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Educational Objectives—After reading this article, you will be familiar with:

• The symptoms that constitute fibromyalgia.
• The proposed pathophysiology of fibromyalgia.
• The affective, behavioral, and cognitive factors that contribute to fibromyalgia.
• The available options for treating symptoms of fibromyalgia.

Who will benefit from reading this article?
Psychiatrists, neurologists, primary care physicians, geriatricians, nurse practitioners, and other health care professionals. Continuing medical education credit is available for most specialists. To determine whether this article meets the continuing education requirements of your specialty, please contact your state licensing board.

Fibromyalgia syndrome (FM) is a chronic condition that consists of a pervasive set of unexplained physical symptoms with widespread pain (involving at least 3 of 4 body quadrants and axials) of at least 3 months duration and point tenderness at 9 bilateral locations (Figure) as the cardinal features.¹ Patients with FM report a set of symptoms, functional limitations, and psychological dysfunctions, including persistent fatigue (78.2%), sleep disturbance (75.6%), feelings of stiffness (76.2%), headaches (54.3%), depression and anxiety (44.9%), and irritable bowel disorders (35.7%).¹ Patients also report cognitive impairment and general malaise, “fibro fog.” This pattern of symptoms has been reported under various names (such as tension myalgia, psychogenic rheumatism, and fibro­myositis) since the early 19th century.

In the United States, there are an estimated 3 to 6 million people who have FM.² The condition is more common in women: the ratio of women to men who seek treatment is approximately 7 to 1. Community samples are closer to 3 to 1. The number of diagnoses of FM tends to increase from the second through the sixth decade of life.

FM may have an insidious onset without an identifiable cause, may develop following a flu-like illness, or may rapidly develop following a physical trauma (such as a motor vehicle accident).³ The natural course of FM symptoms seems to be chronic and nonprogressive; symptoms fluctuate in severity and are often exacerbated by stress. Patients with FM report a diminished sense of physical well-being; they have significant health concerns and are high users of the health care system.⁴

PATHOPHYSIOLOGY

The pathophysiological mechanisms that underlie FM are poorly understood. There is no accepted biological marker, and the results of radiographic and laboratory studies tend to be normal. A number of different peripheral and central mechanism have been proposed, which may not be mutually exclusive.

Peripheral: muscular involvement
The earliest efforts to understand FM assumed that reported pain was caused by abnormalities related to the muscle anatomy, physiological processes (eg, oxygen availability and depletion), or tension myalgia. Research suggests that the involvement of the peripheral pathology is, however, nonspecific, cannot account for the diverse symptoms, and is unlikely to be primary.⁵

Central: neurotransmitter dysregulation
Various neurochemical factors have been studied in patients with FM. These include dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and serotonin imbalance.^4,6 However, no definitive neurochemical features have been consistently identified. What is most notable in studies that have examined various neuroendocrine substances in FM is the large intragroup variability observed in the substances tested. Thus, although persons with FM may differ statistically from those without FM, the large individual differences within patients with FM make it difficult to interpret the results.