Researchers say they
have discovered a tremor disorder in adults that is often mistaken
for Parkinson's or Alzheimer's and is linked to a common cause
of mental retardation in children.
The disorder, which
can also cause memory loss, might affect more than 1 in 3,000
adults, mostly men, according to scientists at the University
of California at Davis.
There is no known
cure for the disorder, but its symptoms can sometimes be treated
with some of the same medications used against Parkinson's and
Alzheimer's.
The researchers
have named the disorder Fragile X-associated Tremor/Ataxia Syndrome,
or FXTAS.
"FXTAS may be one
of the most common causes of tremor and balance problems in
the adult population, yet it is being misdiagnosed because neurologists
who see adults with movement disorders are not aware that they
need to look for a family history of fragile X in grandchildren
or to check for carriers of the gene mutation," said study co-author
Dr. Randi Hagerman, medical director of UC-Davis' MIND Institute.
The findings appear
in the Journal of the American Medical Association.
The disorder affects
some carriers of the same abnormal gene that causes fragile
X syndrome in children, an inherited disease that usually involves
retardation. About 1 in 800 men are fragile X carriers and at
least 30 percent of them might have the tremor disorder, the
researchers said.
Hagerman made the
connection a few years ago after hearing repeated complaints
from mothers of fragile X children about their own elderly fathers
having neurological problems.
Standard DNA blood
tests can identify fragile X carriers and imaging tests can
detect telltale changes in the brain that do not appear in other
diseases, said Dr. Paul Hagerman, a UC-Davis professor of biological
chemistry, Hagerman's husband and the study's senior author.
About 1 in about
250 women are carriers, but Paul Hagerman said it is unclear
how many of them have the disorder because few women carriers
who were studied had symptoms.
The UC-Davis-led
research involved 192 California adults ages 50 and over who
were relatives of children with fragile X. Participants included
99 male and female fragile X carriers and 93 members of a comparison
group.
Overall, 30 percent
of the male carriers studied had the late-onset disorder. It
became increasingly prevalent among older men and was found
in 75 percent of male carriers in their 80s.
In fragile X syndrome,
the body makes insufficient amounts of a protein necessary for
normal neural cell function. By contrast, FXTAS is believed
to be caused by abnormal amounts of genetic material that accumulates
in the brain in an attempt to make enough of that protein, said
study co-author Dr. Elizabeth Berry-Kravis, a pediatric neurologist
at Chicago's Rush University Medical Center.
Fragile X syndrome
in children was identified some 50 years ago and is believed
to affect about 1 in 3,700 boys and 1 in 8,000 girls.
Carriers of the
abnormal gene had been thought to be unaffected until the Hagermans'
discovery, said Dr. Walter Kaufmann, director of the Fragile
X Syndrome Research Program at Kennedy Krieger Institute in
Baltimore.
"The real magnitude
and impact had not been known until this paper," Kaufmann said.
On the Net:
JAMA: http://jama.ama-assn.org
National Fragile
X Foundation: http://www.fragilex.org
Reference
Source 102
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