Prader-Willi Syndrome is a congenital condition (present at birth) and is believed to be caused by an abnormality in the genes that occurs. It's a rare genetic disorder in which seven genes on chromosome 15 are deleted or unexpressed.
The Diagnosis The diagnosis is confirmed by a drug test. The method of testing is a "methylation analysis", which detects 99% of cases including all of the major genetic subtypes of PWS.
Causes of PWS PWS is caused by the loss of genes in a specific region of chromosome 15. Prader-Willi syndrome occurs when the region of the paternal chromosome 15 containing these genes is missing.