Prader Willi Syndrome: Symptoms, Causes, Diagnosis, Treatment, Prevention and Prediction

SPW is a genetic disorder that occurs because of the loss of function of specific genes.

Beginning in childhood, a person constantly suffers from hunger, leading to obesity and type 2 diabetes.

There is also an intellectual deterioration that ranges from mild to moderate behavioral problems.

About 70% of cases occur when part of the father’s chromosome 15 is removed.

In another 25% of cases, the person has two copies of chromosome 15 from his mother and none from his father.

As parts of the mother’s chromosome go out, they end up without copies of specific genes.

SPW is not usually inherited, but genetic changes occur during the formation of the ovum, sperm, or early development.


There are no known risk factors. Those with a child with Prader Willi Syndrome have less than a 1% chance that the next child will inherit this genetic condition.

Prader-Willi syndrome has no cure and affects 1 in 30,000 people.

Both men and women are affected equally. The condition is named after Andrea Prader, Heinrich Willi, and Alexis Labhart, who described it in 1956.

An earlier description occurred in 1887 by John Langdon Down.

Signs and symptoms

There are many recognized signs and symptoms of Prader-Willi syndrome.

Symptoms can range from poor muscle tone to behavioral problems during childhood.

In addition to poor muscle tone, some symptoms usually found more easily in babies are the lack of visual coordination; some are born with almond-shaped eyes, and the baby’s poor muscle tone may not have a strong sucking reflex.

Their cry is weak, and they have difficulty waking up. Another sign of this condition is a thin upper lip.

More aspects of a clinical description include:

  • Hypotonia and abnormal neurological function.
  • Hypogonadism.
  • Cognitive and developmental delays.
  • Hyperphagia and obesity.
  • Short stature.
  • Behavioral and psychiatric disorders.

Holm and Al. (1993) describe the following characteristics and signs as SPW test indicators, although not all will be present simultaneously.

Uterus and birth

  • Reduced fetal movement.
  • Frequent abnormal fetal position.
  • Excess of amniotic fluid
  • Lethargy.
  • Hypotonia.
  • Feeding difficulties (due to poor muscle tone that affects the suction reflex).
  • Difficulty breathing
  • Hypogonadism.


  • Intellectual delay
  • Sleeping excessively
  • Strabismus (crossed eyes).
  • Scoliosis (often not detected at birth)
  • Cryptorchidism.
  • Speech retardation
  • Poor physical coordination
  • Hyperphagia: (overeating) begins between 2 and 8 years and continues into adulthood.
  • Overweight.
  • Sleep disorders.
  • Delayed puberty.
  • Short stature.
  • Obesity.
  • Extreme flexibility.


  • Infertility (men and women).
  • Hypogonadism.
  • Short pubic hair.
  • Obesity.
  • Hypotonia (low muscle tone)
  • Learning disabilities (in some cases, average intelligence).
  • High predisposition to diabetes mellitus.

Physical appearance

  • Prominent nasal bridge.
  • Tiny hands and feet with sharp fingers.
  • Soft skin, which bruises easily.
  • Excess fat, especially in the central part of the body.
  • High and narrow front.
  • Thin upper lip.
  • Mouth down.
  • Almond eyes.
  • Clear skin and hair for other members of the family.
  • Lack of complete sexual development.
  • Stretch marks.
  • Delayed motor development.


Prader-Willi syndrome is a genetic disorder caused by errors in one or more genes.

Although the exact mechanisms responsible for Prader-Willi syndrome have not been identified, the problem lies in genes located in a particular region of chromosome 15.

Except for genes related to sexual characteristics, all genes are presented in pairs: a copy inherited from their father and their mother.

For most genes, if one copy is “active” or manifests itself, the other copy will do so, although it is normal for some types of genes to act alone.

Prader-Willi syndrome occurs because specific paternal genes that must be expressed do not do so for one of these reasons:

  • The paternal genes on chromosome 15 are missing.
  • The child inherited two copies of chromosome 15 from the mother and not one from the father and another from the mother.
  • There is some failure or error in the paternal genes on chromosome 15.

In this syndrome, an irregularity in chromosome 15 interrupts the normal functions of a portion of the brain called the hypothalamus, which controls the release of hormones to our body.

If the hypothalamus does not work correctly, it can obstruct processes that cause problems in sexual development, growth, hunger, body temperature, sleep, and mood.

Determining which genetic defect caused Prader-Willi syndrome may be helpful in genetic counseling.


Most Prader-Willi syndrome (PWS) cases are not inherited and are due to random events during the formation of ovules or sperm or early fetal development.

This is usually the case when the syndrome is caused by maternal uniparental disomy or a deletion in the father’s chromosome 15.

However, a genetic change responsible for SPW can be inherited in rare cases.

The risk to family members of a person with PWS depends on the genetic cause of the condition in the affected person.

Because the genetic causes of PWS are complex, people seeking information about specific risks for themselves or their family members are encouraged to speak with a genetic professional.


The diagnosis of suspected Prader-Willi syndrome (PWS) is usually made by a doctor based on clinical symptoms.

SPW should be suspected in any child born with significant hypotonia (muscle weakness). A blood test confirms the diagnosis.

The preferred test method is a “methylation analysis” that detects 99% of cases, including all significant genetic subtypes of SPW (deletion, uniparental disomy, or imprinting mutation).

A “FISH” test (Fluorescent In Situ Hybridization) will identify those patients with PWS due to deletion. Still, it will not identify those who have Prader-Willi syndrome due to “UPD” (uniparental disomy) or a printing error.

Almost all cases of PWS can be confirmed with one of the previous tests.

However, in the rare case that laboratory tests do not confirm SPW, a clinical diagnosis may be helpful in the development of a management plan for this syndrome.


The treatment of PWS is currently based on treating the disorder’s symptoms as they arise.

Growth hormone deficiency is present in almost all children and adults with PWS.

In multiple studies, it has been discovered that human growth hormone (HGH) is beneficial for people with Prader-Willi syndrome.

In June 2000, HGH was officially approved by the Federal Drug Administration (FDA) in the United States for use in patients with Prader-Willi syndrome.

HGH is effective in increasing height and decreasing body fat, increasing muscle mass, improving weight distribution, and increasing strength and bone mineral density.

In addition, studies suggest its positive effects on development and behavior.

In 2013, guidelines for using HGH in SPW were developed as part of an international meeting of experts.

Despite treatment with HGH, many challenging symptoms associated with PWS are still challenging to treat.

The inability to control food intake is often the biggest obstacle for people with PWS to live independently.

To date, no medication has proven effective in regulating appetite in SPW. Therefore, strict environmental control and constant monitoring are the only ways to prevent overweight and extreme obesity that threaten a patient’s life. With SPW today.

However, several new anti-obesity drugs are in clinical development, some of which may benefit the SPW population. Evaluating these drugs in clinical trials is an essential priority for FPWR.

Meanwhile, a well-balanced diet is recommended, and careful environmental control is needed to minimize uncontrolled food access.

Additional challenges in PWS include sleep disturbances, hormonal abnormalities, scoliosis, dental problems, and skin bites.

Breathing problems during sleep are common, and periodic sleep studies are suggested for all ages, including infants.

Excessive daytime sleepiness can be improved with modafinil medication that stimulates wakefulness.

This medication also improves cognitive performance and decreases appetite in typical individuals.

The common hormonal abnormalities in PWS (low thyroid hormones, testosterone, estrogen, etc.) can be treated by an endocrinologist with standard medications.

Scoliosis is also prevalent in PWS and should be treated by an orthopedic doctor familiar with this syndrome.

Skin flares are standard in those with PWS and can be helped with N-acetylcysteine.

Finally, managing and treating psychiatric and behavioral problems associated with PWS can also be challenging.

Behavioral therapy, environmental control, and medication may be needed.

It is recommended to consult with mental health professionals familiar with Prader Willi Syndrome.


If you already have a child with this condition and want another baby, it is best to seek genetic counseling.

A genetic counselor can help determine your risk of having another child with Prader-Willi syndrome.


Children with Prader-Willi syndrome can be integrated into the classroom setting, although they need additional speech therapy and should have different periods of physical activity instead of rest periods.

They need a structured environment and may require a smaller class for individual attention.

People with PWS usually reach adulthood, function in a group home setting, do vocational work, or attend community college classes.

According to the Prader-Willi Syndrome Association, people with the syndrome can hope to achieve many things their peers do.

However, they need significant support from their families and school, work, and residential service providers.

Even those with IQ in the normal range need dietary supervision throughout life and protection against food availability.

Complications that could affect the quality of life and potentially shorten life expectancy include those related to hypogonadism, behavioral or psychological problems and morbid obesity.