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Chronic fatigue syndrome (CFS) is a disorder characterized by persistent and unexplained fatigue resulting in severe impairment in daily functioning. Besides intense fatigue, most patients with CFS report concomitant symptoms such as pain, cognitive dysfunction, and unrefreshing sleep. Additional symptoms can include headache, sore throat, tender lymph nodes, muscle aches, joint aches, post-exertional malaise, feverishness, difficulty sleeping, psychiatric problems, allergies, and abdominal cramps. Criteria for the diagnosis of CFS have been developed by the U.S. Centers for Disease Control and Prevention (Table 442-1). The Institute of Medicine (IOM; now the National Academy of Medicine) has recently changed the diagnostic criteria and proposed the name systemic exercise intolerance disease (SEID). To date, however, no studies have been reported to demonstrate the usefulness of this change.

TABLE 442-1Diagnostic Criteria for Chronic Fatigue Syndrome


image CFS is seen worldwide, with adult prevalence rates varying between 0.2 and 0.4%. In the United States, the prevalence is higher among women (~75% of cases), members of minority groups (African and Native Americans), and individuals with lower levels of education and occupational status. CFS has been reported to be associated with an increase in mortality from suicide. The mean age of onset is between 29 and 35 years. Many patients probably go undiagnosed and/or do not seek help.


There are numerous hypotheses about the etiology of CFS; there is no definitively identified cause. Distinguishing between predisposing, precipitating, and perpetuating factors in CFS helps to provide a framework for understanding this complex condition (Table 442-2).

TABLE 442-2Predisposing, Precipitating, and Perpetuating Factors in Chronic Fatigue Syndrome

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