Paraneoplastic pemphigus associated with fatal bronchiolitis obliterans and appearance of anti‐BP180 antibodies in the late stage of the disease

Paraneoplastic pemphigus (PNP) is an autoimmune bullous disease, which associates mainly with lymphoproliferative neoplasms. Bronchiolitis obliterans (BO) with progressive respiratory failure is a significant cause of death in PNP. We report a case of PNP associated with follicular lymphoma and BO, which showed findings suggesting coexistence of bullous pemphigoid (BP). The patient showed bullous and ulcerative lesions on the lips and oral cavity, and flaccid blisters on the trunk and thighs associated with anti-desmoglein (Dsg)3 antibodies. At later disease stage after commencement of treatment, anti-BP180 antibodies and tense blister formation were observed. It was proposed that persistent interface dermatitis is the first event in PNP, and subsequently induce the production of autoantibodies to Dsg and components of the basement membrane zone, resulting in both intraepidermal and subepidermal blisters. We speculate that interface dermatitis caused by autoreactive T cells induced autoantibody production against Dsg3, and subsequently against BP180.