Prader-Willi Syndrome

Prader-Willi Syndrome (PWS) is a rare genetic disorder.

What is Prader-Willi Syndrome (PWS)?

Prader-Willi Syndrome (PWS) is a rare genetic disorder. Children with PWS have specific features, which may vary depending on their age.

What are the Signs and Symptoms?

These signs or symptoms may include:

Prenatal Period (Pregnancy)

  • Decreased fetal movements
  • Breech presentation (baby in a “feet first” position before birth)


  • Low birth weight, length or muscle tone
  • Poor sucking/reflexes
  • Weak cry
  • Failure to thrive (may need tube feeding)
  • Narrowing of the skull at the temples
  • Almond-shaped eyes
  • Thin upper lip with some downturn at the corners of the mouth
  • Tapered fingers
  • Crossed eyes
  • Undescended testes/small penis (boys)


  • Delayed motor development (sitting at 12 months and walking at 24 months)
  • Delayed language
  • Mild to moderate intellectual disability
  • Uncontrolled increase in appetite, resulting in weight gain and obesity (typically starting at age 4)


  • Obesity
  • Developmental delays
  • Learning disabilities
  • Speech delays
  • Behavior concerns (including skin picking)
  • Growth hormone deficiencies
  • Delayed puberty
  • Low bone mineral density
  • Disordered sleep
  • Scoliosis

What Causes Prader-Willi Syndrome?

Prader-Willi syndrome is caused by changes in one or more genes located on chromosome 15.  In people who have PWS, the copy of the gene(s) that comes from the father is not functional. 

This occurs for one of the following three reasons:

  1. A small portion of the father’s chromosome 15 is missing (called a “deletion”)
  2. The child has two copies of chromosome 15 from the mother and has no copies of chromosome 15 from the father (called “uniparental disomy” or UPD)
  3. The father’s copy of the gene is not “turned on” properly (called an “imprinting” disorder)

A deletion is the most common cause of PWS, accounting for approximately 70% of cases.

How is PWS Diagnosed?

Although you may suspect Prader-Willi based on physical symptoms, it can only be confirmed through genetic testing.

How is PWS Treated?

There is no cure for Prader-Willi Syndrome yet. Researchers are conducting genetic research with the hope of finding a cure. For now, treatment is directed toward addressing each patients’ complex medical needs to improve their overall health and quality of life.  

  • Endocrine disorders are routinely screened for, and hormone replacement therapy is given for any hormonal deficiencies noted. Growth hormone therapy in particular is very helpful in improving muscle mass and muscle strength.
  • Occupational therapy, physical therapy, and speech therapy are valuable to promote motor development. 
  • Psychological therapy is valuable to minimize behavior challenges.
  • Feeding concerns, including the failure to thrive in infancy and obesity in later childhood, need close supervision by a dietitian.
  • Complications of obesity and sleep apnea are addressed aggressively as well.