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Genes may link autism, muscle-weakening disease

Sun Apr 13, 2008 11:51pm BST

By Steenhuysen

CHICAGO (Reuters) - U.S. researchers have found a genetic link between autism and a muscle-weakening disorder known as mitochondrial disease, they said on Sunday, in a finding that may open new avenues of research into the causes of autism.

"Recent studies have suggested that as many 20 percent of patients with autism have markers for mitochondrial disease," said Dr. Shoffner, a neurologist and geneticist at Medical Neurogenetics in Atlanta, who presented his findings at the American Academy of Neurology meeting in Chicago.

"There has really not been much work done so far to push that issue," Shoffner said in a telephone interview.

Mitochondrial diseases are a set of genetic disorders in which energy-producing structures in cells are impaired. The disease is often triggered by an illness, such as a high fever, which can result in severe muscle weakening.

Shoffner wanted to see if he could identify the underlying genetic mechanisms that might explain this link.

He evaluated genetic samples and clinical information gathered on 37 children diagnosed with autism who had been evaluated at his clinic for mitochondrial disease.

They found more than 60 percent of these children had mitochondrial defects.

Shoffner said the finding needs to be confirmed in other studies, but it does help to validate the hypothesis of a link between the two conditions in a subset of patients.

"This is a fundamental first step," Shoffner said in a telephone interview. "This gives us a great foothold for moving forward with this population -- asking better, more precise questions."

GEORGIA CASE

No one knows what causes autism, but researchers think it is likely that several genes contribute.

Some autism advocates have seized on the case of a Georgia girl with a rare mitochondrial disease and autism-like symptoms who won federal compensation in a case arguing a vaccine led to her condition.

Government health officials say there is no scientific evidence to suggest that vaccines cause autism, which is part of a spectrum of disorders that can have relatively mild symptoms or can severely disable a child by interfering with speech and behavior.

Shoffner said most children with autism spectrum disorders do not have recognizable abnormalities in mitochondria, but a group of these children have significant defects.

"We are opening avenues of additional research into autism spectrum disorders and new ideas about what might be causing these disorders to develop," he said.

The U.S. Centers for Disease Control and Prevention estimates that about one in every 150 U.S. children has autism or a related disorder such as Asperger's syndrome, which is marked by mild social awkwardness.

Several studies have suggested that genes involved with communication pathways in the brain may contribute to autism, and Shoffner thinks it is possible that cells with impaired ability to convert food into energy may play a role.

"It certainly sits at a very important place in cellular metabolism that can significantly alter neuronal (nerve cell) development," he said.

(Editing by Maggie Fox and Beech)

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