CYP24A1 and rheumatoid arthritis: A higher methylation level of CYP24A1 gene promoter revealed in our study may be related to high prevalence of vitamin D deficiency in both study groups, RA and control, since CYP24A1 enzyme is responsible for degradation of calcitriol – an active form of vitamin D. On the other hand, low CYP2R1 and VDR methylation intensity allows normal gene expression and indirectly indicates active vitamin D metabolism process.