Derm Dx: An asymptomatic rash on the lower extremities

A 27-year-old man presents with an asymptomatic rash of the lower extremities, which developed about 1 month prior. The rash started on the ankles and spread upward. Examination revealed reddish-brown macules of the lower extremities. The patient was afebrile, in good health, and took no oral medications or supplements.