Chronic fatigue syndrome

Last updated: July 1, 2022

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Chronic fatigue syndrome (CFS), also known as “myalgic encephalomyelitis,” is a multisystem disease characterized by severe fatigue, cognitive dysfunction, unrefreshing sleep, orthostatic intolerance, and post-exertional malaise. The etiology of CFS is not completely understood but possible factors include genetic predisposition, prior infections, and immune abnormalities to the immune system. Diagnosis is based on clinical examination (i.e., IOM diagnostic criteria for CFS) and exclusion of other causes (e.g., glucose measurement to rule out diabetes mellitus). Since there is no curative treatment, management focuses on alleviating symptoms (e.g., improving quality of sleep). In most cases, symptoms improve with treatment but complete resolution of symptoms is rare.

Epidemiological data refers to the US, unless otherwise specified.

The etiology of CFS is not completely understood. Factors possibly involved include the following:

  • Most common symptoms:
    • Unexplained fatigue that is not relieved by rest
    • Post-exertional malaise (e.g., muscle/joint pain, headache)
    • Unrefreshing sleep (i.e., daytime hypersomnolence and nighttime insomnia)
    • Cognitive impairment (e.g., impaired short term memory, decreased attention span)
    • Orthostatic intolerance (e.g., dizziness, nausea, vomiting)
    • Psychiatric symptoms (e.g., anxiety, depression)
  • Symptoms are typically exacerbated by excessive physical activity or stress (e.g., infection).
  • Physical examination is typically normal.

2015 IOM diagnostic criteria for CFS [2]

  • Presence of all three of the following symptoms:
    • New-onset (not life-long) and often profound fatigue that
      • Is not alleviated by rest.
      • Is not the result of excessive exertion.
      • Substantially impairs academic, professional, leisure, or social function for > 6 months
    • Post-exertional malaise
    • Unrefreshing sleep
  • Presence of at least one of the following two symptoms:
    • Cognitive impairment
    • Orthostatic intolerance
  • Diagnosis should be reassessed if symptoms are not moderate to severe at least 50% of the time.

Rule out other causes

See also “Differential diagnoses” below.

The differential diagnoses listed here are not exhaustive.

Since there is no curative treatment, management focuses on alleviating symptoms.

In most patients, symptoms improve with treatment but complete resolution of symptoms is rare (∼ 2% of cases). [18]

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