Doctors in Australia and New Zealand are starting to unravel the mystery of why apparently healthy young people die unexpectedly.
There is a total of two or three such cases a week in the two countries, and many families never find out the reason.
These are young otherwise healthy people aged one to 35 with no known life-threatening condition, says University of Sydney Professor of Medicine Chris Semsarian, who is leading the study.
They are children who go to school and don't come home. People who go to sleep and don't wake up because of sudden cardiac arrest.
So far the world-first study has shown about half the deaths are not explained by a post mortem, says Prof Semsarian, who is presenting a report at a Royal College of Pathologists of Australasia (RCPA) conference in Melbourne on Saturday.
The tragedy of the death is bad enough but for parents not to know what happened leads to a lot of doubt and suspicion, and a lack of closure.
However, early indications are that about one in three of the unexplained deaths has an underlying genetic heart issue that the family did not know about.
This means the lives of the person's brothers and sisters could be saved if they have a blood test for the faulty gene, he says.
It is essential for them to speak to their GP about being tested.
"We have the tools to stop people dying suddenly. The challenge is to find out who is at risk," Prof Semsarian says.
Preventative measures for people at genetic risk range from advice about avoiding strenuous exercise to medicines like beta blockers or implanted devices to keep the heart beating.
Prof Semsarian is also trying to find out if modern technology can provide a viable alternative to physical post-mortem examinations, which are discouraged by some religions and many families find traumatic.
"We have found in a pilot study that doing an MRI and CT scan of the body is at least as good as a conventional autopsy at explaining what happened, but it is much less upsetting for the family."
