Fibromyalgia, chronic fatigue syndrome, and myofascial pain.

The prevalence of fibromyalgia in the general population was found to be 2% and increased with age. Multiple traumatic factors, including sexual and physical abuse, may be important initiating events. The most important pathophysiologic studies in fibromyalgia included evidence of altered blood flow to the brain and hypothalamic-pituitary-adrenal dysfunction. The prevalence of chronic fatigue syndrome is much less than that of fibromyalgia. Epidemiologic studies demonstrated that chronic fatigue and symptoms of fibromyalgia are distributed as continuous variables in the general population. No association between chronic fatigue and initial infections was seen in primary care practices.