New-onset bullous rash.

Volume 91, Number 4 www.aafp.org/afp American Family Physician 231 A 63-year-old man presented with an asymptomatic rash that began four days earlier, one day after he was treated for an abscess on his right abdomen. The abscess was treated by incision and drainage, and he was prescribed trimethoprim/sulfamethoxazole because he had a history of methicillin-resistant Staphylococcus aureus infection. Physical examination revealed multiple large, erythematous, sharply demarcated circular plaques, some with tense bullae in the center, on his trunk and extremities (Figures 1 and 2). There was no mucosal involvement. Question Based on the patient’s history and physical examination, which one of the following is the most likely diagnosis?