|
| |
Genetics
PWS is caused by absence of the paternally derived PWS/AS region of chromosome
15 (15q11-13) by one of several genetic mechanisms, including uniparental disomy,
imprinting mutations (i.e. inappropriate "paternal imprinting"), chromosome
translocations, and gene deletions. The genes responsible for Prader-Willi
syndrome are expressed only on the paternal chromosome. (Interestingly, a
deletion on the maternal chromosome causes Angelman syndrome.) This is the first
known instance of imprinting in humans, and is a fascinating model of this
genetic phenomenon.
The risk to the sibling of an affected child of having PWS depends upon the
genetic mechanism which caused the disorder. The risk to siblings is <1% if the
affected child has a gene deletion or uniparental disomy, up to 50% if the
affected child has a mutation of the imprinting control center, and up to 25% if
a parental chromosomal translocation is present. Prenatal testing is possible
for any of the known genetic mechanisms.
Neuro-cognitive
Individuals with PWS are at risk for learning and attention difficulties.
| |
|
