(ĐTĐ) - Osteoarthritis is the result of the wear and tear on joints. Rheumatoid arthritis, on the other hand, occurs when the immune system goes haywire and begins attacking joint linings. This chronic inflammatory condition also affects other tissue, but the joints are usually the most severely affected.
Here is what we know about the causes of rheumatoid arthritis.
What causes rheumatoid arthritis?
Although doctors aren't sure of the exact cause, it's thought that rheumatoid arthritis 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 found that could be said to be the cause.
As rheumatoid arthritis develops, some of the body's immune cells recognize a 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 by infection, such as a viral, bacterial, or fungal infection. Other candidate 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 spills to other areas in the body causing joint damage, inflammation, chronic pain, fatigue, and loss of function.
There are many cytokines, but the most important in rheumatoid arthritis are tumor necrosis factor (TNF) and interleukin-1. These cytokines are thought to trigger the process of joint damage in rheumatoid arthritis. Some treatments for rheumatoid arthritis aim to 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 unknown factors are also involved.
Older age and cigarette smoking may increase the risk of getting rheumatoid arthritis. So can stress. In fact, many patients with rheumatoid arthritis tell of having an extremely stressful life event within the six months before the disease appeared.
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.