What Is Prader-Willi Syndrome (PWS)?

Prader-Willi syndrome (PWS) is a variable and complex genetic disorder resulting from an abnormality on the 15th chromosome. It occurs in males and females equally and in all races. Prevalence estimates range from 1:15,000 to 1:25,000.

Experts believe that PWS is a multistage disorder characterized by decreased fetal movement during pregnancy and low birth weight. As toddlers get older, they start gaining more weight. If we don't limit their calories, this can lead to excessive eating (hyperphagia) and obesity.

Obesity, hypotonia, and hypothalamic dysfunction are the main medical problems related to Prader-Willi syndrome. Other factors may include adverse reactions to medications, high pain tolerance, gastrointestinal and respiratory issues, lack of vomiting, and unstable temperature. Adrenal insufficiency may also occur. The main problem for people with this condition is extreme hunger, which can cause dangerous obesity.

Abnormalities on chromosome 15 cause Prader-Willi Syndrome (PWS). This happens 3 different ways:

1. Gene Deletion: In many cases, critical genes on a portion of the father's chromosome 15 are missing. This is the most common cause.
2. Uniparental Disomy: The child has two copies of chromosome 15 from the mother instead of one from each parent.
3. Imprinting Mutation: In less than 3% of cases, there is an imprinting mutation on the father's chromosome 15. The genetic material is there but remains inactive.

PWS varies from person to person but commonly affects the brain, particularly the hypothalamus. This leads to symptoms like:

• Weak muscle tone (hypotonia) from birth.
• Poor sucking in babies, causing feeding difficulties.
• Swallowing problems with saliva and food.
• Overeating (hyperphagia) due to the brain not signaling fullness, potentially causing severe obesity. This starts between 2-4 years old.
• Short height if not treated with growth hormones.
• Bone issues like hip dysplasia and osteoporosis.
• Delayed sexual development.
• Learning difficulties and developmental delays.
• Frequent behavior problems.
• Sensitivity to certain medications.
• High pain tolerance, possibly missing injuries like fractures.
• Digestive problems, including constipation and rare cases of stomach issues after binge eating.
• Breathing problems during sleep, like sleep apnea.
• Trouble regulating body temperature.

Doctors use unique genetic tests that analyze blood and saliva to identify PWS. These tests can be costly as they require specialized lab processing.

The best first test is DNA Methylation Testing, which detects over 99% of PWS cases and checks for all three genetic subtypes. The FISH test is useful but can't identify all subtypes, so it's not the preferred initial test. Chromosome Microarray testing is also effective, especially for detecting chromosome deletions and uniparental disomy (UPD).

Prader-Willi Syndrome (PWS) usually doesn't run in families. It happens because some genes on chromosome 15 aren't working right. This happens if a part of chromosome 15 from the father is missing. It can also occur when the child gets two chromosome 15s from the mother or if the genes from both parents aren't working right.

Scientists are always looking for new ways to treat the syndrome so children and adults can have a better quality of life. However, at this time there is no cure for Prader-Willi syndrome.

In 2000, the Federal Drug Administration approved Human Growth Hormone (HGH) for patients with Prader-Willi Syndrome (PWS). Studies show that HGH offers several benefits. It not only helps increase height and reduce body fat, but also boosts stamina and bone mineral density.

Many individuals with the syndrome participate in a variety of therapies, including physical, occupational, and speech therapies.