The Diagnostic Journey of Mucous Membrane Pemphigoid: Referral Pathways and Diagnostic Delay at a Regional Tertiary Dermatology Center in Japan

Mucous membrane pemphigoid is a rare autoimmune blistering disease that may involve multiple mucosal sites and is often diagnosed after substantial delay. We retrospectively reviewed 23 patients with mucous membrane pemphigoid seen at Toyama University Hospital between January 2016 and January 2026 to characterize their clinical and immunopathological features, referral pathways, and diagnostic delays. Oral involvement was present in all patients, and nine (39.1%) had high-risk disease. IgA deposition on direct immunofluorescence was detected in eight patients (34.8%) and was associated with high-risk disease (75.0% vs. 20.0%; p = 0.023) and differed across severity categories (p = 0.034). Oral symptoms were the initial presentation in 17 patients (73.9%), and dentistry was the most common first specialty consulted (56.5%). Gingivitis, periodontitis, or stomatitis was recorded at the first medical institution in 12 patients (52.2%), whereas autoimmune blistering disease was suspected in only three (13.0%). Median delays from symptom onset to the first medical consultation (patient delay), from the first consultation to definitive diagnosis (professional delay), and from symptom onset to definitive diagnosis (total diagnostic delay) were 1, 7, and 10 months, respectively. Professional delay was significantly longer than patient delay (p = 0.010) and exceeded it in 17 patients (73.9%). These findings from a regional tertiary dermatology center highlight professional delay as the predominant component of diagnostic delay and identify an exploratory association between IgA deposition on direct immunofluorescence and greater disease severity.