Chronic Fatigue Is in the Genes, Study
Finds
Mutations are to blame
for a syndrome often scoffed at
as imaginary, researchers say.
By Thomas H. Maugh II
Times Staff Writer
April
21, 2006
Chronic fatigue syndrome, often dismissed as the imaginings of
depressed and whiny people, is caused by genetic
mutations that impair the central nervous system's ability to adapt to stressful
situations, according to a major new study by the Centers for
Disease Control and Prevention.
Small changes
in many of the genes in the brain prevent the nervous system from rebounding
from everyday stress and from less frequent, stronger pressures, eventually
triggering a cascade of molecular responses that leave the patient severely
debilitated, researchers reported Thursday in 14 separate papers
in the journal Pharmacogenomics.
"This is the first credible evidence
for a biological basis" for the syndrome, said CDC Director Dr. Julie L.
Gerberding.
The findings will provide immediate help in diagnosing the
disorder, which often puzzles physicians because of the broad spectrum of
symptoms and the absence of defining biochemical markers.
It should also
lead to the development of effective treatments for patients, who receive only
therapy to mitigate symptoms — or in some cases are scoffed at as slackers.
"It is very hard to
treat an illness until you understand what it is physiologically," said Dr.
Lucinda Bateman of the Fatigue Consultation Clinic in Salt Lake City. "This is a
very important foundation" for developing new treatments.
Chronic fatigue
syndrome, commonly known as CFS, was first recognized in the 1980s but was long
dismissed as the complaint of "a bunch of hysterical, upper-class white women,"
said Dr. William C. Reeves of the CDC, who led the new study..
Diagnosis
is difficult because many of the psychological symptoms, in mild form, are
common traits of a modern stressful life.
Over the last two decades, most
physicians have come to recognize CFS as a valid illness, he added, but there
has been virtually no information about its causes. It has even been difficult
to provide a precise definition of the disorder.
Experts agree that it
affects as many as 1 million Americans, causing severe exhaustion, widespread
musculoskeletal pain, impairments in thinking and sleep
disturbances.
It strikes
four times as many women as men but is equally debilitating in both. It occurs
most frequently between the ages of 40 to
60.
Physiological manifestations, which must be present
for at least six months for a diagnosis, can include sore throat, tender lymph
nodes, headaches of a new or different type from those experienced in the past,
and malaise after exertion.
"They are as impaired as people with multiple sclerosis or AIDS or
who are undergoing chemotherapy for cancer," Reeves said. "They don't die, but
they are severely debilitated."
To learn more about the
disorder, a CDC team focused on Wichita, Kan., which turns out to be a
statistical microcosm of the United States in terms of wealth, urbanization,
age, race and other factors.
Initially, the team surveyed a quarter of
the population, or about 56,000 people, looking for symptoms of
CFS.
Reeves said they found that about 16% of people with the disorder
had been diagnosed and received some treatment.
The group then identified
227 CFS volunteers who each checked into a hospital for two days to undergo a
complete set of mental, physical, blood, sleep and other tests. Included was an
assessment of the activity of 20,000 genes.
Data in hand, the CDC
assembled four independent teams — each containing experts in medicine,
mathematics, molecular biology and computer science — and challenged them to
interpret the results. Each team produced two or three of the new papers, and
their results were surprisingly consistent.
The teams found that there
were at least four distinct forms of the disease, each with its own genetic
profile and symptoms but all including disabling fatigue. Some had relatively
mild symptoms, whereas others were debilitating.
But all the forms shared genetic mutations —
technically called single nucleotide polymorphisms — related to brain activity
that mediated the response to stress.
In particular, five
polymorphisms in three genes were "very important," said Dr. Suzanne Vernon of
the CDC, co-leader of the study. Those polymorphisms alone were sufficient to
diagnose about 75% of cases.
The genetic findings are particularly
important because they can lead to new drugs, said Dr. K. Kimberly McLeary,
president and chief executive of the Chronic Fatigue and Immune Dysfunction
Syndrome Assn. of America.
"Pharmaceutical companies have been sitting on
the sidelines because they have not been able to get their hands around CFS,"
she said. "This gives them something to latch onto" and identifies treatment
possibilities that haven't been explored.
The teams also found a strong correlation
between the severity of CFS and what they called allostatic load, the cumulative
wear and tear on the body resulting from chronic or inadequate adaptation to
stressors — such as changes in everyday routine, disease, and physical and
emotional trauma.
The CDC is gearing up to attempt to
replicate the findings in a study of 30,000 people in Georgia, Reeves
said.
The data have been given to 30 other groups of scientists who will
meet at Duke University in June to present their own interpretations.