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Chronic fatigue syndrome

Synonym(s) Chronic fatigue immune dysfunction syndrome
Myalgic encephalomyelitis
Prevalence >1 / 1000
Inheritance -
Age of onset Adult
  • G93.3
  • C0015674
  • D015673
  • 10008874
  • 10057244


Chronic fatigue syndrome is characterized by extreme chronic fatigue of an indeterminate cause.

It is not a rare disease: the prevalence is estimated at between 0.4 and 1%. Chronic fatigue syndrome is more common in women than in men (female-to-male ratio of 4:1). It generally occurs in young adults between the ages of 20 and 40.

Patients complain of disabling fatigue that does not improve with rest and that is exacerbated by physical or mental activity. Concentration and memory difficulties are frequent. Some patients are unable to continue their occupational activities. Patients also often present viral symptoms such as fever, sore throat, headache, and general muscle weakness that may be associated with myalgias and arthralgias. The condition may lead to depression.

The etiology is unknown, but chronic fatigue syndrome seems to have a multifactorial origin. Viral or other infectious agents, immune system impairment and hormonal system deregulation may be involved in the etiology of the disease.

Chronic fatigue syndrome is a diagnosis of exclusion. Complete blood counts, blood and serum analyses and thyroid function tests should be performed. The diagnosis is made if four or more of the following symptoms are present for six months or more: impaired memory or concentration, sore throat, cervical or axillary lymph node pain, muscle pain, multiple joint pain without swelling or redness, nonhabitual or usually severe headaches, unrefreshing sleep, and prolonged postexertional malaise.

Differential diagnoses are numerous and include malignancies, liver and renal diseases, hormonal anomalies and some auto-immune diseases. Depression should also be excluded as 80% of cases of unexplained fatigue actually correspond to depression.

Management includes antidepressants with low doses of nonsteroidal anti-inflammatory drugs. Moderate physical activity is recommended. Cognitive-behavioral therapy may be of benefit.

About 50% of patients recover within the first five years after experiencing the initial symptoms of the disease. However, chronic fatigue syndrome often follows a cyclical course.

Expert reviewer(s)

  • Pr Pierre-Yves HATRON

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