CLOCK and rheumatoid arthritis: Moreover, a recent study has shown that circadian rhythm disturbance is partly related to inflammation and cell autonomous, because synovial fibroblasts in rheumatoid arthritis show changes in the circadian expression of several clock genes after circadian rhythm disturbance, and interfere with the production of circadian rhythms of IL-6 and IL-1 β (Kouri et al., 2013).