Prader-Willi (pronounced PRAH-der WILL-ee) Syndrome is a genetic defect on the 15th chromosome that results in this lifelong, life-threatening condition.  Prader-Willi Syndrome (PWS) was first identified in 1956 by Swiss doctors A. Prader, H. Willi and A. Labhart. There is no known cause for PWS nor is there a cure. PWS is one of the ten most common conditions seen in genetics clinics, and is the most common genetic cause of obesity that has been identified.

PWS is a randomly occuring abnormality that is estimated to have an incident rate of 1 in every 10,000 to 15,000 people. PWS affects both males and females and occurs across all races. The two most common types of PWS are Deletion and Uniparental Disomy (UPD). Deletion accounts for approximately 70% of cases and happens when the individual has a non-inherited deletion in the 15q11-q13 region of the paternal 15th chromosome. Uinparental Disomy (UPD) accounts for approximately 25% of cases and happens when the individual receives two maternal 15th chromosomes and no paternal 15th chromosome.

Diagnosis of PWS is confirmed via genetic testing. Deletion can be detected with the FISH (fluorescence in situ hybridization) test and Uniparental Disomy 15 can be detected with the PCR (polymerase chain reaction) test.

For more information about the various symptoms of PWS please explore the “For Professionals” tab and read our Synopsis Brochure.