Rheumatoid Arthritis (RA)
Rheumatoid Arthritis (RA) is an autoimmune disease. The immune system normally identifies and destroys foreign substances in the body, such as viruses and bacteria; in an autoimmune disease, the immune system mistakes the body's own cells for invaders. In RA, the immune system attacks the synovia, the membranes lining the joints. This causes swelling, stiffness, and pain and can eventually damage bones, tendons, and cartilage, causing deformities and limiting motion. Rheumatoid arthritis can also affect other parts of the body, including the heart, lungs and salivary and tear glands.
Approximately 1.3 million Americans have RA. It is two to three times more common in women than in men, and it is most often diagnosed in people between 40 and 60 years old, though it can also occur in younger adults and even children. The largest group of RA suffers is women over 55; about one in 20 of them have RA.
Rheumatoid arthritis is a chronic disease, meaning that patients are affected for a long period of time. Most people with RA experience relatively symptom-free periods, called remissions, punctuated by flare-ups during which symptoms become severe for a short time.
The disease most people refer to as "arthritis" is osteoarthritis, not rheumatoid arthritis. Osteoarthritis is pain and stiffness caused by physical wear and tear on the bones and is most common in the elderly.
Written by: the Healthline Editorial Team
Medically reviewed by Olga Norstrom, M.Sc., M.A.