Utility of Direct Immunofluorescence in Cutaneous Autoimmune Bullous Disorders.

Background Autoimmune bullous disorders (AIBD) are a heterogeneous group of disorders with substantial clinical overlap associated with blistering of skin or mucosa. Aims The present study aimed to study the histopathological spectrum and evaluate the utility of direct immunofluorescence (DIF) on snap-frozen and paraffin-embedded sections in resolving the differential diagnosis of AIBD and connective tissue disorders of the skin. We also compared the efficacy of DIF on paraffin versus the snap-frozen sections in diagnosing AIBD. Methods The present study was conducted for three years (2017-2019) and included 27 biopsies. We also included a retrospective analysis that included 25 biopsies collected over three years (2014-2017). Histopathological examination and DIF were conducted on all samples. Results Pemphigus vulgaris was the most common autoimmune cutaneous disorder constituting 37% (n = 10) in prospective and 36% (n = 9) in the retrospective study. DIF showed a specificity of 81.25% in our prospective study. While on the paraffin-embedded sections, it showed a specificity of 66.6% in our retrospective study. In the prospective study, DIF on paraffin-embedded sections had a positivity rate of 43.75% as compared to 81.25% in DIF done on snap-frozen sections. Conclusion DIF is a sensitive tool for the diagnosis as well as distinguishing immune-mediated bullous disorders from other lesions primarily when performed on snap-frozen sections. The diagnostic yield is enhanced by DIF in cases that pose a diagnostic dilemma both clinically and histologically. The final diagnosis depends on all clinical, histopathological and immunofluorescence findings.