Prader Willi Syndrome is an uncommon genetic disorder. It is commonly placed on tests because it is easily recognizable by clinical characteristics. Patients are morbidly obese, mentally impaired (IQ - 60-70), hypotonic, diabetic and have hypogonadism.

Diagnosis is confirmed by testing for the parent-specific methylation imprint (PSMI) of the PWS/AS region (chromosomal locus 15q11-q13) detects over 99% of cases and is highly specific. Methylation-specific testing is important to confirm the diagnosis of PWS in all children, but especially those who are too young to manifest sufficient features to make the diagnosis on clinical grounds or in individuals who have atypical findings [Cassidy & Schwartz 1998].

It is treated with behavior modification and disallowing excessive eating and controlling food stealing. Early physical therapy improves hypotonia.