Chronic fatigue syndrome is a complex condition characterized by extreme, long-lasting exhaustion. This disorder affects many different body systems, and is often disabling. The main symptom of chronic fatigue syndrome (CFS) is tiredness that does not improve with rest and prevents you from carrying out normal daily activities. The term “chronic fatigue syndrome” was adopted in 1988, when researchers considered fatigue to be the major symptom. Today, physicians and patient groups often refer to this disorder as “chronic fatigue and immune-dysfunction syndrome” (CFIDS) to stress that it involves many other symptoms. Symptoms vary among patients, and can even change in the same person over time. Another name for CFS is myalgic encephalomyelitis.
The cause and cure of CFS are not known. Because it resembles other disorders and can be hard to recognize, doctors often miss it. CFS itself cannot be cured—thus, treatment focuses on relieving symptoms. The disorder may last for years. Although patients usually improve over time, most do not recover completely.
The people who first brought CFS to wide public notice in the 1980s were mostly affluent women. Thus, the illness was nicknamed “yuppie flu.” Since then, researchers have found that the disorder occurs in a wide range of social and economic classes and all races and ethnic groups.
Scientists do not know the exact prevalence of CFS because the disorder is so hard to define. The CDC estimates that up to half a million people in the US have the symptoms of CFS, but have not been diagnosed by a doctor. The chronic fatigue and immune dysfunction syndrome (CFIDS) Association of America (www.cfids.org), a patient support group, estimates the number to be about 800,000. They estimate that 90% of people with CFS have not been diagnosed and are not receiving care.
No one knows what causes CFS. Many physicians suspect that a variety of factors, including viruses and other germs, immune system disorders, brain abnormalities, and blood pressure disorders act together to trigger it. Scientists are studying several possible causes of CFS. In time they may discover a single cause, or find that several factors work together to produce the disorder. Because CFS is so hard to define, some physicians still believe that it is not a real disease, but is psychological in origin. However, the National Institute of Allergy and Infectious Diseases recognizes CFS as a serious illness, and the Centers for Disease Control and Prevention (CDC) have developed criteria to define it.
The following are some possible causes of CFS.
- Viruses and other germs. Many patients develop CFS after an illness resembling a viral infection, and researchers first believed that a virus was the cause. Epstein-Barr virus, which causes mononucleosis, was especially suspect. However, scientists have been unable to link CFS with any specific agent as the single cause. They are trying to discover whether any infectious organisms play a partial role in causing CFS.
- Immune system disorders. Some research has found that people with CFS have either overactive or underactive immune systems. However, these people do not have the diseases that are usually associated with overactive immune systems, such as lupus and rheumatoid arthritis, and they are not more likely to develop cancer or infections, as may people with depressed immune systems.
- Brain abnormalities. Studies show that people with CFS have abnormally low brain levels of a hormone called corticotropin, which helps in coping with stress. These people often report that they were under a great deal of stress just before the condition began. Scientists think that, due to the low hormone levels, their immune systems might overreact to stress, causing the symptoms of CFS. However, CFS patients who were given a replacement hormone that restored their hormone levels to normal did not get better. This result suggests that low hormone levels do not directly cause CFS.
- Blood pressure disorders. Some evidence suggests that CFS is related to a blood pressure disorder called neurally mediated hypotension (NMH), in which the brain signals the heart to slow down when you stand up. Your blood pressure falls, temporarily depriving your brain of oxygen, so that you become light-headed and may even faint. Many people with CFS have such symptoms when they stand for long periods, and scientists are testing whether the medicines given to people with NMH might also help those with CFS.
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