Introduction
Fibromyalgia syndrome (FMS) is relatively common, occurring in approximately 2 percent of the general population. Women are more likely to have symptoms of FMS than men. Ten percent to 30 percent of patients seen in an average rheumatology practice will have fibromyalgia. The average yearly cost to treat FMS is approximately $2,000, about the same cost as the treatment of osteoarthritis.
Definition
All patients with FMS complain of widespread pain. Other very common symptoms include fatigue, sleep difficulties, and often some depression or anxiety. Other non-specific symptoms include intermittent constipation and diarrhea, frequent urination, headaches, numbness and tingling of the arms and legs, and difficulty concentrating.
The American College of Rheumatology classification criteria for FMS include the physical finding of tenderness at anatomic areas called tender points. Eighteen such tender points have been designated. Patients with FMS will feel tenderness at palpation of at least 11 of these 18 points. Traditional laboratory tests and X-rays should be normal.
Conditions that might mimic FMS include other muscle diseases such as polymyositis, endocrine diseases such as hypothyroidism or abnormalities of calcium metabolism, inflammatory diseases such as polymyalgia rheumatica, and neurologic conditions such as Parkinsonism. Most of these conditions can be diagnosed by history and physical examination with minimal laboratory testing.
These show common areas of pain and tenderness (called "tender points") in people who have fibromyalgia.)
The cause of FMS
In the mid 1970s, patients with FMS were studied in a sleep laboratory and discovered to have brain wave abnormalities during deep sleep. This discovery resulted in great interest in the pathophysiology of FMS. Currently, a number of neurohormonal abnormalities — such as elevated substance P in the central nervous system, low circulating growth hormone, and serotonin and other abnormalities — have been found. Recent research suggests that patients with fibromyalgia may have central nervous system dysfunction leading to amplification of normal pain signals. The precise pathophysiological pathway remains unproven. Certain clinical relationships, however, provide insight about the symptoms experienced by patients with FMS. These clinical relationships include:
- Patients with FMS have lower pain thresholds than the general population.
- The mechanisms responsible for low pain thresholds are central, not in the peripheral nerves or muscles.
- Changes in mood and concentration are common.
- FMS is not a discrete disorder. Symptoms of FMS exist as a continuum throughout the population.
- The number and severity of tender points and the severity of FMS symptoms are directly related to the degree of distress.
The fact that FMS exists as a continuum related to distress is a very important concept. People are much more likely to be distressed if they have other chronic illnesses. The occurrence of both lupus erythematosus and FMS together has been well studied. These studies suggest that the fatigue and much of the joint pain that doctors generally attributed to lupus in the past can be caused by simultaneous FMS. In fact, some patients who were thought to have lupus were discovered to have a false positive lupus blood test (antinuclear antibody) and FMS only.
Treatment and prognosis
Treatment of FMS includes education about the illness, participation in exercise to increase aerobic capabilities, and the use of medicines such as doxepin hydrochloride to improve sleep. The U.S. Food and Drug Administration recently approved Lyrica® (pregabalin), the first drug to treat fibromyalgia. It reduces pain and improves function for some patients with fibromyalgia. Cymbalta® (duloxetene) is an antidepressant which acts by elevating levels of serotonin and norepinephrine. It is gaining attention as a treatment fibromyalgia.
Cognitive-behavioral treatment designed to develop active, resourceful, self-management approaches has been reported to be useful. Many health care providers use an approach that combines the resources of education, occupational therapy, physical therapy, and group work.
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