A man who fathered at least 24 children by sperm donation in the US failed to inform fertility clinics that he had a rare genetic defect which is often fatal, ABC news has reported.

This was revealed after Rebecca Blackwell and her son Tyler, who was conceived using donor sperm, tracked down Tyler's biological father three years ago. They discovered that donor 'John' had a rare aortic heart disorder that had nearly killed him after his aorta ruptured at the age of 43. John's father and two of his brothers had the same genetic condition. John also has Marfan's syndrome, a connective tissue disorder, but none of this information was disclosed to the three sperm banks to which he contributed.

Tyler, who is now 18, had corrective surgery last summer, but his mother has questioned why they were never told about John's medical history. 'Tyler had a time bomb ticking in his chest', she said. 'It didn't occur to anyone to tell us'.

A similar case occurred in 2009 in California when a sperm donor passed on hypertrophic cardiomyopathy to nine of his 22 known offspring, one of whom died. Such reports raise the issues of donor anonymity and the sharing of medical records.

The fertility industry in the US is one of the least regulated in the developed world. Wendy Kramer of the Donor Sibling Registry, which has matched 8,400 donor siblings with their half siblings and/or donors, said: 'There are no rules or regulations about donor identification, testing donors, monitoring numbers of children or medical records'.

However, last month Washington became the first US state to grant rights to donor-conceived individuals so that when they turn 18 they can access their donors' medical histories and full names, unless the donor specifically opts out of being identified.

At present, the US Food and Drug Administration guidelines indicate that donated sperm cannot have any 'relevant communicable disease or agent', but medical information is not shared between the donor and the child's family. Advocates argue that donor anonymity should end, and testing should be extended to include genetic conditions such as cystic fibrosis and Tay-Sachs disease.

Sean Tipton, a spokesman from the American Society for Reproductive Medicine, said: 'I don't think there's a way to make human reproduction perfect...all you can do is use the best and most practical screening available at the time of donation'. He added that 'you can't screen for everything'.

Other countries – including Sweden, Austria, New Zealand, the Netherlands, Norway, Switzerland, the UK, and some states in Australia – have already removed donor anonymity and have established systems to help people find their sperm donor. In May, a landmark case in British Columbia banned anonymous gamete donation, although this is currently being appealed by the government.