Prader-Willi syndrome

In Prader-Willi syndrome, another chromosomal deletion syndrome, mental retardation is common. Many symptoms vary according to the child's age.

Newborns with the defect feel limp, feed poorly, and gain weight slowly. Eventually these symptoms resolve. Then, between the ages of 1 and 6, appetite increases, often becoming insatiable. Obsessive-compulsive behaviors are common. Weight gain is excessive, which can lead to other health problems. Obesity can be severe enough to require gastric bypass surgery.