Sex-Specific Autoimmune Comorbidity Patterns in Pemphigus Vulgaris and Bullous Pemphigoid: A Bicenter Retrospective...

Background and Objectives: While pemphigus vulgaris (PV) and bullous pemphigoid (BP) have been linked to autoimmune comorbidities, the spectrum and specificity of these associations remain uncertain. We aimed to investigate the prevalence and patterns of autoimmune diseases (AIDs) in patients with PV and BP compared with age- and sex-matched controls. Materials and Methods: We conducted a bicenter, retrospective case-control study including 287 PV patients with 1148 matched controls and 284 BP patients with 1137 matched controls. Autoimmune comorbidities were identified through medical record review, and disease-specific as well as system-level associations between PV, BP, and AIDs were assessed. Results: Overall AID prevalence was lower in PV (9.4%) and BP (8.1%) than in controls (18% and 15%, respectively; p < 0.001 and p = 0.002). PV was associated with Graves' disease (adjusted OR: 3.16, 95% CI: 1.24-8.06), especially in females. BP was associated with Hashimoto thyroiditis (adjusted OR: 2.51, 95% CI: 1.33-4.75), particularly in males. System-level analyses revealed that cutaneous and multisystem AIDs were less frequent in both PV and BP (p < 0.001 for each and p = 0.001 for each, respectively), whereas endocrine AIDs were more frequent in BP (p = 0.038). Thyroid antibody positivity did not differ significantly between patients and controls. Limitations include retrospective design, possible overrepresentation of cutaneous AIDs in dermatology-based controls, and lack of external validation. Conclusions: Our findings suggest that PV and BP may be associated with selective, sex- and phenotype-specific autoimmune comorbidity patterns rather than a generalized autoimmune burden. Further prospective studies are needed to confirm these exploratory associations and clarify their temporal relationships.