Prader-Willi Syndrome (FAQ)

Answers to questions families often have about caring for their child with Prader-Willi syndrome (PWS)

What is Prader-Willi syndrome (PWS)?

PWS is a complex genetic disorder affecting appetite, growth, metabolism, brain function, and behavior of those with the condition. The genes that are missing in people with PWS have a role in the regulation of the hypothalamus, which produces hormones that help manage appetite, thirst, pain, sleep, sexual development, and release of growth hormone. People with PWS never feel full; they have a constant urge to eat that they can't learn to control. To add to this problem, children with PWS need less food than typically-developing children because their bodies have less muscle and tend to burn fewer calories.

Problems with the hypothalamus are also related to behavior problems and lack of emotional control.

How do you get PWS?

PWS is caused by a mutation on chromosome 15 that occurs at or near the time of conception for unknown reasons. This causes people with PWS to be missing several genes on one of their two copies of chromosome 15, most often the one contributed by the father.

There are three subtypes of PWS:

  • Paternal deletion – when a section of chromosome 15 from the father is missing; this causes about 70% of cases.
  • Maternal uniparental disomy – the child receives two copies of chromosome 15 from the mother and none from the father, causing some genetic material to be turned off; this causes about 25% of cases.
  • Imprinting defect – caused by a mutation called an imprinting defect; this causes <5% of cases. It is important to identify these children as other children in the family may also be affected. Genetic testing can identify the subtype of PWS. See Genetics of PWS for more information.

'Acquired PWS' is a PWS-like disorder, and can develop after birth if the hypothalamus is damaged by injury or surgery.

What are the symptoms?

Babies born with PWS typically have very low muscle tone, little to no appetite, failure to thrive, and lack of infant reflexes.

People with PWS usually have low muscle tone throughout their life. Other symptoms are short stature, incomplete sexual development, intellectual disabilities, problem behaviors, and uncontrollable feelings of hunger and a slowed metabolism that can lead to excessive eating and life-threatening obesity. Strict external controls, which may include padlocking food storage, are needed to maintain normal weight and to help save their lives.

How is it diagnosed?

The diagnosis is usually suspected because of the symptoms noted above and is then confirmed by genetic testing on a blood sample, usually ordered by a geneticist. Testing for the PWS subtype, as mentioned above, is important.

What is the expected outcome?

If obesity is controlled, life expectancy for people with PWS is normal or near normal. In addition to managing access to food, people with PWS should be monitored for other problems, such as sleep apnea. General health is usually good in people with PWS.

With help, people with PWS can expect to do many of the things their typically developing peers do—complete school, participate in their outside areas of interest, be a productive worker under the right conditions, and even move away from the family home. They do still need a significant amount of support from their families and from school, work, and residential service providers, both to reach these goals and to avoid obesity and the serious health consequences that accompany it. People with PWS are usually unable to live independently due to the amount of support needed around food intake and their intellectual disability. Even those with IQs in the normal range need lifelong diet supervision and protection from food availability. Although in the past many people with PWS died in adolescence or young adulthood, prevention of obesity can offer those with the syndrome the probability of having a normal life span.

Will anyone else in the family get PWS?

Usually no, however, at least 20 families have been reported with more than one affected member, including reports in twins. The chance for another child having PWS is less than 1%. However, this risk may be as high as 50% in families where an imprinting defect is the cause of a child’s PWS.

What is the treatment?

Although there is no cure for PWS, there are approaches that can significantly help people with PWS lead healthier lives. Early diagnosis and management are key. For example, treatment with human growth hormone can be started as early as one month of age to increase stature, decrease obesity, and increase muscle mass and capacity for physical activity. Starting growth hormone therapy before one year of age can lead to improvements in IQ and physical development.

Management of PWS is enhanced by a team approach that involves experts in nutrition, neurology, endocrinology, genetics, ophthalmology, psychology, gastroenterology, and orthopedics, as well as speech, occupational, and physical therapy. Seeing these specialists in a PWS-focused clinic offers benefits for patients/families and for developing ongoing improvements in care.

Management early in life usually involves increasing nutrition because most babies with PWS do not eat enough. By toddler age, this resolves and the focus is restricting the amount of food, which is very challenging. Behavioral and educational problems also often require considerable effort on the part of the family and help from professionals.

How will my family's life be changed?

The family will need to be aware of the behaviors and conditions associated with PWS. Family members and other caregivers can support treatment and therapy plans; watch for injurious behaviors and symptoms of complications; and help provide an environment with consistent routines and expectations.

The constant need for food restriction and behavior management may be stressful for family members. Because of the drastic change in lifestyle required to keep people with PWS safe, siblings may need support services. The national Prader-Willi Syndrome Association (USA) can provide information and support for family members and healthcare providers. See Prader-Willi Syndrome Association (USA).

How often does PWS occur?

The prevalence of PWS is approximately 1/25,000 newborns. [Butler: 1990] Although considered a "rare" disorder, PWS is one of the more common conditions seen in genetic clinics and is the most common genetic cause of obesity identified thus far.

What does human growth hormone do for people with PWS?

Use of recombinant human growth hormone (rhGH) is becoming standard of care for children with PWS. It should be prescribed by an experienced endocrinologist. Growth hormone increases growth rate and helps increase muscle mass and reduce fat mass. Children treated with rhGH have improved energy and physical activity levels, strength, agility, endurance, and respiratory function. These improvements are most noticeable in the first year of treatment. For unknown reasons, rhGH may also help with intellectual development. Growth hormone is most helpful if started before the child is one year old.

What is "Food Security"?

The psychological concept of food security is a vital part of the managing PWS; the goal is to maintain food security across all settings. Food security is one of the most basic skills taught to the family or other caretakers.

Food security is reached when food access is controlled so that three criteria are met:

  1. There is no doubt when, what, and how much the person with PWS will eat;
  2. There is no hope of receiving any more; and
  3. There is no disappointment due to false expectations.
Food security = No doubt + No hope + No disappointment.

When food access is restricted, individuals with PWS should have no doubt about their meals and snacks. Menus are planned ahead and posted; calories are controlled, but the amount of food given can still be generous. Although the timing of the meals and snacks remains fixed, it is not focused on the clock; it is set by the sequence of activities across the day. This concept is critical to the achievement of flow through the day and for minimizing negative emotions like anxiety.

As part of maintaining food security, it is vital to:

  • Keep food locked up in the kitchen
  • Put away food right after meals
  • Make sure no food is used in the child’s classroom setting
  • Have someone keep an eye on the child at all times where food is available (such as having dinner in a restaurant)

Does the overeating with PWS begin at birth?

No, in fact newborns with PWS often have difficulty getting enough nourishment because low muscle tone weakens their sucking ability. They may be said to have "failure to thrive," which means not gaining expected growth. Many require special feeding techniques or tube feeding for several months or more after birth until muscle control improves.

PWS is a progressive syndrome with stages, and appetite changes over time. Sometime after infancy, children with PWS may have a normal appetite and show typical growth. Before school age, children with PWS usually develop an intense interest in food, followed by overeating that can quickly lead to excess weight gain if calories aren't restricted.

Do diet medications work for the appetite problems in PWS?

No appetite suppressant has worked consistently for people with PWS. Most require an extremely low-calorie diet all their lives and must have their environments designed so that they have very limited access to food.

Does gastric bypass surgery help with weight loss in PWS?

Because people with PWS have an increased pain tolerance, they can still overeat even after gastric bypass surgery. This makes the surgery dangerous for them.

What is the Red, Yellow, Green System of weight management?

The Red, Yellow, Green System (RYG) was originally developed for obesity management in preteens and has been adapted for people with PWS. RYG is effective for the prevention and treatment of obesity and also decreases food-centered behaviors.

While children with PWS have a common syndrome, nutritional needs are individual and it’s necessary to work with a nutritionist or dietitian to make sure nutritional needs are being met.

What kinds of behavior problems do people with PWS have?

PWS is a spectrum disorder like autism and the resulting behaviors are affected by where the person is on the spectrum. In addition to food-centered behaviors, individuals with PWS tend to have obsessive/compulsive behaviors, including repetitive thoughts and speech; collecting and hoarding; picking at skin irritations; and a strong need for routine and predictability. ADHD may also be present. Frustration or changes in plans can cause loss of emotional control ranging from tears to temper tantrums to physical aggression. The basic strategies for reducing difficult behaviors in PWS are a structured environment and consistent use of positive behavior management and supports. Applied Behavioral Analysis (ABA) therapy has been shown to help children with PWS manage behavior.

Does early diagnosis help?

Yes – early diagnosis of PWS gives parents time to learn about and prepare for the challenges that lie ahead and to establish family routines that will support their child's diet and behavior needs from the start. Also, growth hormone has been found to be most effective if started before the age of one. Using strategies offered through organizations such as Early Intervention can help with development and may help close the gap between children with PWS and their typically developing peers.

How do I help my other children cope with having a sister or brother with PWS?

Though having a sibling with disabilities makes life more complicated, research suggests that children are often strengthened, rather than harmed, by having a sibling with special needs. Siblings of children with PWS may have problems related to the rigid structure needed around food and the needed focus on their sib’s behaviors.

Sibling workshops have been designed to help with those problems (for example see Sibshops: workshops for siblings of children with special needs) and, for some problems, individual or family counseling may be needed. For an interesting viewpoint, try the book The Normal One, written by a typically developing sibling of a child with disabilities. [Safer: 2002] See also A Sibling's Perspective (PWSAUSA).

What does the future hold for people with PWS?

There are currently drug trials in progress to develop medications for appetite management. Medical professionals are hopeful that within 2-3 years there may be a medication to help with the constant hunger experienced by people with PWS. See the Foundation for Prader-Willi Research for more information about research into new treatments for PWS.


Information & Support

Related Portal Content
Prader-Willi Syndrome
Assessment and management information for the primary care clinician caring for the child with Prader-Willi syndrome (PWS).
Care Notebook
Medical information in one place with fillable templates to help both families and providers. Choose only the pages needed to keep track of the current health care summary, care team, care plan, health coverage, expenses, scheduling, and legal documents. Available in English and Spanish.

For Parents and Patients

Genetic Conditions: Prader-Willi Syndrome (MedlinePlus)
Excellent, detailed review of condition for patients and families; National Library of Medicine and National Institutes of Health.

Prader-Willi Syndrome (MedlinePlus)
Information about PWS and links to other reliable sources of information; National Library of Medicine and National Institutes of Health.

Prader-Willi Syndrome Educational Downloads (Pittsburgh Partnership)
Information for providers and families regarding food security, behavioral management, nutrition/weight management, and other issues in individuals with PWS; from the Pittsburgh Partnership, which provides education and consultation.

Services for Patients & Families in Nevada (NV)

For services not listed above, browse our Services categories or search our database.

* number of provider listings may vary by how states categorize services, whether providers are listed by organization or individual, how services are organized in the state, and other factors; Nationwide (NW) providers are generally limited to web-based services, provider locator services, and organizations that serve children from across the nation.


Angelman, Rett, and Prader-Willi Syndromes Research Consortium
An integrated group of academic medical centers, patient support organizations, and clinical research resources dedicated to conducting clinical research in genetic and neurodevelopmental disorders and maintaining a Patient Contact Registry.

Prader-Willi Syndrome Studies (
Studies looking at better understanding, diagnosing, and treating this condition; from the National Library of Medicine.

Authors & Reviewers

Initial publication: October 2012; last update/revision: November 2019
Current Authors and Reviewers:
Author: Lynne M. Kerr, MD, PhD
Reviewer: Alyssa Nielsen
Authoring history
2015: first version: Jennifer Goldman, MD, MRP, FAAPR
AAuthor; CAContributing Author; SASenior Author; RReviewer

Page Bibliography

Butler MG.
Prader-Willi syndrome: current understanding of cause and diagnosis.
Am J Med Genet. 1990;35(3):319-32. PubMed abstract
Reviews of current understanding of the major clinical, cytogenetic, and DNA findings. Summarizes from literature clinical manifestations and cytogenetic abnormalities.

Safer J.
The Normal One.
New York: Delta/Random House; 2002. 0-385-33756-6
Written by a psychotherapist and "normal" sibling of a child with special needs after many years of experience and research into the impact of children with special needs on typically developing siblings.