Fibromyalgia syndrome
Fibromyalgia is a syndrome of persistent widespread pain, stiffness, fatigue, disrupted sleep, and cognitive difficulties, often accompanied by anxiety and/or depression, and functional impairment of activities of daily living. Fibromyalgia is common with a prevalence of 2% in the general population.
According to the American College of Rheumatology's alternative criteria for the diagnosis of fibromyalgia, symptoms and pain locations must have been persistent for at least the past 3 months, the pain location score must be ≥ 17, and the Symptom Impact Questionnaire score must be ≥ 21.
Although patients with fibromyalgia do not typically exhibit abnormalities in laboratory tests, some routine studies are performed to rule out other conditions. Erythrocyte sedimentation rate (ESR) is often recommended to rule out inflammatory disorders that may cause similar symptoms. Anti-nuclear antibody (ANA) or rheumatoid factor are not usually recommended unless patients have signs or symptoms that may indicate systemic lupus erythematosus or rheumatoid arthritis. Low levels of ANA or rheumatoid factor level occur commonly in the general population and may not be clinically significant in patients with fibromyalgia.
The earlier hypothesis that fibromyalgia was associated with inflammation of muscle fascia has been disproven. No histologic abnormalities have been detected. Fibromyalgia appears to be a neurosensory disorder characterized by abnormal pain processing in the central nervous system. The most common biochemical abnormality associated with fibromyalgia is abnormally low serum and platelet serotonin levels. Low serotonin levels in the central nervous system are thought to result from decreased levels of tryptophan, which is the precursor of serotonin. In some patients, altered serotonin metabolism has been linked to a polymorphism in the promoter region of the serotonin transporter gene.
