Rheumatoid arthritis (RA) is a chronic (long-lasting) autoimmune disease that mostly affects joints. RA occurs when the immune system, which normally helps protect the body from infection and disease, attacks its own tissues. The disease causes pain, swelling, stiffness, and loss of function in joints.It affects the lining of the joints, which damages the tissue that covers the ends of the bones in a joint. It often occurs in a symmetrical pattern, meaning that if one knee or hand has the condition, the other hand or knee is often also affected. It can affect the joints in the wrists, hands, elbows, shoulders, feet, spine, knees, and jaw. It may cause fatigue, occasional fevers, and a loss of appetite. It may cause medical problems outside of the joints, in areas such as the heart, lungs, blood, nerves, eyes, and skin.the risk for developing rheumatoid arthritis increases with older age. Children and younger teenagers may be diagnosed with juvenile idiopathic arthritis, a condition related to rheumatoid arthritis.Rheumatoid arthritis is more common among women than men.If a family member has RA, you may be more likely to develop the disease.RA symptoms worsen in “flares” due to a trigger such as stress, environmental factors (such as cigarette smoke or viral infections), too much activity, or suddenly stopping medications.