Abstract

Autoimmune intraepidermal blistering diseases are acantholytic processes characterized by immunoglobulins directed against keratinocyte basement membrane proteins. Their subclassification is based on patterns of immune complex deposition delineating distinct disease entities. Autoantigen heterogeneity, overlapping clinical and histopathologic features, and relative paucity of cases pose diagnostic challenges and hinder elucidation of pathogenic mechanisms. Herein we report a rare case of linear IgA/IgG bullous dermatosis (LAGBD) in a 90-year-old woman with a large rectal tumor with no histologic diagnosis. The patient presented with new-onset generalized tense bullae which evolved over a period of weeks. Serum IgE was elevated at 423 IU/mL (Reference <100 IU/mL). Serum anti-bullous pemphigoid antigen 1 (BPAG1; BP230) and anti-bullous pemphigoid antigen 2 (BPAG2; BP180) IgG antibodies were elevated at >120 RU/mL and 200 RU/mL (Reference <20 RU/mL), respectively. Clinically, a diagnosis of bullous pemphigoid was favored. Histopathologic examination of a skin punch biopsy specimen from the abdomen showed subepidermal clefting with superficial lymphocytic inflammation, rare neutrophils, and conspicuous eosinophilic infiltrate. Direct immunofluorescence showed linear 2-3+ immunoreactivity for IgA, IgG, and C3 along the basement membrane, consistent with LAGBD. Few previous reports have described LAGBD, some in patients with underlying malignancies. While a specific mechanism is not known, it has been hypothesized that paraneoplastic or therapy-related tissue damage can unmask basement membrane epitopes such collagen subtypes. In contrast to the more prevalent paraneoplastic mucous membrane pemphigoid, the lesions in this case were cutaneous, and no mucosal lesions were identified. Documentation of instances of LAGBD is critical for advancing the understanding of this unusual disease process.

Financial Disclosure:
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