The cause of rheumatoid arthritis is unknown, but researchers have identified factors that may increase the risk of developing it.
Although rheumatoid arthritis can run in a family, having the condition does not greatly increase the risk to a person’s children. A genetic marker, HLA-DR4, occurs in 60 to 70 percent of people of European ancestry who have rheumatoid arthritis. More than one in four people who do not have rheumatoid arthritis, however, also have the marker.
This suggests that the presence of HLA-DR4 may indicate a risk of rheumatoid arthritis, but people who have the marker are not necessarily destined to develop the disease.
Other genes that have been linked to rheumatoid arthritis have also been identified, and research in this area continues.
Several types of arthritis occur as a result of infections. The most familiar infection-related form can occur during or after Lyme disease, the result of a bite from an infected deer tick.
The bacterium transmitted by the tick first causes a rash, fever and neck stiffness. Weeks later, severe joint inflammation (Lyme arthritis) may arise and may last for months or even a lifetime.
Some researchers believe that exposure to certain bacteria or viruses can trigger, in a similar way, the abnormal immune response that causes rheumatoid arthritis among people who are genetically susceptible to it.
Several studies have found that heavy smokers and people who have been heavily exposed to cigarette smoke are more likely than nonsmokers to develop rheumatoid arthritis..
Diet has also been implicated. For example, one large study suggested that eating a diet too rich in red meat and other high-protein foods may increase the risk of developing rheumatoid arthritis.
In spite of these and other findings, however, a convincing explanation for the development of rheumatoid arthritis continues to elude researchers.