What is Rheumatoid Arthritis?

Rheumatoid arthritis is a type of arthritis that causes inflammation (swelling) in the membrane lining a joint. The cause of rheumatoid arthritis is not known, but it is considered to be an "autoimmune" disease—that is, a disease in which the immune system attacks other parts of the body. In this case, the immune system attacks the linings of joints, eventually causing damage to various parts of the joint. Different joints may be affected at different rates.

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