Kidney Outcomes in Autoimmune Blistering Diseases: Comparative Real-World Cohort Study of Bullous Pemphigoid and Pemphigus Vulgaris

Background: Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are autoimmune blistering skin disorders that may share underlying immunologic mechanisms with glomerular disease. Although membranous nephropathy has been reported in BP, population-based data on kidney outcomes in these conditions are limited. Methods: Using the TriNetX Global Collaborative Network, we conducted a retrospective cohort study across 147 healthcare organizations. We identified adults (≥18 years) with a new diagnosis of BP (ICD-10: L12.0) or PV (L10.0) between 2005 and 2025. Patients with pre-existing kidney disease including glomerular disease, CKD, dialysis, or kidney transplant, were excluded. Renal outcomes were assessed 12–24 months after diagnosis. Primary outcomes included new diagnoses of chronic kidney disease (CKD; N18.x), acute kidney injury (AKI; N17), glomerulonephritis (GN; N00–N08), hematuria (R31), and proteinuria (R80). Secondary outcomes included dialysis, kidney biopsy, and all-cause mortality. Kaplan-Meier analysis was used to evaluate renal event-free survival. Results: The BP cohort (n = 29,801) had higher incidence rates of CKD (6.8% vs 3.0%), AKI (3.3% vs 1.7%), and hematuria (1.5% vs 0.1%) compared to the PV cohort (n = 10,801). Proteinuria rates were similar (0.6% vs 0.5%). GN was identified in 0.06% of BP patients and not observed in PV. No dialysis or kidney biopsies were recorded in either group. All-cause mortality was higher in BP (4.2% vs 1.5%). Kaplan-Meier curves showed reduced renal event-free survival in BP patients, particularly for CKD and AKI (CKD-free survival: BP 87.8% vs PV 95.6%). Conclusion: This real-world analysis suggests that patients with bullous pemphigoid may be at increased risk for adverse kidney outcomes, including CKD, AKI, and hematuria, compared to those with pemphigus vulgaris. While causality cannot be inferred, these findings highlight a potential renal association in BP and support the need for closer kidney function monitoring in patients with autoimmune blistering skin diseases.