Although often mistaken for osteoarthritis, rheumatoid arthritis (RA) is an autoimmune disease that affects approximately 1.3 million Americans. Along with joint pain and swelling, about four out of 10 people with RA have related problems in other body parts, says Eric Matteson, MD, a consultant rheumatologist at the Mayo Clinic, in Rochester, Minn.

Health.com, Tammy Worth, 11/9/11

Tags: Rheumatology