[Rheumatoid arthritis].

Although many requirements must be met to establish a diagnosis of rheumatoid arthritis (RA), morning stiffness is a characteristic feature of RA. Inflammatory cytokines show high concentrations in human blood and synovial fluid of RA, and excess production of these cytokines plays a central role in the pathogenesis of RA. The inflammatory cytokines in blood also show circadian rhythms peaking from midnight to early morning, which mirrors the timing of morning stiffness. In the treatment of RA, steroids are used to reduce pain and inflammation, and methotrexate are used prior to the development of destructive changes in bones, joints, and organ tissues. In this chapter, I would like to introduce the circadian rhythm of RA and the chronotherapies.