PresentationThe rash that caused a 43-year-old man to be referred to our clinic produced no discomfort, but it signalled a very rare and dangerous disease. Over the previous 6 months he had developed a progressive papular eruption on his trunk, extremities, and genitalia. It did not interfere with his daily activities, and he denied itching or burning. The lesions, about 5 mm in size, were initially dome-shaped red papules covered by normal epidermis (Figure). After a few days, the papules became...