Histopathologic Overlap Between Bullous Lupus Erythematosus and Linear IgA Bullous Dermatosis: A Comparative Study.

Bullous lupus erythematosus (BLE) and linear IgA disease (LAD) are rare autoimmune subepidermal blistering diseases, with overlapping features despite different pathogenetic mechanisms. Diagnosis is based on immunofluorescence and serology. This retrospective study was undertaken to compare the histopathologic features of BLE and LAD (11 cases each). The mean age was 36 years in both groups, and female preponderance was noted in BLE. Clinically, all cases presented as tense, itchy blisters distributed over the trunk, face, and extremities. Subepidermal neutrophil-rich blisters were seen in 60% BLE and 54.54% LAD cases. Eosinophils in the blisters were noted in 4 cases (36.4%) of linear IgA bullous dermatosis, but not in any of the BLE cases. The adjacent epidermal changes noted include spongiosis (33%; 40%), papillary microabscesses (22%; 20%), and basal tagging by neutrophils (77%; 70%). Superficial perivascular inflammation was seen in all cases while deep perivascular inflammation was observed in 54% BLE and 36% LAD cases. Lymphocytes were the predominant infiltrate. Increased dermal mucin was seen in 60% BLE and 45% LAD cases. None of the histopathologic features showed a statistically significant difference between the 2 groups. Hence, histopathology alone is of limited value in distinguishing the 2 groups. Diagnosis rests on immunofluorescence and serologic findings, which should be used even in cases that seem to be classic LAD or patients without history of systemic lupus erythematosus.