A 33-year-old man comes to the office due to a rash. For the last several months, an increasing number of small lesions have appeared on his hands. The spots are associated with intermittent, mild itching but are otherwise asymptomatic. He uses electronic cigarettes regularly and drinks 3-5 alcoholic beverages on weekends. Vital signs are within normal limits. BMI is 32 kg/m². Skin examination findings are shown in the exhibit. Similar lesions are visible in other locations, including the scalp. Which of the following is the most likely diagnosis?

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11ec25c8_d388_885c_bc81_6de5a23fd760_MD0003_00 This patient has a chronic rash characterized by scaly, erythematous plaques consistent with psoriasis. Psoriasis is classically found on the extensor surfaces of the knees and elbows (large plaque) but can also occur on the scalp, hands, and trunk (eg, gluteal cleft) as small plaques. When psoriasis occurs on the hands, it is typically found on the dorsal surface and likely caused by frequent minor trauma (Köbner phenomenon). Other possible manifestations in the hands include nail changes (eg, pitting, subungual debris) and arthritic changes. (Choice A) Irritant contact dermatitis, which commonly affects the hands, presents with erythema, scaling, and fissuring. However, it does not form well-defined plaques and is unlikely to affect the scalp. fissuring (Choice B) Lichen planus presents with pink or purple plaques and papules. It is usually associated with severe pruritis and typically affects the volar surface of the wrists rather than the dorsum of the hands. Concurrent scalp lesions would be unusual. plaques and papules (Choice C) Molluscum contagiosum presents with small, skin-colored papules. The lesions are typically umbilicated and smooth rather than scaly. Children are affected more commonly than adults. skin-colored papules (Choice E) Scabies commonly affects the hands but presents with intensely pruritic papules and burrows on the interdigital spaces, palms, and flexor surface of the wrists. interdigital spaces Educational objective: Psoriasis is characterized by erythematous, scaly plaques. It is classically found on the extensor surfaces of the knees and elbows (large plaque) but can also occur on the scalp, hands, and trunk (eg, gluteal cleft) as small plaques. When psoriasis occurs on the hands, it is typically found on the dorsal surface, likely due to frequent minor trauma.

A 33-Year-Old Man Comes to the Office Due to a Rash