Two cases of cutaneous‐type pemphigus vulgaris and a case of pemphigus foliaceus without mucosal involvement despite high anti‐desmoglein 3 autoantibody levels

Abstract Pemphigus is an autoimmune blistering disease with two major subtypes, pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Although most patients with PV show oral lesions, cutaneous type PV (C‐PV) is a rare subtype clinically characterized by predominant cutaneous involvement with no or subtle mucosal lesions. Patients with PF present with only skin involvement; they do not have mucosal lesions. Serologically, autoantibodies against desmoglein (Dsg) 3 and Dsg1 are observed in C‐PV whereas PF is associated with anti‐Dsg1 antibodies only. Herein, we describe three cases of pemphigus presenting with predominant skin lesions and no mucosal involvement despite high anti‐Dsg 3 autoantibody levels in chemiluminescent enzyme immune assays (CLEIAs). In addition, anti‐Dsg 1 autoantibodies were positive in patients 2 and 3, but negative in patient 1 based on CLEIAs. Histological examination of the skin showed suprabasal acantholysis in patients 1 and 2, and blister formation in the upper epidermis in patient 3. Histopathology of the oral membrane in patients 1 and 2 showed subtle acantholysis in the suprabasal layer. Thus, we diagnosed patients 1 and 2 as having cutaneous type PV and patient 3 as having PF. Ethylenediaminetetraacetic acid‐treated enzyme‐linked immunosorbent assay demonstrated a low proportion of anti‐Dsg3 autoantibodies recognizing Ca2+‐dependent epitopes, antibodies against which are thought to be the main contributor to acantholysis. Thus, along with Dsg1 antibodies, weak anti‐Dsg3 antibodies could induce acantholysis in the skin, but they are insufficient to induce mucosal lesions.