Vitamin D status as a prognostic biomarker in granulomatosis with polyangiitis: Findings from a 10-Year retrospective study

Granulomatosis with polyangiitis (GPA) is a rare but aggressive form of antineutrophil cytoplasmic antibody associated vasculitis, with substantial morbidity and mortality. Despite advances in immunosuppressive therapy, identifying reliable, accessible biomarkers for disease prognosis remains a clinical imperative. Recent evidence implicates vitamin D in the immunopathogenesis of autoimmune diseases, but its prognostic relevance in GPA remains underexplored. This study aimed to assess the prognostic value of serum 25-hydroxyvitamin D [25(OH)D] levels in patients with GPA, with emphasis on disease severity, relapse risk, and survival outcomes. In this 10-year retrospective cohort study, 150 GPA patients from a tertiary referral center were analyzed. Clinical and demographic data, including Birmingham Vasculitis Activity Score (BVAS) were correlated with serum 25(OH)D concentrations. Multivariate logistic regression was employed to identify independent predictors of poor outcomes. The mean 25(OH)D level was 14.3 ± 11.9 ng/mL, with 74.7% of patients classified as deficient. A significant inverse correlation was observed between vitamin D levels and BVAS scores (r = –0.21, P = 0.009). Vitamin D deficiency independently predicted higher disease severity (OR = 0.91, 95% CI: 0.85–0.98, P = 0.014). Trends toward increased relapse and mortality were noted among vitamin D-deficient patients, although these did not reach statistical significance. Vitamin D deficiency is common in GPA and is associated with increased disease activity. Serum 25(OH)D may serve as a cost-effective, immunologically relevant prognostic biomarker in GPA. Prospective interventional studies are warranted to validate these findings and explore the therapeutic potential of vitamin D optimization in vasculitis care.