Mucous membrane pemphigoid (MMP) is a rare autoimmune disorder characterized by blistering lesions affecting the mucous membranes. An accurate diagnosis of the condition is required to avoid therapeutic and diagnostic delay. This study aims to examine the diagnostic accuracy of direct immunofluorescence microscopy (DIM) in patients with suspected MMP.

This retrospective cohort study included a total of 787 patients with suspected MMP, along with at least one mucosal biopsy specimen for DIF and indirect IF. The primary outcome of the study was diagnostic accuracy of DIF and indirect IF in patients with MMP.

The findings showed that 67 patients (55.4%) with MMP had mono site involvement, with the oral site being most affected. There was no significant difference between the sensitivity of DIF on a perilesional buccal biopsy (89.3%) and normal buccal biopsy (76.7%). Furthermore, three patients with solitary ocular involvement demonstrated a positive DIF of the oral mucosa only. 6 patients had a negative mucosal DIF, and a skin biopsy confirmed the oral mucosa in them. In conclusion. Indirect IF on a human salt-split skin substrate (SSS) was less sensitive compared to SSS.

The research concluded that a mucosal biopsy for diagnosis of MMP had a high sensitivity, making it an effective technique to diagnose the condition.