Chronic Fatigue Syndrome
Chronic fatigue syndrome refers to long-standing severe and disabling fatigue without a proven physical or psychologic cause.
Chronic fatigue syndrome may occur in up to 40 of 10,000 people in the United States; it affects people primarily between the ages of 20 and 50 and is about 1½ times more common in women than in men.
Cause
Despite considerable research, the cause of chronic fatigue syndrome remains unknown. Controversy exists as to whether there is a single cause or many causes and whether the cause is physical or psychologic.
Earlier studies have suggested infection with the Epstein-Barr virus, rubella, herpesvirus, or human immunodeficiency virus (HIV) as a possible cause of chronic fatigue syndrome. However, current research indicates that viral infections probably do not cause this syndrome, although in some cases they may hasten the onset of symptoms.
Some evidence suggests abnormalities of the immune system as a possible cause. Other suggested causes include allergies (about 65% of people with chronic fatigue syndrome report previous allergies), hormonal abnormalities, low blood pressure, decreased blood flow to the brain, and lack of certain nutrients in the diet.
Chronic fatigue syndrome seems to run in families, which may support an infectious agent as a cause. Alternatively, members of the same family may respond similarly to physical and psychosocial stress.
Some researchers have suggested that prolonged bedrest during convalescence from an illness may play a role in causing this disorder.
Symptoms and Diagnosis
The most important symptom is fatigue, usually lasting at least 6 months, that is severe enough to interfere with daily activities. Severe fatigue is present even on awakening and persists throughout the day. The fatigue often worsens with physical exertion or psychologic stress. However, evidence of muscle weakness or of joint or nerve abnormalities is rare. Symptoms often begin after a coldlike illness that involves swollen lymph nodes that are tender or painful; extreme fatigue begins with a fever, runny nose, and chest congestion (accumulation of fluid within the air sacs).
Other symptoms that may occur are difficulty in concentrating and sleeping, sore throat, headache, joint pains, muscle pains, and abdominal pain.
No laboratory tests are available to confirm a diagnosis of chronic fatigue syndrome. Doctors therefore must rule out other diseases that may cause similar symptoms, such as thyroid disease, psychosis, and alcoholism. The diagnosis of chronic fatigue syndrome is made only if no other cause, including side effects of drugs, is found to explain the fatigue.
 See the sidebar Diagnosis of Chronic Fatigue Syndrome.
Treatment
In most cases, symptoms of chronic fatigue syndrome lessen over time.
Regular aerobic exercise, such as walking, swimming, cycling, or jogging, under close medical supervision may reduce fatigue and improve physical function. Psychotherapy, including individual and group behavioral therapy, may be helpful as well.
Drug therapy has had mixed results. Antidepressants and corticosteroids have been useful in some cases, although their safety and effectiveness in the treatment of chronic fatigue syndrome have not been established. A number of other treatments, including use of interferons and antiviral drugs, have been mostly disappointing. Dietary supplements, such as evening primrose oil, fish oil supplements, and high-dose vitamins, are commonly used, but their benefits remain unproved. Intramuscular injections of magnesium sulfate have been shown to improve mood and energy levels in a few cases. Intravenous injections of immunoglobulin have benefitted some people, but the side effects of this drug can be very harmful.
Excessive periods of prolonged rest may worsen symptoms of chronic fatigue syndrome.
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