The average height for people with Prader-Willi syndrome is 150 cm in women and 155 cm in men.


Prader-Willi syndrome is thought to occur as a result of an abnormality in the chromosome number 15. How this issue causes Prader-Willi is still unclear. 

Signs and Complications

  • Low birth weight.
  • Muscle weakness – the child may not be able to move properly and will sleep a lot. 
  • Narrow forehead and almond-shaped eyes, small hands and feet.
  • In boys, the penis is generally small.
  • Behavioural problems - the child may have obsessive behaviour. 
  • Delayed sexual development.
  • Feeding problems - babies will often feed very slowly and drink very little.
  • Enormous appetite - by the time the child reaches a pre-school age, they will have developed a very strong appetite. Parents will have to regulate the diet to prevent obesity. 
  • Delayed motor development - the child will be slow to sit, crawl and walk. The assistance of a physiotherapist is often required.
  • Delayed mental development – the child may have learning difficulties and need to go to a special school.


Requires a multi-disciplinary approach to tackle each symptom specifically. Includes using tubes or special bottle nipples to help the infant feed, as well as treatment with growth hormone.

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