Prader-Willi syndrome is a complex genetic disorder involving the impairment of several body systems. At birth, it shows up with hypotonia (floppy muscle tone), difficulty in feeding, and delayed development. With growth, children experience uncontrollable appetite, leading to chronic overeating (hyperphagia) and obesity. 

This excessive weight gain increases the risk of several health complications, including type 2 diabetes, especially in individuals with severe obesity. Awareness of the aetiology, presentation, and risk factors of Prader-Willi syndrome allows early treatment and optimal long-term management. 

For future NEET PG medical students, the clinical understanding of this condition enhances academic capacity as well as diagnostic competence and skills of patient care in actual cases.

Read more for detailed insights on the causes, symptoms, diagnosis and treatment of this condition.

What is Prader-Willi Syndrome?

Prader-Willi syndrome (PWS) is a rare, multi-system congenital disorder that impacts a child’s metabolism, growth, and behaviour. Infants with PWS have extremely low muscle tone and are finicky eaters. As the child ages, typically between the ages of 2 and 6, the child gets excessively hungry, so if left unchecked, it leads to overeating and at times life-threatening obesity.

While uncommon, Prader-Willi syndrome can also lead to potentially life-threatening conditions like sleep apnea, diabetes, obesity-cardiac complications, and recurrent respiratory infections.

What are the Causes of Prader-Willi Syndrome?

Prader-Willi syndrome is a genetic condition resulting from an abnormality in specific genes on chromosome 15. Although the mechanism is not always precise, the problem relates to the expression of genes which are supposed to be inherited from the father.

In most cases, genes come in pairs, one from each parent. Both the maternal and paternal forms are found in most of the genes. There are genes, though, that entirely depend on activation from either copy of either of the parents. In PWS, some of those genes that need activation from the father’s copy are not working as they should. It may be because of:

• Missing paternal genes on chromosome 15.
• Two maternal chromosomes 15s with no contribution from the father (a condition known as maternal uniparental disomy).
• Paternal chromosome 15 mutations or structural abnormalities.

These genetic defects impede the activity of the hypothalamus, an essential component of the brain that controls hunger, body heat, mood, sleep, hormone release, and sexual maturation. When the hypothalamus is impaired, it results in the majority of the symptoms of PWS.

Prader-Willi syndrome is most commonly caused by spontaneous mutations that are not inherited. Identification of the underlying genetic cause is essential for proper diagnosis and genetic counselling.

What are the Risk Factors of Prader-Willi Syndrome?

The children with a single or multiple gene defect on chromosome 15 are at the maximum risk of developing Prader-Willi syndrome. The genetic alteration, missing part or mutation, in the majority of cases, is not inherited from either parent and is random in nature.

But if you already have a child with PWS and are considering having another child, it is advisable to speak with a genetic counsellor. Genetic counselling can help explain the risk of recurrence and what prenatal tests you might have available to you.

What are the Symptoms of Prader-Willi Syndrome?

The physical and behavioural signs and symptoms of Prader-Willi syndrome differ among individuals. During infancy, the most frequent earliest symptoms are:

• A faint or weak cry.
• Excessive sleepiness or lack of alertness.
• Difficulty feeding or sucking.
• Floppy or low muscle tone (hypotonia).

As your child develops, some other physical features may become apparent, such as:

• Almond-shaped eyes.
• A narrow, elongated head shape.
• A mouth shaped like a triangle.
• Short stature or below-average height.
• Smaller than usual hands and feet.
• Underdeveloped sex organs (hypogonadism).

Other than physical appearance, PWS affects behaviour and intellectual development. Behavioural and developmental symptoms can include:

• Changes in mood, tantrums, or resistance to change.
• Slowed learning or intellectual impairment.
• Stereotypic behaviours, such as picking at the skin or compulsive behaviour.
• Sleep disturbance or excess daytime somnolence.
• Enormous hunger and unquenchable appetite with hyperphagia (binge eating).

In the absence of surveillance, hyperphagia may contribute to morbid (class III) obesity, significantly increasing the risk of conditions such as type 2 diabetes, hypertension, and cardiovascular disease.

How is Prader-Willi Syndrome Diagnosed?

Medical doctors diagnose Prader-Willi syndrome with a combination of physical examination and genetic testing. During the physical examination, the doctor will be observing common presentations of PWS and asking about feeding habits, growth history, and emotional characteristics in the child.

If PWS is suspected after clinical presentation, a genetic test is performed. This will most typically be a blood test looking at the child’s DNA (deoxyribonucleic acid) for some abnormality of chromosome 15. The results are then utilised to confirm the diagnosis and determine the underlying cause in genetic terms.

What is the Treatment for Prader-Willi Syndrome?

Early detection and treatment can significantly improve the life of a person with Prader-Willi syndrome (PWS). A comprehensive care approach involving multiple healthcare providers is usually required.

Although treatment plans vary according to symptom and individual requirement, the majority of children with PWS respond favorably to the following interventions:

• Proper Nutrition: Many babies with PWS struggle to feed due to poor muscle strength. The doctor can suggest high-calorie formula feeds or special feeding methods to ensure good weight gain. The child’s growth should be checked regularly to ensure proper growth.
• Growth Hormone Treatment (HGH): Human growth hormone can be administered to encourage height growth, muscle development, and body fat reduction in children with PWS. Others can also receive HGH by prescription as adults. A physician can determine whether treatment is appropriate and what side effects will be.
• Sex Hormone Replacement: Since sex hormones are usually low in PWS children, puberty is incomplete or delayed. Your endocrinologist may recommend hormone replacement, testosterone in males and estrogen plus progesterone in females. This will help develop puberty and can decrease the risk of osteoporosis. Males with undescended testicles may need surgery.
• Weight and Diet Control: Under the guidance of a dietician, you can create a low-calorie but nutritionally sound meal plan to control weight in an effective manner. Due to strict diet restrictions, your child may also need supplementation with vitamins and minerals. Regular exercise and physical activity are most crucial to develop and maintain a normal weight and learn motor skills.
• Sleep Management: Treatment of conditions like sleep apnea or other sleep disorders may reduce daytime drowsiness and behavioural issues so that your child can respond more effectively during the day.
• Therapeutic Interventions: There are various therapies that are found to be beneficial in children with PWS. Physical therapy for developing strength and coordination, speech therapy for language development, and occupational therapy for developing self-care skills are some examples. 

Social and developmental therapies also assist in developing age-related behaviour and social skills.

• Behaviour Management: Long, formal routines and strict rules about access to food are typically needed. Your child must have clear expectations established for their behaviour. Medications may be required to control extreme behavioural problems.
• Treatment for Mental Health: Emotional or psychiatric issues like skin picking because of compulsivity, anxiety, or mood disorders are treated by mental health professionals. In others, medication can be prescribed to decrease symptoms.
• Other Treatments: Other diseases need to be cured and managed separately. They include vision disorder screening, scoliosis screening, thyroid hormone function, or symptoms of early diabetes.

FAQs About Prader-Willie Syndrome

1. What exercises are suitable for Prader-Willi syndrome?

Moderate aerobic exercise, such as walking, swimming, cycling, and dancing, is suitable for PWS individuals. They help increase heart rate, burn fat, build muscle, and improve mood. Exercise improves physical functioning and overall health, too.

2. What type of disability is Prader-Willi syndrome?

Prader-Willi syndrome is a genetic and neurodevelopmental disorder. It comprises infantile feeding difficulties, delayed development, low muscle tone, and childhood compulsive feeding. These factors make it a physical and intellectual disability requiring lifelong care.

3. How does Prader-Willi syndrome impact the brain?

PWS results from defective genes on chromosome 15 that harm the hypothalamus, the hormone, appetite, and sleep centre of the brain. This leads to difficulties with appetite control, growth, puberty, mood, and sleep control.

4. How does Prader-Willi syndrome impact sleep?

PWS patients are more prone to sleep apnea, daytime drowsiness, insomnia, and motor problems like restless leg syndrome. These sleeping conditions aggravate behaviour and learning, and therefore, their detection and treatment in the initial phase are imperative.

Conclusion

People with the disorder are generally developmentally delayed and may need lifelong supportive therapy in an effort to avoid complications. Open communication with the child’s medical care provider is the basis of understanding the condition and making informed care decisions at each turn.

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