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Prader-Willi syndrome is a rare genetic condition that affects many body systems. It often results in obesity and mild to moderate cognitive disability. The genetic change that causes PWS occurs at random when the baby is in the womb. Infants with PWS typically have low muscle tone (floppiness in muscles), growth problems, and trouble sucking or feeding. They also experience delays reaching developmental milestones such as walking, talking, learning new things, and social skills. A defining feature of PWS is an appetite that the child cannot satisfy. This desire to eat often develops between ages three and eight years and results in major weight gain. People with PWS often have behavior problems, such as anxiety and compulsive habits, like picking at their skin. PWS affects about one in 10,000 to 30,000 people of all genders and ethnic backgrounds worldwide.

Physical therapists work with children who have PWS to address physical, mental, and behavioral challenges. They work with them and their families to help each child reach their greatest potential. Early on physical therapists help children improve their balance, strength, and coordination skills.

Physical therapists are movement experts. They improve quality of life through hands-on care, patient education, and prescribed movement. You can contact a physical therapist directly for an evaluation. To find a physical therapist in your area, visit Find a PT.

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What Is Prader-Willi Syndrome?

Prader-Willi syndrome is a genetic disorder first described in 1956. A defective or missing gene causes the disorder, which occurs randomly. The severity of symptoms varies from person to person.

With careful weight management and a good support system, people with PWS can remain healthy and live a normal life span. But related obesity can lead to:

People with PWS have the best chance for managing their weight successfully and an increased life span, with:

  • Early diagnosis.
  • Healthy diet and nutrition education.
  • Controlled access to food.
  • Exercise programs.

Signs and Symptoms

Symptoms of PWS have a wide range. They vary from person to person and in severity. People with PWS have distinct facial and body features, including:

  • Almond-shaped eyes.
  • Short height with small hands and feet.
  • A down-turned mouth.
  • Lighter hair color and fairer skin than their family members.

They also may have disturbed sleep with excessive daytime sleepiness and a decreased response to pain.

PWS has two stages.

First Stage: Birth to About Two Years

The first stage of PWS is marked by:

  • Low muscle tone (floppiness in muscles).
  • Developmental delays.
  • Feeding problems due to a poor ability to suck and use the muscles of the mouth. Most infants six months and younger need help feeding. Some infants may need specialized nipples, feeding tubes, and specific feeding positions.

Second Stage: Between One and Four Years and Into Adulthood

In the second stage of PWS, children develop hunger they can't satisfy (called hyperphagia). This type of hunger often begins between three and eight years and leads to rapid weight gain. Children with PWS never feel full. They have a constant need to eat and find food.

The fact is people with PWS need less food per day to meet their calorie needs than those without it.

Other symptoms that may occur during stage two include:

  • Low muscle tone (floppiness in muscles).
  • Hip dysplasia (problems with the hip joint).
  • Osteoporosis (low bone mass).
  • Short height (due to growth-hormone deficiency) with small hands and feet.
  • Problems breathing when sleeping (such as sleep apnea).
  • Absent or incomplete puberty.
  • Behavior problems including anxiety, obsessive-compulsive symptoms, impulse control, and skin picking.
  • Learning problems.
  • Scoliosis (curvature of the spine).
  • Vision problems.
  • Lack of response to pain, which can mask other symptoms.

How Is It Diagnosed?

Medical doctors diagnose PWS based on traits reported by a family member, a physical therapist, or noted by the doctor during a checkup. Newborns and infants with PWS always have low muscle tone. Infants who have problems feeding or who are failing to thrive will need further testing. Health care providers consider PWS in any infant born with unexplained low muscle tone. A doctor-ordered blood test, which detects 99% of cases, can confirm the diagnosis.

How Can a Physical Therapist Help?

Your physical therapist will serve as a valuable partner to help your child reach their potential. Physical therapists play an important role in the overall medical management of PWS. Managing PWS includes:

  • Proper diet.
  • Exercise.
  • Growth hormones.
  • Strategies to address behavior and learning problems.

Physical therapists may provide treatment services in the home, at school, or in an outpatient clinic. The goal of physical therapy is to improve strength, endurance, coordination, and mobility. Your physical therapist will focus on different goals at each stage of your child's life to help them take part in family, school, and community activities.

Your physical therapist will perform an evaluation that includes:

  • Parental concerns. Your physical therapist will ask about your concerns and goals for your child.
  • Birth and developmental history. Your physical therapist will ask about your child's birth, hospital treatment, and motor development. Motor development includes skills such as head control, rolling, sitting on their own, crawling, and walking.
  • Medical history/health and behavioral concerns. Your physical therapist will ask about other medical conditions your child may have. They also will ask questions to learn what a normal day looks like for your child.
  • Physical exam. Your physical therapist will do a physical exam to find your child's strengths and weaknesses.

Your physical therapist will work with other members of your child's health care team. They also will coordinate care to ensure your child's needs and goals are addressed in the safest, most effective way possible.

Physical Therapy in the Early Years: Birth to Age Four

Physical therapists educate parents about their infant's condition. They teach activities parents can do with their child to promote movement and muscle strength. Children at this age learn through play. Your physical therapist will develop a fun, play-focused treatment plan. It will be based on your child's specific strengths and weaknesses. They also will address your goals and help you to include these activities in your daily family routines.

Physical Therapy in the School Years: Ages Five to 17

As children with PWS age, they often will struggle with obesity and inactivity. Your physical therapist may suggest a fitness program or provide strategies to promote physical activity and improve fitness. Some children with PWS may receive human growth hormone, or rhGH, therapy. RhGH combined with physical activity has the greatest benefits. Scoliosis is also common in children with PWS. This condition may be partially managed with physical therapy.

Physical Therapy Into Adulthood: Age 18+

For adults with PWS, inactivity and obesity-related health issues can result in:

  • Decreased mobility.
  • Less independence.
  • Lack of participation.

A physical therapist can continue to provide an exercise program and targeted training to help adults with PWS:

  • Improve daily activity.
  • Keep and improve overall mobility.
  • Sustain quality of life.
  • Get access to devices to assist with walking and moving later in life.

Can This Injury or Condition Be Prevented?

Because the genetic change that causes PWS happens at random when the baby is developing in the womb, there is no way to prevent it. Expectant mothers may get genetic testing during pregnancy if there is concern for a genetic disorder.

PWS affects many aspects of health. Improvements in care mean many people with PWS can now live a full life span. Physical therapists and other health care providers can help lessen some of the effects of the syndrome, including obesity and a potential inactive lifestyle.

What Kind of Physical Therapist Do I Need?

Every physical therapist is trained by education and practical experience to treat a wide variety of conditions and injuries. Some things to consider as you choose a physical therapist for people with PWS include:

  • A physical therapist who focuses on treating infants and children.
  • A physical therapist with experience treating obesity.
  • A physical therapist who is a board-certified clinical specialist or who has completed a residency or fellowship in pediatric physical therapy. This physical therapist will have clinical expertise, knowledge, and experience that may apply to developmental conditions such as PWS.

You can find physical therapists in your area with these credentials and clinical expertise on Find a PT, a tool built by the American Physical Therapy Association.

General tips when you are searching for a physical therapist (or any health care provider):

  • Ask family, friends, or other health care providers for recommendations.
  • When you contact a physical therapy clinic or agency, ask about the physical therapists' experience in treating children with PWS, or other developmental or genetic conditions.
  • Be prepared to describe your child's symptoms and motor skills in as much detail as possible during your first visit.

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The APTA Academy of Pediatric Physical Therapy contributed to this consumer resource. It is for informational purposes only and is not intended to represent the position of APTA Pediatrics.

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The American Physical Therapy Association believes that consumers should have access to information to help them make informed decisions and prepare them for their visit with a health care provider.

The following resources offer some of the best scientific evidence related to physical therapy treatment for PWS. They report recent research and provide information on the standards of practice both in the United States and internationally. They link to a PubMed* abstract (which may also offer free access to the full text) or other resources. You can read them or print out a copy to bring with you to your health care provider.

Medscape. Prader-Willi syndrome. Medscape website. Updated October 14, 2020. Accessed March 7, 2021.

Morales JS, Valenzuela PL, Pareja-Galeano H, Rincón-Castanedo C, Rubin DA, Lucia A. Physical exercise and Prader-Willi syndrome: a systematic review. Clin Endocrinol (Oxf). 2019;90(5):649–661. Article Summary on PubMed.

Passone CB, Pasqualucci PL, Franco RR, et al. Prader-Willi syndrome: what is the general pediatrician supposed to do? A review [article in English, Portuguese]. Rev Paul Pediatr. 2018;36(3):345–352. Article Summary on PubMed.

Moix Gil E, Giménez-Palop O, Caixàs A. Treatment with growth hormone in the prader-willi syndrome [article in English, Spanish]. Endocrinol Diabetes Nutr (Engl Ed). 2018;65(4):229–236. Article Summary on PubMed .

Butler M, Manzardo A, Heinemann J, et al. Causes of death in Prader-Willi syndrome: Prader-Willi Syndrome Association (USA) 40-year mortality survey. Genet Med. 2017;19(6):635–642. Article Summary on PubMed.

Driscoll DJ, Miller JL, Schwartz S, et al. Prader-Willi Syndrome. GeneReviews. Seattle, Washington: University of Washington – Seattle; 2017. Article Summary on PubMed.

National Institutes of Health, National Center for Advancing Translational Sciences. Prader-Willi syndrome. Updated July 7, 2016. Accessed March 7, 2021.

Reus L, Pelzer BJ, Otten BJ, et al. Growth hormone combined with child-specific motor training improves motor development in infants with Prader-Willi syndrome: a randomized controlled trial. Res Dev Disabil. 2013;34(10):3092–3103. Article Summary on PubMed .

MedlinePlus. Prader-Willi syndrome. MedlinePlus website. Accessed March 7, 2021.

Foundation for Prader-Willi Research. Diagnosis and treatment. Accessed March 7, 2021.

* PubMed is a free online resource developed by the National Center for Biotechnology Information. PubMed contains millions of citations to biomedical literature, including citations in the National Library of Medicine's MEDLINE database.