Diagnosis of fibromyalgia includes a history of a least three months of widespread pain, and pain in at least 11 of 18 tender-point sites. The overwhelming characteristic of fibromyalgia is long-standing pain at defined tender points, which are not the same as trigger points. Tender points hurt only when pressed. Trigger points can be tender locally and lead to traveling or spreading pain. Fibromyalgia sufferers tend to waken with body aches and stiffness.
Pain improves during the day and often increases again during the evening.
Possible causes can include physical or emotional trauma. One hypothesis suggests that the disorder may be associated with changes in craniofacial and skeletal muscle metabolism, such as decreased blood flow, which could cause chronic fatigue and weakness. Another hypothesis is that an infectious microbe, such as a virus, triggers the illness. At this point, no virus or microbe has been identified. Pilot studies have shown a possible inherited tendency toward the disease.