(CNN) About 15 years ago, an Amish family in the eastern US was hit by an unexplainable tragedy -- one of their children died suddenly while playing and running around. Just a few months later, the same fate befell another one of their children. Six years later, they lost another child. Two years after that, another one.

The autopsies didn't offer any clues. The children's hearts appeared normal. The family had what they referred to as "the curse of sudden death." And medical examiners couldn't figure out why.

After the deaths of the first two children, a medical examiner who conducted the autopsies got in touch with researchers at the Mayo Clinic Windland Smith Rice Sudden Death Genomics Laboratory in 2004. Researchers at the lab had pioneered the concept of molecular autopsy, using genetic testing to understand the cause of death in sudden unexplained cases, and the examiner wanted to see if they could shed light on the mystery affecting the Amish community.

The team suspected that a gene called RYR2 could be the culprit -- mutations of the gene can cause a cardiac arrhythmic disorder that can lead to exercise-fainting spells, seizures or even sudden cardiac death. But when they analyzed the gene to check for mutations, nothing turned up.

The case remained cold for more than a decade. As the years went by, pediatric cardiologists and genetic counselors from other parts of the country reached out to the lab about other Amish families whose children had also died sudden deaths -- all looking for answers about this heartbreaking phenomenon.

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