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What Are the Symptoms of Prader-Willi Syndrome?

A. Gamm
A. Gamm

Prader-Willi syndrome is one of the rare genetic diseases that results from an error with chromosomes at conception. It affects the hypothalamus, which controls the body’s hunger signal, usually leaving the person affected with a feeling of constant hunger. The symptoms of Prader-Willi syndrome typically begin to appear in two stages: infanthood and early childhood. Symptoms beyond always feeling hungry usually include poor muscle tone, speech and learning problems, possible behavioral changes if denied food, and distinctive physical features. Not all symptoms may appear and are likely to range in severity.

The first of the two stages of Prader-Willi syndrome typically begins at birth until about 12 months old. Infants usually have poor muscle tone, which makes them feel limp when held. This also means they usually have poor suckling reflexes, making weight gain harder. Other symptoms of Prader-Willi syndrome in infanthood include poor eye control and limited responses to stimuli. It may also take babies longer to reach important developmental milestones.


When children reach one to six years of age, the second phase of symptoms of Prader-Willi syndrome typically begins. Children may start to have constant cravings for different foods and as such, may rapidly gain weight. This is usually made worse due to the poor muscle tone in children with Prader-Willi syndrome. As children begin to feel the need for food at this stage, they may develop behavior changes including tantrums if denied food, obsessive-compulsive disorder, and hoarding.

By the second stage children usually display signs of cognitive disabilities, which may range from mild to severe. Although this is not a symptom in all children with this syndrome, almost all children will have some form of learning disability. Motor skills are also typically impaired, with many toddlers sitting up unassisted by one year old and walking around two years old.

Symptoms of Prader-Willi syndrome sometimes also affect the sex organs by inhibiting their development. This means that the sex organs never fully develop and release little to no hormones. Puberty is then never fully completed — women may menstruate late in life or never at all, and voice changes and hair growth never fully develop in men. As a result, it is rare for people with Prader-Willi syndrome to become fertile.

Physical appearances of people with Prader-Willi syndrome are usually distinctive. In infants, almond shaped eyes, down-turned, thin lips, and skin fairer than the rest of the family are common. As adults, they tend to be shorter and have smaller hands and feet.

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