Cocaine-Induced Plasma Cell Dermatomucositis (CI-PCDM): Clinical and Histopathological Features of a UK Cohort

BACKGROUND: Cocaine-induced plasma cell dermatomucositis (CI-PCDM) is an emerging clinical entity involving ulcerated, nodular lesions of the nasolabial region. While it shares some clinical features with other cocaine-induced midline disorders, CI-PCDM is increasingly recognized as a distinct inflammatory process characterized by specific histological patterns. METHODS: This retrospective, multi-center case series identified six patients from two UK pathology archives. Data were retrieved from electronic records and medical photography, while histopathology and immunohistochemistry reports were reviewed to evaluate diagnostic features and exclude alternative pathologies. RESULTS: The cohort consisted of five males and one female (mean age 50.3 years). Patients typically presented with exophytic, ulcerated masses in the nasolabial area. Cocaine exposure was confirmed in all cases through clinical history or toxicology. Histology consistently revealed dense, polyclonal plasmacytic infiltrates in perivascular and periadnexal distributions. Serological and immunohistochemical variations were noted, including instances of antibody positivity and altered protein ratios. Management strategies, including medical and surgical interventions, generally resulted in partial clinical improvement. CONCLUSION: This first UK-based case series highlights CI-PCDM as an emerging diagnostic challenge. The prominent cellular infiltrate may reflect a chronic, antigen-driven immune response, potentially related to localized cytokine activity triggered by cocaine and/or certain adulterants, such as benzocaine. The clinical presentation often mimics other common mucocutaneous lesions, necessitating thorough clinicopathological correlation. Increased clinical awareness is essential for accurate identification and for establishing optimal management protocols for affected patients.