Prader Willi Syndrome

WHAT CAUSES PWS?

It has now been estabilshed that about 70% of those with PWS have a deletion in the proximal part of the long arm of chromosome 15 inhertited from the father. Most of the remainder have two chromosome 15s inherited from the mother (maternal disomy), instead of one from each parent. However, a small proportion (about 5%) of cases is hereditary, and is caused by an error in the imprinting in chromosome 15 or another anomaly. Additionally, a very small minority pf people retain a clinical diagnosis of PWS whilst appearing to have unaffected chromosomes.

There appears to be some physical and psychological differences between those woth deletion, disomy and imprinting errors, but these are not of a relitively minor nature, many are still to be fully proven and, as a general rule, they do not affect the overlall management of the person.
It is thought that several genes are affected in PWS and researchers are now trying to clarify how these genes affect (or not) the make-up of people with the syndrome.