What is germline mosaicism, and how does it affect recurrence risk?

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What is germline mosaicism, and how does it affect recurrence risk?

Germline mosaicism means a genetic variant is present in some of a parent’s germ cells (sperm or eggs) but not in their somatic cells, so the parent appears unaffected. Because only a fraction of gametes carry the mutation, multiple children can inherit the variant even though parental testing in blood looks normal. This raises recurrence risk for future offspring compared with the general population, but it does not guarantee that every child will be affected or that all gametes carry the mutation. The exact risk is variable and often difficult to quantify, which is why a previously unaffected parent can have more than one affected child in some families.

Germline mosaicism means a genetic variant is present in some of a parent’s germ cells (sperm or eggs) but not in their somatic cells, so the parent appears unaffected. Because only a fraction of gametes carry the mutation, multiple children can inherit the variant even though parental testing in blood looks normal. This raises recurrence risk for future offspring compared with the general population, but it does not guarantee that every child will be affected or that all gametes carry the mutation. The exact risk is variable and often difficult to quantify, which is why a previously unaffected parent can have more than one affected child in some families.

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