Acute Localized Exanthematous Pustulosis (ALEP) Caused by Topical Application of Minoxidil

Acute Localized Exanthematous Pustulosis (ALEP) is a rare skin reaction characterized by the sudden onset of multiple, small, sterile, non-follicular pustules in an erythematous and edematous base succeeding systemic drug administration. ALEP is considered a subtype of Acute Generalized Exanthematous Pustulosis (AGEP), although the exact pathogenic mechanism of the disease remains poorly defined. Numerous drugs have been implicated in the pathogenesis of ALEP, while contact mechanisms have also been reported. Herein, we describe the first case of ALEP attributed to minoxidil in a female patient with androgenetic alopecia. The positivity of patch tests and the topical application of minoxidil proposes a contact-induced hypersensitivity reaction. Identifying new agents—including minoxidil—which serve as inducers of drug-specific T-cell-mediated responses in the clinical spectrum of ALEP, adds further value in understanding the complex, yet unknown, pathophysiological mechanisms of this rare drug hypersensitivity reaction.