Prader-Willi Syndrome (PWS) is a rare genetic disorder. It causes poor muscle tone, low levels of sex hormones and a constant feeling of hunger. The part of the brain that controls feelings of fullness or hunger does not work properly in people with PWS. They overeat, leading to obesity.

Babies with PWS are usually floppy, with poor muscle tone, and have trouble sucking. Boys may have undescended testicles. Later, other signs appear. These include

• Short stature
• Poor motor skills
• Weight gain
• Underdeveloped sex organs
• Mild intellectual and learning disabilities

There is no cure for PWS. Growth hormone, exercise, and dietary supervision can help build muscle mass and control weight. Other treatments may include sex hormones and behavior therapy. Most people with PWS will need specialized care and supervision throughout their lives.

NIH: National Institute of Child Health and Human Development