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Prader-Willi Syndrome - Causes, Symptoms, and Treatment

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Prader-Willi syndrome is a genetic disorder in which the person suffering has obesity, shortened height, and intellectual disability. Read further to know more.

Written by

Dr. Kirti Maan

Medically reviewed by

Dr. Kaushal Bhavsar

Published At September 22, 2022
Reviewed AtJuly 27, 2023

What Is Prader-Willi Syndrome?

A genetic disorder that is characterized by severe infantile hypotonia (decreased muscle tone), genital hypoplasia (caused due to hypogonadism), and pubertal insufficiency. Pubertal insufficiency is flagged off by characteristic facial features.

Hallmark features of Prader-Willi syndromes include early-onset obesity (childhood), atypically increased appetite (hyperphagia), delay in achieving developmental milestones (developmental delay), intellectual disability (mild to moderate, in rare cases severe), reduced height (short stature), and a specific behavioral phenotype. The characteristic facial feature of the child is a narrow forehead, abnormally small hands and feet, and short stature with light skin and hair. A proven feature of the Prader-Willi syndrome is impotence. A person suffering from Prader-Willi syndrome has an abnormally increased appetite which makes them eat more, which ultimately leads to obesity and often diabetes (type II).

Prader-Willi syndrome is caused due to missing or non-working chromosome 15 (gene on). The majority of the cases are random in occurrence but rarely inherited. Symptoms of someone suffering from Prader-Willi syndrome differ based on the developmental stage of the child.

What Causes Prader-Willi Syndrome?

As has been proven by studies, Prader-Willi syndrome is a genetic disorder caused due to the gene located on chromosome 15. The mechanism or the lacking factor of the gene on chromosome 15 is yet to be known.

The human body contains all of its genes in pairs except for that on the sex chromosome. While all the genes are in pairs, one pair is from the paternal side (father), and the copy gene or the other gene is from the maternal side (mother). Usually, among the pair, one is an active or expressed gene, and the other is the stable gene. The missing gene or the missing genetic material of the gene on chromosome number 15.

The reason Prader-Willi syndrome occurs is because of one of the following reasons:

  • Gene (paternal) on chromosome 15 is missing.

  • An individual inherits two copies of chromosome 15 from the maternal side and no copy of chromosome 15 from the paternal side.

  • Often a defect or an error in the paternal gene on chromosome 15.

In Prader-Willi syndrome, a defect on chromosome 15 interrupts basic and normal functions of the part of the brain called the hypothalamus, which is responsible for controlling the release of hormones. When the hypothalamus does not function well or properly, it interferes with the daily routine of life, such as appetite, growth, development (general and sexual), body temperature, mood, and sleep pattern. There is no definite way to prevent the Prader-Willi syndrome from occurring since there is no definite course of action for it to happen. The genetic cause happens at random or by chance; anyone and everyone can be affected by it.

What Are the Symptoms of Prader-Willi Syndrome?

Prader-Willi syndrome affects children at many ages. The symptoms of the Prader-Willi syndrome are categorized into the following subgroups:

1. In utero or at birth.

2. Infants.

3. Childhood and adulthood.

4. Common physical symptoms (appearances).

1. In Utero or at Birth: A child suffering from Prader-Willi syndrome may show the following symptoms in utero or at birth -

  • Decreased fetal movement.

  • Atypical fetal position (often frequently).

  • The occasional case of polyhydramnios (increased quantity of amniotic fluid in the skull).

  • Increased risk of cesarean births.

  • Lethargic mothers and, in some cases, infants too.

  • Reduced muscle tone (hypotonia).

  • Difficulty eating or feeding.

  • Respiratory difficulty or difficulty breathing (due to poor muscle tone).

  • Little to no sex hormone is produced (hypogonadism).

2. Infants: An infant with a missing or defective gene on chromosome number 15, shows the following symptoms-

  • Defective or poor muscle tone (a primary sign of Prader-Willi syndrome).

  • Floppy and loose extremities.

  • Prominent facial features such as almond-shaped eyes, a narrow head (at temples), a thin upper lip distinctive feature as a turned-down mouth.

  • Poor sucking reflex due to hypotonia which causes difficulty in feeding and difficulty in the development of the child.

  • Poor response action. The infant is often tired, poorly stimulated, not responsive to food, and cries weakly.

  • Underdeveloped genitals. Males suffer from cryptorchidism (barely descended or small testicles). In females, the clitoris and labia are small.

3. Childhood And Adulthood: While the in-utero and infantile signs and symptoms of the Prader-Willi syndrome are clear indications of the disorder, they differ from the childhood symptoms of the Prader-Willi syndrome. Childhood symptoms of the Prader-Willi syndrome are-

  • Delay in achieving developmental milestones.

  • Disrupted sleep patterns are often seen as excessive sleeping.

  • Crossed eyes.

  • Scoliosis (sideways curvature of the spine).

  • Delay in speech.

  • Poor physical condition.

  • Hyperphagia.

  • Weight gain.

  • Delay in puberty.

  • Short stature or height.

  • Obesity.

  • Flexible extremities.

4. Common Physical Symptoms: Except for the symptoms presented with the infant child and adulthood. Common symptoms seen in all the age groups are-

  • Prominent nasal bridge.

  • Small extremities.

  • Soft skin.

  • High forehead.

  • Light skin (in comparison to other family members).

  • Infrequent skin picking.

  • Delayed or absent motor development.

What Is the Treatment for Prader-Willi Syndrome?

Since the conformity of the syndrome is often lately diagnosed, there is no definitive cure for the said syndrome. An individual suffering from different symptoms may seek treatment for the specific symptoms.

What Are the Complications Concerning Prader-Willi Syndrome?

Complications of Prader-Willi syndrome are due to the increased severity of the symptoms and lack of prevention of the said syndrome. Some of the complications are:


An individual, or more closely, a child suffering from the Prader-Willi syndrome, constitutes living differently and more complicatedly in their personal life.

There is no definite treatment posed for the said syndrome. However, treatment for the symptoms increases the life potency. Managing symptoms of Prader-Willi syndrome is often difficult but possible. The affinity of life increases due to the treatment provided by a healthcare professional. Support groups and coping mechanisms are an essential part of the treatment plan.

Frequently Asked Questions


What Are the Five Primary Signs of Prader-Willi Syndrome?

The most common sign of Prader-Willi Syndrome is almond-shaped eyes. 
The other signs can include;
 - Problems related to eyes.
 - Narrow forehead.
 - Narrow ridge of the nose.
 - Thin upper lip.
 - Downturnned mouth.
 - Unusually fair skin, hair, and nose


What Are the Causes Of Prader-Willi?

A genetic mutation on chromosome 15 causes Prader-Willi syndrome. A part of this gene is called unstable because it is prone to getting shuffled. It usually affects the hypothalamus of the brain. During the early development stages, genetic changes can cause the condition in a portion of the chromosome. This is called the Prader-Willi critical region.


How Is Prader-Willi Diagnosed?

Genetic tests used to check for genetic defects can be used to detect the condition. These tests enable the identification of defects in the genetic makeup, thereby helping to understand genetic disorders. A blood test on the child after they are born confirms the condition. Another important factor is whether another child of the same couple is prone to the condition.


What Is Another Name for Prader-Willi Syndrome?

Prader Willi was earlier known as hypogonadism, hypotonia, hypomania, and obesity (HHHO). It was later renamed after the experts who found the condition, Andrea Prader, Alexis Labhart, and Heinrich Willi. They were the ones to describe the genetic anomalies related to the condition, along with the signs noted.


How Is Prader-Willi Syndrome Treated?

There is no specific treatment for the condition. However, a supervised diet will help them improve their quality of life. Artificial human growth hormone (HGH) is recommended for children with the condition. It has benefits like increasing the body's muscle without increasing the body's fat.


What Are the Complications of Prader-Willi Syndrome?

The condition's complications can include small hands and legs, curvature of the spine, a decrease in the flow of saliva, etc. Vision problems like nearsightedness are common. They usually have problems regulating their normal body temperature. A low pain tolerance level is seen in this condition.


Is Prader-Willi a Neurological Disorder?

It is a complex neurological disorder. The symptoms indicate hypothalamic and central nervous system (CNS) dysfunctions. It is a genetic disorder whose exact mechanism is still unclear. It can be considered a neurodevelopmental genetic disorder.


Is Prader-Willi Preventable?

Prader Willi syndrome is a non curable condition. There is no prevention yet discovered for the condition. The treatments provided help ease the condition. Dietary supervision is an essential part of the treatment. However, there are no ways to curb appetite.


What Is the Diet for PWS Syndrome?

A diet low in starch and high in protein is usually recommended. The use of processed food should be limited or avoided. Drinks like milk or water can be given to children. Sweetened drinks and carbohydrates should be avoided.


How Long Does Prader-Willi Live?

The average life expectancy of a person with Prader-Willi syndrome is 30 years. However, some people with the condition have lived for about 60 years. People with the condition die prematurely due to respiratory issues. Ninety-eight percent of the affected people were found to be obese.


Does Prader-Willi Syndrome Affect the Intellectual Status?

Most people with the condition will have a mild to moderate intellectual disability. Their intelligence quotient (IQ) will range from 60 to 65. They will also face learning disabilities. They would also have behavioral problems like temper outbursts, stubbornness, and compulsive behaviors like picking at the skin. Abnormalities in sleeping patterns can also be seen.


Does Prader-Willi Cause Infertility?

Most people with Prader-Willi syndrome are usually infertile - they would be unable to conceive. They usually have underdeveloped genitalia. The condition is associated with hypogonadism (decreased function of the testes or ovary). They have also undergone incomplete puberty.


How Does PWS Affect the Family?

PWS usually puts a burden on the caregiver. They affect their quality of life. It can be stressful for the family. Children with PWS report poorer QoL (Quality of life) scores.
Dr. Kaushal Bhavsar
Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)


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