Fibromyalgia Syndrome
Fibromyalgia syndrome (FMS), previously called fibrositis, is a diffuse pain syndrome and one of the most common causes of chronic musculoskeletal pain. FMS is observed in up to 15% of patients seen in a general rheumatology practice and 5% of general medicine clinic patients. It’s characterized by diffuse musculoskeletal pain, daily fatigue, and sleep disturbances, along with multiple tender
points (in specific areas) on examination. Females are affected more often than males and, although FMS may occur at almost any age, it occurs most often from ages 20 to 60. (See Fibromyalgia syndrome in males.)
points (in specific areas) on examination. Females are affected more often than males and, although FMS may occur at almost any age, it occurs most often from ages 20 to 60. (See Fibromyalgia syndrome in males.)
FMS has also been reported in children, who have more diffuse pain and sleep disturbances than do adult patients. They may have fewer tender points and often improve over 2 to 3 years of follow-up. (See Tender points in fibromyalgia, page 304.)
Causes
The cause of FMS is obscure, but it may be a primary disorder or may occur in association with an underlying disease, such as systemic lupus erythematosus, rheumatoid arthritis, osteoarthritis, and sleep apnea syndromes.
Many theories regarding the pathophysiology of FMS have been studied over the years. The pain is located mainly in muscle areas, but no distinct abnormalities have been documented on microscopic evaluation of biopsies of tender points when compared with normal muscle. One theory suggests that blood flow to the muscle is decreased (due to poor muscle aerobic conditioning rather than other physiologic abnormalities); another suggests that blood flow in the thalamus and caudate nucleus is decreased, leading to a lowered pain threshold. Still other theories suggest that the cause lies in an endocrine dysfunction such as abnormal pituitary-adrenal axis responses, or in abnormal levels of the neurotransmitter serotonin, which affect pain and sleep. Abnormal functioning of other pain-processing pathways may also be involved.
Considerable overlap of symptoms with other pain syndromes, such as chronic fatigue syndrome, raises the question of an association with infections such as parvovirus B19.
The development of FMS may be multifactorial; stress (physical and mental), physical conditioning, sleep disburbances, neuroendocrine factors, psychiatric factors and, possibly, hormonal factors (due to the predominance in females) may play roles.
Gender differencesFibromyalgia syndrome in males
Although current statistics indicate that females are more commonly affected by fibromyalgia syndrome (FMS) than males, the relationship between the condition and gender continues to cause confusion and controversy among researchers. Some studies indicate that males exhibit milder symptoms than females, whereas other studies indicate the reverse. Some researchers believe that reports of greater severity of symptoms in female patients arise from females’ willingness to verbalize complaints as compared to males’ reluctance to voice such complaints, rather than to objective clinical findings of gender-related variations in severity.
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