People with Prader-Willi syndrome have a problem in their hypothalamus, a part of the brain that normally controls feelings of fullness or hunger. As a result, they never feel full and have a constant urge to eat that they cannot control.
Most cases of Prader-Willi syndrome result from a spontaneous genetic error in genes on chromosome 15 that occurs at conception. In very rare cases, the mutation is inherited.
- Stage 1–As newborns, babies with Prader-Willi can have low muscle tone, which can affect their ability to suck properly. As a result, babies may need special feeding techniques to help them eat, and infants may have problems gaining weight. As these babies grow older, their strength and muscle tone usually get better. They meet motor milestones, but are usually slower in doing so.
- Stage 2–Between the ages of 1 and 6 years old, the disorder changes to one of constant hunger and food seeking. Most people with Prader-Willi syndrome have an insatiable appetite, meaning they never feel full. In fact, their brains are telling them they are starving. They may have trouble regulating their own eating and may need external restrictions on food, including locked kitchen and food storage areas.This problem is made worse because people with Prader-Willi syndrome use fewer calories than those without the syndrome because they have less muscle mass. The combination of eating massive amounts of food and not burning enough calories can lead to life-threatening obesity if the diet is not kept under strict control.
There are other symptoms that may affect people with Prader-Willi, including:
- Behavioral problems, usually during transitions and unanticipated changes, such as stubbornness or temper tantrums
- Delayed motor skills and speech due to low muscle tone
- Cognitive problems, ranging from near normal intelligence to mild intellectual and developmental disabilities; learning disabilities are common
- Repetitive thoughts and verbalizations
- Collecting and hoarding of possessions
- Picking at skin
- Low sex hormone levels
Prader-Willi syndrome is considered a spectrum disorder, meaning not all symptoms will occur in everyone affected and the symptoms may range from mild to severe.
People with Prader-Willi often have some mental strengths as well, such as skills in jigsaw puzzles. If obesity is prevented, people with the syndrome can live a normal lifespan.
Human growth hormone has been found to be helpful in treating Prader-Willi syndrome. It can help to increase height, decrease body fat, and increase muscle mass. However, no medications have yet been found to control appetite in those with Prader-Willi.
NIH – Last updated March 2010