Abstract

Epidermolysis bullosa aquisita (EBA) is a subepidermal bullous disorder mediated by autoantibodies targeting basement membrane zone (BMZ) anchoring fibrils. Although most EBA cases involve IgG antibodies directed against type VII collagen, rare cases of IgA-mediated and IgM-mediated presentations have been documented. Here, we present a case of skin fragility and mechanobullous eruption clinically and histologically most compatible with mixed IgA and IgM-mediated EBA. An 81-year-old woman with a three-year history of extremely fragile skin was admitted to for a right hip hemiarthroplasty status-post mechanical fall. Post-op, she was noted to have numerous shallow erosions in areas of tape placement and where she came in direct contact with operating room equipment. Lesional skin biopsy showed a cell-poor subepidermal bulla with minimal associated inflammatory infiltrate on hematoxylin and eosin. Perilesional direct immunofluorescence (DIF) revealed strong 3+ linear IgA, moderate 2+ linear IgM, and patchy weak 0-1+ IgG and fibrin along the BMZ. Serum immunobullous autoantibody studies were negative. The uncommon IgA subtype of EBA (IgA-EBA), previously considered a variant of linear IgA bullous dermatosis (LABD), features a subepidermal split accompanied by prominent neutrophilic infiltrate, occasional eosinophils, and linear anti-type VII collagen IgA deposition along the dermal side in salt-split skin. Rarer still are the linear IgM subtype of EBA (IgM-EBA) with only two cases reported and mixed IgA and IgG-mediated EBA with a single case reported. The accurate diagnosis of EBA can be challenging given its clinical overlap with other immunobullous disorders that involve autoantibodies targeting BMZ components. Our case highlights the complexities in acquiring an accurate diagnosis for immunobullous eruptions with overlapping clinical presentations, autoantibody subtyping, and target antigen specificity.

Financial Disclosure:
No current or relevant financial relationships exist.