Rheumatoid arthritis is a disease that causes chronic abnormal inflammation. Its most common signs are swelling, pain and joint stiffness. The disease initially affects the small joints in the hands and feet, with larger joints in the hips, shoulders and knees becoming involved as the disease progresses. Rheumatoid arthritis tends to manifest itself in a symmetrical pattern i.e. both sides of the body being involved. People with this condition often say that their joint pain and stiffness is worse when getting out of bed in the morning or after a long rest.
Rheumatoid arthritis is classified as an autoimmune disorder, a condition wherein the immune system attacks the body’s own tissues and organs.
In people affected with rheumatoid arthritis, the immune system causes inflammation and thickening of the synovium (the membrane that lines the joints). Pain, swelling and joint stiffness happens when the synovium gets inflamed. The inflammation may even cause even serious damage by affecting the bone, cartilage, and other tissues within the joint if the disease goes unchecked. Over time, there will be loss of cartilage, rendering the joints loose and unstable. There may also be joint deformity.
Rheumatoid arthritis can also cause inflammation of other tissues and organs, including eyes, lungs and blood vessels. Additional signs and symptoms of the condition can include a loss of energy, a low fever, weight loss, and a shortage of red blood cells (anemia). Some affected individuals develop rheumatoid nodules, which are firm lumps of noncancerous tissue that can grow under the skin and elsewhere in the body.
The signs and symptoms of rheumatoid arthritis usually appear in mid- to late adulthood. Many affected people have episodes of symptoms (flares) followed by periods with no symptoms (remissions) for the rest of their lives. In severe cases, affected individuals have continuous health problems related to the disease for many years. The abnormal inflammation can lead to severe joint damage, which limits movement and can cause significant disability.
Rheumatoid arthritis affects about 1% of the global population. In the U.S., rheumatoid arthritis affects about 1.3 million. The disease is two to three times more common in women than in men, which may be related to hormonal factors.
Rheumatoid arthritis probably results from a combination of genetic and environmental factors, many of which are unknown.
Other, nongenetic factors are also believed to play a role in rheumatoid arthritis. These factors may trigger the condition in people who are at risk, although the mechanism is unclear. Potential triggers include changes in sex hormones (particularly in women), occupational exposure to certain kinds of dust or fibers, and viral or bacterial infections. Long-term smoking is a well-established risk factor for developing rheumatoid arthritis; it is also associated with more severe signs and symptoms in people who have the disease.
Several genes have been studied as risk factors for rheumatoid arthritis. Most of these genes are known or suspected to be involved in immune system function. Having these genes increases your risk of having RA. However, not everyone with these genes has RA and vice versa.
Some of these genes include:
- HLA (Human Leukocyte Antigen) – Proteins from the HLA genes help the body distinguish its own proteins against those from a foreign invader, such as bacteria and viruses.
- STAT4 – Plays a role in regulating and activating the immune system.
- TRAF1 and C5 – Plays a part in causing chronic inflammation.
- PTPN22 – The gene that associated with the onset of rheumatoid arthritis and the progression of the disease.
The inheritance angle for rheumatoid arthritis is unclear at this point due to various genetic and environmental factors involved. However, your genetics may increase your chances of developing this disorder.