Fibromyalgia Syndrome (FMS) is a chronic debilitating condition that is characterized by the primary symptom of diffuse musculoskeletal pain and a number of associated features such as fatigue, sleep disturbance, headaches, and cognitive and affective disturbance (among others).  The cause is not clearly understood nor is there a clearly defined profile for the disorder that distinguishes it as a diagnosis.     

As such, the diagnosis of FMS is based on a history of widespread pain, defined as bilateral, upper and lower body, as well as spine, and the presence of excessive tenderness on applying pressure at 11 or more of 18 specific muscle tendon sites.  This profile must be apparent along with the exclusion other possible medical or psychiatric explanations.
 
Fibromyalgia is the third most common disorder in rheumatologic practice after rheumatoid arthritis and osteoarthritis and its prevalence in the general population has been estimated to be between 1% and 4%. The prevalence of FMS in primary care settings is much higher, where it is estimated to be between 5% and 20%. The course of FMS is chronic, and large costs are incurred on the wider community for treatment, rehabilitation, and loss of productivity.