Rheumatoid arthritis is a common disease. More than 2 million Americans have RA, and people of all races and ethnic backgrounds get the disease. Approximately 75 percent of people with the disease are women. It can occur at any age; however, RA often begins when people are between the ages of 30 and 60 years old.
The cause of rheumatoid arthritis is not known. Scientists have learned that there are both genetic and environmental components to developing the disease. In other words, while there are certain genes associated with RA, there are many people with RA who do not have any specific genetic tendency for the disease. This means that something else, besides a person's genetic make-up, is needed to get the disease.
We also know that RA is an autoimmune disease. This means that the body's natural immune system does not act as it should. Instead of serving to fight off infections from bacteria and viruses, the immune system of a person with RA attacks its own body. This causes inflammation and damage. In RA, many parts of the body can be attacked by the immune system, but joints are the most common targets.