Chronic pain and fatigue are common symptoms of both fibromyalgia and chronic fatigue syndrome. The difference is that, in fibromyalgia, fatigue often takes a backseat to debilitating muscle pain. In chronic fatigue syndrome, people have an overwhelming lack of energy, but also can experience some pain.
What prompted the condition. Many people diagnosed with fibromyalgia fatigue report that their symptoms followed some sort of trauma — a physical injury or an emotional shock. On the other hand, chronic fatigue syndrome appears to spring from a viral infection like mononucleosis or influenza.
Distinct pain sites. People are diagnosed with fibromyalgia fatigue if they feel tenderness or pain in at least 11 of 18 distinct locations on their bodies. People with chronic fatigue syndrome do not have these pain sites.
Inflammation. People with chronic fatigue syndrome often complain of fever, swollen glands, and other signs of inflammation. Doctors find no evidence of inflammatory response in patients with fibromyalgia fatigue.
Sleep. Although chronic fatigue syndrome and fibromyalgia are both associated with disrupted REM sleep, a recent study from Japan found key differences in other sleep disturbances between people with CFS alone and those with CFS and fibromyalgia.