Introduction:

Chronic fatigue syndrome (CFS), sometimes called immune dysfunction syndrome or myalgic encephalomyelitis (in Europe), is not a new disorder. In the 19th century the term neurasthenia, or nervous exhaustion, was applied to symptoms resembling CFS. In the 1930s through the 1950s, outbreaks of disease marked by prolonged fatigue were reported in the United States and many other countries. Beginning in the early- to mid-1980s, interest in chronic fatigue syndrome was revived by reports in America and other countries of various outbreaks of long-term debilitating fatigue.

Unexplained chronic fatigue describes fatigue that lasts for more than 6 months, impairs normal activities, and has no identifiable medical or psychological problems to account for it. In addition to fatigue, people may complain of other problems, such as difficulty with memory or concentration, headaches, or sore muscles or joints.

The symptoms of CFS may be categorized as follows:

• Chronic fatigue syndrome (CFS). A number of criteria must be met in order for a patient's symptoms to be described as CFS. Six million patient visits are made each year because of fatigue, although only a very small percentage of these visits can be attributed to actual chronic fatigue syndrome.
• Idiopathic chronic fatigue. If the symptoms do not meet the criteria for CFS, the condition is referred to as idiopathic chronic fatigue, meaning the cause is unknown.

Although the exact causes of CFS are not known, researchers think infection, genetics, hormonal imbalances, and chemical toxins play roles in different patients.