Prader-Willi Syndrome (PWS)

Prader–Willi Syndrome (PWS) a is genetic disorder caused by a loss of function of specific genes on chromosome 15. At birth, individuals will have muscle weakness, failure to feed, and slowed development. Characteristic hyperphagia begins in childhood, and children become at high risk for obesity and type 2 diabetes. Individuals have marked mild to moderate intellectual impairment and behavioural difficulties throughout the lifespan.

  • PWS affects between 1 in 10,000 and 1 in 30,000 people.
Risk Factors

No risk factors are known for the disorder. Parents of children with PWS have a less than a 1% chance of another child with PWS.

  • PWS is closely linked to a very similar genetic disorder, Angelman syndrome. In both disorders, region 15q11-13 of chromosome 15 is involved. The loss of the UBE3A gene in this region on the maternal chromosome causes Angelman syndrome, while a loss of a different cluster of genes within the same region on the paternal chromosome causes PWS.
  • PWS is not generally inherited, but rather develops from genetic during the formation of gametes (egg, or sperm)
  • About 74% of cases occur when part of the father's chromosome 15 is deleted.
    • In another 25% of cases, the affected individual has two copies of the maternal chromosome 15 from the mother and lacks the paternal copy, because of genetic imprinting, the maternal chromosome is turned off, and the individual ends up with no working copies of chromosome 15.
For Patients
For Providers