Genetics and Symptoms of Prader-Willi Syndrome

prader-willi-syndrome

Prader-Willi Syndrome (PWS) is a genetic disorder that typically does not run in families.

PWS affects many parts of the body and results in physical, mental, and behavioral problems.

It mainly affects the child’s metabolism. During infancy, children have weak muscle tone and poor feeding ability. Later, at the age of 2 to 6, there is a tremendous increase in their appetite leading to obesity and related complications. If eating is not managed, this may even lead to life-threatening obesity.

How Prevalent is Prader-Willi Syndrome?

PWS affects about 1 in 15,000 to 30,000 people worldwide. The disease occurs in equal frequency in men and women.

Symptoms

PWS affects most body parts. It mainly affects the metabolism and causes physical, mental, and behavioral changes. The symptoms change over time.

There are two general stages of the symptoms:

1. Early Life

  • Weak muscle tone
  • Poor feeding ability
  • Distinct facial features
  • Weak cry
  • Underdeveloped genitals

2. Childhood and Beyond

  • Unregulated diet leading to obesity
  • Intellectual disability
  • Difficulty in controlling emotions
  • Obsessive-compulsive disorder
  • Short stature due to deficiency in growth hormone
  • Sleep abnormalities

Genetics

What is the Genetic cause of Prader-Willi Syndrome?

We inherit one copy of chromosome 15 from our mother (maternal copy) and one from our father (paternal copy).

Normally, the paternal genes present in a specific region (15q11.2–q13) of chromosome 15 are active while the maternal genes are inactive (also called silenced).

In Prader-Willi Syndrome, there is a loss of expression of paternal genes present in the 15q11.2–q13 region. This occurs due to one of the following reasons:

  1. Paternal deletion. About 65-75% of PWS occurs due to the deletion of this region.
  2. Maternal uniparental disomy. In 20-30% of PWS, both copies of chromosome 15 are inherited from the mother and none from the father.
  3. Imprinting defect. It occurs only in 1-2% of PWS wherein the parental PWS region is present but does not express.

How is Prader-Willi Syndrome Inherited?

Most cases of PWS are not inherited. People with PWS typically have no family history of the disorder. The genetic changes causing the disease occur in the reproductive cells (eggs and sperm) or during early embryonic development.

It is rare to inherit the condition if it runs in your family.

Diagnosis and Testing

How to Diagnose Prader-Willi Syndrome?

The diagnosis of PWS includes Clinical Assessments and Genetic Testing by the specialists.

In Clinical Assessments, the doctor will look for the physical signs of the disorder and ask about the symptoms (like eating habits and behavior).

If PWS is suspected, then Genetic Testing called Methylation Analysis is done. The genetic test is a blood test to determine any abnormalities in the region specific to PWS.

Treatment, Cure, and Prevention

What is the treatment for Prader-Willi Syndrome?

Treatment for PWS focuses on the management of the symptoms and prevention of any complications related to the disorder. It includes:

  • Use of special bottles to feed the infants.
  • Medications to supplement deficient hormones.
  • Following a specific diet plan to control weight gain.
  • Physical therapy, speech therapy, and special education to improve physical and cognitive functions.

Can Prader-Willi syndrome be Cured?

There is no cure for Prader-Willi Syndrome to date.

How to Prevent Prader-Willi Syndrome?

PWS is a genetic condition and therefore, cannot be prevented. There is nothing a parent can do before or during the pregnancy that can prevent PWS since the disorder develops due to a random genetic event.

Further Reading

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