Chronic Fatigue Syndrome

Chronic Fatigue Syndrome

National Organization for Rare Disorders, Inc.


It is possible that the main title of the report Chronic Fatigue Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • CFS
  • Chronic Fatigue and Immune Dysfunction Syndrome

Disorder Subdivisions

  • None

General Discussion

Chronic fatigue syndrome (CFS) is a complex disorder characterized by profound fatigue and other related symptoms. Standards for the diagnosis of CFS have been defined by researchers at the Centers for Disease Control and Prevention (CDC). These include excessive fatigue that does not respond to bed rest, combined with four or more of the following symptoms: substantial impairment in short-term memory or concentration; sore throat; tender lymph nodes; muscle pain; pain in multiple joints without redness or stiffness; headaches of a new type, pattern or severity; unrefreshing sleep; and a general feeling of ill health (malaise) for up to 24 hours after exertion.

Chronic fatigue syndrome has generated significant debate and controversy in the medical community. It remains a poorly understood and potentially debilitating illness. Scientists believe chronic fatigue syndrome is not contagious and that multiple factors including immunological, genetic, environmental ones working in combination cause the development of chronic fatigue syndrome. Laboratory tests (blood, urine, etc.) are of little value in diagnosing the syndrome.


After years of debate and controversy, chronic fatigue syndrome has been defined by an international group of physicians brought together by the Centers for Disease Control and Prevention (CDC). To receive a diagnosis of chronic fatigue syndrome, a patient must satisfy two criteria:

Have severe chronic fatigue of six months or longer duration with other known medical conditions excluded by clinical diagnosis, and

Concurrently, have four or more of the following symptoms: substantial impairment in short-term memory or concentration; sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern or severity; unrefreshing sleep; and post-exertional malaise lasting more than 24 hours.

The symptoms must have persisted or recurred during six or more consecutive months of illness and must not have predated the fatigue.

The onset of these symptoms is usually sudden, sometimes following a flu-like illness. The syndrome may persist for months or years, and disappear without treatment. The many symptoms of chronic fatigue syndrome do not always occur with the same degree of severity or at the same time. There are usually instances when symptoms may disappear for periods of time.

Additional symptoms may develop in some individuals including visual disturbances such as light sensitivity or blurred vision; chills; night sweats, gastrointestinal abnormalities; cognitive impairment; a chronic cough; jaw pain; chest pain; difficulty breathing; and morning stiffness. Some individuals may also have psychological problems including depression, anxiety or panic attacks.


The exact cause of chronic fatigue syndrome is not known although researchers are continually investigating this disorder. Many clinical researchers believe that chronic fatigue syndrome is overdiagnosed. It is possible that many people diagnosed with CFS have another disease that has similar symptoms, and may be easily confused with CFS. Only those individuals who meet the strict diagnostic criteria set by the CDC actually have chronic fatigue syndrome.

Many researchers believe that chronic fatigue syndrome is a complex disorder in which several different factors contribute to the development of the disorder. Such factors include infectious, immunological, and genetic factors. Researchers have theorized that abnormalities of the immune system, the brain and the hypothalamic-pituitary-adrenal (HAP) axis may all play a role in the development of chronic fatigue syndrome. Some researchers believe that some affected individuals have a genetic predisposition to the disorder. A genetic predisposition means that a person carries a gene or genes for a disease, but that it may not be expressed unless other additional factors are present. The genetic factors associated with narcolepsy are insufficient to cause the disorder by themselves.

Researchers have investigated the role of viruses as a possible cause of chronic fatigue syndrome. During the 1980's physicians believed that the virus that causes mononucleosis, Epstein Barr virus, was the cause of this illness. However, that theory was disproven and tests for antibodies to this virus are no longer used to diagnose chronic fatigue syndrome. During 1990, a team of scientists at the Wistar Institute isolated a virus from the blood of adults and children with chronic fatigue syndrome. The virus, Human T- Cell Lymphotrophic, Type II (HTLV-2) is a slow virus or "retrovirus." Slow viruses may stay dormant in humans for extended periods of time, then for reasons yet unknown may unexplainably become reactivated. It is not clear how or if the virus may be transmitted, nor is there evidence yet to prove that this HTLV virus is actually associated with the cause or progression of chronic fatigue syndrome. More recent studies indicate that there is no evidence for the involvement of any slow virus as a cause for CFS.

Other studies suggest that HHV-6, a herpes virus, may be partially responsible for the development of chronic fatigue syndrome. However, this evidence remains inconclusive.

Researchers are also investigating abnormalities in the immune system of individuals with chronic fatigue syndrome. Some research suggests that an unknown immune defect, along with a viral disease which triggers the illness, may cause this disorder. Other information suggests that susceptibility to chronic fatigue syndrome may be associated with subtle immune system defects.

Another theory is that chronic fatigue syndrome may occur as the result of the immune system's over-reaction to infectious agents in highly allergic people. Some researchers suspect that chemicals called cytokines, which help regulate the immune system, may cause some symptoms of CFS in individuals with severe allergies. However, none of these theories have been scientifically proven, and the cause of CFS is still unknown.

Affected Populations

Chronic fatigue syndrome was once considered a rare disorder and, although some physicians believe it to be overdiagnosed, studies conducted by the CDC place the incidence at between 1-4 million people in the United States. The CDC also states that fewer than 20 percent of individuals with chronic fatigue syndrome have been properly diagnosed.

Women are affected 2-4 times more often than men. Some researchers believe that this disparity results from women being more likely to report their symptoms to a doctor than men. Chronic fatigue syndrome is most likely to develop in individuals in their 40s or 50s. However, it can affect individuals of any age including children. Chronic fatigue syndrome affects individuals of every race and ethnicity.

In approximately 70 percent of cases, the onset of chronic fatigue syndrome is associated with an acute infectious illness. These illnesses include infectious mononucleosis, influenza, upper respiratory infections, acute inflammation of the liver (hepatitis), and flu-like diseases.

Standard Therapies

Evaluation, Screening and Diagnosis

Chronic fatigue symptom experts have developed a five-stage process for evaluating a patient for CFS. These steps are:

A detailed medical history followed by a complete physical examination

A mental status examination is administered by the physician by means of a short discussion and/or a brief oral test.

A standard set of laboratory tests of the patient's blood and urine is required in order to eliminate or identify other causes of fatigue.

If these lab tests indicate another source for the fatigue, additional tests will be administered in order to confirm the diagnosis.

If the results of the lab tests do not indicate an alternative cause of the fatigue, the physician will determine if the patient meets the CDC criteria for a diagnosis of CFS.

For a comprehensive description of the tests used to screen for CFS see:


There is no cure for chronic fatigue syndrome; treatment is aimed at alleviating symptoms. Treatment is highly individualized; treatment that is effective in one person may not be effective in others. A wide and diverse range of therapies have been used to treat individuals with chronic fatigue syndrome.

Counseling may help individuals adjust to the chronic nature of the illness. Anti-viral medications as well as many other drugs have not proven effective. Although rest, eating a balanced diet, and moderate exercise are recommended, there is no evidence that these measures cure chronic fatigue syndrome. For some people, physical and emotional stress may make the symptoms worse. The choice to begin any drug therapy that presumes to relieve symptoms depends on the patient's specific complaints, the potential for side effects, and the advice of a qualified caregiver.

Various therapies that may be used to treat chronic fatigue syndrome include behavioral modification, physical therapy, stretching exercise and nutritional supplementation. Certain over-the-counter medications can be used to treat specific symptoms such as gastrointestinal abnormalities, sleep problems, allergies and depression.

Investigational Therapies

A variety of drugs such as corticosteroids, immunoglobulins, stimulants such as methylphenidate (Ritalin) and others are being studied for the treatment of chronic fatigue syndrome. Acupuncture, yoga, massage therapy and other alternative therapies are also being studied. More research is necessary to determine the long-term safety and effectiveness of these potential therapies for individuals with chronic fatigue syndrome.

Information on current clinical trials is posted on the Internet at All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010


For information about clinical trials sponsored by private sources, contact:



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National Chronic Fatigue Syndrome & Fibromyalgia Association

P.O. Box 18426

Kansas City, MO 64133


Tel: (816)737-1343

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American Autoimmune Related Diseases Association, Inc.

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American Academy of Allergy, Asthma and Immunology

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CFIDS Association of America

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National CFIDS Foundation, Inc.

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Wisconsin Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Association, Inc.

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Tel: (608)834-1001



New Horizons Un-Limited, Inc.

811 East Wisconsin Ave

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Genetic and Rare Diseases (GARD) Information Center

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Autoimmune Information Network, Inc.

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European Society for Immunodeficiencies

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