Abstract
Background Autoimmune vesiculobullous diseases (AIBDs) are a group of diseases characterized by blisters of the skin/mucosa due to the presence of circulating autoantibodies against antigens in the epidermis or the dermo-epidermal junction. Direct immunofluorescence (DIF) for immunoglobulin (Ig)G, IgC3, and IgA on fresh-frozen tissue is the gold standard diagnostic test for AIBDs. However, DIF in the absence of frozen tissue is challenging for the diagnosis of AIBDs. This study aimed to analyze the practical utility of DIF using paraffin-embedded skin biopsy rather than fresh frozen tissue for the diagnosis of AIBDs. Methodology This cross-sectional comparative study included 30 cases of AIBDs. DIF for IgG and IgA was performed on paraffin-embedded tissue (PE-DIF) after proteinase digestion on histopathologically confirmed 15 pemphigus vulgaris (PV), three pemphigus foliaceous (PF), four bullous pemphigoid (BP), three dermatitis herpetiformis (DH), three subcorneal pustular dermatosis (SCPD), and one case each of linear IgA disease and pemphigoid gestationis (PG). PE-DIF staining pattern was compared with the DIF on fresh frozen tissue (FF-DIF). Results All cases of PV and PF showed an intercellular IgG chicken wire staining pattern similar to FF-DIF. However, background staining was more intense in PV cases while less intense in PF cases. Three BP cases showed linear IgG staining in PE-DIF. DH, SCPD, linear IgA disease, and PG cases did not show IgG positivity. Out of three DH cases, two cases showed granular IgA positivity while linear IgA positivity along the basement membrane was seen in a single case of linear IgA disease. Negative IgG staining was observed in SCPD. Immunofluorescence in PE-DIF was rapidly deteriorating than in FF-DIF. Conclusions DIF done on paraffin-embedded tissue can be used as a supplement and salvage technique with histopathology for the diagnosis of AIBDs, particularly when a cryostat facility for frozen tissue is not available and the patient is unable to undergo a second biopsy procedure.