Rheumatoid arthritis (RA) is an autoimmune disease that causes your body to mistakenly attack the membranes that line your joints. This causes inflammation and pain as well as potential damage to other body systems, including:
- blood vessels
RA is a chronic disease. People with RA experience periods of intense disease activity called flare-ups. Some people experience periods of remission in which symptoms go away. The American College of Rheumatology estimates that 1.3 million people in the United States have RA.
The exact cause of the immune system’s faulty response is unclear. As with other autoimmune diseases, researchers think that certain genes may increase your risk of developing RA. But they also don’t consider RA an inherited disorder. This means that a geneticist can’t calculate your chances for RA based on your family history. Also, other factors can trigger this abnormal autoimmune response, such as:
- viruses or bacteria
- emotional stress
- physical trauma
- certain hormones
Read on to learn more about the link between genetics and causes of RA.
Your immune system protects you by attacking foreign substances — like bacteria and viruses — that invade the body. Sometimes the immune system is fooled into attacking healthy parts of your bodies. Researchers have identified some of the genes that control the immune responses. Having these genes increases your risk for RA. However, not everyone who has RA has these genes, and not everyone with these genes has RA.
Some of these genes include:
- HLA: The HLA gene site is responsible for distinguishing between your body’s proteins and the proteins of the infecting organism. A person with the HLA genetic marker is five times more likely to develop rheumatoid arthritis than those who do not have this marker. This gene is one of the most significant genetic risk factors for RA.
- STAT4: This gene plays a role in regulating and activating the immune system.
- TRAF1 and C5: This gene has a part in causing chronic inflammation.
- PTPN22: This gene is associated with the onset of RA and the progression of the disease.
Some of the genes thought to be responsible for RA are also involved in other autoimmune diseases, such as type 1 diabetes and multiple sclerosis. This may be why some people develop more than one autoimmune disease.
One study reported that first-degree relatives of a person with RA are three times more likely to develop the condition than first-degree relatives of people who don’t have RA. This means that parents, siblings, and children of someone with RA are at a slightly increased risk of developing RA. This risk doesn’t include various environmental factors.
Another study estimated that genetic factors attribute to 53 to 68 percent of the causes for RA. Researchers calculated this estimate by observing twins. Identical twins have exactly the same genes. About 15 percent of identical twins are likely to develop RA. In fraternal twins, who have different genes like other siblings, the number is 4 percent.
RA can be found in every gender, age, and ethnic group, but an estimated 70 percent of people with RA are women. These women with RA are usually diagnosed between the ages of 30 and 60. Men are usually diagnosed later, as overall risk increases with age. Researchers attribute this number to female hormones that may contribute to developing RA.
Pregnancy and RA risk
A 2014 study presented at the American Society of Human Genetics found that women who carried babies with genes known to contribute to RA were more likely to have RA. Examples include babies born with the HLA-DRB1 gene. This is because during pregnancy, a number of fetal cells remain in the mother’s body. Having remaining cells with DNA present is known as microchimerism. These cells have the potential to change existing genes in a woman’s body. This may also be a reason why women are more likely to have RA than men.
Environmental and behavioral risk factors also play a huge role your chances of developing RA. Smoking, or having a history of smoking, can increase your risk for developing RA by 1.3 to 2.4 times compared to nonsmokers. Smokers also tend to experience more severe RA symptoms.
Other potential risk factors include the use of oral contraceptives or hormone replacement therapy. There may be a link between an irregular menstrual history and RA. Women who have given birth or breastfed may have a slightly decreased risk of developing RA.
Additional examples of environmental and behavioral risk factors that could contribute to RA include:
- exposure to air pollution
- exposure to insecticides
- occupational exposure to mineral oil and/or silica
- response to trauma, including physical or emotional stress
Some of these are modifiable risk factors that you can change or manage with your lifestyle. Quitting smoking, losing weight, and reducing stress in your life could also potentially reduce your risk for RA.
While RA isn’t hereditary, your genetics can increase your chances of developing this autoimmune disorder. Researchers have established a number of the genetic markers that increase this risk. These genes are associated with the immune system, chronic inflammation, and with RA in particular. It’s important to note that not everyone with these markers develops RA. Not everyone with RA has the markers, either. This suggests that developing RA can be due to a combination of genetic predisposition and hormonal and environmental exposures.