Cocaine-Induced Dermatomucositis: Clarifying Diagnostic Controversies and Introducing IgG4 Positivity as a New Histopathological Feature

Cocaine-induced dermatomucositis is a recently described clinical entity with significant controversy regarding its diagnostic criteria and pathophysiology. While previous reports have identified a distinct pattern of chronic inflammatory mucocutaneous lesions in people who use cocaine, the absence of standardized diagnostic markers has led to inconsistencies in classification. This case series aims to clarify and unify the defining characteristics of cocaine-induced dermatomucositis by analyzing its clinical presentations, histopathologic findings, and immunologic features. Notably, we introduce immunoglobulin G4 (IgG4) positivity as a newly observed characteristic, challenging previous assumptions that excluded IgG4-related immune responses from its pathogenesis. By consolidating clinical and histologic patterns, this study contributes to the ongoing effort to establish cocaine-induced dermatomucositis as a distinct and recognizable disorder, paving the way for improved diagnosis and management.