Cause

The cause of rheumatoid arthritis (RA) is not fully understood. Genes play a role, but experts don't know exactly what that role is. For most people with RA, the disease doesn't run in their families and they don't pass it along to their children. One or more genes may make it more likely that the body's immune system will attack the tissues of the joints. This immune response may also be triggered by bacteria, a virus, or some other foreign substance.

Symptoms

Joint pain can be an early symptom of many different diseases. In rheumatoid arthritis, symptoms often develop slowly over a period of weeks or months. Fatigue and stiffness are usually early symptoms. Weight loss and a low-grade fever can also occur.

Joint symptoms include:

• Painful, swollen, tender, stiff joints. The same joints on both sides of the body (symmetrical) are usually affected, especially the hands, wrists, elbows, feet, ankles, knees, or neck.
• Morning stiffness. Joint stiffness may develop after long periods of sleeping or sitting. It lasts at least 60 minutes and often up to several hours.
• Bumps (nodules). Rheumatoid nodules ranging in size from a pea to a mothball develop in nearly one-third of people who have rheumatoid arthritis. Nodules usually form over pressure points in the body such as the elbows, knuckles, spine, and lower leg bones.

In addition to specific joint symptoms, rheumatoid arthritis can cause symptoms throughout the body (systemic). These include:

• Fatigue.
• A loss of appetite.
• Weight loss.
• Mild fever.

Some of the symptoms of rheumatoid arthritis may be similar to symptoms of other health conditions.