Researchers have identified a genetic cause for epilepsy, which could lead to the development of medicines to treat epilepsy and autism, the Translational Genomics Research Institute announced Thursday.

"This is the first step" in finding a cure for the childhood-onset diseases, said Dr. Dietrich Stephan, director of the neurogenomic division of TGen, the Phoenix-based research group that focuses on treatments and cures for genetically related illnesses.

"It allows us to better understand what causes the diseases," Stephan said of the discovery of a genetic mutation in Old Order Amish children in Pennsylvania.

TGen and the Clinic for Special Children in Strasburg, Pa. made the finding together.

Currently, medications treating epilepsy don't work on about 40 percent of the varying types of the disease, Stephan said. And the only treatment for autism are behavioral therapies — working with kids extensively on a daily basis to teach them life skills, he said.

Most epileptic symptoms, including recurring seizures, have been traced to abnormalities of the brain structure or chemistry that alter the electrical activity in nerve cells.

Autistic traits also are believed to be caused by disrupted nerve networks.

An estimated 2 million Americans are affected by epilepsy, while autism occurs in about 1.5 million, including about 100,000 school-age children. Seizures are the primary symptoms of epilepsy while autism can affect speech and the ability to interact with others.

The new finding was published in the New England Journal of Medicine. It describes a mutated gene that causes an epileptic disorder in Old Order Amish children in Pennsylvania. All of the affected children had relatively normal development until the onset of frequent seizures in early childhood.

They later developed language regression and other features of autism, which implicate the gene as a cause of autism in the general population, as well, Stephan said.

The next step for TGen researchers will be to develop drugs to prevent the disease by changing the way the brain reacts to the broken gene, he said.

Physicians at the Pennsylvania clinic isolated DNA from four of the affected children and their six parents and, in collaboration with TGen, identified a mutation that causes the gene to abnormally produce a protein called CASPR2.

For the first time, researchers showed that the protein plays an important role in early human brain development, said Dr. Erik Puffenberger, laboratory director at the Clinic for Special Children.

"Although these patients were from an isolated population, we anticipate that CASPR2 mutations will be found in children from other populations with mental retardation, seizures and autism," he said.

The discovery of the protein-related mutation in the clinic's Amish patients has already allowed doctors to identify at-risk newborns before they show symptoms, said Dr. Holmes Morton, the clinic's medical director.

"Our hope is that early treatment and prevention of prolonged seizures in these infants will lessen the effects of the disorder upon the lives of the children and their families," he said.