Chronic Fatigue Syndrome Not Caused by Virus, So What Does?

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For nearly two years, many people thought a cause for chronic fatigue syndrome had been found: a virus called XMRV. Now the editor-in-chief of Science, the journal that published the original research article, says that finding is “now seriously in question,” leaving the patients to ask, if chronic fatigue is not caused by a virus, what does?

Chronic fatigue is not in your head

In October 2009, a study by VC Lombardi et al showed that a retrovirus called XMRV (xenotropic murine leukemia virus-related virus) was found in the blood of 67 percent of people who had chronic fatigue syndrome (CFS), but in only 3.7 percent of healthy individuals. Unfortunately, this finding was not repeated in subsequent research by other investigators.

For people who suffer with CFS, Lombardi’s article provided hope for effective treatments for a condition characterized by significant fatigue, memory problems, muscle pain, and other symptoms that can be life-altering and debilitating. It also gave legitimacy to a condition that some doctors say is in a patient’s head.

Now, in an “Editorial Expression of Concern” by Science editor-in-chief Bruce Alberts, he explains that the journal is publishing “two Reports that strongly support the growing view that the association between XMRV and CFS described by Lombardi et al. likely reflects contamination of laboratories and research reagents with the virus.”

Alberts also adds that the US National Institutes of Health is sponsoring studies “to ascertain whether the association between XMRV and CFS can be confirmed,” and that Science “will take appropriate action when their results are known.” In the meantime, the questions surrounding what causes chronic fatigue syndrome reenter the spotlight.

Although there are several theories about what causes chronic fatigue, no main cause has been identified that can explain all cases, and experts generally believe more than one factor is involved. Adding to the frustration is the fact that there are no brain scans or blood tests that can provide a definitive diagnosis.

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A new study published in BMC Neurology suggests heredity plays a role. Investigators report “significant excess relatedness” for first, second, and third degree relatives, and their findings “provide strong support for a heritable contribution to predisposition to Chronic Fatigue Syndrome.”

Genetic defects have been named as a possible factor. Genes in the hypothalamic-pituitary-adrenal axis and sympathetic nervous system that control response to stressful events have been linked to chronic fatigue, and variations in genes involved with immune function and cell communication have also been suggested as causes.

Some studies have found abnormal levels of certain chemicals that regulate the hypothalamus-pituitary-adrenal axis, such as serotonin, dopamine, and cortisol, in chronic fatigue patients and suggest these may be a cause of the syndrome. A disturbance of the sleep/wake cycle has also been named as a possible cause.

The possibility that infections may cause chronic fatigue syndrome, such as the XMRV, has long been a popular one, because many people with the syndrome have symptoms similar to those of long-term viral illness. In addition, up to 80 percent of cases of chronic fatigue start abruptly with a flu-like condition. Infections as a cause is still under much investigation.

Other possible causes include abnormalities in the immune system, including allergies and the presence of autoantibodies (antibodies that attack the body’s tissues). Psychological factors may play a part in increasing a person’s susceptibility to chronic fatigue, but generally they are not believed to be a main cause.

What causes chronic fatigue syndrome? The answer is still elusive. If not the XMRV virus, perhaps another virus will emerge, or scientists will uncover an entirely new cause. For those who suffer with chronic fatigue syndrome, the wait for answers is an exhausting one.

SOURCES:
Alberts B. Science, published online 31 May 2011; 10.1126/science.1208542
Albright F et al. BMC Neurologyy 2011 May 27; 11(1): 62
University of Maryland Medical Center

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