Fixed Drug Eruption

A 35-year-old man presented with a 10-day history of a cutaneous lesion on the left anterior chest. Examination revealed an annular, scaly, blistering, violaceous plaque, 5 cm in diameter, with an erythematous periphery. The lesion had appeared 24 hours after the patient began a self-prescribed course of oral trimethoprim–sulfamethoxazole for a respiratory tract infection. Six months earlier, an identical lesion had appeared in the same location after the patient had taken the same drug for 3 days. This first lesion healed after 3 weeks, but residual hyperpigmentation remained. On the basis of this characteristic presentation, a diagnosis of fixed drug . . .