Rheumatoid arthritis This is the most common type of inflammatory arthritis, affecting about one in 100 people.

In this article

What causes it? Who gets it?

What happens? What does it feel like?

Does it run in families?

Rheumatoid arthritis is an autoimmune disease in which the body's defence mechanisms go into action when there's no threat. In this case, the immune system attacks the joints and sometimes other parts of the body. It's not yet known why the immune system acts in this way in some people.

Rheumatoid arthritis is a common disease affecting about one in 100 people. People of all ages have the condition, but it most commonly starts between the ages of 30 and 50. Three times as many women are affected as men.

The joints become inflamed, particularly:

• the synovial membrane
• the tendon sheaths
• the bags of fluid that allow muscles and tendons to move smoothly over one another (bursae)

Inflammation sometimes becomes far worse - known as a 'flare-up' - when the joints become warm and red as blood flow to the area increases. The synovial membrane produces extra fluid, causing swelling and a stretching of the ligaments around the joint. The result is a stiff, swollen and painful joint.

In one in five cases, rheumatoid arthritis develops very rapidly but more often the symptoms develop over several months. For about one in 20 people with the disease the cycles of inflammation cause severe damage in many joints, but others have little or no damage. Treating inflammation as quickly as possible is vital because once joint damage has occurred it can't be reversed.

In a few cases, symptoms typical of rheumatoid arthritis come and go. These patients may have a different, but probably related, condition called palindromic rheumatism, which may be mistaken for rheumatoid arthritis. (There may also be other symptoms, such as certain skin rashes, which are not seen in rheumatoid arthritis.) Most importantly, the damage to bones or joints that occurs in rheumatoid arthritis is not seen in this condition. However, over time, as many as 50 per cent of patients will go on to develop rheumatoid arthritis.

Most people get fluctuating pain and stiffness that gets worse during flare-ups. Whereas in osteoarthritis morning stiffness wears off quickly, in rheumatoid and other forms of inflammatory arthritis it usually lasts more than 45 minutes. Many people find that the condition gives them flu-like symptoms and makes them tired, irritable or depressed.

There is no single gene to blame for rheumatoid arthritis, and when one family member develops the disease the risk to others in the family is small. However, although about 0.5-1.0 per cent of people in most populations will develop rheumatoid arthritis, it is much more common among the Pima Indians (5.3 per cent) and the Chippewa Indians (6.8 per cent) and far less common in China and Japan. This shows that genetics do play some part in predisposing to rheumatoid arthritis.

The main risk comes from a group of genes known as HLA-DRB1 alleles, but several genes appear to be involved, each of which exerts only small effects to different degrees in different people. In 2007, researchers in Manchester identified a genetic variant in part of chromosome 6 that is associated with rheumatoid arthritis. It’s thought that this variant, although not a gene itself, may affect the behaviour of a nearby gene called tumour necrosis factor associated protein gene (TNFAIP3), which is known to be involved in the process of inflammation.

This article was last medically reviewed by Dr Rob Hicks in July 2008.
First published in October 1999.