RA is an autoimmune disease. There are some genetic factors; in addition, smoking increases the risk of RA.
Our immune system normally protects us from infection by attacking germs such as bacteria and viruses. However, in people who develop autoimmune diseases, the immune system becomes confused and overactive, and attacks our own body. For patients with RA, this results in joint inflammation that can eventually damage the joint, cartilage and surrounding bones. The joints most commonly affected by RA are the small joints of the hands, wrists, ankles and feet; however, any joints can be affected.