Chronic fatigue syndrome overview

Overview
Chronic fatigue syndrome (CFS) is one of several names given to a poorly understood, variably debilitating disorder of uncertain causation. CFS is thought, based on a 1999 study, to affect approximately 4 per 1,000 adults in the United States. For unknown reasons, CFS occurs more often in women than men, and in people in their 40s and 50s. The illness is estimated to be less prevalent among children and adolescents, but studies are contradictory as to the degree.

CFS often manifests with widespread myalgia and arthralgia, cognitive difficulties, chronic mental and physical exhaustion, often severe, and other characteristic symptoms in a previously healthy and active person. Despite promising avenues of research, there remains no assay or pathological finding which is widely accepted to be diagnostic of CFS. It remains a diagnosis of exclusion based largely on patient history and symptomatic criteria, although a number of tests can aid diagnosis. Whereas there is agreement on the genuine threat to health, happiness, and productivity posed by CFS, various physicians' groups, researchers, and patient activists champion very different nomenclature, diagnostic criteria, etiologic hypotheses, and treatments, resulting in controversy about nearly all aspects of the disorder. Even the term chronic fatigue syndrome is controversial because a large part of the patient community believes the name trivializes the illness.

Chronic fatigue syndrome is not the same as "chronic fatigue". Fatigue is a common symptom in many illnesses, but CFS is a multi-systemic disease and is relatively rare by comparison. Definitions (other than the 1991 UK Oxford criteria) require a number of features, the most common being severe mental and physical exhaustion which is "unrelieved by rest" (1994 Fukuda definition), and may be worsened by even trivial exertion (a mandatory diagnostic criterion according to some systems). Most diagnostic criteria require that symptoms must be present for at least six months, and all state the symptoms must not be caused by other medical conditions. CFS patients may report many symptoms which are not included in all diagnostic criteria, including muscle weakness, cognitive dysfunction, hypersensitivity, orthostatic intolerance, digestive disturbances, depression, poor immune response, and cardiac and respiratory problems. It is unclear if these symptoms represent co-morbid conditions or are produced by an underlying etiology of CFS. Some cases improve over time, and treatments (though none are universally accepted) bring a degree of improvement to many others, though full resolution may be only 5-10% according to the United States Centers for Disease Control and Prevention (CDC).