VDR Polymorphic Variants Are Related to Improvements in CRP and Disease Activity in Patients with Axial Spondyloarthritis That Undergo Anti-TNF Treatment

Vitamin D deficiency is related with susceptibility or progression of various autoimmune diseases. The aim of the study was to assess potential relations between single nucleotide polymorphisms (SNPs) in the vitamin D receptor-coding gene (VDR): rs1544410 (BsmI), rs2228570 (FokI), rs731236 (TaqI), rs7975232 (ApaI), and disease activity in patients with axial spondyloarthritis (axSpA) undergoing anti-TNF therapy. The VDR rs731236 CT genotype was statistically more common among female patients (p = 0.027). An improvement of CRP equal to or higher than 50% after 3 months of anti-TNF therapy was observed for rs2228570 T allele (p = 0.002). After 6 months, CRP improvement equal to or higher than 75% was related to presence of the rs1544410 AA genotype (p = 0.027) and the rs731236 CC homozygotes (p = 0.047). Baseline BASDAI values were lower in individuals with the rs2228570 TT genotype (p = 0.036) and rs7975232 C allele (p = 0.029). After 6 months of treatment, lower BASDAI values were observed in AC heterozygotes (p = 0.005). The same AC genotype was more frequently detected in patients with remission (BASDAI ≤ 2) (p = 0.001) and in those achieving BASDAI improvement equal to or higher than 75% (p = 0.006). In conclusion, VDR SNPs were found to relate to CRP and BASDAI values at different time points of anti-TNF therapy