Prader-Willi syndrome (PWS) is a genetic condition that affects various parts of the body. It’s caused by changes in chromosome 15. There’s no cure, but treatment can improve a person’s quality of life.

Experts estimate that 1 in 10,000 to 30,000 people are born with PWS each year. Approximately 10,000 to 20,000 people are living with the condition in the United States.

Here are the symptoms a person may experience with PWS, what causes it, and what the outlook is for people living with the condition.

PWS is a rare genetic condition, meaning that a person is born with it. It was first discovered in the 1950s by Andrea Prader and Heinrich Willi.

The effects of PWS may be different for each person who has it. One of its most characteristic features is overeating, which usually begins sometime in the toddler years.

The syndrome may also affect a person’s mood and behavior as well as their physical and intellectual development.

You may notice symptoms of PWS shortly after your child is born. Symptoms evolve over time as babies grow into children and adults.

Symptoms in infants

Babies born with PWS typically have distinct facial features, such as almond-shaped eyes, a thin upper lip, and a narrowing of the head starting at their temples.

Other symptoms include:

Symptoms in children and adults

Between a child’s first and fourth birthday, you may notice a dramatic increase in their appetite. In fact, a child’s appetite may increase so much that it leads to excessive overeating — also called polyphagia — and weight gain or obesity.

Hormonal issues

Behavioral issues

Other issues

PWS is caused by genes that are totally missing or partially missing in a specific area of chromosome 15. The missing genes affect the hypothalamus in the brain, causing issues with hormones, appetite, and development.

In most people with PWS, the syndrome isn’t inherited. Instead, the genes are missing by chance.

  • In 60% of people with PWS, the copy of chromosome 15 from the father during conception becomes altered or deleted.
  • In 35% of people with PWS, two copies of chromosome 15 are inherited from the mother during conception and none from the father.
  • In less than 5% of people with PWS, the paternal (male) copy of chromosome 15 is fully together – but the genes in the Prader-Willi region do not function as they should.
  • For the remaining people with PWS, something called a translocation happens. The genes on chromosome 15 from the father get mixed up with genes from other chromosomes.

Language matters

You’ll notice we use the binary term “father” in this article. While we realize this term may not match your gender experience, it’s the term used by the researchers whose data was cited.

In this case, genetic conception requires contributions from two “parents” – genetically, one XX chromosomed person and one XY chromosomed person.

We try to be as specific as possible when reporting on research participants and clinical findings, and these are the terms the researcher used to describe the genetic contribution of the XY parent.

Unfortunately, the studies and surveys referenced in this article didn’t report data for or may not have had participants who are transgender, nonbinary, gender nonconforming, genderqueer, agender, or genderless.

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Most complications from PWS develop from obesity and may be prevented with treatments and weight control.

Obesity-related complications include:

Hormonal complications include infertility (inability to have children) and osteoporosis (loss of bone density).

Binge eating is another complication. People with PWS may excessively eat dangerous foods, like garbage. The compulsion to eat may be so strong that people hide food, try to steal food, or engage in other harmful behaviors around food.

There’s no cure for PWS. Treatment may help to address specific health difficulties a person has and improve their quality of life.

Infancy and childhood


Most adults with PWS can’t live independently. Those who don’t live with their parents may benefit from a supportive living environment, such as a group home. In residential settings, adults with PWS can socialize, work at supervised jobs, and get the medical care they need.

If your child is nearing adulthood, reach out to a doctor to discuss the next steps. You may also want to look into designating an alternative guardian as you age.


Getting regular medical care is important for someone with PWS. A doctor may also suggest additional measures you can take at home, including:

  • getting regular exercise and movement to promote a moderate weight
  • eating a varied diet with scheduled meals
  • limiting free access to food to help with bingeing
  • structuring the day to help with behavior issues
  • leaning into support groups for resources

The mean life expectancy for someone with PWS is around 30 years. That said, research has reported death as early as 2 months or as late as 67 years. Respiratory issues are the most common cause of death.

Control of weight is the most important factor here. If a person with PWS is able to maintain a moderate weight, their life expectancy may not be affected as greatly.

Diagnosis can be made through a basic physical examination and genetic testing.

A doctor will look for classic signs of the syndrome, such as weakness or floppiness, related facial features, and excessive weight gain in young children.

To confirm a diagnosis, your doctor will order genetic blood testing to look for issues with chromosome 15.

Again, the gene change that causes PWS usually happens by chance. As a result, you can’t prevent the syndrome.

Likewise, there are no specific risk factors. PWS affects both sexes equally and has been seen in all populations across the globe.

What are the chances of having more than one child with PWS?

If you have one child with PWS, your chance of having another child with the syndrome is less than 1%.

For most people with PWS, it happens because of a random genetic change during reproduction.

Can PWS be diagnosed before a child is born?

Your doctor may order a diagnostic methylation test if you show signs that your baby may have PWS. Potential signs include intrauterine growth restriction, decreased movements, and an increase in your baby’s head-to-abdomen ratio.

What support is available for people with PWS and their families?

Check out the Prader-Willi Syndrome Association. Your doctor may also be able to suggest local support groups and resources.

PWS is a rare genetic condition that affects the body and behavior. If your child received a diagnosis of PWS, they may need a team of doctors to help with various health and development issues as they crop up. With the right care and support, a person with PWS can live a full life and potentially avoid obesity-related complications.