Abstract

Bullous pemphigoid (BP), epidermolysis bullosa acquisita (EBA), and bullous systemic lupus erythematosus (SLE) are autoimmune bullous diseases with antibodies that target components of the epidermal basement membrane zone (BMZ). These autoantibodies target desmosomes or type VII collagen and frequently result in a linear n- or u-serrated pattern at the BMZ on direct immunofluorescence (DIF). Our objective was to better characterize the presence of u-serrated and n-serrated patterns in BP, EBA, and bullous SLE to aid in diagnosis and treatment. In this single-site retrospective review, we identified specimens by reviewing every digitized dermatopathology DIF specimen stored at our institution from 2004-2022. The following diagnoses were included: BP, EBA, bullous SLE, mucous membrane pemphigoid (MMP), gestational pemphigoid, linear IgA bullous disease, and ocular cicatricial pemphigoid. Three-hundred twenty-five specimens were eligible for this study. Two-hundred ninety-eight cases demonstrated n-serrated patterns, three demonstrated u-serrated patterns, and 24 were indeterminate. Ninety-six percent of BP cases had n-serrated waves; the remainder were indeterminate. Twenty percent of bullous SLE cases demonstrated u-serrated patterns, while 50% demonstrated n-serrated patterns. All three cases of EBA showed indeterminate serration patterns. Aside from bullous lupus cases, only one case with an indeterminate diagnosis (EBA vs. bullous SLE) had a u-serrated pattern. Our study confirms the 100% specificity of the u-serrated immunodeposition pattern in bullous lupus and EBA seen in prior studies, but further data is needed to estimate its sensitivity. Importantly, we found that an n-serrated immunodeposition pattern cannot rule out bullous lupus.