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.
Disorder often misdiagnosed
“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 Wednesday’s 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.
More common in men
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.