By Robert Langreth - 2012-06-13T18:00:00Z

Scanning the genes of children with inherited brain disorders pinpoints the precise cause more than a quarter of the time, often changing the diagnosis, according to one of the largest studies of child DNA sequencing.

The study published today in Science Translational Medicine examined the genes in 118 people with child-onset brain development disorders where obvious causes had been excluded. Researchers found new disease-causing mutations in 22 patients. In 10 more people, the scans found rare genetic diseases that had been misdiagnosed because symptoms were atypical. In two cases, the new diagnosis led to changes in treatment.

The study is a remarkable demonstration of the power of sequencing in the clinic -- precise, molecular, root cause diagnosis, said Eric Topol, a professor of genomics at the Scripps Research Institute in San Diego in an e-mail. Virtually all diseases will be more precisely defined through gene sequencing in the not-too-distant future, he wrote.

The research shows how often DNA scans can improve diagnosis in kids with brain disorders such as autism, severe epilepsy, or intellectual disability, said Joseph Gleeson, a child neurologist and study author. Brain development disorders afflict as much as 4 percent of children and are often genetic, yet the precise causes can be elusive, he said. Sequencing lets researchers examine all genes for abnormalities, instead of testing for one genetic disorder at a time as done now.

The biggest surprise is that some children with genetic brain disorders have diseases that have been known for a long time, said Gleeson, of the University of California, San Diego. The kids werent diagnosed correctly because frequently their symptoms dont match those in the textbook.

As a consequence, doctors may not have thought of ordering gene tests for those rare diseases, Gleeson said.

This is taking the whole medical field by surprise, Gleeson said. It used to be that the gray-haired professor was the gold standard, and if patient didnt respond to treatment then patient was an anomaly.

Gene sequencing eliminates the problem of misleading or vague symptoms by testing all genes, Gleeson said. It will change the way we practice medicine, he said.

The study follows research published in the June issue of the Journal of Medical Genetics, where scientists at Duke University used sequencing to diagnose six of 12 kids with genetic disease of unknown origin. In five of the cases, the children had had mutations in genes known to cause disease, said David Goldstein, the study leader and director of the Center for Human Genome Variation at Dukes School of Medicine in Durham, North Carolina. One child had been diagnosed with autism, yet turned out to actually have Pitt-Hopkins Syndrome.

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DNA Scans Can Spot Cause of Brain Issue in 25% of Kids