CYP2R1 and rheumatoid arthritis: Notably, few studies (seven studies) evaluate the association of the GC (rs2282679), CYP2R1 (rs10751657), and CYP27B1 (rs10877012) SNPs with MS, RA, or SLE, compared to several studies (fifty-four studies) assessing the FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) VDR SNPs in these autoimmune conditions.