What causes rheumatoid arthritis?

As with other autoimmune diseases, RA is caused by the immune system inappropriately targeting ‘self’ tissues or proteins. The mechanism by which this occurs is an active area of research but is not well understood. In the case of RA, the immune system targets the synovial lining of joints, causing inflammation and progressive damage to the joint and eventual loss of joint function. Both genetics and environmental factors are known to play a role in the disease, but the specific mechanisms driving the autoimmunity are not clear.