Rheumatology focuses on diseases of the musculoskeletal system as well as systemic autoimmune conditions, often called rheumatic diseases. Autoimmune conditions occur when the immune system causes areas of the body to become unnecessarily inflamed, resulting in damage to joints or other structures and producing symptoms of pain, swelling, and stiffness. There are more than 100 types of autoimmune diseases treated by rheumatologists.  Common conditions include rheumatoid arthritis, gout, lupus, back pain, osteoporosis, fibromyalgia, and tendonitis.