A 22-Year-Old Man with an Itchy Patch of Skin

A 22-year-old man presents to urgent care with a round, hyperpigmented patch on his arm. He reports that it’s “itchy,” and that it appeared soon after taking a second dose of a sulfonamide he’s taking for a persistent sinus infection.

View the photo and consider what your diagnosis and next steps would be. Resolution of the case is described on the next page.