A sperm donor with a genetic mutation which increases the risk of cancer by up to 90 per cent has fathered at least 197 children across Europe.
The BBC reported that the man was paid to donate sperm as a student and that his sperm was used for about 17 years.
According to RTÉ, the sperm was sold to Ireland but no children in Ireland were born from it.
The man, who has not been named, passed donor screening tests.
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But the BBC reported that 20 per cent of his sperm carry a genetic mutation of the TP53 gene.
Any children born by this affected sperm will carry this mutation.
The TP53 gene protects from cancer by controlling the growth of cells. People with a change in the TP53 gene have Li-Fraumeni syndrome.
And people with this syndrome have up to 90 per cent increased risk of developing cancer before they turn 60.
This includes breast cancer; brain tumours; osteosarcoma; soft tissue sarcomas and childhood cancers.
Li-Fraumeni is a “rare syndrome”, according to an article from the National Institutes of Health in the US, which adds that there are likely more than 1,000 multi-generational families with the syndrome around the world.
Affected people have regular monitoring to look for tumours.
A small number of British women have received sperm from the donor while seeking fertility treatment abroad, the fertility regulator has confirmed.
This includes a “very small” number of women who received sperm from the donor while getting fertility care in Denmark, the UK’s Human Fertilisation and Embryology Authority (HFEA) said.
It is understood that the women have all been informed.
The HFEA confirmed that the sperm was not distributed to licensed UK clinics.
Peter Thompson, chief executive of the HFEA, said: “We can confirm that the Danish Patient Safety Authority has informed us that a very small number of UK women have been treated in Danish Fertility clinics with this sperm donor.
“We understand that they have been told about the donor by the Danish clinic at which they were treated.
“As the UK regulator, we only collect or hold information about treatment which takes place in the UK.
“As the treatment took place at Danish clinics, further inquiries should be directed to the competent authority in Denmark.”
In the UK, a donor’s sperm can only be used to create children in up to 10 families.
But in different countries, the limits are different.
The European Sperm Bank in Denmark told the BBC that the “donor himself and his family members are not ill” and such a mutation is “not detected preventively by genetic screening”.
Clare Turnbull, professor of cancer genetics at The Institute of Cancer Research, London, said: “This represents a highly unfortunate coincidence of two exceptionally unusual events: that the donor’s sperm carry mutations for an extremely rare genetic condition affecting fewer than 1 in 10,000 people and that his sperm has been used in the conception of such an extraordinarily large number of children.
“Li Fraumeni syndrome is a devastating diagnosis to impart to a family. There is a very high risk of cancer throughout the lifetime.
“Unlike most cancer genetic susceptibility syndromes we encounter in clinic such as Lynch syndrome or that caused by the BRCA-genes for which the cancers are adult-onset, inherited mutations [pathogenic variants] in TP53 are associated with a sizeable risk of childhood-onset cancers.”
