What sort of disorder is fibromyalgia?

Pain amplification. Fibromyalgia syndrome [fms] is a chronic illness characterized by widespread body pain and low pain threshold. The pain results from central nervous system [spinal cord and brain] amplification of stimuli [pressure, heat, cold, etc] to peripheral tissues [skin, muscle, bone] that would not have been perceived as pain by a person without fms. There are many other very troublesome symptoms in fms.
Fibromyalgia. Fm is a common syndrome associated w/widespread pain; may be accompanied by fatigue, sleep disturbances, stiffness, cognitive/ memory problems, anxiety, depression. To meet criteria for diagnosis: widespread pain in all 4 quadrants of body for >3 months and 11-18 tender points (determined by md). Cause is unknown however research looks to a disorder of central processing and pain amplification.
Good question. There are lots of theories and unfortunately very few solid answers. Fibromyalgia is a disease resulting in muscle pain, but no defect in the muscles is seen on tests. Some believe it to come about through an over stimulation processing of the central nervous system. Unfortunately, many mds feel this is a diagnosis applied when other diagnoses do not apply and no specific treatment is available.
Unusual. As to what sort of disorder is fibromyalgia? Disorder has a curious nature, & is label given to a constellation of symptoms absent significant objective signs. Sufferers develop symptom profiles via different etiologies. IMO unifying injury seems to be primary ligament damage causing postural deviations invoking muscle spasms and chronic widespread pain.