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Prader-Willi syndrome

Other Names for this Disease
  • Obesity, muscular hypotonia, mental retardation, short stature, hypogonadotropic hypogonadism, and small hands and feet
  • Prader Labhart Willi syndrome
  • PWS
  • Willi-Prader syndrome
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What are the signs and symptoms of Prader-Willi syndrome?

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. There are generally two stages of symptoms for people with Prader-Willi syndrome [1]:

  • Stage 1 -- As newborns with Prader-Willi can have low muscle tone, which can affect their ability to suck properly. As a result, these babies may need special feeding techniques to help them eat. Infants may also 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, 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.[1]

There are other symptoms that may affect people with Prader-Willi, including [1]:

  • 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 mental retardation; learning disabilities are common
  • Repetitive thoughts and verbalizations
  • Collecting and hoarding of possessions
  • Picking at skin
  • Low sex hormone levels

Many people with this disorder also have distinctive facial features and short stature. The genitals in both males and females are underdeveloped, and most affected individuals are unable to conceive children (infertile). Additionally, some people with Prader-Willi syndrome have unusually fair skin and light-colored hair.[2]
Last updated: 4/1/2011

  1. Prader-Willi Syndrome. National Institute of Child Health and Human Development (NICHD). March 24, 2010; Accessed 3/24/2011.
  2. Prader-Willi syndrome. Genetics Home Reference (GHR). July 2009; Accessed 3/24/2011.