Danish sperm donor’s genetic mutation linked to cancer in over 200 children

A 19-year-old Danish woman, conceived via sperm donor “Kjeld,” has survived cancer twice due to a rare and life-threatening genetic mutation inherited from the donor—who has fathered at least 211 children worldwide, a DR investigation reveals.

Julie Jepsen was first diagnosed with aggressive lymphoma at age four, undergoing chemotherapy and hospital treatments that left her mother questioning why her child had to endure such suffering. Years later, after unusual growth spurts prompted genetic testing, doctors discovered Jepsen carried a defective TP53 gene, a mutation that cripples the body’s primary defense against cancer. A precautionary full-body scan then uncovered a brain tumor she had no symptoms of.

“If I hadn’t gotten tested by chance, I’d probably be dead,” Jepsen told DR.

Now, she is warning her 210 half-siblings—many potentially unaware of their shared genetic risk—that they may carry the same mutation. Through regular scans at Copenhagen’s Rigshospitalet, Jepsen’s condition is monitored so interventions can begin immediately if cancer returns. Denmark’s public healthcare system provides this lifesaving surveillance, but she fears donor-conceived siblings in other countries lack access to testing or support.

“We can help each other,” she said, urging those with the mutation to seek medical monitoring. “If you’ve just found out you have this gene, it’ll be okay. Reach out if you need someone who understands.”

Jepsen’s case is part of what experts call the largest known cluster of donor-conceived children affected by a single genetic disorder. The sperm bank involved, European Sperm Bank, declined an interview but issued a statement expressing “deep sympathy” for the families impacted. The company acknowledged systemic failures in tracking donor-conceived children after a donor is blocked for genetic risks, calling for mandatory EU and national registries to prevent future cases.

“This case shows that post-donation tracing has functioned inadequately,” the statement read. “The system only works if all parties act as intended—and authorities ensure they do.”

Jepsen, who lives with her mother and was conceived via fertility treatment in 2007, refuses to let her diagnosis define her. “You have to adapt,” she said. “Luckily, your hair grows back. It just takes time—and maybe a few new hairstyles along the way.”