Buccal Mucosa as Substrate for Direct Immunofluorescence Should Be Included Early in the Diagnostic Work Up of Ocular Mucous Membrane Pemphigoid

ABSTRACT Background In ocular mucous membrane pemphigoid (MMP) direct immunofluorescence (DIF) represents the gold standard for definitive diagnosis. However, up to 50% of ocular MMP cases do not meet the immunopathological criteria. In addition, the risk of exacerbating conjunctival cicatrization makes ocular biopsy technically difficult to obtain. Despite current guidelines suggesting that biopsies could occasionally be taken from non‐ocular sites if the conjunctiva is inflamed, studies describing the use of buccal mucosa as a substrate for DIF are scarce. Objectives The aim of the present study was to describe the utility of DIF in buccal samples from patients with suspected ocular MMP and contraindication for conjunctival biopsy. Methods Medical records of patients with suspected ocular MMP were retrospectively reviewed. Inclusion criteria were (1) clinical diagnosis of ocular pemphigoid; (2) contraindication for conjunctival biopsy; (3) DIF performed on buccal mucosa; (4) ELISA tests for BP180 and BP230 at presentation. DIF results were compared with ELISA tests and clinical data. Results Nine patients met the inclusion criteria. DIF positivity was seen in four out of nine (44%) patients, confirming the diagnosis of ocular MMP. Three out of four (75%) patients with positive DIF were off treatment. By contrast, five out of five (100%) with non‐specific/negative DIF results were on prolonged (> 6 months) immunosuppressive therapy. Only one out of nine (11%) showed circulating anti‐BP180 Abs and anti‐BP230 Abs exceeding the cut‐off of 20 U/mL (44 and 88 U/mL, respectively). Conclusions Buccal DIF is a very attractive procedure for confirming diagnosis in suspected ocular MMP patients when conjunctival biopsy is unavailable and appears superior to BP180/BP230 ELISA. The higher prevalence of positive results in patients off‐therapy suggests that the diagnostic yield may improve if buccal DIF is performed before treatment.