The cause of
rheumatoid arthritis (RA) is not fully understood.
Genes play a role, but experts
don't know exactly what that role is. For most people with RA, the disease
doesn't run in their families and they don't pass it along to their children.
One or more genes may make it more likely that the body's
immune system will attack the tissues of the
joints. This immune response may also be triggered by
bacteria, a virus, or some other foreign substance.