Arm and neck rash

The manifestation of what appeared to be an exaggerated sunburn with associated pruritis and blistering (made worse after sun exposure), along with the recent initiation of HCTZ, led to the diagnosis of a phototoxic drug reaction.

There are 2 principal mechanisms of photosensitive drug reactions, phototoxic and photoallergic. Phototoxic reactions occur when the drug absorbs UVA light, causing a chemical reaction that produces either free radicals or stable photoproducts, both of which can cause DNA and tissue damage. This mechanism is more common; the time of onset between exposure and reaction is minutes to hours (as seen with this patient), and the reaction manifests with an exaggerated sunburn appearance.¹

Photoallergic reactions typically occur by a delayed-immune response, mediated by photoallergic-specific T-cells reacting to photohaptens. This mechanism is less common, and the time of onset is greater than 24 hours. Photoallergic reactions often present as an eczematous dermatitis and can involve regions not directly exposed to sun.

In this case, the presumed offending agent—HCTZ—was discontinued, and the patient was advised to take sun-protective measures and use topical emollients, cool compresses, and oral analgesics for his acute symptoms. Photoallergic reactions look less like a discrete sunburn and can be treated symptomatically with topical or oral steroids. In addition, the implicated medication should be discontinued.

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Text courtesy of Amanda Yaney, MD, and Daniel Stulberg, MD, Department of Family and Community Medicine, University of New Mexico School of Medicine, Albuquerque. Image courtesy of Daniel Stulberg, MD.

The manifestation of what appeared to be an exaggerated sunburn with associated pruritis and blistering (made worse after sun exposure), along with the recent initiation of HCTZ, led to the diagnosis of a phototoxic drug reaction.

There are 2 principal mechanisms of photosensitive drug reactions, phototoxic and photoallergic. Phototoxic reactions occur when the drug absorbs UVA light, causing a chemical reaction that produces either free radicals or stable photoproducts, both of which can cause DNA and tissue damage. This mechanism is more common; the time of onset between exposure and reaction is minutes to hours (as seen with this patient), and the reaction manifests with an exaggerated sunburn appearance.¹

Photoallergic reactions typically occur by a delayed-immune response, mediated by photoallergic-specific T-cells reacting to photohaptens. This mechanism is less common, and the time of onset is greater than 24 hours. Photoallergic reactions often present as an eczematous dermatitis and can involve regions not directly exposed to sun.

In this case, the presumed offending agent—HCTZ—was discontinued, and the patient was advised to take sun-protective measures and use topical emollients, cool compresses, and oral analgesics for his acute symptoms. Photoallergic reactions look less like a discrete sunburn and can be treated symptomatically with topical or oral steroids. In addition, the implicated medication should be discontinued.

‌

Text courtesy of Amanda Yaney, MD, and Daniel Stulberg, MD, Department of Family and Community Medicine, University of New Mexico School of Medicine, Albuquerque. Image courtesy of Daniel Stulberg, MD.

The manifestation of what appeared to be an exaggerated sunburn with associated pruritis and blistering (made worse after sun exposure), along with the recent initiation of HCTZ, led to the diagnosis of a phototoxic drug reaction.

There are 2 principal mechanisms of photosensitive drug reactions, phototoxic and photoallergic. Phototoxic reactions occur when the drug absorbs UVA light, causing a chemical reaction that produces either free radicals or stable photoproducts, both of which can cause DNA and tissue damage. This mechanism is more common; the time of onset between exposure and reaction is minutes to hours (as seen with this patient), and the reaction manifests with an exaggerated sunburn appearance.¹

Photoallergic reactions typically occur by a delayed-immune response, mediated by photoallergic-specific T-cells reacting to photohaptens. This mechanism is less common, and the time of onset is greater than 24 hours. Photoallergic reactions often present as an eczematous dermatitis and can involve regions not directly exposed to sun.

In this case, the presumed offending agent—HCTZ—was discontinued, and the patient was advised to take sun-protective measures and use topical emollients, cool compresses, and oral analgesics for his acute symptoms. Photoallergic reactions look less like a discrete sunburn and can be treated symptomatically with topical or oral steroids. In addition, the implicated medication should be discontinued.

‌

Text courtesy of Amanda Yaney, MD, and Daniel Stulberg, MD, Department of Family and Community Medicine, University of New Mexico School of Medicine, Albuquerque. Image courtesy of Daniel Stulberg, MD.