Definition of Rheumatoid arthritis:

Rheumatoid arthritis (RA) is a long-term disease that causes inflammation of the joints and surrounding tissues. It can also affect other organs.

Causes, incidence, and risk factors:

The cause of RA is unknown. It is considered autoimmune disease. The body's immune system normally fights off foreign substances, like viruses. But in an autoimmune disease, the immune system confuses healthy tissue for foreign substances. As a result, the body attacks itself.

RA can occur at any age. Women are affected more often than men.

RA usually affects joints on both sides of the body equally. Wrists, fingers, knees, feet, and ankles are the most commonly affected. The course and the severity of the illness can vary considerably. Infection, genes, and hormones may contribute to the disease.