10 Kids Conceived with Same Sperm Donor Develop Cancer, Sperm Used by More Families

After 10 children developed cancer, some of their families traced the diagnoses back to a singular sperm donor with a rare genetic variant.

The situation began when two of the children’s families reached out to their respective fertility clinics after the kids were diagnosed with cancers linked to a rare genetic mutation, according to a new report from The Guardian. The report was published on May 23, one day before Dr. Edwige Kasper, a French biologist, presented the case at the European Society of Human Genetics conference in Milan.

European Sperm Bank, which supplied the sperm, confirmed that the rare variant — which Kasper’s lab concluded was likely to cause Li-Fraumeni syndrome, an inherited predisposition to cancer — was found in some of the sperm, according to The Guardian. And more than two children were affected.

Separate but simultaneous investigations revealed that the variant, found in a gene called TP53, was present in 23 total children, 10 of whom had already been diagnosed with leukemia, non-Hodgkin lymphoma and other cancers, the outlet reported.

Though 10 kids have been diagnosed thus far, the company also confirmed that the donor’s sperm was used to conceive many more children.

European Sperm Bank — which recruits sperm donors in Denmark, Germany and the Netherlands, according to its website — said that more than 67 kids were conceived using the donor’s sperm, and that all relevant fertility clinics were alerted to the situation. (It did not, however, confirm the exact number, citing a company privacy policy.)

European Sperm Bank did not immediately respond to PEOPLE’s request for comment on Sunday, May 25.

A spokesperson for the company, Julie Paulli Budtz, told The Guardian the company is “deeply affected by this case.”

Budtz also said that, even with thorough testing prior to sperm donation, “it is scientifically simply not possible to detect disease-causing mutations in a person’s gene pool if you don’t know what you are looking for.”

Even if testing had unearthed the mutation, it was not yet linked to cancer in 2008 (the time of the donation) and would not have been detectable through standard screening procedures, The Guardian reported. The outlet also said the donor is in good health.

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Given the recent diagnoses linked to a single donor, however, Kasper argues that there should be a limit on the number of births or families for a single donor instated across Europe.

Speaking with The Guardian, the biologist said: “We can’t do whole-genome sequencing for all sperm donors — I’m not arguing for that. But this is the abnormal dissemination of genetic disease. Not every man has 75 children across Europe.”

That figure is a reference to European Sperm Bank’s self-imposed limit. Reacting to calls for a limit placed on the number of children conceived with the sperm of a single donor, Budtz told The Guardian, “We welcome continued dialogue on setting an internationally mandated family limit and have advocated for this on several occasions.”

“This is also why we have proactively implemented our own international limit of 75 families per donor,” Budtz added.