Although the mechanism of the VitD effect on RA is incompletely understood, VitD may play a potential role in the occurrence and development of RA by decreasing the production of proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1, interleukin-6, and interleukin-17 (9). The gene discussed is IL17A; the disease is rheumatoid arthritis.