What Causes Rheumatoid Arthritis (RA)?

The cause of RA is not yet known, although we do know that the body’s immune system plays an important role in the inflammation and joint damage that occur in RA. The immune system is the body’s defense against bacteria, viruses and other foreign cells.

In RA, your body’s own immune system mistakes cells found in your joints and other organs as foreign cells and it wants to attack them to protect your body. In the process of attacking your own cells, inflammation and tissue damage occurs. The fluid and cells in the inflamed joint produce many substances, including enzymes, antibodies and cytokines that cause joint damage. If inflammation persists, it leads to damage to the smooth, protective lining (cartilage) that covers the ends of the bones. Once this structure is damaged, it does not repair itself. Bone can rub against bone and the joint can become loose, unstable and painful, and lose its mobility.

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Genes play an important role in the development of RA. However, some of the genes known to be associated with RA are common, and it is believed that these genes create a tendency to develop RA. Why some people with these genes develop RA and others do not remains an area of research. It has recently been learned that smoking increases the risk of developing RA in people who also have a specific gene that is sometimes found with RA and increases the disease’s severity. Scientists are investigating these genes and other factors (such as infection, injury, hormonal changes and environmental factors) that may lead to the development of RA.