Fibromyalgia, a disorder of brain chemicals characterized by chronic muscle pain, fatigue, and nonrestorative sleep, is an illness that frustrates physicians as much as patients. It can be associated with many symptoms: irritable bowel, urinary urgency, and headache are among the most common that laboratory tests fail to confirm, often causing doctors to wonder if the patient is not just an attention-seeking hypochondriac. Presenting symptoms can come and go with such rapidity that even the patient herself may wonder if she is imagining things, although her suffering is real enough.

More properly referred to as the fibromyalgia syndrome (FMS), because it is in fact a collection of symptoms without a known cause, it affects an estimated 5 percent of the population, women outnumbering men by about eight to one. The classical diagnostic criteria for FMS are a history of pain in all four quadrants of the body with a duration of more than three months, and exquisite pain when pressure is applied to certain specific places on the body, each at a point near a muscle's attachment to bone.

Fibromyalgia is not new, although awareness of it is now growing rapidly. Hippocrates described it. In Victorian times it was known as neurasthenia. More recently it was called fibrositis a misnomer, because the suffix "itis" suggests inflammation. FMS is not an inflammatory condition, unlike lupus, and polyarthralgia rheumatica. Nor is it degenerative, like multiple sclerosis. Yet fibromyalgia's symptoms often mimic these diseases, leading to erroneous and frightening misdiagnosis. Fibromyalgia is not progressive, it is not life-threatening, but it is as yet incurable. However, with proper care, it can be managed, although about one-third of the people with fibromyalgia are partially or totally disabled. Thus, its economic cost to society as a whole is considerable.

Fibromyalgics are often depressed, but depression does not cause fibromyalgia. Indeed, if one is in constant pain and unable get a decent night's sleep, depression may be a rational response. Additionally, blood studies have suggested a deficiency in serotonin among people with fibromyalgia. Since serotonin modulates mood, among its other functions, low levels of this neurohormone might well cause depression.

FMS most commonly appears in adults, but it is also present in children. A study of school children in Israel found FMS in 8 percent of the sample. Children who have difficulty sleeping and complain of pain should be evaluated by a physician familiar with fibromyalgia. So-called "growing pains" are often a sign of FMS in children. The youngest child reported to have FMS so far was four years old at the time of diagnosis. A small child who is told that pain is normal may grow to adulthood believing that everyone is in pain all of the time.

Fibromyalgia tends to run in families, although the precise genetic mechanism is not yet known. The taut, ropy muscles of people with fibromyalgia were found in one study to be present in family members who had no chronic pain. It is thought by most fibromyologists that the syndrome can be triggered by illness or injury, indeed by anything that robs one of sleep, which may account for the preponderance of females in the affected population, since women more often than men have their sleep disturbed by the need to care for infants and small children. Sleep apnea the sudden, involuntary, and momentary cessation of breathing during deep sleep is the leading cause of FMS in men. Treating this problem often results in remission of symptoms.

Conventional treatment for fibromyalgia consists of low doses of a tricyclic antidepressant or serotonin reuptake inhibitor, which serve to increase the availability of serotonin; the institution of habits that improve sleep; proper nutrition; and daily aerobic exercise. The need for exercise is a significant issue for most people with fibromyalgia; muscle pain may increase after exercise, and repetitive motions of any sort make most fibromyalgics hurt more.

But most experts agree that exercise is the single most important factor in a fibromyalgic's well-being. It need not be strenuous: Riding a stationary bicycle and walking are the two most recommended forms of exercise. People with fibromyalgia may have to start with two or three minutes of exercise and work up from there a minute at a time, but without exercise FMS can indeed seem to be a progressive disorder, as unused muscles stiffen and atrophy, causing more pain and muscle damage.

Future articles will explore various theories of the process that causes fibromyalgia, as well as specific therapies that have been and are being tested.

5/30/98

Miryam Williamson, a contributing editor to SelfhelpMagazine, is a technical journalist and author of "Fibromyalgia: A Comprehensive Approach What You Can Do About Chronic Pain and Fatigue," published by Walker and Company, New York, 1996, ISBN 0-8027-7484-9. At bookstores in early June, or from the publisher at 800-289-2553.