Differential Diagnosis of Fibromyalgia

To diagnose fibromyalgia, imaging tests and electrophysiological studies of the nerves and muscles may be performed to rule out illnesses with similar symptoms, such as rheumatoid arthritis, lupus, chronic fatigue syndrome (CFS), Lyme disease, muscle diseases (e.g., myofascial pain syndrome), hypothyroidism, and bacterial and viral infections.

Research shows that 50–70 percent of patients with fibromyalgia also fit the criteria for CFS. However, patients with CFS usually do not meet the criteria for diagnosing fibromyalgia that has been established by the American College of Rheumatology. There is additional physical evidence that the two disorders are distinct.

Pain is the hallmark of fibromyalgia and fatigue is the hallmark of CFS. Patients with fibromyalgia may have high levels of substance P in their spinal fluid and CFS patients may not. CFS is thought to be viral in origin, and while a virus is suspected in fibromyalgia, there is no evidence to support this theory. Symptoms such as fever, sore throat, and swollen glands are more common in patients with CFS. Aerobic exercise often improves muscle function and reduces pain in fibromyalgia, but CFS patients often find that exercise is impossible and worsens symptoms.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 31 Dec 1999

Last Modified: 15 Sep 2015