Prader-Willi syndrome (pronounced PRAH-der WILL-ee) is a complex, rare genetic disorder that results from an abnormality on the 15th chromosome. Identified in 1956, it occurs in about one in 15,000 live births, in both males and females equally, and in all races.

Though Prader-Willi syndrome is a rare disease, it is one of the ten most common conditions seen in genetics clinics and is the most common genetic cause of obesity that has been identified.

PWS affects growth, metabolism, appetite, behavior, and overall development. Persons with PWS typically have weaker muscles, short stature if not treated with growth hormone, incomplete sexual development, and a chronic feeling of hunger that, coupled with a metabolism that utilizes drastically fewer calories than normal, can lead to excessive eating and life-threatening obesity. The drive to eat is never satisfied no matter how much food is consumed, necessitating constant and continuous supervision.

A blood test can confirm a diagnosis in most cases. If you suspect your child (or you) has Prader-Willi syndrome print the Diagnostic Criteria Sheet and mark the traits you have observed then discuss with your doctor. Consultation with a geneticist is recommended. Ideally you should start with a methylation test which detects approximately 99% of PWS cases. If the methylation test is positive you will then need either a FISH test or a PCR test to determine the sub-type, deletion or UPD respectively. There have been numerous instances when a negative FISH test results in a family being told their child does not have PWS only later (sometimes much later) to discover via a methylation or PCR test that their child has the UPD sub-type.

PWS is a lifelong, life-threatening condition, and there is no cure – yet.

Researchers continue to study Prader-Willi syndrome in hope of finding answers that could lead to effective treatments.

PWS is a randomly occurring genetic disruption that occurs at conception; there is no known cause for the genetic anomaly.  PWS is found in both males and females and across all races.

For more information about the genetics of PWS please read Genetics of PWS

There is no treatment for PWS as a whole, instead each symptom is “treated” or “managed”.  For example, many symptoms are improved through the use of growth hormone therapy.  Behavior therapy help manage the behavioral aspects of the syndrome, and proper Food Security helps manage weight.

Unfortunately, currently there is no effective treatment for the hyperphagia (excessive appetite) of PWS which is a hallmark symptom of the syndrome.  However, there are current research studies which may lead to a treatment for this symptom.

PWS is estimated to occur once in every 12,000 – 15,000 people.  As such it is a rare disease, however it is the most common genetic cause of obesity.

PWS occurs in both males and females and across all races.

Yes, the National Institutes for Health defines a rare disease as one that affects less than 200,000 people in the United States.

Given the incident rate of one in every 12,000 – 15,000 people there are approximately 20,000 – 25,000 people in the United States who have PWS. Unfortunately approximately 65% of these are not known to the national organization (PWSA-USA) and therefore are probably not receiving necessary support and services.

No – While there is a genetic disposition toward obesity, due to the combination of an insatiable appetite (hyperphagia) and an extremely low metabolism, with good food management by the parents or caregivers (individuals with PWS cannot be relied on to manage their own food intake) and regular physical activity, a healthy weight can be maintained.

Early diagnosis and growth hormone therapy has also helped prevent many children from becoming obese at a young age (as was almost certain in prior generations); this often leads to a healthier weight in adulthood as well.

No, in fact most infants with PWS are diagnosed with failure to thrive. The global hypotonia (weak muscles) make early feeding extremely difficult.

As with most syndromes, PWS is a spectrum disorder so each individual is unique. There is no set age at which the hyperhpagia (excessive appetite) begins; no one knows what causes the onset. For some the onset is as young as 2 or 3, yet for others the onset is not until much later. It is important to note that proper food management is crucial regardless of when hyperphagia begins. Most people with PWS have extreme anxiety about food even if they are not actively seeking food.

Make Connections

PWCF maintains online and in-person Support Groups for parents and professionals.

PWSA (USA) maintains several Facebook support groups.