Unlike osteoarthritis, a condition caused by wear and tear on joints, rheumatoid arthritis occurs when the immune system targets a person's joint linings. Rheumatoid arthritis is a chronic inflammatory condition that also affects other tissue, but the joints are usually the most severely affected.
Although doctors aren't sure of the exact cause of rheumatoid arthritis, it's thought that it may result from a combination of genetics and environmental triggers. Some researchers believe an infection with a bacteria or virus can trigger the development of rheumatoid arthritis in someone who's genetically susceptible. However, to date, no infection or organism has been identified as the cause.
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As rheumatoid arthritis develops, some of the body's immune cells recognize one type of the person's own protein as a foreign intruder. The exact protein is unknown and may be one of any number of potential candidates. Some of them are produced in response to infection, such as a viral, bacterial, or fungal infection. Other possible proteins may have a genetic connection or stem from other causes.
Whatever the source, cells called lymphocytes react to this protein. The reaction then causes the release of cytokines, which are chemical messengers that trigger more inflammation and destruction. With rheumatoid arthritis, the main target of inflammation is the synovium, the thin membrane that lines the joints. The inflammation also spreads to other areas in the body, ultimately causing not only joint damage but inflammation, chronic pain, fatigue, and loss of function.
The most significant cytokines in rheumatoid arthritis are tumor necrosis factor (TNF) and interleukin-1, both triggers of joint damage. Some treatments for rheumatoid arthritis block these cytokines, reducing inflammation and joint damage.
What Risk Factors Increase the Chance of Rheumatoid Arthritis?
Rheumatoid arthritis is more common in women than in men. In fact, 70% of the patients with rheumatoid arthritis are women. In addition, there's an increased risk of rheumatoid arthritis in women who have never been pregnant and in those who have recently given birth.
Rheumatoid arthritis has a genetic link, and the disease can run in families. People with specific human leukocyte antigen (HLA) genes have a greater chance of developing rheumatoid arthritis than people who do not have the HLA genes. Still, not everyone with the HLA genes develops rheumatoid arthritis. In other words, genes can increase the risk of rheumatoid arthritis, but other factors are also involved. For example, older age and cigarette smoking may increase the risk of getting rheumatoid arthritis.
Symptoms of rheumatoid arthritis include joint pain, swelling, stiffness, and fatigue -- which can be mild or severe. Doctors recommend treating rheumatoid arthritis early, before there are visible signs of joint destruction.
National Institute of Arthritis and Musculoskeletal Diseases: "What is Rheumatoid Arthritis?"
American College of Rheumatology: "Rheumatoid Arthritis."
Arthritis Foundation: "Frequently Asked Questions about Rheumatoid Arthritis."
eMedicine.com: "Rheumatoid Arthritis."
McIlwain, H, MD and Bruce, D, PhD. A Diet for a Pain-Free Life, Marlowe, 2007.