Prader-Willi syndrome is a rare genetic disorder. It is characterized by:

  • Developmental delays
  • Insatiable appetite leading to obesity]]> by age six
  • Mental disabilities
  • Incomplete sexual development
  • Short adult stature



Prader-Willi syndrome is believed to be caused by a genetic defect on chromosome 15, passed on by the father.

Genetic Material

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Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Since Prader-Willi syndrome is caused by a random genetic defect, there are no known risk factors. However, in about 1% of cases, this defect may recur in the same family. Some genetic counselors recommend testing of affected children to identify very rare situations where the risk of recurrence might be 50%.


Symptoms of an infant born with Prader-Willi syndrome may include:

  • Poor muscle tone
  • Poor reflexes
  • Small to normal size
  • Inability to suck well
  • A weak, squeaky cry
  • Lethargy

As a toddler, new symptoms may include:

  • Delay of normal development, such as language skills and walking
  • Behavior problems, such as temper tantrums and stubbornness

As the child gets older, symptoms may include:

  • Insatiable hunger, resulting in compulsive eating and often obesity
  • Continuing behavior problems, such as anger and inflexibility
  • Learning disabilities
  • Low to normal IQ
  • Incomplete sexual development, and infertility as an adult
  • High threshold for pain
  • Insensitivity to temperature extremes


The diagnosis is usually evident shortly after birth based on symptoms and a characteristic physical appearance:

  • Almond-shaped eyes
  • Strabismus]]> (misalignment of the eyes)
  • Thin upper lip
  • Narrow forehead
  • Down-turned mouth
  • Lighter coloring compared with other family members

Diagnosis can be confirmed by genetic testing of a blood sample.



Treatment, which continues into adulthood, is managed by the parents or caregivers of children with Prader-Willi syndrome. Key areas include:

Appetite and Weight

Perhaps the most important concern is managing food intake. People with Prader-Willi syndrome are unable to resist food. This is due to a defect in the part of the brain that controls the normal feelings of fullness when the body has had enough food. In addition, people with Prader-Willi syndrome have a slow metabolism. These traits can cause excessive weight gain, morbid obesity, and other related health problems. Research into the use of novel anti-obesity medications is underway.


  • Food restriction and supervision
  • Regular exercise

Behavior Issues

Infants and young children with Prader-Willi syndrome are typically happy and loving. But as they get older, you may notice behavior changes. Common behaviors include:


  • Daily structure and routine
  • Firm rules
  • Rewards for good behavior
  • Psychotropic drugs may be necessary

Developmental Issues

Children with Prader-Willi syndrome may experience the following:

  • Delay in motor skill development
  • Cognitive delay or limits
  • Delays in physical growth
  • Incomplete sexual development in adolescence


For certain conditions, such as delayed physical growth or sexual development, growth hormone therapy may be helpful.

Related Health Conditions

The following conditions are associated with Prader-Willi syndrome and will require life-long management:


There are no guidelines for preventing Prader-Willi syndrome.