

Atopic Dermatitis

Atopic dermatitis (AD) is “one of the prototypical diseases related to diet,” Dr. Shi said. A different meta-analysis looked at randomized controlled trials of synbiotics (a combination of prebiotics and probiotics) for treatment of AD.
These researchers found that synbiotics do not prevent AD, but they can help treat it in adults and children older than 1 year. In addition, synbiotics are more beneficial than probiotics in treating the condition, although there are no head-to-head comparison studies. In addition, the meta-analysis found that prebiotics alone can lower AD severity.
However, Dr. Shi said, there are no recommendations from the American Academy of Dermatology (AAD) on prebiotics or probiotics for AD, and the AAD does not recommend any supplement or essential oil for AD.
In a 2022 review, investigators ranked the efficacy of different supplements for AD based on available evidence. They found the greatest benefit associated with vitamin D supplementation, followed by vitamin E, probiotics, hemp seed oil, histidine, and oolong tea. They also noted the ‘Six Food Elimination Diet and Autoimmune Protocol’ featured the least amount of evidence to back it up. 

Rosacea

Rosacea appears to be caused by “all the fun things in life” like sunlight, alcohol, chocolate, spicy foods, and caffeine, Dr. Shi said. In people with rosacea, they can cause facial flushing, edema, burning, and an inflammatory response.
Certain foods can activate skin receptors and sensory neurons, which can release neuropeptides that act on mast cells in blood that lead to flushing. The skin-gut axis may also be involved, evidence suggests. “And that is why food has a pretty profound impact on rosacea,” Dr. Shi said. 
Dr. Shi reported no relevant financial relationships.

A version of this article appeared on Medscape.com.

ORLANDO, FLORIDA — Amid all the hype, claims, and confusion, there is evidence linking some foods and drinks to an increased risk for acne, psoriasis, atopic dermatitis, rosacea, and other common skin conditions. So, what is the connection in each case? And how can people with any of these skin conditions potentially improve their health and quality of life with dietary changes?

Acne

One of the major areas of interest is diet and acne. “We’ve all heard sugar and dairy are bad, and the Western diet is high in sugar and dairy,” Dr. Shi said at the ODAC Dermatology, Aesthetic & Surgical Conference.
Dairy, red meat, and carbohydrates can break down into leucine, an essential amino acid found in protein. Leucine and sugar together, in turn, can produce insulin and insulin-like growth factor 1 (IGF-1), which, through different pathways, can reach the androgen receptors throughout the body, including the skin. This results in sebogenesis, lipogenesis, and keratinization, which triggers follicular inflammation and results in more of the acne-causing bacteria Cutibacterium acnes. 
Milk and other dairy products also can increase IGF-1 levels, which can alter hormonal mediators and increase acne.
Not all types of dairy milk are created equal, however, when it comes to acne. Dr. Shi wondered why 2% milk has overall color and nutritional content very similar to that of whole milk. “I looked into this.” She discovered that when milk manufacturers remove the fat, they often add whey proteins to restore some nutrients. Whey protein can increase acne, Dr. Shi added. 
“So, if you’re going to choose any milk to drink, I think from an acne perspective, it’s better to use whole milk. If you can get it organic, even better.” Skim milk is the most acnegenic, she said.

Psoriasis

A systematic review of 55 studies evaluating diet and psoriasis found obesity can be an exacerbating factor. The strongest evidence for dietary weight reduction points to a hypocaloric diet in people with overweight or obesity, according to the review. Other evidence suggests alcohol can lower response to treatment and is linked with more severe psoriasis. Furthermore, a gluten-free diet or vitamin D supplements can help some subpopulations of people with psoriasis. 
“An overwhelming majority of our psoriasis patients are vitamin D deficient,” Dr. Shi said. 
The National Psoriasis Foundation (NPF) publishes dietary modification guidelines, updated as recently as November 2023. The NPF states that “there is no diet that will cure psoriatic disease, but there are many ways in which eating healthful food may lessen the severity of symptoms and play a role in lowering the likelihood of developing comorbidities.”
Healthier choices include fruits, vegetables, whole grains, and fat-free or low-fat dairy products. Include lean meats, poultry, fish, beans, eggs, and nuts. Adherence to a Mediterranean diet has been linked to a lower severity of psoriasis.

Atopic Dermatitis

Atopic dermatitis (AD) is “one of the prototypical diseases related to diet,” Dr. Shi said. A different meta-analysis looked at randomized controlled trials of synbiotics (a combination of prebiotics and probiotics) for treatment of AD.
These researchers found that synbiotics do not prevent AD, but they can help treat it in adults and children older than 1 year. In addition, synbiotics are more beneficial than probiotics in treating the condition, although there are no head-to-head comparison studies. In addition, the meta-analysis found that prebiotics alone can lower AD severity.
However, Dr. Shi said, there are no recommendations from the American Academy of Dermatology (AAD) on prebiotics or probiotics for AD, and the AAD does not recommend any supplement or essential oil for AD.
In a 2022 review, investigators ranked the efficacy of different supplements for AD based on available evidence. They found the greatest benefit associated with vitamin D supplementation, followed by vitamin E, probiotics, hemp seed oil, histidine, and oolong tea. They also noted the ‘Six Food Elimination Diet and Autoimmune Protocol’ featured the least amount of evidence to back it up. 

Rosacea

Rosacea appears to be caused by “all the fun things in life” like sunlight, alcohol, chocolate, spicy foods, and caffeine, Dr. Shi said. In people with rosacea, they can cause facial flushing, edema, burning, and an inflammatory response.
Certain foods can activate skin receptors and sensory neurons, which can release neuropeptides that act on mast cells in blood that lead to flushing. The skin-gut axis may also be involved, evidence suggests. “And that is why food has a pretty profound impact on rosacea,” Dr. Shi said. 
Dr. Shi reported no relevant financial relationships.

A version of this article appeared on Medscape.com.

“You have psoriasis,” I say all the time. I mean it when I say it, of course. But I don’t always to the same degree. Sometimes I’m trying to say, “You probably have psoriasis.” Other times I mean, “You most definitely have psoriasis.” I rarely use those terms though.

One 36-year-old man with a flaky scalp and scaly elbows wasn’t satisfied with my assessment. His dad has psoriasis. So does his older brother. He was in to see me to find out if he had psoriasis too. “Probably” was what I gave him. He pushed back, “What percent chance?” That’s a good question — must be an engineer. I’m unsure.

Kaiser Permanente

With the exception of the poker players, our species is notoriously bad at probabilities. We’re wired to notice the significance of events, but terrible at understanding their likelihood. This is salient in lottery ticket holders and some NFL offensive coordinators who persist despite very long odds of things working out. It’s also reflected in the language we use. Rarely do we say, there’s a sixty percent chance something will happen. Rather, we say, “it’s likely.” There are two problems here. One, we often misjudge the actual probability of something occurring and two, the terms we use are subjective and differences in interpretation can lead to misunderstandings.

Let’s take a look. A 55-year-old man with a chronic eczematous rash on his trunk and extremities is getting worse despite dupilumab. He recently had night sweats. Do you think he has atopic dermatitis or cutaneous T-cell lymphoma? If you had to place a $100 bet, would you change your answer? Immanuel Kant thinks you would. In his “Critique of Pure Reason,” the German philosopher proposes that betting helps clarify the mind, an antidote to brashness. The example Kant uses is of a physician who observes a patient and concludes he has phthisis (tuberculosis), but we really don’t know if the physician is confident. Kant proposes that if he had to bet on his conclusion, then we’d have insight into just how convinced he is of phthisis. So, what’s your bet?

If you’re a bad poker player, then you might bet he has cutaneous T-cell lymphoma. However, not having any additional information, the smart call is atopic dermatitis, which has a base rate 1000-fold higher than CTCL. It is therefore more probable to be eczema even in a case that worsens despite dupilumab or with recent night sweats, both of which could be a result of common variables such as weather and COVID. Failure to account for the base rate is a mistake we physicians sometimes make. Economists rarely do. Try to think like one before answering a likelihood question.

For my scaly patient, we know psoriasis is common and so it’s likely he has it. The trouble is what “probably” means to me might mean something different to him. If you think about it, “probably” means something different even to me, depending on the situation. I might say I’ll probably go to Montana this summer and I’ll probably retire at 65. The actual likelihoods might be 95% and 70%. That’s a big difference. What about between probably and likely? Or possibly and maybe? Do they mean the same to you as to the person you’re speaking with? For much of the work we do, precise likelihoods aren’t critical. Yet, it can be important in decision making and in discussing probabilities, such as the risk of hepatitis on terbinafine or of melanoma recurrence after Mohs.

I told my patient “I say about a 70% chance you have psoriasis. I could do a biopsy today to confirm.” He thought for a second and asked, “What is the chance it’s psoriasis if the biopsy shows it?” “Eighty six percent,” I replied.

Seemed like a good bet to me.

Dr. Benabio is director of Healthcare Transformation and chief of dermatology at Kaiser Permanente San Diego. The opinions expressed in this column are his own and do not represent those of Kaiser Permanente. Dr. Benabio is @Dermdoc on X. Write to him at dermnews@mdedge.com.

“You have psoriasis,” I say all the time. I mean it when I say it, of course. But I don’t always to the same degree. Sometimes I’m trying to say, “You probably have psoriasis.” Other times I mean, “You most definitely have psoriasis.” I rarely use those terms though.

One 36-year-old man with a flaky scalp and scaly elbows wasn’t satisfied with my assessment. His dad has psoriasis. So does his older brother. He was in to see me to find out if he had psoriasis too. “Probably” was what I gave him. He pushed back, “What percent chance?” That’s a good question — must be an engineer. I’m unsure.

Kaiser Permanente

With the exception of the poker players, our species is notoriously bad at probabilities. We’re wired to notice the significance of events, but terrible at understanding their likelihood. This is salient in lottery ticket holders and some NFL offensive coordinators who persist despite very long odds of things working out. It’s also reflected in the language we use. Rarely do we say, there’s a sixty percent chance something will happen. Rather, we say, “it’s likely.” There are two problems here. One, we often misjudge the actual probability of something occurring and two, the terms we use are subjective and differences in interpretation can lead to misunderstandings.

Let’s take a look. A 55-year-old man with a chronic eczematous rash on his trunk and extremities is getting worse despite dupilumab. He recently had night sweats. Do you think he has atopic dermatitis or cutaneous T-cell lymphoma? If you had to place a $100 bet, would you change your answer? Immanuel Kant thinks you would. In his “Critique of Pure Reason,” the German philosopher proposes that betting helps clarify the mind, an antidote to brashness. The example Kant uses is of a physician who observes a patient and concludes he has phthisis (tuberculosis), but we really don’t know if the physician is confident. Kant proposes that if he had to bet on his conclusion, then we’d have insight into just how convinced he is of phthisis. So, what’s your bet?

If you’re a bad poker player, then you might bet he has cutaneous T-cell lymphoma. However, not having any additional information, the smart call is atopic dermatitis, which has a base rate 1000-fold higher than CTCL. It is therefore more probable to be eczema even in a case that worsens despite dupilumab or with recent night sweats, both of which could be a result of common variables such as weather and COVID. Failure to account for the base rate is a mistake we physicians sometimes make. Economists rarely do. Try to think like one before answering a likelihood question.

For my scaly patient, we know psoriasis is common and so it’s likely he has it. The trouble is what “probably” means to me might mean something different to him. If you think about it, “probably” means something different even to me, depending on the situation. I might say I’ll probably go to Montana this summer and I’ll probably retire at 65. The actual likelihoods might be 95% and 70%. That’s a big difference. What about between probably and likely? Or possibly and maybe? Do they mean the same to you as to the person you’re speaking with? For much of the work we do, precise likelihoods aren’t critical. Yet, it can be important in decision making and in discussing probabilities, such as the risk of hepatitis on terbinafine or of melanoma recurrence after Mohs.

I told my patient “I say about a 70% chance you have psoriasis. I could do a biopsy today to confirm.” He thought for a second and asked, “What is the chance it’s psoriasis if the biopsy shows it?” “Eighty six percent,” I replied.

Seemed like a good bet to me.

Dr. Benabio is director of Healthcare Transformation and chief of dermatology at Kaiser Permanente San Diego. The opinions expressed in this column are his own and do not represent those of Kaiser Permanente. Dr. Benabio is @Dermdoc on X. Write to him at dermnews@mdedge.com.

“You have psoriasis,” I say all the time. I mean it when I say it, of course. But I don’t always to the same degree. Sometimes I’m trying to say, “You probably have psoriasis.” Other times I mean, “You most definitely have psoriasis.” I rarely use those terms though.

One 36-year-old man with a flaky scalp and scaly elbows wasn’t satisfied with my assessment. His dad has psoriasis. So does his older brother. He was in to see me to find out if he had psoriasis too. “Probably” was what I gave him. He pushed back, “What percent chance?” That’s a good question — must be an engineer. I’m unsure.

Kaiser Permanente

With the exception of the poker players, our species is notoriously bad at probabilities. We’re wired to notice the significance of events, but terrible at understanding their likelihood. This is salient in lottery ticket holders and some NFL offensive coordinators who persist despite very long odds of things working out. It’s also reflected in the language we use. Rarely do we say, there’s a sixty percent chance something will happen. Rather, we say, “it’s likely.” There are two problems here. One, we often misjudge the actual probability of something occurring and two, the terms we use are subjective and differences in interpretation can lead to misunderstandings.

Let’s take a look. A 55-year-old man with a chronic eczematous rash on his trunk and extremities is getting worse despite dupilumab. He recently had night sweats. Do you think he has atopic dermatitis or cutaneous T-cell lymphoma? If you had to place a $100 bet, would you change your answer? Immanuel Kant thinks you would. In his “Critique of Pure Reason,” the German philosopher proposes that betting helps clarify the mind, an antidote to brashness. The example Kant uses is of a physician who observes a patient and concludes he has phthisis (tuberculosis), but we really don’t know if the physician is confident. Kant proposes that if he had to bet on his conclusion, then we’d have insight into just how convinced he is of phthisis. So, what’s your bet?

If you’re a bad poker player, then you might bet he has cutaneous T-cell lymphoma. However, not having any additional information, the smart call is atopic dermatitis, which has a base rate 1000-fold higher than CTCL. It is therefore more probable to be eczema even in a case that worsens despite dupilumab or with recent night sweats, both of which could be a result of common variables such as weather and COVID. Failure to account for the base rate is a mistake we physicians sometimes make. Economists rarely do. Try to think like one before answering a likelihood question.

For my scaly patient, we know psoriasis is common and so it’s likely he has it. The trouble is what “probably” means to me might mean something different to him. If you think about it, “probably” means something different even to me, depending on the situation. I might say I’ll probably go to Montana this summer and I’ll probably retire at 65. The actual likelihoods might be 95% and 70%. That’s a big difference. What about between probably and likely? Or possibly and maybe? Do they mean the same to you as to the person you’re speaking with? For much of the work we do, precise likelihoods aren’t critical. Yet, it can be important in decision making and in discussing probabilities, such as the risk of hepatitis on terbinafine or of melanoma recurrence after Mohs.

I told my patient “I say about a 70% chance you have psoriasis. I could do a biopsy today to confirm.” He thought for a second and asked, “What is the chance it’s psoriasis if the biopsy shows it?” “Eighty six percent,” I replied.

Seemed like a good bet to me.

Dr. Benabio is director of Healthcare Transformation and chief of dermatology at Kaiser Permanente San Diego. The opinions expressed in this column are his own and do not represent those of Kaiser Permanente. Dr. Benabio is @Dermdoc on X. Write to him at dermnews@mdedge.com.

Women with autoimmune disease are more likely to have perinatal depression (PND), according to findings from a new study that also suggested the reverse relationship is true: Women with a history of PND have a higher risk of developing autoimmune disease.

The research, published online on January 9, 2024, in Molecular Psychiatry, was led by Emma Bränn, PhD, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.

The researchers used data from the Swedish Medical Birth Register and identified all women who had given birth in Sweden between 2001 and 2013. Out of the group of approximately 815,000 women and 1.3 million pregnancies, just more than 55,000 women had been diagnosed with depression during their pregnancy or within a year after delivery.

The researchers then compared the incidence of 41 autoimmune diseases in women who had and did not have PND. They controlled for factors including genetic makeup and childhood environment.

Results indicated that women with autoimmune disease were 30% more likely to have PND (odds ratio, 1.30; 95% CI, 1.25-1.35). Conversely, women with PND were 30% more likely than women with no PND to develop an autoimmune disease (hazard ratio, 1.30; 95% CI, 1.25-1.36).

A sibling comparison helped confirm the results by controlling for some shared genetic and early life environmental factors related to the household in which sisters grew up.
 

Potential Shared Biological Mechanisms

The association was independent of psychiatric comorbidities, suggesting there may be shared biological mechanisms.

Dr. Bränn told this news organization that the research team wanted to do the study because previous research has shown involvement of the immune system in depression, with similarities in both the symptoms of immune system–activated diseases and depression and the molecular pathways activated by the immune system.

“Adding on top of the tremendous changes in the immune system that we see in the body of the woman during the perinatal period, we hypothesized that autoimmune diseases could be associated to perinatal depression,” she said. “This had also been shown in some previous literature but not to the extent as what we have investigated in this paper.”

She said their results help make a case for counseling women at several points in healthcare interactions — before and after conception and childbirth — and in rheumatology visits to inform women with autoimmune diseases who are contemplating motherhood of the association with developing PND. The results may also demonstrate a need for monitoring women in these groups for depression or autoimmune disease.

Fred Miller, MD, PhD, retired Scientist Emeritus of the Environmental Autoimmunity Group at the National Institute of Environmental Health Sciences, who was not part of the study, said the results seem plausible as they build on early work that demonstrated selected associations between autoimmune conditions and mental illness.

“These associations may be the result of shared genetic and environmental risk factors, including stress, hormonal changes, medications, and the proinflammatory states that can lead to both,” he said.

The novelty, he said, is in the relatively strong associations of PND with autoimmune disease overall and with specific autoimmune diseases.
 

Strong Link Found With Multiple Sclerosis (MS)

According to the paper, a significant positive bidirectional link was found for autoimmune thyroid disease, psoriasis, MS, ulcerative colitis, and celiac disease.

Researchers found a particularly strong association — double the risk in both directions — between PND and MS.

Dr. Miller said though it is unclear from this study why the association of PND with MS was stronger than with other autoimmune diseases, people with MS are known to be at a high risk for depression in general. That may come from greater shared genetic and environmental risk factors, he added.

Additionally, MS is one of the more common autoimmune diseases, he noted, so the population is larger for study.

He said he was surprised the researchers didn’t investigate medication use because medications used in depression have immunologic effects and medications used in autoimmune diseases could have effects on mental conditions.

The study has implications for clinicians in a wide variety of specialties, Dr. Miller noted.

“It suggests that caregivers be more alert to the signs of developing autoimmune disease in women with perinatal depression and to the signs of developing perinatal depression in those with autoimmune disease,” Dr. Miller said, “so that appropriate screening, diagnostics, and interventions may be undertaken.”

The researchers say they will continue to examine the long-term effects of depression during pregnancy and in the year after childbirth.

“Depression during this sensitive period can have serious consequences for both the mother and the baby,” Dr. Bränn said. “We hope that our results will help decision-makers to steer funding toward maternal healthcare so that more women can get help and support in time.”

The study was financed by Karolinska Institute, Forte (the Swedish Research Council for Health, Working Life and Welfare), the Swedish Research Council, and the Icelandic Research Fund.

The researchers and Dr. Miller reported no relevant financial relationships.

A version of this article appeared on Medscape.com.

Women with autoimmune disease are more likely to have perinatal depression (PND), according to findings from a new study that also suggested the reverse relationship is true: Women with a history of PND have a higher risk of developing autoimmune disease.

The research, published online on January 9, 2024, in Molecular Psychiatry, was led by Emma Bränn, PhD, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.

The researchers used data from the Swedish Medical Birth Register and identified all women who had given birth in Sweden between 2001 and 2013. Out of the group of approximately 815,000 women and 1.3 million pregnancies, just more than 55,000 women had been diagnosed with depression during their pregnancy or within a year after delivery.

The researchers then compared the incidence of 41 autoimmune diseases in women who had and did not have PND. They controlled for factors including genetic makeup and childhood environment.

Results indicated that women with autoimmune disease were 30% more likely to have PND (odds ratio, 1.30; 95% CI, 1.25-1.35). Conversely, women with PND were 30% more likely than women with no PND to develop an autoimmune disease (hazard ratio, 1.30; 95% CI, 1.25-1.36).

A sibling comparison helped confirm the results by controlling for some shared genetic and early life environmental factors related to the household in which sisters grew up.
 

Potential Shared Biological Mechanisms

The association was independent of psychiatric comorbidities, suggesting there may be shared biological mechanisms.

Dr. Bränn told this news organization that the research team wanted to do the study because previous research has shown involvement of the immune system in depression, with similarities in both the symptoms of immune system–activated diseases and depression and the molecular pathways activated by the immune system.

“Adding on top of the tremendous changes in the immune system that we see in the body of the woman during the perinatal period, we hypothesized that autoimmune diseases could be associated to perinatal depression,” she said. “This had also been shown in some previous literature but not to the extent as what we have investigated in this paper.”

She said their results help make a case for counseling women at several points in healthcare interactions — before and after conception and childbirth — and in rheumatology visits to inform women with autoimmune diseases who are contemplating motherhood of the association with developing PND. The results may also demonstrate a need for monitoring women in these groups for depression or autoimmune disease.

Fred Miller, MD, PhD, retired Scientist Emeritus of the Environmental Autoimmunity Group at the National Institute of Environmental Health Sciences, who was not part of the study, said the results seem plausible as they build on early work that demonstrated selected associations between autoimmune conditions and mental illness.

“These associations may be the result of shared genetic and environmental risk factors, including stress, hormonal changes, medications, and the proinflammatory states that can lead to both,” he said.

The novelty, he said, is in the relatively strong associations of PND with autoimmune disease overall and with specific autoimmune diseases.
 

Strong Link Found With Multiple Sclerosis (MS)

According to the paper, a significant positive bidirectional link was found for autoimmune thyroid disease, psoriasis, MS, ulcerative colitis, and celiac disease.

Researchers found a particularly strong association — double the risk in both directions — between PND and MS.

Dr. Miller said though it is unclear from this study why the association of PND with MS was stronger than with other autoimmune diseases, people with MS are known to be at a high risk for depression in general. That may come from greater shared genetic and environmental risk factors, he added.

Additionally, MS is one of the more common autoimmune diseases, he noted, so the population is larger for study.

He said he was surprised the researchers didn’t investigate medication use because medications used in depression have immunologic effects and medications used in autoimmune diseases could have effects on mental conditions.

The study has implications for clinicians in a wide variety of specialties, Dr. Miller noted.

“It suggests that caregivers be more alert to the signs of developing autoimmune disease in women with perinatal depression and to the signs of developing perinatal depression in those with autoimmune disease,” Dr. Miller said, “so that appropriate screening, diagnostics, and interventions may be undertaken.”

The researchers say they will continue to examine the long-term effects of depression during pregnancy and in the year after childbirth.

“Depression during this sensitive period can have serious consequences for both the mother and the baby,” Dr. Bränn said. “We hope that our results will help decision-makers to steer funding toward maternal healthcare so that more women can get help and support in time.”

The study was financed by Karolinska Institute, Forte (the Swedish Research Council for Health, Working Life and Welfare), the Swedish Research Council, and the Icelandic Research Fund.

The researchers and Dr. Miller reported no relevant financial relationships.

A version of this article appeared on Medscape.com.

Women with autoimmune disease are more likely to have perinatal depression (PND), according to findings from a new study that also suggested the reverse relationship is true: Women with a history of PND have a higher risk of developing autoimmune disease.

The research, published online on January 9, 2024, in Molecular Psychiatry, was led by Emma Bränn, PhD, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.

The researchers used data from the Swedish Medical Birth Register and identified all women who had given birth in Sweden between 2001 and 2013. Out of the group of approximately 815,000 women and 1.3 million pregnancies, just more than 55,000 women had been diagnosed with depression during their pregnancy or within a year after delivery.

The researchers then compared the incidence of 41 autoimmune diseases in women who had and did not have PND. They controlled for factors including genetic makeup and childhood environment.

Results indicated that women with autoimmune disease were 30% more likely to have PND (odds ratio, 1.30; 95% CI, 1.25-1.35). Conversely, women with PND were 30% more likely than women with no PND to develop an autoimmune disease (hazard ratio, 1.30; 95% CI, 1.25-1.36).

A sibling comparison helped confirm the results by controlling for some shared genetic and early life environmental factors related to the household in which sisters grew up.
 

Potential Shared Biological Mechanisms

The association was independent of psychiatric comorbidities, suggesting there may be shared biological mechanisms.

Dr. Bränn told this news organization that the research team wanted to do the study because previous research has shown involvement of the immune system in depression, with similarities in both the symptoms of immune system–activated diseases and depression and the molecular pathways activated by the immune system.

“Adding on top of the tremendous changes in the immune system that we see in the body of the woman during the perinatal period, we hypothesized that autoimmune diseases could be associated to perinatal depression,” she said. “This had also been shown in some previous literature but not to the extent as what we have investigated in this paper.”

She said their results help make a case for counseling women at several points in healthcare interactions — before and after conception and childbirth — and in rheumatology visits to inform women with autoimmune diseases who are contemplating motherhood of the association with developing PND. The results may also demonstrate a need for monitoring women in these groups for depression or autoimmune disease.

Fred Miller, MD, PhD, retired Scientist Emeritus of the Environmental Autoimmunity Group at the National Institute of Environmental Health Sciences, who was not part of the study, said the results seem plausible as they build on early work that demonstrated selected associations between autoimmune conditions and mental illness.

“These associations may be the result of shared genetic and environmental risk factors, including stress, hormonal changes, medications, and the proinflammatory states that can lead to both,” he said.

The novelty, he said, is in the relatively strong associations of PND with autoimmune disease overall and with specific autoimmune diseases.
 

Strong Link Found With Multiple Sclerosis (MS)

According to the paper, a significant positive bidirectional link was found for autoimmune thyroid disease, psoriasis, MS, ulcerative colitis, and celiac disease.

Researchers found a particularly strong association — double the risk in both directions — between PND and MS.

Dr. Miller said though it is unclear from this study why the association of PND with MS was stronger than with other autoimmune diseases, people with MS are known to be at a high risk for depression in general. That may come from greater shared genetic and environmental risk factors, he added.

Additionally, MS is one of the more common autoimmune diseases, he noted, so the population is larger for study.

He said he was surprised the researchers didn’t investigate medication use because medications used in depression have immunologic effects and medications used in autoimmune diseases could have effects on mental conditions.

The study has implications for clinicians in a wide variety of specialties, Dr. Miller noted.

“It suggests that caregivers be more alert to the signs of developing autoimmune disease in women with perinatal depression and to the signs of developing perinatal depression in those with autoimmune disease,” Dr. Miller said, “so that appropriate screening, diagnostics, and interventions may be undertaken.”

The researchers say they will continue to examine the long-term effects of depression during pregnancy and in the year after childbirth.

“Depression during this sensitive period can have serious consequences for both the mother and the baby,” Dr. Bränn said. “We hope that our results will help decision-makers to steer funding toward maternal healthcare so that more women can get help and support in time.”

The study was financed by Karolinska Institute, Forte (the Swedish Research Council for Health, Working Life and Welfare), the Swedish Research Council, and the Icelandic Research Fund.

The researchers and Dr. Miller reported no relevant financial relationships.

A version of this article appeared on Medscape.com.

Diagnosis: Infection-induced psoriasis (guttate-type, induced by streptococcal intertrigo)

Psoriasis is a chronic inflammatory disorder characterized by well-defined, scaly, erythematous plaques. Guttate psoriasis is a distinct variant of psoriasis that is more common in children and adolescents. Guttate psoriasis usually presents with multiple, scattered, small, drop-like (“guttate”), scaly, erythematous papules and plaques. Guttate psoriasis may be triggered by infections, most commonly recent streptococcal infections.

The pathophysiology of psoriasis involves an interplay between genetic and environmental factors. Guttate psoriasis is a chronic T-cell–mediated inflammatory disease in which there is an altered balance between T-helper-1 (TH1) and TH2 cells, transcription factor genes, and their products. HLA B-13, B-17, and Cw6 are human leukocyte antigen alleles implicated in genetic susceptibility. It is hypothesized that streptococcal infection precipitates guttate psoriasis by streptococcal superantigen–driven activation of cutaneous lymphocyte-associated antigen (CLA)–positive lymphocytes. It has been shown that streptococcal exotoxins and streptococcal M proteins act as superantigens.

Diagnosis is often made clinically based on characteristic physical findings and a possible preceding history of streptococcal infection. In patients with streptococcal infection, culture from an appropriate site and measurement of serum antistreptococcal antibody titers (for example, anti-DNase, antihyaluronidase and antistreptolysin-O) can help. A skin biopsy is usually not necessary but may be considered.

This patient presented with intertrigo of the neck and axillae at the time of presentation with the papulosquamous rash. Culture of the intertrigo yielded 4+ Group A beta streptococcus.
 

Treatment

Although there is currently no cure for guttate psoriasis, various treatment options can relieve symptoms and clear skin lesions, and infection-triggered lesions may remit, usually within several months. However, guttate psoriasis may persist and progress to chronic plaque psoriasis. Many treatment options are based mainly on clinical trials targeted for plaque psoriasis treatment.

For mild psoriasis, topical corticosteroids are first-line treatment. Other topical steroids include vitamin D analogs (calcipotriene), topical retinoids (tazarotene), topical calcineurin inhibitors (tacrolimus and pimecrolimus), and newer non-steroidal anti-inflammatory agents (roflumilast or tapinarof), neither approved yet in this young age group. In more severe cases, phototherapy with UVB light, traditional systemic immunosuppressive agents (methotrexate, cyclosporine) or targeted biologic therapies may be considered.
 

Differential Diagnosis

The differential diagnosis may include generalized intertrigo, pityriasis rubra pilaris, tinea corporis, atopic dermatitis, and staphylococcal scalded skin syndrome. Guttate psoriasis can be distinguished by history and physical exam. Further studies such as potassium hydroxide (KOH) scrapings may be helpful in ruling out the other disorders.

Intertrigo is an inflammatory condition of the flexural surfaces irritated by warm temperatures, friction, moisture, and poor ventilation that is commonly associated with Candida infection and/or streptococcal infection. Candidal intertrigo can present with erythematous patches or plaques in an intertriginous area that may develop erosions, macerations, fissures, crust, and weeping. Satellite papules and pustules are pathognomonic for Candida species. Streptococcal intertrigo usually presents with bright red color and may be painful or pruritic. Perianal streptococcal infection is reported as a trigger of guttate psoriasis in pediatric patients.

Pityriasis rubra pilaris is a rare inflammatory papulosquamous disorder with an unknown etiology. Red-orange papules and plaques, hyperkeratotic follicular papules, and palmoplantar hyperkeratosis are primary features. Diagnosis is based on clinical and histopathology. Pityriasis rubra pilaris is self-limited and asymptomatic in many cases. Treatment may not be required, but combination therapy with topical agents includes emollients, keratolytic agents (for example, urea, salicylic acid, alpha-hydroxy acids), topical corticosteroids, tazarotene, and topical calcineurin inhibitors. Systemic agents include oral retinoids and methotrexate.

Atopic dermatitis is a chronic inflammatory skin disease that involves genetic and environmental factors, leading to abnormalities in the epidermis and the immune system presenting with its typical morphology and distribution. The morphology of eczematous lesions is distinct from papulosquamous lesions of psoriasis.

Staphylococcal scalded skin syndrome is a toxin-mediated skin disorder which presents with denuded, peeling skin due to epidermolytic exotoxin producing Staphylococcus species. Fever, erythematous rash, malaise, skin pain, and irritability presents initially. Progressive desquamation with accentuation in folds is typical, with progression usually within 1-2 days. Systemic antibiotics covering Staphylococcus should be administered early. Emollients and nonadherent dressings should be applied to affected areas to promote healing. Supportive care includes dehydration management, temperature regulation, and nutrition. Skin desquamation usually occurs within 5 days with resolution within 2 weeks.

This infant displayed streptococcal intertrigo which triggered an early presentation of guttate psoriasis. The patient was managed with completion of a course of oral cephalexin, midstrength topical corticosteroids to the truncal lesions, and mild topical corticosteroids to the face and diaper area with good clinical response.
 

Danny Lee and Samuel Le serve as research fellows in the Pediatric Dermatology Division of the Department of Dermatology at the University of California San Diego and Rady Children’s Hospital, San Diego. Dr. Eichenfield is Distinguished Professor of Dermatology and Pediatrics and Vice-Chair of the Department of Dermatology at the University of California San Diego and Rady Children’s Hospital, San Diego. The authors have no relevant financial disclosures.

Suggested Reading

Leung AK et al. Childhood guttate psoriasis: An updated review. Drugs Context. 2023 Oct 23:12:2023-8-2. doi: 10.7573/dic.2023-8-2.

Galili E et al. New-onset guttate psoriasis: A long-term follow-up study. Dermatology. 2023;239(2):188-194. doi: 10.1159/000527737.

Duffin KC et al. Advances and controversies in our understanding of guttate and plaque psoriasis. J Rheumatol. 2023 Nov;50(Suppl 2):4-7. doi: 10.3899/jrheum.2023-0500.

Saleh D, Tanner LS. Guttate Psoriasis. [Updated 2023 Jul 31]. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2023 Jan-. Available from: www.ncbi.nlm.nih.gov/books/NBK482498/

Dupire G et al. Antistreptococcal interventions for guttate and chronic plaque psoriasis. Cochrane Database Syst Rev. 2019 Mar 5;3(3):CD011571. doi: 10.1002/14651858.CD011571.pub2.

Diagnosis: Infection-induced psoriasis (guttate-type, induced by streptococcal intertrigo)

Psoriasis is a chronic inflammatory disorder characterized by well-defined, scaly, erythematous plaques. Guttate psoriasis is a distinct variant of psoriasis that is more common in children and adolescents. Guttate psoriasis usually presents with multiple, scattered, small, drop-like (“guttate”), scaly, erythematous papules and plaques. Guttate psoriasis may be triggered by infections, most commonly recent streptococcal infections.

The pathophysiology of psoriasis involves an interplay between genetic and environmental factors. Guttate psoriasis is a chronic T-cell–mediated inflammatory disease in which there is an altered balance between T-helper-1 (TH1) and TH2 cells, transcription factor genes, and their products. HLA B-13, B-17, and Cw6 are human leukocyte antigen alleles implicated in genetic susceptibility. It is hypothesized that streptococcal infection precipitates guttate psoriasis by streptococcal superantigen–driven activation of cutaneous lymphocyte-associated antigen (CLA)–positive lymphocytes. It has been shown that streptococcal exotoxins and streptococcal M proteins act as superantigens.

Diagnosis is often made clinically based on characteristic physical findings and a possible preceding history of streptococcal infection. In patients with streptococcal infection, culture from an appropriate site and measurement of serum antistreptococcal antibody titers (for example, anti-DNase, antihyaluronidase and antistreptolysin-O) can help. A skin biopsy is usually not necessary but may be considered.

This patient presented with intertrigo of the neck and axillae at the time of presentation with the papulosquamous rash. Culture of the intertrigo yielded 4+ Group A beta streptococcus.
 

Treatment

Although there is currently no cure for guttate psoriasis, various treatment options can relieve symptoms and clear skin lesions, and infection-triggered lesions may remit, usually within several months. However, guttate psoriasis may persist and progress to chronic plaque psoriasis. Many treatment options are based mainly on clinical trials targeted for plaque psoriasis treatment.

For mild psoriasis, topical corticosteroids are first-line treatment. Other topical steroids include vitamin D analogs (calcipotriene), topical retinoids (tazarotene), topical calcineurin inhibitors (tacrolimus and pimecrolimus), and newer non-steroidal anti-inflammatory agents (roflumilast or tapinarof), neither approved yet in this young age group. In more severe cases, phototherapy with UVB light, traditional systemic immunosuppressive agents (methotrexate, cyclosporine) or targeted biologic therapies may be considered.
 

Differential Diagnosis

The differential diagnosis may include generalized intertrigo, pityriasis rubra pilaris, tinea corporis, atopic dermatitis, and staphylococcal scalded skin syndrome. Guttate psoriasis can be distinguished by history and physical exam. Further studies such as potassium hydroxide (KOH) scrapings may be helpful in ruling out the other disorders.

Intertrigo is an inflammatory condition of the flexural surfaces irritated by warm temperatures, friction, moisture, and poor ventilation that is commonly associated with Candida infection and/or streptococcal infection. Candidal intertrigo can present with erythematous patches or plaques in an intertriginous area that may develop erosions, macerations, fissures, crust, and weeping. Satellite papules and pustules are pathognomonic for Candida species. Streptococcal intertrigo usually presents with bright red color and may be painful or pruritic. Perianal streptococcal infection is reported as a trigger of guttate psoriasis in pediatric patients.

Pityriasis rubra pilaris is a rare inflammatory papulosquamous disorder with an unknown etiology. Red-orange papules and plaques, hyperkeratotic follicular papules, and palmoplantar hyperkeratosis are primary features. Diagnosis is based on clinical and histopathology. Pityriasis rubra pilaris is self-limited and asymptomatic in many cases. Treatment may not be required, but combination therapy with topical agents includes emollients, keratolytic agents (for example, urea, salicylic acid, alpha-hydroxy acids), topical corticosteroids, tazarotene, and topical calcineurin inhibitors. Systemic agents include oral retinoids and methotrexate.

Atopic dermatitis is a chronic inflammatory skin disease that involves genetic and environmental factors, leading to abnormalities in the epidermis and the immune system presenting with its typical morphology and distribution. The morphology of eczematous lesions is distinct from papulosquamous lesions of psoriasis.

Staphylococcal scalded skin syndrome is a toxin-mediated skin disorder which presents with denuded, peeling skin due to epidermolytic exotoxin producing Staphylococcus species. Fever, erythematous rash, malaise, skin pain, and irritability presents initially. Progressive desquamation with accentuation in folds is typical, with progression usually within 1-2 days. Systemic antibiotics covering Staphylococcus should be administered early. Emollients and nonadherent dressings should be applied to affected areas to promote healing. Supportive care includes dehydration management, temperature regulation, and nutrition. Skin desquamation usually occurs within 5 days with resolution within 2 weeks.

This infant displayed streptococcal intertrigo which triggered an early presentation of guttate psoriasis. The patient was managed with completion of a course of oral cephalexin, midstrength topical corticosteroids to the truncal lesions, and mild topical corticosteroids to the face and diaper area with good clinical response.
 

Danny Lee and Samuel Le serve as research fellows in the Pediatric Dermatology Division of the Department of Dermatology at the University of California San Diego and Rady Children’s Hospital, San Diego. Dr. Eichenfield is Distinguished Professor of Dermatology and Pediatrics and Vice-Chair of the Department of Dermatology at the University of California San Diego and Rady Children’s Hospital, San Diego. The authors have no relevant financial disclosures.

Suggested Reading

Leung AK et al. Childhood guttate psoriasis: An updated review. Drugs Context. 2023 Oct 23:12:2023-8-2. doi: 10.7573/dic.2023-8-2.

Galili E et al. New-onset guttate psoriasis: A long-term follow-up study. Dermatology. 2023;239(2):188-194. doi: 10.1159/000527737.

Duffin KC et al. Advances and controversies in our understanding of guttate and plaque psoriasis. J Rheumatol. 2023 Nov;50(Suppl 2):4-7. doi: 10.3899/jrheum.2023-0500.

Saleh D, Tanner LS. Guttate Psoriasis. [Updated 2023 Jul 31]. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2023 Jan-. Available from: www.ncbi.nlm.nih.gov/books/NBK482498/

Dupire G et al. Antistreptococcal interventions for guttate and chronic plaque psoriasis. Cochrane Database Syst Rev. 2019 Mar 5;3(3):CD011571. doi: 10.1002/14651858.CD011571.pub2.

Diagnosis: Infection-induced psoriasis (guttate-type, induced by streptococcal intertrigo)

Psoriasis is a chronic inflammatory disorder characterized by well-defined, scaly, erythematous plaques. Guttate psoriasis is a distinct variant of psoriasis that is more common in children and adolescents. Guttate psoriasis usually presents with multiple, scattered, small, drop-like (“guttate”), scaly, erythematous papules and plaques. Guttate psoriasis may be triggered by infections, most commonly recent streptococcal infections.

The pathophysiology of psoriasis involves an interplay between genetic and environmental factors. Guttate psoriasis is a chronic T-cell–mediated inflammatory disease in which there is an altered balance between T-helper-1 (TH1) and TH2 cells, transcription factor genes, and their products. HLA B-13, B-17, and Cw6 are human leukocyte antigen alleles implicated in genetic susceptibility. It is hypothesized that streptococcal infection precipitates guttate psoriasis by streptococcal superantigen–driven activation of cutaneous lymphocyte-associated antigen (CLA)–positive lymphocytes. It has been shown that streptococcal exotoxins and streptococcal M proteins act as superantigens.

Diagnosis is often made clinically based on characteristic physical findings and a possible preceding history of streptococcal infection. In patients with streptococcal infection, culture from an appropriate site and measurement of serum antistreptococcal antibody titers (for example, anti-DNase, antihyaluronidase and antistreptolysin-O) can help. A skin biopsy is usually not necessary but may be considered.

This patient presented with intertrigo of the neck and axillae at the time of presentation with the papulosquamous rash. Culture of the intertrigo yielded 4+ Group A beta streptococcus.
 

Treatment

Although there is currently no cure for guttate psoriasis, various treatment options can relieve symptoms and clear skin lesions, and infection-triggered lesions may remit, usually within several months. However, guttate psoriasis may persist and progress to chronic plaque psoriasis. Many treatment options are based mainly on clinical trials targeted for plaque psoriasis treatment.

For mild psoriasis, topical corticosteroids are first-line treatment. Other topical steroids include vitamin D analogs (calcipotriene), topical retinoids (tazarotene), topical calcineurin inhibitors (tacrolimus and pimecrolimus), and newer non-steroidal anti-inflammatory agents (roflumilast or tapinarof), neither approved yet in this young age group. In more severe cases, phototherapy with UVB light, traditional systemic immunosuppressive agents (methotrexate, cyclosporine) or targeted biologic therapies may be considered.
 

Differential Diagnosis

The differential diagnosis may include generalized intertrigo, pityriasis rubra pilaris, tinea corporis, atopic dermatitis, and staphylococcal scalded skin syndrome. Guttate psoriasis can be distinguished by history and physical exam. Further studies such as potassium hydroxide (KOH) scrapings may be helpful in ruling out the other disorders.

Intertrigo is an inflammatory condition of the flexural surfaces irritated by warm temperatures, friction, moisture, and poor ventilation that is commonly associated with Candida infection and/or streptococcal infection. Candidal intertrigo can present with erythematous patches or plaques in an intertriginous area that may develop erosions, macerations, fissures, crust, and weeping. Satellite papules and pustules are pathognomonic for Candida species. Streptococcal intertrigo usually presents with bright red color and may be painful or pruritic. Perianal streptococcal infection is reported as a trigger of guttate psoriasis in pediatric patients.

Pityriasis rubra pilaris is a rare inflammatory papulosquamous disorder with an unknown etiology. Red-orange papules and plaques, hyperkeratotic follicular papules, and palmoplantar hyperkeratosis are primary features. Diagnosis is based on clinical and histopathology. Pityriasis rubra pilaris is self-limited and asymptomatic in many cases. Treatment may not be required, but combination therapy with topical agents includes emollients, keratolytic agents (for example, urea, salicylic acid, alpha-hydroxy acids), topical corticosteroids, tazarotene, and topical calcineurin inhibitors. Systemic agents include oral retinoids and methotrexate.

Atopic dermatitis is a chronic inflammatory skin disease that involves genetic and environmental factors, leading to abnormalities in the epidermis and the immune system presenting with its typical morphology and distribution. The morphology of eczematous lesions is distinct from papulosquamous lesions of psoriasis.

Staphylococcal scalded skin syndrome is a toxin-mediated skin disorder which presents with denuded, peeling skin due to epidermolytic exotoxin producing Staphylococcus species. Fever, erythematous rash, malaise, skin pain, and irritability presents initially. Progressive desquamation with accentuation in folds is typical, with progression usually within 1-2 days. Systemic antibiotics covering Staphylococcus should be administered early. Emollients and nonadherent dressings should be applied to affected areas to promote healing. Supportive care includes dehydration management, temperature regulation, and nutrition. Skin desquamation usually occurs within 5 days with resolution within 2 weeks.

This infant displayed streptococcal intertrigo which triggered an early presentation of guttate psoriasis. The patient was managed with completion of a course of oral cephalexin, midstrength topical corticosteroids to the truncal lesions, and mild topical corticosteroids to the face and diaper area with good clinical response.
 

Danny Lee and Samuel Le serve as research fellows in the Pediatric Dermatology Division of the Department of Dermatology at the University of California San Diego and Rady Children’s Hospital, San Diego. Dr. Eichenfield is Distinguished Professor of Dermatology and Pediatrics and Vice-Chair of the Department of Dermatology at the University of California San Diego and Rady Children’s Hospital, San Diego. The authors have no relevant financial disclosures.

Suggested Reading

Leung AK et al. Childhood guttate psoriasis: An updated review. Drugs Context. 2023 Oct 23:12:2023-8-2. doi: 10.7573/dic.2023-8-2.

Galili E et al. New-onset guttate psoriasis: A long-term follow-up study. Dermatology. 2023;239(2):188-194. doi: 10.1159/000527737.

Duffin KC et al. Advances and controversies in our understanding of guttate and plaque psoriasis. J Rheumatol. 2023 Nov;50(Suppl 2):4-7. doi: 10.3899/jrheum.2023-0500.

Saleh D, Tanner LS. Guttate Psoriasis. [Updated 2023 Jul 31]. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2023 Jan-. Available from: www.ncbi.nlm.nih.gov/books/NBK482498/

Dupire G et al. Antistreptococcal interventions for guttate and chronic plaque psoriasis. Cochrane Database Syst Rev. 2019 Mar 5;3(3):CD011571. doi: 10.1002/14651858.CD011571.pub2.

TOPLINE:

Nearly half of the US Food and Drug Administration (FDA) approvals for dermatologic drugs between 2012 and 2022 were considered first in class or first in indication.

METHODOLOGY:

• Only five new drugs for diseases treated mostly by dermatologists were approved by the FDA between 1999 and 2009.
• In a cross-sectional analysis to characterize the frequency and degree of innovation of dermatologic drugs approved more recently, researchers identified new and supplemental dermatologic drugs approved between January 1, 2012, and December 31, 2022, from FDA lists, Centers for Medicare & Medicaid Services CenterWatch, and peer-reviewed articles.
• They used five proxy measures to estimate each drug’s degree of innovation: FDA designation (first in class, advance in class, or addition to class), independent clinical usefulness ratings, and benefit ratings by health technology assessment organizations.

TAKEAWAY:

• The study authors identified 52 new drug applications and 26 supplemental new indications approved by the FDA for dermatologic indications between 2012 and 2022.
• Of the 52 new drugs, the researchers categorized 11 (21%) as first in class and 13 (25%) as first in indication.
• An analysis of benefit ratings available for 38 of the drugs showed that 15 (39%) were rated as being clinically useful or having high added therapeutic benefit.
• Of the 10 supplemental new indications with ratings by any organization, 3 (30%) were rated as clinically useful or having high added therapeutic benefit.

IN PRACTICE:

While innovative drug development in dermatology may have increased, “these findings also highlight opportunities to develop more truly innovative dermatologic agents, particularly for diseases with unmet therapeutic need,” the authors wrote.

SOURCE:

First author Samir Kamat, MD, of the Medical Education Department at Icahn School of Medicine at Mount Sinai, New York City, and corresponding author Ravi Gupta, MD, MSHP, of the Internal Medicine Division at Johns Hopkins University, Baltimore, Maryland, led the research. The study was published online as a research letter on December 20, 2023, in JAMA Dermatology.

LIMITATIONS:

They include the use of individual indications to assess clinical usefulness and benefit ratings. Many drugs, particularly supplemental indications, lacked such ratings. Reformulations of already marketed drugs or indications were not included.

DISCLOSURES:

Dr. Kamat and Dr. Gupta had no relevant disclosures. Three coauthors reported having received financial support outside of the submitted work.

A version of this article appeared on Medscape.com.

TOPLINE:

Nearly half of the US Food and Drug Administration (FDA) approvals for dermatologic drugs between 2012 and 2022 were considered first in class or first in indication.

METHODOLOGY:

• Only five new drugs for diseases treated mostly by dermatologists were approved by the FDA between 1999 and 2009.
• In a cross-sectional analysis to characterize the frequency and degree of innovation of dermatologic drugs approved more recently, researchers identified new and supplemental dermatologic drugs approved between January 1, 2012, and December 31, 2022, from FDA lists, Centers for Medicare & Medicaid Services CenterWatch, and peer-reviewed articles.
• They used five proxy measures to estimate each drug’s degree of innovation: FDA designation (first in class, advance in class, or addition to class), independent clinical usefulness ratings, and benefit ratings by health technology assessment organizations.

TAKEAWAY:

• The study authors identified 52 new drug applications and 26 supplemental new indications approved by the FDA for dermatologic indications between 2012 and 2022.
• Of the 52 new drugs, the researchers categorized 11 (21%) as first in class and 13 (25%) as first in indication.
• An analysis of benefit ratings available for 38 of the drugs showed that 15 (39%) were rated as being clinically useful or having high added therapeutic benefit.
• Of the 10 supplemental new indications with ratings by any organization, 3 (30%) were rated as clinically useful or having high added therapeutic benefit.

IN PRACTICE:

While innovative drug development in dermatology may have increased, “these findings also highlight opportunities to develop more truly innovative dermatologic agents, particularly for diseases with unmet therapeutic need,” the authors wrote.

SOURCE:

First author Samir Kamat, MD, of the Medical Education Department at Icahn School of Medicine at Mount Sinai, New York City, and corresponding author Ravi Gupta, MD, MSHP, of the Internal Medicine Division at Johns Hopkins University, Baltimore, Maryland, led the research. The study was published online as a research letter on December 20, 2023, in JAMA Dermatology.

LIMITATIONS:

They include the use of individual indications to assess clinical usefulness and benefit ratings. Many drugs, particularly supplemental indications, lacked such ratings. Reformulations of already marketed drugs or indications were not included.

DISCLOSURES:

Dr. Kamat and Dr. Gupta had no relevant disclosures. Three coauthors reported having received financial support outside of the submitted work.

A version of this article appeared on Medscape.com.

TOPLINE:

Nearly half of the US Food and Drug Administration (FDA) approvals for dermatologic drugs between 2012 and 2022 were considered first in class or first in indication.

METHODOLOGY:

• Only five new drugs for diseases treated mostly by dermatologists were approved by the FDA between 1999 and 2009.
• In a cross-sectional analysis to characterize the frequency and degree of innovation of dermatologic drugs approved more recently, researchers identified new and supplemental dermatologic drugs approved between January 1, 2012, and December 31, 2022, from FDA lists, Centers for Medicare & Medicaid Services CenterWatch, and peer-reviewed articles.
• They used five proxy measures to estimate each drug’s degree of innovation: FDA designation (first in class, advance in class, or addition to class), independent clinical usefulness ratings, and benefit ratings by health technology assessment organizations.

TAKEAWAY:

• The study authors identified 52 new drug applications and 26 supplemental new indications approved by the FDA for dermatologic indications between 2012 and 2022.
• Of the 52 new drugs, the researchers categorized 11 (21%) as first in class and 13 (25%) as first in indication.
• An analysis of benefit ratings available for 38 of the drugs showed that 15 (39%) were rated as being clinically useful or having high added therapeutic benefit.
• Of the 10 supplemental new indications with ratings by any organization, 3 (30%) were rated as clinically useful or having high added therapeutic benefit.

IN PRACTICE:

While innovative drug development in dermatology may have increased, “these findings also highlight opportunities to develop more truly innovative dermatologic agents, particularly for diseases with unmet therapeutic need,” the authors wrote.

SOURCE:

First author Samir Kamat, MD, of the Medical Education Department at Icahn School of Medicine at Mount Sinai, New York City, and corresponding author Ravi Gupta, MD, MSHP, of the Internal Medicine Division at Johns Hopkins University, Baltimore, Maryland, led the research. The study was published online as a research letter on December 20, 2023, in JAMA Dermatology.

LIMITATIONS:

They include the use of individual indications to assess clinical usefulness and benefit ratings. Many drugs, particularly supplemental indications, lacked such ratings. Reformulations of already marketed drugs or indications were not included.

DISCLOSURES:

Dr. Kamat and Dr. Gupta had no relevant disclosures. Three coauthors reported having received financial support outside of the submitted work.

A version of this article appeared on Medscape.com.

An experimental topical phosphodiesterase 4 (PDE4) inhibitor showed superior efficacy to vehicle in patients with mild to moderate atopic dermatitis (AD) and plaque psoriasis, results from a phase 2a study showed.

PDE4 inhibitors are a promising therapeutic target for inflammatory diseases because “they can increase cyclic adenosine monophosphate levels and subsequently reduce the production of proinflammatory cytokines,” lead study author Lawrence F. Eichenfield, MD, of the dermatology department at the University of California, San Diego, and colleagues wrote. The paper was published online in JAMA Dermatology.

Currently Available Treatments

For plaque psoriasis, the FDA approved the topical PDE4 inhibitor roflumilast in 2022. The oral PDE4 inhibitor apremilast has shown to be effective for plaque psoriasis and is well tolerated, and “it has been associated with gastrointestinal adverse events (AEs) such as nausea and diarrhea,” the researchers wrote.

For AD, crisaborole is the only approved topical PDE4 treatment, and it is associated with application site burning and stinging, they wrote.

An Experimental Alternative

The new study tested a topical PDE4 inhibitor known as PF-07038124, which is being developed by Pfizer. It is designed to be “a potent, oxaborole-based PDE4 inhibitor [that shows] immunomodulatory activity in T-cell–based assays, contributing to inhibition of [interleukin]-4 and IL-13; thus, it could provide therapeutic benefit in the treatment of AD and plaque psoriasis,” the authors wrote.

The phase 2a study was conducted from December 21, 2020, to August 18, 2021. Researchers at 34 sites in four countries randomized 104 patients with mild to moderate AD (70) or plaque psoriasis (34) to receive PF-07038124 as a 0.001% topical ointment or a vehicle only once daily for 6 weeks.

The primary end point was the percent change from baseline in the Eczema Area and Severity Index (EASI) total score among patients with AD and in the Psoriasis Area and Severity Index (PASI) score among patients with plaque psoriasis at week 6. Safety measures of interest included treatment-emergent adverse events.

Overall, the mean age of the 104 patients was 43 years, 52.9%, were women, 3.8% were Asian, 12.5% were Black, and 83.7% were White. Most had moderate disease.

At week 6 in patients with AD, the PF-07038124 group showed statistically significantly greater improvement in the EASI total score, compared with vehicle group (−74.9% vs −35.5% respectively; least squares mean [LSM] difference, −39.4%; 90% CI, −58.8% to−20.1%]; P < .001).

Similarly, at week 6 in patients with plaque psoriasis, the PF-07038124 group demonstrated a significantly greater improvement in the PASI total score, compared with the vehicle group (LSM, −4.8; 90% CI, −6.2 to −3.4] vs 0.1; 90% CI, −1.5 to 1.7), for a difference of −4.9; 90% CI, −7.0 to −2.8; P < .001.

In safety outcomes, treatment-emergent adverse events were reported in 16 people receiving PF-07038124 and 26 people receiving a vehicle. The treatment-related adverse events were reported only in the vehicle groups across all indications, while no patients in the PF-07038124 groups experienced pain or skin reactions at the application sites.

The researchers acknowledged certain limitations of the trial, including its small size and the 6-week treatment period. “Unlike crisaborole, topical PF-07038124 was not associated with application site burning and stinging,” they noted. “To confirm persistence of efficacy and the safety profile of PF-07038124, long-term data should be collected in larger studies.”

Pfizer supported the study. Dr. Eichenfield reported receiving personal fees from Pfizer during the conduct of the study. He also has received grant support from, is consultant to, and/or is a member of the advisory board for many other pharmaceutical companies. Several other study authors reported similar disclosures.

An experimental topical phosphodiesterase 4 (PDE4) inhibitor showed superior efficacy to vehicle in patients with mild to moderate atopic dermatitis (AD) and plaque psoriasis, results from a phase 2a study showed.

PDE4 inhibitors are a promising therapeutic target for inflammatory diseases because “they can increase cyclic adenosine monophosphate levels and subsequently reduce the production of proinflammatory cytokines,” lead study author Lawrence F. Eichenfield, MD, of the dermatology department at the University of California, San Diego, and colleagues wrote. The paper was published online in JAMA Dermatology.

Currently Available Treatments

For plaque psoriasis, the FDA approved the topical PDE4 inhibitor roflumilast in 2022. The oral PDE4 inhibitor apremilast has shown to be effective for plaque psoriasis and is well tolerated, and “it has been associated with gastrointestinal adverse events (AEs) such as nausea and diarrhea,” the researchers wrote.

For AD, crisaborole is the only approved topical PDE4 treatment, and it is associated with application site burning and stinging, they wrote.

An Experimental Alternative

The new study tested a topical PDE4 inhibitor known as PF-07038124, which is being developed by Pfizer. It is designed to be “a potent, oxaborole-based PDE4 inhibitor [that shows] immunomodulatory activity in T-cell–based assays, contributing to inhibition of [interleukin]-4 and IL-13; thus, it could provide therapeutic benefit in the treatment of AD and plaque psoriasis,” the authors wrote.

The phase 2a study was conducted from December 21, 2020, to August 18, 2021. Researchers at 34 sites in four countries randomized 104 patients with mild to moderate AD (70) or plaque psoriasis (34) to receive PF-07038124 as a 0.001% topical ointment or a vehicle only once daily for 6 weeks.

The primary end point was the percent change from baseline in the Eczema Area and Severity Index (EASI) total score among patients with AD and in the Psoriasis Area and Severity Index (PASI) score among patients with plaque psoriasis at week 6. Safety measures of interest included treatment-emergent adverse events.

Overall, the mean age of the 104 patients was 43 years, 52.9%, were women, 3.8% were Asian, 12.5% were Black, and 83.7% were White. Most had moderate disease.

At week 6 in patients with AD, the PF-07038124 group showed statistically significantly greater improvement in the EASI total score, compared with vehicle group (−74.9% vs −35.5% respectively; least squares mean [LSM] difference, −39.4%; 90% CI, −58.8% to−20.1%]; P < .001).

Similarly, at week 6 in patients with plaque psoriasis, the PF-07038124 group demonstrated a significantly greater improvement in the PASI total score, compared with the vehicle group (LSM, −4.8; 90% CI, −6.2 to −3.4] vs 0.1; 90% CI, −1.5 to 1.7), for a difference of −4.9; 90% CI, −7.0 to −2.8; P < .001.

In safety outcomes, treatment-emergent adverse events were reported in 16 people receiving PF-07038124 and 26 people receiving a vehicle. The treatment-related adverse events were reported only in the vehicle groups across all indications, while no patients in the PF-07038124 groups experienced pain or skin reactions at the application sites.

The researchers acknowledged certain limitations of the trial, including its small size and the 6-week treatment period. “Unlike crisaborole, topical PF-07038124 was not associated with application site burning and stinging,” they noted. “To confirm persistence of efficacy and the safety profile of PF-07038124, long-term data should be collected in larger studies.”

Pfizer supported the study. Dr. Eichenfield reported receiving personal fees from Pfizer during the conduct of the study. He also has received grant support from, is consultant to, and/or is a member of the advisory board for many other pharmaceutical companies. Several other study authors reported similar disclosures.

An experimental topical phosphodiesterase 4 (PDE4) inhibitor showed superior efficacy to vehicle in patients with mild to moderate atopic dermatitis (AD) and plaque psoriasis, results from a phase 2a study showed.

PDE4 inhibitors are a promising therapeutic target for inflammatory diseases because “they can increase cyclic adenosine monophosphate levels and subsequently reduce the production of proinflammatory cytokines,” lead study author Lawrence F. Eichenfield, MD, of the dermatology department at the University of California, San Diego, and colleagues wrote. The paper was published online in JAMA Dermatology.

Currently Available Treatments

For plaque psoriasis, the FDA approved the topical PDE4 inhibitor roflumilast in 2022. The oral PDE4 inhibitor apremilast has shown to be effective for plaque psoriasis and is well tolerated, and “it has been associated with gastrointestinal adverse events (AEs) such as nausea and diarrhea,” the researchers wrote.

For AD, crisaborole is the only approved topical PDE4 treatment, and it is associated with application site burning and stinging, they wrote.

An Experimental Alternative

The new study tested a topical PDE4 inhibitor known as PF-07038124, which is being developed by Pfizer. It is designed to be “a potent, oxaborole-based PDE4 inhibitor [that shows] immunomodulatory activity in T-cell–based assays, contributing to inhibition of [interleukin]-4 and IL-13; thus, it could provide therapeutic benefit in the treatment of AD and plaque psoriasis,” the authors wrote.

The phase 2a study was conducted from December 21, 2020, to August 18, 2021. Researchers at 34 sites in four countries randomized 104 patients with mild to moderate AD (70) or plaque psoriasis (34) to receive PF-07038124 as a 0.001% topical ointment or a vehicle only once daily for 6 weeks.

The primary end point was the percent change from baseline in the Eczema Area and Severity Index (EASI) total score among patients with AD and in the Psoriasis Area and Severity Index (PASI) score among patients with plaque psoriasis at week 6. Safety measures of interest included treatment-emergent adverse events.

Overall, the mean age of the 104 patients was 43 years, 52.9%, were women, 3.8% were Asian, 12.5% were Black, and 83.7% were White. Most had moderate disease.

At week 6 in patients with AD, the PF-07038124 group showed statistically significantly greater improvement in the EASI total score, compared with vehicle group (−74.9% vs −35.5% respectively; least squares mean [LSM] difference, −39.4%; 90% CI, −58.8% to−20.1%]; P < .001).

Similarly, at week 6 in patients with plaque psoriasis, the PF-07038124 group demonstrated a significantly greater improvement in the PASI total score, compared with the vehicle group (LSM, −4.8; 90% CI, −6.2 to −3.4] vs 0.1; 90% CI, −1.5 to 1.7), for a difference of −4.9; 90% CI, −7.0 to −2.8; P < .001.

In safety outcomes, treatment-emergent adverse events were reported in 16 people receiving PF-07038124 and 26 people receiving a vehicle. The treatment-related adverse events were reported only in the vehicle groups across all indications, while no patients in the PF-07038124 groups experienced pain or skin reactions at the application sites.

The researchers acknowledged certain limitations of the trial, including its small size and the 6-week treatment period. “Unlike crisaborole, topical PF-07038124 was not associated with application site burning and stinging,” they noted. “To confirm persistence of efficacy and the safety profile of PF-07038124, long-term data should be collected in larger studies.”

Pfizer supported the study. Dr. Eichenfield reported receiving personal fees from Pfizer during the conduct of the study. He also has received grant support from, is consultant to, and/or is a member of the advisory board for many other pharmaceutical companies. Several other study authors reported similar disclosures.

Patients with psoriasis being treated with biologics have a low overall risk for developing the paradoxical symptoms of eczema, with interleukin (IL)-23 inhibitors found to confer the lowest risk of the drug classes examined in a large observational analysis.

Using data from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR) database, Ali Al-Janabi, MA, from the University of Manchester (England) and associates found that 273 (1%) of approximately 25,000 drug exposures in 13,699 biologic-treated patients with psoriasis were associated with paradoxical eczema.

The incidence of paradoxical eczema was found to vary by class. The highest rate was seen for IL-17 inhibitors, at 1.22 per 100,000 person-years, and the lowest rate was seen with IL-23 inhibitors, at 0.56 per 100,000 person-years. The respective incidence rates for tumor necrosis factor (TNF) inhibitors and IL-12/IL-23 inhibitors were a respective 0.94 and 0.80 per 100,000 person-years.

“Compared with TNF inhibitors, IL-23 inhibitor exposure was associated with significantly lower risk of paradoxical eczema,” the BADBIR Study Group reported in JAMA Dermatology. Indeed, patients treated with IL-23 inhibitors were 61% less likely than were those taking TNF-inhibitors to experience a paradoxical eczema event.

“These findings remained when restricting the analysis to first-line biologic exposures and were specific to this eczema phenotype” the group said.

Cautious Interpretation

As the corresponding author for the work, Mr. Al-Janabi observed in an email that the research needs to be replicated, and the findings need to be interpreted with caution.

“As well as usual clinical variables influencing biologic selection, clinicians could consider IL-23 inhibitors in patients with previous atopic dermatitis, hay fever, or paradoxical eczema episodes, as this class was associated with the lowest risk of paradoxical eczema,” he suggested.

A prior history of atopic dermatitis (AD) and hay fever appears to be particularly relevant, as both substantially upped the chances that paradoxical eczema would occur, with hazard ratios of 12.40 and 3.78, respectively. Increasing age also increased the risk, albeit slightly (hazard ratio [HR], 1.02 per year), and there was an apparent lower risk (HR, 0.60) comparing men and women.

The BADBIR Study Group authors believe that, to the best of their knowledge, this is the first study to compare paradoxical eczema risk by biologic class. “Based on clinical experience and prevalence of eczematous reactions reported in some IL-17 inhibitor clinical trials, we suspected an association between IL-17 inhibitor exposure and paradoxical eczema,” they wrote.

“While the incidence of paradoxical eczema was numerically highest among IL-17 inhibitor exposures, it was not significantly different from the incidence among TNF inhibitor exposures.” The low overall incidence of paradoxical eczema “may be reassuring for patients and clinicians,” they added, “but it is possible that the incidence was underestimated due to underreporting or exclusion of adverse events with insufficient detail.”

Details of the Analysis, Other Findings

To explore the risk of paradoxical eczema by biologic class and identify possible risk factors, the BADBIR Study Group performed a prospective cohort study using data held within the BADBIR database between September 2007 and December 2022.

Adults over the age of 18 year or older with plaque psoriasis and who had been treated with at least one of the following biologics were eligible for inclusion: the TNF inhibitors adalimumab, certolizumab pegol, etanercept, and infliximab; the IL-17 inhibitors bimekizumab, brodalumab, ixekizumab, and secukinumab; the IL-12/23 inhibitor ustekinumab; and the IL-23 inhibitors guselkumab, risankizumab, and tildrakizumab.

Patient records and adverse event data were reviewed to determine the incidence of paradoxical eczema events, using terms such as eczema, eczematized, eczematous, atopy, atopic, and dermatitis.

Of 24,952 drug exposures analyzed, the majority (11,819) were for TNF inhibitors, followed by IL-17 inhibitors (4,776), IL-12/23 inhibitors (6,423), and finally, IL-23 inhibitors (1,934).

Mr. Al-Janabi and coauthors reported that the median time to onset of paradoxical eczema events was 294 days — approximately 9.8 months. The earliest that these events were recorded was at 120 days (4 months), and the latest at 699 days (almost 2 years).

The face and neck were the most common sites affected (26% of exposures), with other sites including the limbs (23%), the trunk (13%), and hands or feet (12%). Itching (18%), redness (7%), and dryness (4%) were the most commonly reported symptoms.

The researchers noted that 21 patients had skin biopsies taken and “all showed spongiosis or a feature of eczema, with 1 having overlapping features of psoriasis.”

In the majority (92 %) of cases, patients experienced only one eczema event. Of the 20 patients who had more than one event, just over one-fifth of repeat events occurred after receiving the same biologic as for the index event. A quarter of events occurred after a different biologic of the same class had been used, and just over half of events occurred after a different class of biologic had been given.

Strengths and Limitations

The “large sample size and inclusion of multiple lines of exposure per participant” are strengths of the study, said the researchers. “We included data for all currently available biologics, originating from more than 160 dermatology centers in the UK and Ireland.”

They added, however, that the “main limitation is the small numbers of observations within certain subgroups, such as specific biologic exposures or participants in ethnic minority groups, restricting generalizability of our findings and the interpretation of some subgroup analyses.”

Moreover, the small number of paradoxical eczema events seen may have resulted in imprecise effect estimates, they observe, noting that the number of exposures to IL-23 inhibitors was low compared with other classes.

“Future studies with more exposures and paradoxical eczema events would enable a more robust analysis of individual drugs and patient subgroups,” the authors concluded.

The study was funded by the Medical Research Council. BADBIR is coordinated by The University of Manchester, and funded by the British Association of Dermatologists (BAD). The BAD receives income from AbbVie, Almirall, Amgen, Celgene, Janssen, LEO Pharma, Lilly, Novartis, Samsung Bioepis, Sandoz Hexal AG, and UCB Pharma for providing pharmacovigilance services. This income finances a separate contract between the BAD and The University of Manchester, which coordinates BADBIR. Mr. Al-Janabi reported receiving grants from the Medical Research Council during the conduct of the study; nonfinancial support from UCB, Almirall, and Janssen; and personal fees from UCB outside the submitted work.

Patients with psoriasis being treated with biologics have a low overall risk for developing the paradoxical symptoms of eczema, with interleukin (IL)-23 inhibitors found to confer the lowest risk of the drug classes examined in a large observational analysis.

Using data from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR) database, Ali Al-Janabi, MA, from the University of Manchester (England) and associates found that 273 (1%) of approximately 25,000 drug exposures in 13,699 biologic-treated patients with psoriasis were associated with paradoxical eczema.

The incidence of paradoxical eczema was found to vary by class. The highest rate was seen for IL-17 inhibitors, at 1.22 per 100,000 person-years, and the lowest rate was seen with IL-23 inhibitors, at 0.56 per 100,000 person-years. The respective incidence rates for tumor necrosis factor (TNF) inhibitors and IL-12/IL-23 inhibitors were a respective 0.94 and 0.80 per 100,000 person-years.

“Compared with TNF inhibitors, IL-23 inhibitor exposure was associated with significantly lower risk of paradoxical eczema,” the BADBIR Study Group reported in JAMA Dermatology. Indeed, patients treated with IL-23 inhibitors were 61% less likely than were those taking TNF-inhibitors to experience a paradoxical eczema event.

“These findings remained when restricting the analysis to first-line biologic exposures and were specific to this eczema phenotype” the group said.

Cautious Interpretation

As the corresponding author for the work, Mr. Al-Janabi observed in an email that the research needs to be replicated, and the findings need to be interpreted with caution.

“As well as usual clinical variables influencing biologic selection, clinicians could consider IL-23 inhibitors in patients with previous atopic dermatitis, hay fever, or paradoxical eczema episodes, as this class was associated with the lowest risk of paradoxical eczema,” he suggested.

A prior history of atopic dermatitis (AD) and hay fever appears to be particularly relevant, as both substantially upped the chances that paradoxical eczema would occur, with hazard ratios of 12.40 and 3.78, respectively. Increasing age also increased the risk, albeit slightly (hazard ratio [HR], 1.02 per year), and there was an apparent lower risk (HR, 0.60) comparing men and women.

The BADBIR Study Group authors believe that, to the best of their knowledge, this is the first study to compare paradoxical eczema risk by biologic class. “Based on clinical experience and prevalence of eczematous reactions reported in some IL-17 inhibitor clinical trials, we suspected an association between IL-17 inhibitor exposure and paradoxical eczema,” they wrote.

“While the incidence of paradoxical eczema was numerically highest among IL-17 inhibitor exposures, it was not significantly different from the incidence among TNF inhibitor exposures.” The low overall incidence of paradoxical eczema “may be reassuring for patients and clinicians,” they added, “but it is possible that the incidence was underestimated due to underreporting or exclusion of adverse events with insufficient detail.”

Details of the Analysis, Other Findings

To explore the risk of paradoxical eczema by biologic class and identify possible risk factors, the BADBIR Study Group performed a prospective cohort study using data held within the BADBIR database between September 2007 and December 2022.

Adults over the age of 18 year or older with plaque psoriasis and who had been treated with at least one of the following biologics were eligible for inclusion: the TNF inhibitors adalimumab, certolizumab pegol, etanercept, and infliximab; the IL-17 inhibitors bimekizumab, brodalumab, ixekizumab, and secukinumab; the IL-12/23 inhibitor ustekinumab; and the IL-23 inhibitors guselkumab, risankizumab, and tildrakizumab.

Patient records and adverse event data were reviewed to determine the incidence of paradoxical eczema events, using terms such as eczema, eczematized, eczematous, atopy, atopic, and dermatitis.

Of 24,952 drug exposures analyzed, the majority (11,819) were for TNF inhibitors, followed by IL-17 inhibitors (4,776), IL-12/23 inhibitors (6,423), and finally, IL-23 inhibitors (1,934).

Mr. Al-Janabi and coauthors reported that the median time to onset of paradoxical eczema events was 294 days — approximately 9.8 months. The earliest that these events were recorded was at 120 days (4 months), and the latest at 699 days (almost 2 years).

The face and neck were the most common sites affected (26% of exposures), with other sites including the limbs (23%), the trunk (13%), and hands or feet (12%). Itching (18%), redness (7%), and dryness (4%) were the most commonly reported symptoms.

The researchers noted that 21 patients had skin biopsies taken and “all showed spongiosis or a feature of eczema, with 1 having overlapping features of psoriasis.”

In the majority (92 %) of cases, patients experienced only one eczema event. Of the 20 patients who had more than one event, just over one-fifth of repeat events occurred after receiving the same biologic as for the index event. A quarter of events occurred after a different biologic of the same class had been used, and just over half of events occurred after a different class of biologic had been given.

Strengths and Limitations

The “large sample size and inclusion of multiple lines of exposure per participant” are strengths of the study, said the researchers. “We included data for all currently available biologics, originating from more than 160 dermatology centers in the UK and Ireland.”

They added, however, that the “main limitation is the small numbers of observations within certain subgroups, such as specific biologic exposures or participants in ethnic minority groups, restricting generalizability of our findings and the interpretation of some subgroup analyses.”

Moreover, the small number of paradoxical eczema events seen may have resulted in imprecise effect estimates, they observe, noting that the number of exposures to IL-23 inhibitors was low compared with other classes.

“Future studies with more exposures and paradoxical eczema events would enable a more robust analysis of individual drugs and patient subgroups,” the authors concluded.

The study was funded by the Medical Research Council. BADBIR is coordinated by The University of Manchester, and funded by the British Association of Dermatologists (BAD). The BAD receives income from AbbVie, Almirall, Amgen, Celgene, Janssen, LEO Pharma, Lilly, Novartis, Samsung Bioepis, Sandoz Hexal AG, and UCB Pharma for providing pharmacovigilance services. This income finances a separate contract between the BAD and The University of Manchester, which coordinates BADBIR. Mr. Al-Janabi reported receiving grants from the Medical Research Council during the conduct of the study; nonfinancial support from UCB, Almirall, and Janssen; and personal fees from UCB outside the submitted work.

Patients with psoriasis being treated with biologics have a low overall risk for developing the paradoxical symptoms of eczema, with interleukin (IL)-23 inhibitors found to confer the lowest risk of the drug classes examined in a large observational analysis.

Using data from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR) database, Ali Al-Janabi, MA, from the University of Manchester (England) and associates found that 273 (1%) of approximately 25,000 drug exposures in 13,699 biologic-treated patients with psoriasis were associated with paradoxical eczema.

The incidence of paradoxical eczema was found to vary by class. The highest rate was seen for IL-17 inhibitors, at 1.22 per 100,000 person-years, and the lowest rate was seen with IL-23 inhibitors, at 0.56 per 100,000 person-years. The respective incidence rates for tumor necrosis factor (TNF) inhibitors and IL-12/IL-23 inhibitors were a respective 0.94 and 0.80 per 100,000 person-years.

“Compared with TNF inhibitors, IL-23 inhibitor exposure was associated with significantly lower risk of paradoxical eczema,” the BADBIR Study Group reported in JAMA Dermatology. Indeed, patients treated with IL-23 inhibitors were 61% less likely than were those taking TNF-inhibitors to experience a paradoxical eczema event.

“These findings remained when restricting the analysis to first-line biologic exposures and were specific to this eczema phenotype” the group said.

Cautious Interpretation

As the corresponding author for the work, Mr. Al-Janabi observed in an email that the research needs to be replicated, and the findings need to be interpreted with caution.

“As well as usual clinical variables influencing biologic selection, clinicians could consider IL-23 inhibitors in patients with previous atopic dermatitis, hay fever, or paradoxical eczema episodes, as this class was associated with the lowest risk of paradoxical eczema,” he suggested.

A prior history of atopic dermatitis (AD) and hay fever appears to be particularly relevant, as both substantially upped the chances that paradoxical eczema would occur, with hazard ratios of 12.40 and 3.78, respectively. Increasing age also increased the risk, albeit slightly (hazard ratio [HR], 1.02 per year), and there was an apparent lower risk (HR, 0.60) comparing men and women.

The BADBIR Study Group authors believe that, to the best of their knowledge, this is the first study to compare paradoxical eczema risk by biologic class. “Based on clinical experience and prevalence of eczematous reactions reported in some IL-17 inhibitor clinical trials, we suspected an association between IL-17 inhibitor exposure and paradoxical eczema,” they wrote.

“While the incidence of paradoxical eczema was numerically highest among IL-17 inhibitor exposures, it was not significantly different from the incidence among TNF inhibitor exposures.” The low overall incidence of paradoxical eczema “may be reassuring for patients and clinicians,” they added, “but it is possible that the incidence was underestimated due to underreporting or exclusion of adverse events with insufficient detail.”

Details of the Analysis, Other Findings

To explore the risk of paradoxical eczema by biologic class and identify possible risk factors, the BADBIR Study Group performed a prospective cohort study using data held within the BADBIR database between September 2007 and December 2022.

Adults over the age of 18 year or older with plaque psoriasis and who had been treated with at least one of the following biologics were eligible for inclusion: the TNF inhibitors adalimumab, certolizumab pegol, etanercept, and infliximab; the IL-17 inhibitors bimekizumab, brodalumab, ixekizumab, and secukinumab; the IL-12/23 inhibitor ustekinumab; and the IL-23 inhibitors guselkumab, risankizumab, and tildrakizumab.

Patient records and adverse event data were reviewed to determine the incidence of paradoxical eczema events, using terms such as eczema, eczematized, eczematous, atopy, atopic, and dermatitis.

Of 24,952 drug exposures analyzed, the majority (11,819) were for TNF inhibitors, followed by IL-17 inhibitors (4,776), IL-12/23 inhibitors (6,423), and finally, IL-23 inhibitors (1,934).

Mr. Al-Janabi and coauthors reported that the median time to onset of paradoxical eczema events was 294 days — approximately 9.8 months. The earliest that these events were recorded was at 120 days (4 months), and the latest at 699 days (almost 2 years).

The face and neck were the most common sites affected (26% of exposures), with other sites including the limbs (23%), the trunk (13%), and hands or feet (12%). Itching (18%), redness (7%), and dryness (4%) were the most commonly reported symptoms.

The researchers noted that 21 patients had skin biopsies taken and “all showed spongiosis or a feature of eczema, with 1 having overlapping features of psoriasis.”

In the majority (92 %) of cases, patients experienced only one eczema event. Of the 20 patients who had more than one event, just over one-fifth of repeat events occurred after receiving the same biologic as for the index event. A quarter of events occurred after a different biologic of the same class had been used, and just over half of events occurred after a different class of biologic had been given.

Strengths and Limitations

The “large sample size and inclusion of multiple lines of exposure per participant” are strengths of the study, said the researchers. “We included data for all currently available biologics, originating from more than 160 dermatology centers in the UK and Ireland.”

They added, however, that the “main limitation is the small numbers of observations within certain subgroups, such as specific biologic exposures or participants in ethnic minority groups, restricting generalizability of our findings and the interpretation of some subgroup analyses.”

Moreover, the small number of paradoxical eczema events seen may have resulted in imprecise effect estimates, they observe, noting that the number of exposures to IL-23 inhibitors was low compared with other classes.

“Future studies with more exposures and paradoxical eczema events would enable a more robust analysis of individual drugs and patient subgroups,” the authors concluded.

The study was funded by the Medical Research Council. BADBIR is coordinated by The University of Manchester, and funded by the British Association of Dermatologists (BAD). The BAD receives income from AbbVie, Almirall, Amgen, Celgene, Janssen, LEO Pharma, Lilly, Novartis, Samsung Bioepis, Sandoz Hexal AG, and UCB Pharma for providing pharmacovigilance services. This income finances a separate contract between the BAD and The University of Manchester, which coordinates BADBIR. Mr. Al-Janabi reported receiving grants from the Medical Research Council during the conduct of the study; nonfinancial support from UCB, Almirall, and Janssen; and personal fees from UCB outside the submitted work.

Patients with psoriatic disease have significantly higher risks of myocardial infarction, stroke, and cardiovascular mortality than does the general population, yet research consistently paints what dermatologist Joel M. Gelfand, MD, calls an “abysmal” picture: Only a minority of patients with psoriatic disease know about their increased risks, only a minority of dermatologists and rheumatologists screen for cardiovascular risk factors like lipid levels and blood pressure, and only a minority of patients diagnosed with hyperlipidemia are adequately treated with statin therapy.

In the literature and at medical meetings, Dr. Gelfand and others who have studied cardiovascular disease (CVD) comorbidity and physician practices have been urging dermatologists and rheumatologists to play a more consistent and active role in primary cardiovascular prevention for patients with psoriatic disease, who are up to 50% more likely than patients without it to develop CVD and who tend to have atherosclerosis at earlier ages.

According to the 2019 joint American Academy of Dermatology (AAD)–National Psoriasis Foundation (NPF) guidelines for managing psoriasis “with awareness and attention to comorbidities,” this means not only ensuring that all patients with psoriasis receive standard CV risk assessment (screening for hypertension, diabetes, and hyperlipidemia), but also recognizing that patients who are candidates for systemic therapy or phototherapy — or who have psoriasis involving > 10% of body surface area — may benefit from earlier and more frequent screening.

CV risk and premature mortality rises with the severity of skin disease, and patients with psoriatic arthritis (PsA) are believed to have risk levels similar to patients with moderate-severe psoriasis, cardiologist Michael S. Garshick, MD, director of the cardio-rheumatology program at New York University Langone Health, said in an interview.

NYU Langone

Dr. Barbieri

In many cases, dermatologists and rheumatologists may be the primary providers for patients with psoriatic disease. So, “the question is, how can the dermatologist or rheumatologist use their interactions as a touchpoint to improve the patient’s well-being?” Dr. Barbieri said in an interview.

For the dermatologist, educating patients about the higher CVD risk fits well into conversations about “how there may be inflammation inside the body as well as in the skin,” he said. “Talk about cardiovascular risk just as you talk about PsA risk.” Both specialists, he added, can incorporate blood pressure readings and look for opportunities to measure lipid levels and hemoglobin A1c (HbA1c). These labs can easily be integrated into a biologic work-up.

“The hard part — and this needs to be individualized — is how do you want to handle [abnormal readings]? Do you want to take on a lot of the ownership and calculate [10-year CVD] risk scores and then counsel patients accordingly?” Dr. Barbieri said. “Or do you want to try to refer, and encourage them to work with their PCP? There a high-touch version and a low-touch version of how you can turn screening into action, into a care plan.”


 

Beyond traditional risk elevation, the primary care hand-off

Rheumatologists “in general may be more apt to screen for cardiovascular disease” as a result of their internal medicine residency training, and “we’re generally more comfortable prescribing ... if we need to,” said Alexis R. Ogdie, MD, a rheumatologist at the Hospital of the University of Pennsylvania, Philadelphia, and director of the Penn Psoriatic Arthritis Clinic.

Penn Medicine

Referral to a preventive cardiologist for management of abnormal lab results or ongoing monitoring and prevention is ideal, but when hand-offs to primary care physicians are made — the more common scenario — education is important. “A common problem is that there is underrecognition of the cardiovascular risk being elevated in our patients,” she said, above and beyond risk posed by traditional risk factors such as dyslipidemia, hypertension, metabolic syndrome, and obesity, all of which have been shown to occur more frequently in patients with psoriatic disease than in the general population.

Morsa Images/DigitalVision/Getty Images

‘Patients trust us’

Dr. Gelfand has been at the forefront of research on psoriasis and heart disease. A study he coauthored in 2006, for instance, documented an independent risk of MI, with adjusted relative risks of 1.29 and 3.10 for a 30-year-old patient with mild or severe disease, respectively, and higher risks for a 60-year-old. In 2010, he and coinvestigators found that severe psoriasis was an independent risk factor for CV mortality (HR, 1.57) after adjusting for age, sex, smoking, diabetes, hypertension, and hyperlipidemia.

Today, along with Dr. Barbieri, Dr. Ogdie, and others, he is studying the feasibility and efficacy of a proposed national, “centralized care coordinator” model of care whereby dermatologists and rheumatologists would educate the patient, order lipid and HbA1c measurements as medically appropriate, and then refer patients as needed to a care coordinator. The care coordinator would calculate a 10-year CVD risk score and counsel the patient on possible next steps.

In a pilot study of 85 patients at four sites, 92% of patients followed through on their physician’s recommendations to have labs drawn, and 86% indicated the model was acceptable and feasible. A total of 27% of patients had “newly identified, previously undiagnosed, elevated cardiovascular disease risk,” and exploratory effectiveness results indicated a successful reduction in predicted CVD risk in patients who started statins, Dr. Gelfand reported at the NPF meeting.

With funding from the NPF, a larger, single-arm, pragmatic “CP3” trial (NCT05908240) is enrolling 525 patients with psoriasis at 10-20 academic and nonacademic dermatology sites across the United States to further test the model. The primary endpoint will be the change in LDL cholesterol measured at 6 months among people with a 10-year risk ≥5%. Secondary endpoints will cover improvement in disease severity and quality of life, behavior modification, patient experience, and other issues.

“We have only 10-15 minutes [with patients] ... a care coordinator who is empathetic and understanding and [informed] could make a big difference,” Dr. Gelfand said at the NPF meeting. If findings are positive, the model would be tested in rheumatology sites as well. The hope, he said, is that the NPF would be able to fund an in-house care coordinator(s) for the long-term.

Notably, a patient survey conducted as part of exploratory research leading up to the care coordinator project showed that patients trust their dermatologist or rheumatologist for CVD education and screening. Among 160 patients with psoriasis and 162 patients with PsA, 76% and 90% agreed that “I would like it if my dermatologist/rheumatologist educated me about my risk of heart disease,” and 60% and 75%, respectively, agree that “it would be convenient for me to have my cholesterol checked by my dermatologist/rheumatologist.”

“Patients trust us,” Dr. Gelfand said at the NPF meeting. “And the pilot study shows us that patients are motivated.”
 

Taking an individualized, holistic, longitudinal approach

“Sometimes you do have to triage bit,” Dr. Gelfand said in an interview. “For a young person with normal body weight who doesn’t smoke and has mild psoriasis, one could just educate and advise that they see their primary care physician” for monitoring.

“But for the same patient who is obese, maybe smokes, and doesn’t have a primary care physician, I’d order labs,” he said. “You don’t want a patient walking out the door with an [undiagnosed] LDL of 160 or hypertension.”

Age is also an important consideration, as excess CVD risk associated with autoimmune diseases like psoriasis rises with age, Dr. Gelfand said during a seminar on psoriasis and PsA held at NYU Langone in December. For a young person, typically, “I need to focus on education and lifestyle … setting them on a healthy lifestyle trajectory,” he said. “Once they get to 40, from 40 to 75 or so, that’s a sweet spot for medical intervention to lower cardiovascular risk.”

Even at older ages, however, lipid management is not the be-all and end-all, he said in the interview. “We have to be holistic.”

One advantage of having highly successful therapies for psoriasis, and to a lesser extent PsA, is the time that becomes available during follow-up visits — once disease is under control — to “focus on other things,” he said. Waiting until disease is under control to discuss diet, exercise, or smoking, for instance, makes sense anyway, he said. “You don’t want to overwhelm patients with too much to do at once.”

Indeed, said dermatologist Robert E. Kalb, MD, of the Buffalo Medical Group in Buffalo, NY, “patients have an open mind [about discussing cardiovascular disease risk], but it is not high on their radar. Most of them just want to get their skin clear.” (Dr. Kalb participated in the care coordinator pilot study, and said in an interview that since its completion, he has been more routinely ordering relevant labs.)

Rheumatologists are less fortunate with highly successful therapies, but “over the continuum of care, we do have time in office visits” to discuss issues like smoking, exercise, and lifestyle, Dr. Ogdie said. “I think of each of those pieces as part of our job.”

In the future, as researchers learn more about the impact of psoriasis and PsA treatments on CVD risk, it may be possible to tailor treatments or to prescribe treatments knowing that the therapies could reduce risk. Observational and epidemiologic data suggest that tumor necrosis factor-alpha inhibitor therapy over 3 years reduces the risk of MI, and that patients whose psoriasis is treated have reduced aortic inflammation, improved myocardial strain, and reduced coronary plaque burden, Dr. Garshick said at the NPF meeting.

“But when we look at the randomized controlled trials, they’re actually inconclusive that targeting inflammation in psoriatic disease reduces surrogates of cardiovascular disease,” he said. Dr. Garshick’s own research focuses on platelet and endothelial biology in psoriasis.

Dr. Barbieri reported he had no relevant disclosures. Dr. Garshick reported consulting fees from Bristol-Myers Squibb, Kiniksa, Horizon Therapeutics, and Agepha. Dr. Ogdie reported financial relationships with AbbVie, Amgen, Bristol-Myers Squibb, Celgene, Eli Lilly, Gilead, GlaxoSmithKline, Janssen, Novartis, Pfizer, Takeda, and UCB. Dr. Gelfand reported serving as a consultant for AbbVie, Artax, Bristol-Myers Squibb, GlaxoSmithKline, and other companies.

Patients with psoriatic disease have significantly higher risks of myocardial infarction, stroke, and cardiovascular mortality than does the general population, yet research consistently paints what dermatologist Joel M. Gelfand, MD, calls an “abysmal” picture: Only a minority of patients with psoriatic disease know about their increased risks, only a minority of dermatologists and rheumatologists screen for cardiovascular risk factors like lipid levels and blood pressure, and only a minority of patients diagnosed with hyperlipidemia are adequately treated with statin therapy.

In the literature and at medical meetings, Dr. Gelfand and others who have studied cardiovascular disease (CVD) comorbidity and physician practices have been urging dermatologists and rheumatologists to play a more consistent and active role in primary cardiovascular prevention for patients with psoriatic disease, who are up to 50% more likely than patients without it to develop CVD and who tend to have atherosclerosis at earlier ages.

According to the 2019 joint American Academy of Dermatology (AAD)–National Psoriasis Foundation (NPF) guidelines for managing psoriasis “with awareness and attention to comorbidities,” this means not only ensuring that all patients with psoriasis receive standard CV risk assessment (screening for hypertension, diabetes, and hyperlipidemia), but also recognizing that patients who are candidates for systemic therapy or phototherapy — or who have psoriasis involving > 10% of body surface area — may benefit from earlier and more frequent screening.

CV risk and premature mortality rises with the severity of skin disease, and patients with psoriatic arthritis (PsA) are believed to have risk levels similar to patients with moderate-severe psoriasis, cardiologist Michael S. Garshick, MD, director of the cardio-rheumatology program at New York University Langone Health, said in an interview.

NYU Langone

Dr. Barbieri

In many cases, dermatologists and rheumatologists may be the primary providers for patients with psoriatic disease. So, “the question is, how can the dermatologist or rheumatologist use their interactions as a touchpoint to improve the patient’s well-being?” Dr. Barbieri said in an interview.

For the dermatologist, educating patients about the higher CVD risk fits well into conversations about “how there may be inflammation inside the body as well as in the skin,” he said. “Talk about cardiovascular risk just as you talk about PsA risk.” Both specialists, he added, can incorporate blood pressure readings and look for opportunities to measure lipid levels and hemoglobin A1c (HbA1c). These labs can easily be integrated into a biologic work-up.

“The hard part — and this needs to be individualized — is how do you want to handle [abnormal readings]? Do you want to take on a lot of the ownership and calculate [10-year CVD] risk scores and then counsel patients accordingly?” Dr. Barbieri said. “Or do you want to try to refer, and encourage them to work with their PCP? There a high-touch version and a low-touch version of how you can turn screening into action, into a care plan.”


 

Beyond traditional risk elevation, the primary care hand-off

Rheumatologists “in general may be more apt to screen for cardiovascular disease” as a result of their internal medicine residency training, and “we’re generally more comfortable prescribing ... if we need to,” said Alexis R. Ogdie, MD, a rheumatologist at the Hospital of the University of Pennsylvania, Philadelphia, and director of the Penn Psoriatic Arthritis Clinic.

Penn Medicine

Referral to a preventive cardiologist for management of abnormal lab results or ongoing monitoring and prevention is ideal, but when hand-offs to primary care physicians are made — the more common scenario — education is important. “A common problem is that there is underrecognition of the cardiovascular risk being elevated in our patients,” she said, above and beyond risk posed by traditional risk factors such as dyslipidemia, hypertension, metabolic syndrome, and obesity, all of which have been shown to occur more frequently in patients with psoriatic disease than in the general population.

Morsa Images/DigitalVision/Getty Images

‘Patients trust us’

Dr. Gelfand has been at the forefront of research on psoriasis and heart disease. A study he coauthored in 2006, for instance, documented an independent risk of MI, with adjusted relative risks of 1.29 and 3.10 for a 30-year-old patient with mild or severe disease, respectively, and higher risks for a 60-year-old. In 2010, he and coinvestigators found that severe psoriasis was an independent risk factor for CV mortality (HR, 1.57) after adjusting for age, sex, smoking, diabetes, hypertension, and hyperlipidemia.

Today, along with Dr. Barbieri, Dr. Ogdie, and others, he is studying the feasibility and efficacy of a proposed national, “centralized care coordinator” model of care whereby dermatologists and rheumatologists would educate the patient, order lipid and HbA1c measurements as medically appropriate, and then refer patients as needed to a care coordinator. The care coordinator would calculate a 10-year CVD risk score and counsel the patient on possible next steps.

In a pilot study of 85 patients at four sites, 92% of patients followed through on their physician’s recommendations to have labs drawn, and 86% indicated the model was acceptable and feasible. A total of 27% of patients had “newly identified, previously undiagnosed, elevated cardiovascular disease risk,” and exploratory effectiveness results indicated a successful reduction in predicted CVD risk in patients who started statins, Dr. Gelfand reported at the NPF meeting.

With funding from the NPF, a larger, single-arm, pragmatic “CP3” trial (NCT05908240) is enrolling 525 patients with psoriasis at 10-20 academic and nonacademic dermatology sites across the United States to further test the model. The primary endpoint will be the change in LDL cholesterol measured at 6 months among people with a 10-year risk ≥5%. Secondary endpoints will cover improvement in disease severity and quality of life, behavior modification, patient experience, and other issues.

“We have only 10-15 minutes [with patients] ... a care coordinator who is empathetic and understanding and [informed] could make a big difference,” Dr. Gelfand said at the NPF meeting. If findings are positive, the model would be tested in rheumatology sites as well. The hope, he said, is that the NPF would be able to fund an in-house care coordinator(s) for the long-term.

Notably, a patient survey conducted as part of exploratory research leading up to the care coordinator project showed that patients trust their dermatologist or rheumatologist for CVD education and screening. Among 160 patients with psoriasis and 162 patients with PsA, 76% and 90% agreed that “I would like it if my dermatologist/rheumatologist educated me about my risk of heart disease,” and 60% and 75%, respectively, agree that “it would be convenient for me to have my cholesterol checked by my dermatologist/rheumatologist.”

“Patients trust us,” Dr. Gelfand said at the NPF meeting. “And the pilot study shows us that patients are motivated.”
 

Taking an individualized, holistic, longitudinal approach

“Sometimes you do have to triage bit,” Dr. Gelfand said in an interview. “For a young person with normal body weight who doesn’t smoke and has mild psoriasis, one could just educate and advise that they see their primary care physician” for monitoring.

“But for the same patient who is obese, maybe smokes, and doesn’t have a primary care physician, I’d order labs,” he said. “You don’t want a patient walking out the door with an [undiagnosed] LDL of 160 or hypertension.”

Age is also an important consideration, as excess CVD risk associated with autoimmune diseases like psoriasis rises with age, Dr. Gelfand said during a seminar on psoriasis and PsA held at NYU Langone in December. For a young person, typically, “I need to focus on education and lifestyle … setting them on a healthy lifestyle trajectory,” he said. “Once they get to 40, from 40 to 75 or so, that’s a sweet spot for medical intervention to lower cardiovascular risk.”

Even at older ages, however, lipid management is not the be-all and end-all, he said in the interview. “We have to be holistic.”

One advantage of having highly successful therapies for psoriasis, and to a lesser extent PsA, is the time that becomes available during follow-up visits — once disease is under control — to “focus on other things,” he said. Waiting until disease is under control to discuss diet, exercise, or smoking, for instance, makes sense anyway, he said. “You don’t want to overwhelm patients with too much to do at once.”

Indeed, said dermatologist Robert E. Kalb, MD, of the Buffalo Medical Group in Buffalo, NY, “patients have an open mind [about discussing cardiovascular disease risk], but it is not high on their radar. Most of them just want to get their skin clear.” (Dr. Kalb participated in the care coordinator pilot study, and said in an interview that since its completion, he has been more routinely ordering relevant labs.)

Rheumatologists are less fortunate with highly successful therapies, but “over the continuum of care, we do have time in office visits” to discuss issues like smoking, exercise, and lifestyle, Dr. Ogdie said. “I think of each of those pieces as part of our job.”

In the future, as researchers learn more about the impact of psoriasis and PsA treatments on CVD risk, it may be possible to tailor treatments or to prescribe treatments knowing that the therapies could reduce risk. Observational and epidemiologic data suggest that tumor necrosis factor-alpha inhibitor therapy over 3 years reduces the risk of MI, and that patients whose psoriasis is treated have reduced aortic inflammation, improved myocardial strain, and reduced coronary plaque burden, Dr. Garshick said at the NPF meeting.

“But when we look at the randomized controlled trials, they’re actually inconclusive that targeting inflammation in psoriatic disease reduces surrogates of cardiovascular disease,” he said. Dr. Garshick’s own research focuses on platelet and endothelial biology in psoriasis.

Dr. Barbieri reported he had no relevant disclosures. Dr. Garshick reported consulting fees from Bristol-Myers Squibb, Kiniksa, Horizon Therapeutics, and Agepha. Dr. Ogdie reported financial relationships with AbbVie, Amgen, Bristol-Myers Squibb, Celgene, Eli Lilly, Gilead, GlaxoSmithKline, Janssen, Novartis, Pfizer, Takeda, and UCB. Dr. Gelfand reported serving as a consultant for AbbVie, Artax, Bristol-Myers Squibb, GlaxoSmithKline, and other companies.

Patients with psoriatic disease have significantly higher risks of myocardial infarction, stroke, and cardiovascular mortality than does the general population, yet research consistently paints what dermatologist Joel M. Gelfand, MD, calls an “abysmal” picture: Only a minority of patients with psoriatic disease know about their increased risks, only a minority of dermatologists and rheumatologists screen for cardiovascular risk factors like lipid levels and blood pressure, and only a minority of patients diagnosed with hyperlipidemia are adequately treated with statin therapy.

In the literature and at medical meetings, Dr. Gelfand and others who have studied cardiovascular disease (CVD) comorbidity and physician practices have been urging dermatologists and rheumatologists to play a more consistent and active role in primary cardiovascular prevention for patients with psoriatic disease, who are up to 50% more likely than patients without it to develop CVD and who tend to have atherosclerosis at earlier ages.

According to the 2019 joint American Academy of Dermatology (AAD)–National Psoriasis Foundation (NPF) guidelines for managing psoriasis “with awareness and attention to comorbidities,” this means not only ensuring that all patients with psoriasis receive standard CV risk assessment (screening for hypertension, diabetes, and hyperlipidemia), but also recognizing that patients who are candidates for systemic therapy or phototherapy — or who have psoriasis involving > 10% of body surface area — may benefit from earlier and more frequent screening.

CV risk and premature mortality rises with the severity of skin disease, and patients with psoriatic arthritis (PsA) are believed to have risk levels similar to patients with moderate-severe psoriasis, cardiologist Michael S. Garshick, MD, director of the cardio-rheumatology program at New York University Langone Health, said in an interview.

NYU Langone

Dr. Barbieri

In many cases, dermatologists and rheumatologists may be the primary providers for patients with psoriatic disease. So, “the question is, how can the dermatologist or rheumatologist use their interactions as a touchpoint to improve the patient’s well-being?” Dr. Barbieri said in an interview.

For the dermatologist, educating patients about the higher CVD risk fits well into conversations about “how there may be inflammation inside the body as well as in the skin,” he said. “Talk about cardiovascular risk just as you talk about PsA risk.” Both specialists, he added, can incorporate blood pressure readings and look for opportunities to measure lipid levels and hemoglobin A1c (HbA1c). These labs can easily be integrated into a biologic work-up.

“The hard part — and this needs to be individualized — is how do you want to handle [abnormal readings]? Do you want to take on a lot of the ownership and calculate [10-year CVD] risk scores and then counsel patients accordingly?” Dr. Barbieri said. “Or do you want to try to refer, and encourage them to work with their PCP? There a high-touch version and a low-touch version of how you can turn screening into action, into a care plan.”


 

Beyond traditional risk elevation, the primary care hand-off

Rheumatologists “in general may be more apt to screen for cardiovascular disease” as a result of their internal medicine residency training, and “we’re generally more comfortable prescribing ... if we need to,” said Alexis R. Ogdie, MD, a rheumatologist at the Hospital of the University of Pennsylvania, Philadelphia, and director of the Penn Psoriatic Arthritis Clinic.

Penn Medicine

Referral to a preventive cardiologist for management of abnormal lab results or ongoing monitoring and prevention is ideal, but when hand-offs to primary care physicians are made — the more common scenario — education is important. “A common problem is that there is underrecognition of the cardiovascular risk being elevated in our patients,” she said, above and beyond risk posed by traditional risk factors such as dyslipidemia, hypertension, metabolic syndrome, and obesity, all of which have been shown to occur more frequently in patients with psoriatic disease than in the general population.

Morsa Images/DigitalVision/Getty Images

‘Patients trust us’

Dr. Gelfand has been at the forefront of research on psoriasis and heart disease. A study he coauthored in 2006, for instance, documented an independent risk of MI, with adjusted relative risks of 1.29 and 3.10 for a 30-year-old patient with mild or severe disease, respectively, and higher risks for a 60-year-old. In 2010, he and coinvestigators found that severe psoriasis was an independent risk factor for CV mortality (HR, 1.57) after adjusting for age, sex, smoking, diabetes, hypertension, and hyperlipidemia.

Today, along with Dr. Barbieri, Dr. Ogdie, and others, he is studying the feasibility and efficacy of a proposed national, “centralized care coordinator” model of care whereby dermatologists and rheumatologists would educate the patient, order lipid and HbA1c measurements as medically appropriate, and then refer patients as needed to a care coordinator. The care coordinator would calculate a 10-year CVD risk score and counsel the patient on possible next steps.

In a pilot study of 85 patients at four sites, 92% of patients followed through on their physician’s recommendations to have labs drawn, and 86% indicated the model was acceptable and feasible. A total of 27% of patients had “newly identified, previously undiagnosed, elevated cardiovascular disease risk,” and exploratory effectiveness results indicated a successful reduction in predicted CVD risk in patients who started statins, Dr. Gelfand reported at the NPF meeting.

With funding from the NPF, a larger, single-arm, pragmatic “CP3” trial (NCT05908240) is enrolling 525 patients with psoriasis at 10-20 academic and nonacademic dermatology sites across the United States to further test the model. The primary endpoint will be the change in LDL cholesterol measured at 6 months among people with a 10-year risk ≥5%. Secondary endpoints will cover improvement in disease severity and quality of life, behavior modification, patient experience, and other issues.

“We have only 10-15 minutes [with patients] ... a care coordinator who is empathetic and understanding and [informed] could make a big difference,” Dr. Gelfand said at the NPF meeting. If findings are positive, the model would be tested in rheumatology sites as well. The hope, he said, is that the NPF would be able to fund an in-house care coordinator(s) for the long-term.

Notably, a patient survey conducted as part of exploratory research leading up to the care coordinator project showed that patients trust their dermatologist or rheumatologist for CVD education and screening. Among 160 patients with psoriasis and 162 patients with PsA, 76% and 90% agreed that “I would like it if my dermatologist/rheumatologist educated me about my risk of heart disease,” and 60% and 75%, respectively, agree that “it would be convenient for me to have my cholesterol checked by my dermatologist/rheumatologist.”

“Patients trust us,” Dr. Gelfand said at the NPF meeting. “And the pilot study shows us that patients are motivated.”
 

Taking an individualized, holistic, longitudinal approach

“Sometimes you do have to triage bit,” Dr. Gelfand said in an interview. “For a young person with normal body weight who doesn’t smoke and has mild psoriasis, one could just educate and advise that they see their primary care physician” for monitoring.

“But for the same patient who is obese, maybe smokes, and doesn’t have a primary care physician, I’d order labs,” he said. “You don’t want a patient walking out the door with an [undiagnosed] LDL of 160 or hypertension.”

Age is also an important consideration, as excess CVD risk associated with autoimmune diseases like psoriasis rises with age, Dr. Gelfand said during a seminar on psoriasis and PsA held at NYU Langone in December. For a young person, typically, “I need to focus on education and lifestyle … setting them on a healthy lifestyle trajectory,” he said. “Once they get to 40, from 40 to 75 or so, that’s a sweet spot for medical intervention to lower cardiovascular risk.”

Even at older ages, however, lipid management is not the be-all and end-all, he said in the interview. “We have to be holistic.”

One advantage of having highly successful therapies for psoriasis, and to a lesser extent PsA, is the time that becomes available during follow-up visits — once disease is under control — to “focus on other things,” he said. Waiting until disease is under control to discuss diet, exercise, or smoking, for instance, makes sense anyway, he said. “You don’t want to overwhelm patients with too much to do at once.”

Indeed, said dermatologist Robert E. Kalb, MD, of the Buffalo Medical Group in Buffalo, NY, “patients have an open mind [about discussing cardiovascular disease risk], but it is not high on their radar. Most of them just want to get their skin clear.” (Dr. Kalb participated in the care coordinator pilot study, and said in an interview that since its completion, he has been more routinely ordering relevant labs.)

Rheumatologists are less fortunate with highly successful therapies, but “over the continuum of care, we do have time in office visits” to discuss issues like smoking, exercise, and lifestyle, Dr. Ogdie said. “I think of each of those pieces as part of our job.”

In the future, as researchers learn more about the impact of psoriasis and PsA treatments on CVD risk, it may be possible to tailor treatments or to prescribe treatments knowing that the therapies could reduce risk. Observational and epidemiologic data suggest that tumor necrosis factor-alpha inhibitor therapy over 3 years reduces the risk of MI, and that patients whose psoriasis is treated have reduced aortic inflammation, improved myocardial strain, and reduced coronary plaque burden, Dr. Garshick said at the NPF meeting.

“But when we look at the randomized controlled trials, they’re actually inconclusive that targeting inflammation in psoriatic disease reduces surrogates of cardiovascular disease,” he said. Dr. Garshick’s own research focuses on platelet and endothelial biology in psoriasis.

Dr. Barbieri reported he had no relevant disclosures. Dr. Garshick reported consulting fees from Bristol-Myers Squibb, Kiniksa, Horizon Therapeutics, and Agepha. Dr. Ogdie reported financial relationships with AbbVie, Amgen, Bristol-Myers Squibb, Celgene, Eli Lilly, Gilead, GlaxoSmithKline, Janssen, Novartis, Pfizer, Takeda, and UCB. Dr. Gelfand reported serving as a consultant for AbbVie, Artax, Bristol-Myers Squibb, GlaxoSmithKline, and other companies.