Prader-Willi syndrome is a genetic disorder usually caused by the deletion of a part of chromosome 15 passed down by the father. The most common symptoms of Prader-Willi syndrome are behavioral problems, intellectual disability, and short stature. Hormonal symptoms include delayed puberty and constant hunger leading to obesity. There is no cure for Prader-Willi syndrome but many patients will benefit from a supervised diet. Some symptoms can be treated with hormone therapy.