In a family with a de novo pathogenic variant and no family history, what is the recurrence risk for future siblings?

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Multiple Choice

In a family with a de novo pathogenic variant and no family history, what is the recurrence risk for future siblings?

A de novo pathogenic variant means the change occurred in the germ cell that formed the child or in the very early embryo, so usually neither parent carries it in their blood. The recurrence risk for future pregnancies is therefore low. However, there is a real possibility of parental germline mosaicism, where a parent has some eggs or sperm carrying the variant, even if blood tests look normal. If germline mosaicism is present, the risk of having another affected child is higher than the general population risk, though still overall low. That combination—low overall risk with a potential small increase due to germline mosaicism—is why the best answer is low, though parental germline mosaicism can raise it.

A de novo pathogenic variant means the change occurred in the germ cell that formed the child or in the very early embryo, so usually neither parent carries it in their blood. The recurrence risk for future pregnancies is therefore low. However, there is a real possibility of parental germline mosaicism, where a parent has some eggs or sperm carrying the variant, even if blood tests look normal. If germline mosaicism is present, the risk of having another affected child is higher than the general population risk, though still overall low. That combination—low overall risk with a potential small increase due to germline mosaicism—is why the best answer is low, though parental germline mosaicism can raise it.

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