Pathogenesis & Mucosal-Cutaneous Phenotypes

Pemphigus vulgaris (PV) is an autoimmune intraepidermal blistering disorder caused by IgG4/IgG1 autoantibodies against desmosomal cadherins (Dsg3 in mucosal-dominant; Dsg3 + Dsg1 in mucocutaneous PV) with positive Nikolsky sign.

Diagnostic Gold Standard

1. Lesional Edge 4 mm Punch (10% Formalin for H&E): Suprabasal acantholysis with basal keratinocytes attached to the basement membrane like a 'row of tombstones'.
2. Perilesional 4 mm Punch (Michel's Medium for DIF): Intercellular 'fishnet' IgG and C3 deposition across the epidermis.
3. First-Line Management: Rituximab (1,000 mg IV Day 1 & Day 15 or modified IADVL protocol) + tapering prednisolone; always screen HBsAg + Anti-HBc Total prior to infusion.