Prader-Willi Syndrome

What is Prader-Willi Syndrome?

The Prader-Willi syndrome (PWS) is a rare syndrome that results from a defect in the genetic make-up. It occurs in around 1-9 per 100,000 births worldwide. Both boys and girls can be affected by Prader-Willi syndrome.

Affected people are short, have low muscle tension even as newborns and suffer from obesity later in life. Mental abnormalities and a reduced intelligence are also characteristic of Prader-Willi syndrome.

Also read: What is Klinefelter Syndrome?


The cause of the Prader-Willi syndrome is a so-called “paternal deletion”. This means that on chromosome 15 inherited from the father, a piece of the genetic information is deleted and is now missing. In most cases, this deletion arises spontaneously (new mutation) and is not inherited.

Read more on the subject at: Chromosome mutations

It is assumed that this change in the genetic material leads to a malfunction of the hypothalamus (part of the midbrain). The hypothalamus is an important control center of the body that is also responsible for the release of many hormones. In Prader-Willi syndrome, among other things, too little growth hormone is released, which leads to short stature.


The suspected Prader-Willi syndrome can be made by the pediatrician shortly after the birth. The newborns have muscular weakness, poor drinking and weak newborn reflexes. When determining the hormone values ​​in the blood, decreased values ​​for the growth and sex hormones are noticeable.

Only a genetic test can confirm the diagnosis. The deletion on chromosome 15 is detected here.

Read more on the subject at: Genetic examination

Do you recognize these symptoms as having Prader-Willi syndrome?

Affected children are noticed immediately after birth because they have low muscle tension (“floppy infant”), are particularly small and light and do not drink properly.

Read more on the subject at: Muscle weakness in the baby

Children with Prader-Willi syndrome have a distinctive appearance: almond-shaped eyes, a thin upper lip, a narrow bridge of the nose, and small hands and feet. Affected children often squint too. In boys, a small scrotum is noticed early and there is often an undescended testicle.

Child development is delayed and development milestones such as walking and speaking are reached later.

Read more on the subject at: Child development

From around the age of three, those affected develop an uncontrollable appetite without a feeling of satiety when they eat. This pathologically increased appetite leads to obesity. Overweight can be associated with secondary diseases such as diabetes, sleep disorders and cardiovascular diseases.

Read more on the subject at: Obesity in children

Even in puberty there is no growth spurt due to the reduced release of growth hormones. The genitals also remain underdeveloped. Most Prader-Willi patients remain sterile.

Read more on the subject at: Short stature

Decreased intelligence and learning difficulties are also typical of Prader-Willi syndrome. Mental health problems such as impulse control disorders and mood swings are also common in those affected.


There is no cure for Prader-Willi syndrome.
The main focus of symptomatic therapy is a strict diet. Strict calorie restriction and an adequate supply of vitamins and other nutrients must be observed here in order to prevent obesity and promote healthy development.

Physiotherapy can help improve children's motor development.

The administration of growth hormones can be started at an early stage. This should be done under strict supervision as the therapy can also have side effects, e.g. foot edema or worsening of existing scoliosis. With the onset of puberty, sex hormones can be replaced.

Psychotherapy in the form of behavioral therapy can be used and special care should take place in school in order to promote social development.

Duration and prognosis

There is no cure for Prader-Willi syndrome. However, early therapy can reduce its severity.

If the obesity can be managed through a strict diet, a normal life expectancy can be assumed. Serious secondary diseases such as diabetes and cardiovascular diseases can thus be prevented.

However, those affected remain sterile for life and are more susceptible to infections.