Utility of Direct Immunofluorescence Studies in Subclassification of Autoimmune Sub-Epidermal Bullous Diseases: A 2-Year Study in a Tertiary Care Hospital.

Objective: Sub-epidermal bullous disorders belong to immunobullous diseases which develop as a result of autoantibody action against epidermal basement membrane proteins. Clinically, they are tense bullae and do not rupture easily. They are classified into various forms based on histopathology and direct immunofluorescence patterns. This study was undertaken to assess the incidence of various sub-epidermal bullous disorders and the utility of direct immunofluorescence in accurately classifying them, and to study the intensity and pattern of immunofluorescence in various sub-epidermal bullous disorders Material and Method: A 2-year study of 38 cases of sub-epidermal bullous disorders sent for direct immunofluorescence studies formed the study group. The specimens were processed as per standard protocols. The clinical details were obtained from case files and requisition sent for histopathological and direct immunofluorescence studies.

Results: Thirty-eight patients were diagnosed to have sub-epidermal bullous disorders over the period of 2 years. Twenty five cases of Bullous Pemphigoid, 5 cases of Dermatitis Herpetiformis, 3 cases of Linear IgA Bullous disorder, 2 cases of Bullous Systemic Lupus Erythematoses and 1 case each of Epidermolysis Bullosa Acquisita, Cicatricial Pemphigoid and Pemphigus Gestationis was diagnosed. Positive direct immunofluorescence was seen in 91.3% of the cases.

Conclusion: Histopathology alone cannot classify sub-epidermal bullous disorders and direct immunofluorescence studies are mandatory in all of them. Bullous Pemphigoid needs to be distinguished from Epidermolysis Bullosa Acquisita which requires Salt split direct immunofluorescence studies. Dermatitis Herpetiformis, Bullous Systemic Lupus Erythematosus and Linear IgA Bullous disorder show more or less similar histological picture with neutrophilic microabscess. Direct immunofluorescence studies help in the majority of cases but further testing such as immunoblotting, immunoelectron microscopy or indirect immunofluorescence becomes essential in cases with overlapping features.