Vitamin D Receptor BsmI Polymorphism and Inflammatory Features in Juvenile Idiopathic Arthritis

Background Vitamin D and vitamin D receptor (VDR) gene polymorphisms influence immune regulation, but their role in juvenile idiopathic arthritis (JIA) remains unclear. We aimed to examine the association between BsmI VDR gene polymorphism and JIA susceptibility in children and evaluate its relationship with inflammatory biomarkers.Methods Sixty-nine children with JIA and 69 healthy controls were enrolled over two years. Serum vitamin D levels were analyzed using the calcidiol 25-hydroxyvitamin D (25(OH)D) enzyme-linked immunosorbent assay (ELISA). Participants’ biochemical and inflammatory markers, hematological parameters, demographics, medical histories, and dietary patterns were also assessed. Genotyping of the BsmI VDR gene polymorphism (rs1544410) was done using real-time polymerase chain reaction (PCR).Results Interleukin-6 (IL-6), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were significantly higher in patients with JIA (p = 0.001, < 0.001, and < 0.001, respectively). The BsmI AA genotype was significantly associated with JIA (p < 0.001). Multivariate analysis revealed that the rs1544410 VDR gene polymorphism (AA versus GG) and age were independent factors associated with JIA (OR 8.404, 95% CI 2.835–24.913, p < 0.001; OR 1.325, 95% CI 1.063–1.653, p = 0.012, respectively). No significant differences were observed in inflammatory markers, tumor necrosis factor-alpha (TNF-α), IL-6, ESR, and CRP, among VDR genotypes (all p > 0.05).Conclusion The BsmI (rs1544410) VDR gene polymorphism is significantly associated with susceptibility to JIA, with the AA genotype as an independent predictor. However, no significant relationship was observed between genotypes and inflammatory biomarkers, suggesting that this polymorphism may contribute to disease susceptibility rather than modulating inflammatory activity.