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Research led by Mayo Clinic has solved a two-decade-old mystery about why so many otherwise healthy children and young people in Amish communities have been dying from sudden unexplained cardiac deaths.

Examining the DNA of four Amish siblings who suffered cardiac deaths while playing or exercising, researchers found they all had a duplication of specific genetic material that put them at risk.

Further research found the same genetic defect in children from other Amish families who suffered unexplained cardiac deaths — and that the defect could be passed down only if both birth parents carried the defect.

Genetic testing wasn't sophisticated enough to find the defect after the deaths of the first two adolescents in 2004, and before the more recent deaths of two of their siblings. But the discovery now provides a way to find out if future generations of children are at risk, said Dr. Michael Ackerman of Mayo's Windland Smith Rice Sudden Death Genomics Laboratory.

"What we have for this community is a gold standard biomarker for them to figure out who are the carriers," he said. He said there are no known heart scans or tests that identify the at-risk children.

The genetic defect in these children is linked to the practice in some Amish communities of close relatives marrying and having children together.

Screening and genetic counseling could dissuade carriers of the defect from having children together, though Ackerman said that could be disruptive to the Amish social order. He said researchers hope that ongoing work will find medications or treatments that can protect at-risk children. Families also can consider having defibrillators implanted in children who received "double doses" of the genetic defect from their parents.

The discovery was reported in the medical Journal JAMA Cardiology. Ackerman said the researchers studied cases from Amish communities in Delaware, Kentucky, Pennsylvania and Iowa, and that they all probably trace back to the same ancestry and "founder gene."

Despite stereotypes of shunning technology, the Amish families have been open to medical testing and to taking steps to prevent the risks of cardiac deaths in their children, Ackerman said.

The paper was based on the discovery of the genetic defect in 23 children, 18 of whom suffered sudden cardiac deaths. While the actual risk is probably lower, because the researchers don't know how many healthy people live with the defect, Ackerman said it is severe and frightening to families.

Discovering it has brought some solace to parents who are grieving. "It's closure," he said. "We can tell them the root cause … why their children died tragically and suddenly while playing. That is powerful medicine itself."

Jeremy Olson • 612-673-7744 • @stribjo