Table 1.
Genetic defect | Proportion of cases [7] | Recurrence risk |
---|---|---|
De novo deletion of 15q11q13 on the paternal chromosome | 70–75% | <1%a |
Maternal uniparental disomy (UPD) of chromosome 15 | 25–30% | <1%b |
Imprinting defects (without an imprinting centre deletion) | 1% | <1% |
Imprinting centre deletion | ≈10–15% of patients with an imprinting defect | 50% (if present in a non-mosaic state in the father) |
aIf paternal karyotype is normal
bIf parental karyotypes are normal