Complement fragment 4d staining as a potential diagnostic tool for bullous disorders with esophageal involvement

Abstract

Mucous membrane pemphigoid (MMP) is an autoimmune blistering disorder that can affect the esophagus, leading to complications such as stricture or stenosis. The diagnosis of MMP is particularly challenging due to its overlapping clinical features with other subepithelial blistering diseases and the limitations of established diagnostic techniques. While direct immunofluorescence (DIF) remains the gold standard, it requires fresh tissue samples which are not always available, especially in cases without active mucosal or cutaneous lesions. Complement fragment 4d (C4d) immunohistochemistry (IHC) on formalin-fixed tissue has shown diagnostic utility in bullous pemphigoid but is less explored for MMP. This case demonstrates that C4d IHC may be a useful ancillary test to support MMP diagnosis, particularly for mucosal or esophageal biopsies received in formalin, offering a potential diagnostic pathway in the absence of fresh biopsy samples