A Persistent Flexural Dermatosis Unmasking Adult Langerhans Cell Histiocytosis: A Case Report.

Langerhans cell histiocytosis (LCH) is a rare histiocytic neoplasm that may present with isolated cutaneous involvement or multisystem disease. In adults, cutaneous manifestations are often polymorphic and may mimic more common dermatologic conditions, leading to delayed diagnosis. A 41-year-old woman with a history of treated breast carcinoma presented with a two-year history of chronic erosive lesions involving the vulvar and intertriginous regions. Additional lesions affected the scalp, retroauricular folds, umbilicus, and external auditory canals. Histopathological examination of a vulvar biopsy, supported by positive CD1a and S100 immunostaining, confirmed the diagnosis of LCH. A comprehensive extension workup revealed no evidence of visceral, pulmonary, lymph node, or skeletal involvement. The patient was treated with topical clobetasol propionate, local wound care, and treatment of secondary bacterial superinfection, resulting in marked improvement of the vulvar and intertriginous lesions during follow-up. Adult cutaneous LCH remains a diagnostic challenge because of its ability to mimic inflammatory and infectious dermatoses, particularly when flexural and genital areas are affected. Histopathological examination with immunohistochemical confirmation is essential for establishing the diagnosis and guiding further evaluation. LCH should be considered in the differential diagnosis of persistent erosive vulvar and intertriginous lesions that are unresponsive to conventional therapies. Early biopsy is crucial to avoid diagnostic delay and to ensure appropriate staging and management.