Direct Immunofluorescence in Immunobullous Disorders of Skin With Histopathological Correlation Among Patients Attending a Tertiary Care Center.

BACKGROUND: Autoimmune blistering diseases (AIBDs) are a heterogeneous group of disorders characterized by autoantibody-mediated damage to skin and mucous membranes. Accurate diagnosis relies on a combination of clinical, histopathological, and immunopathological findings. Direct immunofluorescence (DIF) is a cornerstone in the diagnosis of AIBDs, as it enables visualization of in vivo-bound immunoreactants. AIM: This study aimed to assess the histopathological patterns and DIF findings among patients presenting with vesiculobullous lesions, focusing on the distribution, pattern, intensity, and type of antibody deposition. METHODS: A total of 30 biopsy specimens from patients with clinically suspected vesiculobullous disorders were analyzed. Routine histopathology was performed, followed by DIF using anti-IgG, IgA, and C3 conjugates. Data on the pattern (linear basement membrane zone (BMZ) vs. intercellular (ICS)), intensity (weak, moderate, strong), and type of immunoglobulin deposition were recorded and analyzed. RESULTS: Among the 30 cases, bullous pemphigoid (n=13) was the most common, followed by pemphigus vulgaris (n=5) and pemphigus foliaceous (n=4). DIF showed positivity in 20 cases (66.7%). Bullous pemphigoid exhibited a linear BMZ pattern with IgG and C3 deposition, showing moderate intensity in 10 and weak intensity in 3 cases. Pemphigus vulgaris and pemphigus foliaceous showed ICS IgG deposition, with pemphigus foliaceous also demonstrating weak IgA positivity. Granular C3 dermatosis showed BMZ C3 deposition with weak intensity. A highly significant association between IgG (p = 0.0001) and C3 (p = 0.002) positivity with specific histopathological diagnoses, while IgA showed no significant association (p = 0.987). CONCLUSION: DIF is an invaluable diagnostic tool that complements histopathology, enabling accurate differentiation of AIBDs based on antibody type and distribution pattern. Other blistering conditions, including subcorneal pustules and acute inflammatory lesions, showed no or minimal immunoglobulin deposition. These findings highlight the diagnostic utility of DIF in differentiating AIBDs based on the type and intensity of antibody deposition.