Prader-Willi Syndrome

Prader-Willi syndrome is a rare genetic condition that affects a child’s metabolism. It can also affect your child’s body and behavior. This condition causes your child to have a strong appetite and not feel full after meals. Supportive therapies and diet management help treat PWS and prevent complications that can affect your child’s health.


What is Prader-Willi syndrome?

Prader-Willi syndrome (PWS) is a rare genetic condition that affects your child’s metabolism and causes changes to their body and behavior. They have severe low muscle tone and poor feeding during early infancy, followed by a tremendous appetite that develops between 2 and 6 years of age. This can lead to severe obesity if excessive eating isn’t managed.

PWS typically also causes a delay in childhood milestones and puberty. Although rare, life-threatening complications can occur and include respiratory illnesses, obesity-related cardiovascular problems, sleep apnea and diabetes.


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Who does Prader-Willi syndrome affect?

Anyone can develop Prader-Willi syndrome because it’s a genetic condition that happens randomly when reproductive cells form. In rare cases, you can inherit the condition if it runs in your biological family history.

How common is Prader-Willi syndrome?

Throughout the world, PWS affects an estimated 1 in 10,000 to 30,000 people.


Symptoms and Causes

Symptoms of Prader-Willi syndrome vary based on age.
Prader-Willi syndrome causes symptoms that appear as your child grows.

What are the symptoms of Prader-Willi syndrome?

Prader-Willi syndrome affects each person differently. Symptoms that appear in infancy may include:

Symptoms that affect your child’s body may be present at birth but become more apparent as they grow. These may include:

  • Almond-shaped eyes.
  • A long, narrow head.
  • A triangular mouth.
  • Short height.
  • Small hands and feet.
  • Underdeveloped genitals.

Additional symptoms that affect your child’s development and behavior include:

  • Temper tantrums, emotional outbursts or stubbornness.
  • Problems with cognitive development (intellectual disability).
  • Obsessive or compulsive behaviors like skin picking.
  • Sleep abnormalities.
  • Eating challenges like not feeling satisfied after eating or eating an unusually large amount of food (hyperphagia).

Hyperphagia may lead to class III obesity, which increases the likelihood of other complications, such as diabetes and heart disease.

What causes Prader-Willi syndrome?

Genes on chromosome 15 that lose function cause Prader-Willi syndrome. At conception, you inherit one copy of chromosome 15 from each of your biological parents. The paternal copy of chromosome 15 is the only one that activates or turns on. The maternal copy is turned off. Both copies are necessary for your genes to get the instructions your body needs to function. This process is called genomic imprinting.

There are different causes of this genetic change to chromosome 15:

  • Chromosomal deletion: Nearly 70% of all PWS cases occur when part of the paternal chromosome 15 is missing in each cell. Symptoms arise because the paternal copy of chromosome 15 is missing or not working properly and the maternal copy is turned off.
  • Maternal uniparental disomy: About 25% of PWS cases happen when a child inherits two maternal copies of chromosome 15 instead of one from each biological parent. This means that both copies of chromosome 15 don’t work because they’re inactive.
  • Translocation: Less than 1% of all cases occur when a piece of chromosome 15 relocates itself to another chromosome. This makes the genes that the chromosome produces work ineffectively since they’re not where they’re supposed to be.

Chromosome 15 is responsible for providing instructions for making small nucleolar RNAs (snoRNAs). The job of snoRNAs is to regulate the function of other RNA molecules. RNA molecules create proteins that help cells complete many functions within your body. A change to chromosome 15 limits its ability to create snoRNAs or they don’t receive the instructions they need to complete their jobs correctly.


Diagnosis and Tests

How is Prader-Willi syndrome diagnosed?

A healthcare provider will diagnose Prader-Willi syndrome after a physical exam and genetic tests. A provider will look for physical signs of the condition during the exam and ask you questions about your child’s symptoms, including their eating habits and behavior. If your provider suspects PWS, they’ll run a genetic test, which is a blood test that detects abnormalities due to changes to your child’s DNA.

Management and Treatment

How is Prader-Willi syndrome treated?

Treatment for Prader-Willi syndrome focuses on managing symptoms and preventing complications. Treatment could include:

  • Devices, such as special bottle nipples, to help infants get enough nutrition.
  • Helping your child eat properly, including a low-calorie diet and managing how much they eat.
  • Medications to increase amounts of certain hormones, such as growth hormone, and testosterone or human chorionic gonadotropin (HCG) for boys or children assigned male at birth (AMAB) and estrogen for girls or children assigned female at birth (AFAB).
  • Supportive therapies such as physical therapy, speech-language therapy and special education to improve physical and cognitive function.

What are the complications associated with Prader-Willi syndrome?

Many people with Prader-Willi syndrome develop obesity from overeating. Complications from obesity may include:

Obesity is a complex but manageable condition. Your child’s healthcare provider can offer guidance on how you can help your child and prevent complications.


How can I prevent Prader-Willi syndrome?

You can’t prevent Prader-Willi syndrome because it’s a genetic condition. Many cases are the result of a random genetic change that’s unpredictable and not the result of something the biological parents did before or during pregnancy. To learn more about your risks of having a child with a genetic condition, talk to your healthcare provider about genetic testing.

Outlook / Prognosis

What can I expect if my child has Prader-Willi syndrome?

With early and ongoing treatment, many individuals with Prader-Willi syndrome have a normal lifespan. Needing extra help in school is common. Each person with PWS needs lifelong support to achieve as much independence as possible. Your provider might recommend that you visit a nutritionist to help facilitate a meal plan and diet that can help your child manage their eating. Meeting with a mental health professional or joining a support group is a great resource for parents and families. It can help them find ways to adapt and learn how to help their child grow and meet their full potential.

Is there a cure for Prader-Willi syndrome?

There isn’t a cure for Prader-Willi syndrome. Research is ongoing to learn more about the condition.

Living With

When should I see a healthcare provider?

If you notice your child has signs of Prader-Willi syndrome, visit their healthcare provider. It’s especially important to see their provider if they miss developmental milestones during infancy. With an early diagnosis, your child’s provider can help you manage your child’s condition, help them meet developmental milestones and manage their diet to reduce complications from the condition.

What questions should I ask my doctor?

  • How can I help my child avoid obesity?
  • What will my child’s treatment involve?
  • What kinds of behavioral issues might my child have?
  • Are there support groups to help us learn about and cope with PWS?
  • Should others in my family have genetic testing?

A note from Cleveland Clinic

It may be overwhelming to learn that your child has a rare genetic condition without a cure. Your child’s care team will offer support and guidance so you can give your child the care they need as they grow and develop. Your child may need more time than others their age to reach their milestones. They’ll also need supportive care throughout their life to prevent complications. If you have questions about your child’s diagnosis or how to best care for your child, talk to your child’s provider.

Medically Reviewed

Last reviewed on 01/27/2023.

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