While severe stomatitis is usually a hallmark feature of PNP, it may present with the absence of oral manifestations. Proposed diagnostic criteria include the presence of mucosal lesions with or without cutaneous involvement, concomitant internal neoplasm, anti-plakin autoantibodies, histopathology with acantholysis and/or lichenoid interface changes, and direct immunofluorescence (DIF) with intercellular and/or basement membrane deposition of immunoglobulin G (IgG) or complement component-3 (C3). This evidence concerns the gene C3 and stomatitis.