Table 2

Molecular defects and recurrence risks in AS.

Genetic defect

Proportion of cases

Recurrence risk

De novo deletion of 15q11-q13 on the maternal chromosome

70-75%

<1%

Paternal uniparental disomy (UPD) of chromosome 15

3-7%

<1%

Imprinting defect (with an imprinting centre deletion excluded)

2-3%

<1%

Deletions of the imprinting centre

≈ 10-15% of patients with an imprinting defect

Up to 50% (if present in mother)

UBE3A mutation

≈10%

50% if present in mother

No identifiable molecular abnormality

≈10%

Unknown (up to 50%)

Ramsden et al. BMC Medical Genetics 2010 11:70   doi:10.1186/1471-2350-11-70