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Genetic and Rare Diseases Information Center (GARD)

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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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Does the menstrual cycle happen earlier in Prader-Willi syndrome?

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What is Prader-Willi syndrome?

Prader-Willi syndrome (PWS) is a complex genetic condition that affects many parts of the body.[1] At birth, babies with PWS have poor muscle tone and a weak cry. Initially, they are slow feeders and appear undernourished. The feeding problems improve after infancy and often between 2 to 4 years of age, children with PWS become very focused on food and have difficulty controlling their appetite. The overeating often results in rapid weight gain and obesity. Individuals with PWS also often have developmental delays and less-than-average adult height. PSW is caused by missing or non-working genes on chromosome 15. Most cases are not inherited, but occur randomly.[2][3]
Last updated: 4/1/2011

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 [4]:

  • 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.[4]

There are other symptoms that may affect people with Prader-Willi, including [4]:

  • 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.[1]
Last updated: 4/1/2011

Is puberty altered in individuals with Prader-Willi syndrome?

Hypogonadism is present and manifests as genital hypoplasia (underdevelopment), incomplete pubertal development, and infertility in the vast majority of individuals with Prader-Willi syndrome. The hypogonadism, which is largely of hypothalamic origin and usually associated with low serum concentration of gondaotropins, causes incomplete, delayed, and sometimes disordered pubertal development.[5] A small percentage of individuals with Prader-Willi syndrome may have early pubarche (first appearance of pubic hair) or, more rarely, precocious puberty (unusually early onset of puberty-- before the age of 8).[6]
Last updated: 4/1/2011

Can the menstrual cycle happen early in individuals with Prader-Willi syndrome?

Many individuals with Prader-Willi syndrome experience delayed puberty which fails to reach completion. Most females never have regular menstrual cycles, with spontaneous menarche occurring in only about 50% of cases [5][7] Even in those who do experience menstruation, the cycles are often just a periodical vaginal spotting.[5] Still, a few cases of precocious puberty with menarche at or before age 8 in individuals with Prader-Willi syndrome have been reported.[6][7]
Last updated: 3/24/2011