In 1990, the American College of Rhematology published the first official diagnostic criteria for the disorder.  Fibromyalgia literally means: fibro (fibrous tissue) myo (muscle) algia (pain). The ACR committee determined that a diagnosis of fibromyalgia would depend on the presence of all of the following:

Widespread pain for at least 3 months defined as:

• pain on the right and left sides of body
  pain above and below the waistline including shoulder and buttock pain
• pain in the distribution of the axial skeleton - cervical, thoracic and lumbar spine,        and anterior chest wall
  tenderness to palpation with 4kg force (a blanched thumbnail upon downward
         pressure) at 11 of 18 discrete areas known as tender points

As the definition provided by the American College of Rheumatology suggests, fibromyalgia has traditionally been considered a rheumatological disorder involving the muscles and soft connective tissues, which seems natural given that the pain of a fibromyalgia patient is felt in these areas. There is more to fibromyalgia than the experience of chronic widespread aches and pain.   Many researchers believe Chronic Fatigue Syndrome and Fibromyalgia might be the same event, and if not, are definitely overlapping.  Dr. Lucinda Bateman, who has a chronic fatigue syndrome/fibromyalgia clinic in Salt Lake City (and is not accepting new patients) presented the following in the O.F.F.E.R. Conference May 5, 2007. The CFS case definitions are:

6 months of new onset fatigue that reduces function, unexplained by other
       medical illness or major psychiatric co-morbidity
post exertional relapse/malaise
attention/concentration and cognitive complaints
unrefreshing sleep
arthralgia (joint pain)
myalgia (muscle pain)
painful lymph nodes
new headaches
sore throat

There are additional symptoms of fibromyalgia:

anxiety and/or panic attacks
chronic fatigue and low energy
depression
intolerance to cold temperatures
irritable bladder syndrome
neck and back pain
poor circulation (cold hands and feet)
cardiovascular problems (dizziness, palpitations)
tension headaches and/or migraines
post exertional pain

The associated fibromyalgia conditions are:

chronic fatigue syndrome
multiple chemical sensitivity
TMJ/TJD
memory and concentration problems, called “fibro fog”
pelvic pain in women (painful menstrution and/or PMS)
sleep disturbances and/or restless leg syndrome
stiffness (especially in the morning)
muscle twitching
subjective soft tissue swelling or paresthesia in hands, arms, feet, or legs
gastrointestinal disturbances/irritable bowel syndrome
somatoform disorders
orthostatic instability
Gulf War illness

Dr. Bateman believes that CFS/FMS are complex illnesses that:

represent alterations in complex systems of homeostasis;
are not a result of a single mutation or single environmental factor; and
arise from a combined action of many genes, environmental factors and risk
     conferring behavior.