Speakers - 2026

Title: Immunobullous crossroads: Navigating serological overlap between pemphigus and pemphigoid without paraneoplastic autoimmune multiorgan syndrome

Abstract

We present a rare case of an autoimmune blistering disease with serological features of both pemphigus vulgaris (PV) and mucous membrane pemphigoid (MMP), in the absence of paraneoplastic autoimmune multiorgan syndrome (PAMS). A XX aged patient presented with painful oral erosions (desquamative gingivitis, and cutaneous erosions). Clinically, the distribution and morphology of lesions were consistent with PV. Histopathology of a lesional biopsy showed (suprabasal acantholysis with acantholytic keratinocytes, while direct immunofluorescence (DIF) demonstrated intercellular IgG deposition throughout the epithelium, confirming a diagnosis of pemphigus). However, serological testing via ELISA revealed high titres of anti-desmoglein-3 (Dsg3) antibodies, along with positive anti-BP180 antibodies, raising the possibility of a concurrent pemphigoid process. No linear IgG or C3 deposition was observed along the basement membrane zone on DIF, and there was no subepithelial clefting histologically, suggesting against MMP. Given the dual serological profile, PAMS was considered. Indirect immunofluorescence on rat bladder epithelium and immunoblotting for envoplakin and periplakin were performed, but all results were negative. Comprehensive malignancy screening clinically was also unremarkable. Hence a fully body CT scan was necessary. The presence of autoantibodies targeting both desmosomal and hemidesmosomal antigens in the absence of clinical or histologic features of pemphigoid or PAMS may suggests epitope spreading as a likely underlying mechanism. Chronic mucosal inflammation may have led to exposure of normally sequestered basement membrane zone antigens, resulting in a broadened autoimmune response. The patient responded well to systemic immunosuppressive therapy, with no progression to a pemphigoid phenotype over time. This case highlights the diagnostic complexity of autoimmune blistering diseases and emphasises the need for integrated clinical, histological, and immunological assessment and multidisciplinary approach. Further research is needed to understand the significance and long-term implications of overlapping autoantibody profiles in these disorders and biomechanisms underpinning cases like this.