Leucogen-induced pemphigus foliaceus: the first case report.

Drug-induced pemphigus (DIP) is a distinct subgroup of rare autoimmune blistering disorders, most commonly associated with thiol-containing medications such as penicillamine and captopril. Currently, an increasing number of pemphigus cases induced by non-thiol and non-phenolic drugs have been reported. Herein, we describe a 61-year-old woman with stage IV breast cancer who developed pemphigus foliaceus (PF) after receiving leucogen administration during anti-HER2 (THP) therapy. Cutaneous lesions resolved after leucogen withdrawal and corticosteroid treatment but recurred upon drug re-administration, confirming a probable causal relationship. Histopathological examination and direct immunofluorescence confirmed PF, characterized by intercellular IgG deposition and elevated anti-desmoglein 1 (anti-Dsg1) autoantibody titers. This case highlights that leucogen, a sulfur-containing agent with a thiazolidine-related structure, may represent a potential trigger for DIP, although the underlying mechanism remains speculative.