[Secondary osteoporosis. Bone metabolic disorder in Rheumatoid arthritis.]

Rheumatoid arthritis(RA)is an immune-mediated disease marked by chronic synovial inflammation, which leads to cartilage and bone destruction as well as systemic bone loss. Osteoporosis or the systemic bone loss associated with RA increases the risk for fragility fractures, which can affect quality of life dramatically in RA patients. Inflammatory cytokines such as TNF and IL-6 in inflamed synovium induce the differentiation of osteoclasts, while suppresses the differentiation of osteoblasts, resulting in imbalance in bone metabolism. Although RA treatment targeting inflammatory cytokines can deter the progression of cartilage and bone destruction directly or indirectly, it can not stop systemic osteoporosis. Although it is important to avoid immobility by introducing an early remission, it is necessary to thoroughly manage the risks of individuals of RA patients and to effectively use osteoporosis drugs such as anti-RANKL antibodies that also have the effect of suppressing bone erosion in RA.