Rheumatoid arthritis is not considered an inherited disorder. However, having certain genes may increase the risk of developing it.

The exact cause of rheumatoid arthritis (RA) is unclear. As with other autoimmune diseases, researchers think certain genes may increase your risk of developing RA. But they don’t consider RA an inherited disorder.

A geneticist can’t calculate your chances for RA based on your family history.

People with specific genes called HLA class II genotypes may be at a higher risk of developing RA. The risk of RA can increase in the presence of other environmental factors. Factors that may trigger the autoimmune response of RA can include:

  • viruses or bacteria
  • emotional stress
  • physical trauma
  • certain hormones
  • smoking
  • secondhand smoke

Read on to learn more about the link between genetics and causes of RA.

RA is an autoimmune disease that causes the body to mistakenly send antibodies that attack the membranes that line the joints. This causes inflammation and pain as well as potential damage to other body systems, including:

  • eyes
  • lungs
  • heart
  • 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 when symptoms lessen considerably or go away.

The American College of Rheumatology estimates that 1.3 million people in the United States have RA.

Your immune system protects you by attacking foreign substances — like bacteria and viruses — that enter the body. But sometimes, the immune system may mistakenly attack healthy parts of your body.

Researchers have identified some of the genes that control these 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 more likely to develop rheumatoid arthritis than those who don’t 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-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 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.

According to the National Rheumatoid Arthritis Society (NRAS), 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.

Genetic factors may be involved in 53% to 68% of the causes of RA. Researchers calculated this estimate by observing twins. Identical twins have the same genes.

According to NRAS, about 15% of identical twins are likely to develop RA. In fraternal twins, who have different genes like other siblings, the number is 4%.

RA can be found in every sex, age, and ethnicty. But an estimated 75% of people with RA are assigned female at birth. People assigned female at birth may be two to three times more likely to develop RA than people assigned male at birth.

People assigned female at birth who have RA usually receive a diagnosis between ages 30 and 60. Researchers attribute this number to female hormones that may contribute to developing RA.

People assigned male at birth usually receive a diagnosis later, after the age of 45, and the overall risk increases with age.

Environmental and behavioral risk factors also play a huge role in your chances of developing RA and in disease progression. Smokers also tend to experience more severe RA symptoms.

People who have given birth or breastfed may have a slightly decreased risk of developing RA, according to the Centers for Disease Control and Prevention (CDC).

Environmental and behavioral risk factors that could contribute to RA can include:

  • exposure to air pollution
  • cigarette smoking, which can trigger the development of RA and affect its severity
  • exposure to secondhand smoke, though to a lesser degree
  • exposure to insecticides
  • obesity
  • occupational exposure to mineral oil and/or silica
  • response to trauma, including physical or emotional stress
  • eating a diet that’s high in calories and low in fiber

Some of these are modifiable risk factors you can change or manage with your lifestyle. Quitting smoking, if you smoke, losing weight, if you have obesity, and reducing stress in your life, if applicable, may also potentially reduce your risk for RA.

While RA isn’t hereditary, genetics can increase your chances of developing this autoimmune disorder. Researchers have established several genetic markers that can 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 genetic predisposition along with hormonal and environmental exposures.

Still more to find

Researchers have only found half of the genetic markers that increase your risk for RA. Most of the precise genes are unknown, except HLA and PTPN22.