Solitary Fixed Drug Eruption Caused by Finasteride

This document describes a case of a 39-year-old Japanese male who developed a solitary fixed drug eruption (FDE) on the penile shaft after taking finasteride for androgenic alopecia. An oral challenge test with finasteride reproduced the symptomatic eruption at the previously affected skin site. FDE is a unique skin reaction characterized by reappearing, well-defined lesions at exactly the same site when the causative medication is repeated. The pathogenesis of the disease remains enigmatic, although recent research suggests that the involvement of a restricted T cell population the interferon-y-producing CD8+ phenotype-mediated by a drug-specific antigen presentation in the lesional skin. The conclusion is that dermatologists should urgently recognize the possible incidence of FDE caused by this generally approved drug.