Correlation of Serum and Tissue Eosinophils and Immunoglobulin E with Disease Severity in Bullous Pemphigoid: A Prospective Observational Study

Abstract Background: Bullous pemphigoid (BP) is a subepidermal autoimmune blistering disorder in which eosinophils and immunoglobulin E (IgE) are implicated in disease pathogenesis and are potential markers of disease activity. Aim and Objective: To evaluate the association of serum and tissue eosinophils and IgE levels with disease severity in BP. Patients and Methods: A prospective observational study was conducted from October 2023 to December 2024 at a tertiary care center in South India. Thirty-five patients with clinically and histopathologically confirmed BP were included, disease severity was assessed using the bullous pemphigoid disease activity index (BPDAI). Serum eosinophil counts, serum IgE levels, histopathology, and direct immunofluorescence (DIF) findings for IgE deposition at the basement membrane zone (BMZ) were analyzed. Results: Higher disease activity (BPDAI >20/372) was observed in 77% of patients (27/35). Fisher’s exact test showed no significant association between higher BPDAI scores and elevated serum eosinophil counts (>500 cells/μL), elevated serum IgE levels (>500 IU/mL) or DIF-detected IgE deposition at BMZ. However, biopsy evidence of eosinophil-predominant inflammatory infiltrates was significantly associated with higher disease activity (odds ratio [OR] =9.638; 95% confidence interval [CI]: 1.613–56.952; P = 0.029). Limitations: Small sample size, cross-sectional analysis, biopsy site variability and immunofluorescence methodology may have limited detection of IgE-related associations. Sample size calculation was based on the expected prevalence of IgE reactivity, but the significant association identified in our study involved tissue eosinophilia, for which the study was not specifically powered. Conclusion: Eosinophilic infiltration is strongly associated with BP severity, reinforcing its pathogenic role. Although serum IgE was frequently elevated, its correlation with severity was more evident when also detected in tissue.