Prader-Willi Syndrome (PWS): Meaning, Causes, Symptoms, Treatment

Written by Medicover Team and Medically Reviewed by Dr Seepana Rajesh , Pediatrician

Prader-Willi Syndrome (PWS) is a rare genetic disorder that affects many parts of the body like growth, metabolism, behaviour and development. It is caused by a defect on chromosome 15, which disrupts the normal functioning of specific genes.

One of the most recognisable features of Prader-Willi syndrome is an insatiable appetite that can lead to excessive eating (hyperphagia) and severe obesity if not carefully managed. Children with PWS show low muscle tone (hypotonia), developmental delays and behavioural difficulties.

The condition affects both males and females equally and it is estimated to occur in about 1 in 10,000 to 30,000 births worldwide. Although there is no permanent cure but early diagnosis and supportive treatments can improve the quality of life.

Types of Prader-Willi Syndrome

Prader-Willi Syndrome can develop because of different types of genetic changes on chromosome 15. Doctors classify the condition based on what kind of genetic error has occurred:

Paternal deletion (around 70%): In most children with PWS, a small section of chromosome 15 inherited from the father is missing. This deletion prevents specific genes from functioning, which causes the classic features of the syndrome.
Maternal uniparental disomy (UPD) (about 25 to 30%): In this case, instead of getting one copy of chromosome 15 from each parent, the child inherits both copies from the mother and none from the father. Because the father's copy is missing and important genes do not work correctly.
Imprinting defects (1 to 3%): Sometimes the father's chromosome 15 is present but fails to function properly due to an imprinting error, which means the genes are inactive when they should be active.

All three genetic causes interfere with normal growth, appetite regulation and development. While the cause may differ, the symptoms of PWS are very similar but severity and associated complications can vary from person to person.

Signs and Symptoms of Prader-Willi Syndrome

The symptoms of Prader-Willi Syndrome change as the child grows. Many features are noticeable in infancy, while others become more prominent in childhood or adulthood. Some of the common signs of PWS are:

In Infants:

Weak muscle tone (hypotonia): Babies usually feel floppy and have difficulty moving their arms and legs.
Feeding difficulties: Poor sucking reflex and weak muscles make breastfeeding or bottle-feeding challenging and sometimes require feeding support.
Delayed motor milestones: Rolling, sitting, crawling and walking may occur later than usual.

In Children and Adults:

Excessive hunger and overeating (hyperphagia): A constant sense of hunger begins in early childhood, which leads to uncontrolled eating and rapid weight gain.
Obesity: Children with PWS can become severely overweight at an early age, without strict supervision.
Growth and physical changes: Short stature, small hands and feet and reduced muscle mass are common.
Delayed puberty: Underdeveloped sexual organs and hormone imbalances usually result in infertility.
Learning and intellectual disability: Most children have mild to moderate intellectual challenges in problem-solving and academics.
Behavioural and emotional problems: Stubbornness, frequent temper outbursts, obsessive-compulsive behaviours and difficulty adjusting to change.
Sleep disturbances: Daytime sleepiness, restless sleep or sleep apnea contribute to fatigue and affect learning and behaviour.

Causes of Prader-Willi Syndrome

There are three main genetic reasons for the development of PWS and are as follows:

Paternal chromosome 15 deletion: In the majority of cases, a section of the chromosome inherited from the father is missing. This is the most common cause of PWS.
Maternal uniparental disomy (UPD): In some children, both copies of chromosome 15 come from the mother instead of one from each parent. Since the father's copy is absent, the required genes cannot work.
Imprinting defect: Rarely, the father's chromosome 15 is present but does not function properly because the genes are incorrectly switched off.

These changes usually occur by chance during early development and are not inherited from parents. For couples planning future pregnancies, genetic counselling is recommended to understand risks and available options.

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Prader-Willi Syndrome Features

Children and adults with PWS show a mix of physical, developmental and behavioural features that help doctors recognise the syndrome. Not every person will have all features but some patterns are common:

Physical Features:

Narrow forehead, almond-shaped eyes and a thin upper lip.
Small hands and feet compared to body size.
Fair skin, light hair and lighter eye colour compared to other family members.
Short stature and delayed growth due to hormone deficiencies.
Low muscle tone (hypotonia) is noticeable from birth.

Developmental Features:

Delayed motor milestones such as sitting, walking and running.
Speech and language delays that affect communication.
Mild to moderate intellectual disability affecting problem-solving and academic skills.

Health-Related Features:

Obesity is linked to constant hunger and slower metabolism.
Hormonal imbalances leading to delayed puberty and infertility.
Sleep problems like sleep apnea and daytime drowsiness.

Complications of Prader-Willi Syndrome

If Prader-Willi Syndrome is not diagnosed and treated on time, it can cause several health and lifestyle complications. The following complications develop due to uncontrolled eating, hormonal imbalances and developmental challenges associated with the condition.

Severe obesity and related conditions like type 2 diabetes, heart disease, sleep apnea, etc.
Infertility due to underdeveloped sexual organs.
Behavioural and emotional problems affecting family and social life.
Learning difficulties that require special education support and care.
Osteoporosis or weak bones due to hormone deficiencies.
Respiratory problems and are linked to obesity and sleep apnea.

When to See a Doctor

Parents should consult a doctor if their child shows:

Low muscle tone and feeding difficulties in infancy.
Developmental delays such as delayed walking or speech.
Rapid weight gain or uncontrollable appetite in early childhood.
Behavioural challenges like temper outbursts, food-seeking or obsessive habits.
Concerns about growth, puberty or fertility.

Prader-Willi Syndrome Diagnosis

Prader-Willi Syndrome is usually appears in early childhood when symptoms such as poor muscle tone, feeding difficulties or unusual growth patterns become noticeable. As many of these signs can overlap with other conditions, so doctors depend on several clinical observations and genetic testing to confirm the syndrome.

Clinical evaluation: Here, doctors start by examining the child's physical features, growth patterns and developmental progress. Some common findings include weak muscle tone, delayed movement, excessive appetite and rapid weight gain.
Genetic testing:

DNA methylation analysis is the most reliable test and can detect nearly all cases of PWS by showing whether the father's genes on chromosome 15 are missing or inactive.
Other genetic tests such as fluorescence in situ hybridisation (FISH) or chromosomal microarray (CMA) may be used to confirm whether the cause is a deletion, uniparental disomy or imprinting defect.

Other assessments: After diagnosis, further evaluations may be necessary to detect associated complications. These may include hormone level testing, sleep studies and developmental assessments.

Treatment & Management of Prader-Willi Syndrome

There is currently no cure for Prader-Willi Syndrome but effective management and care can control symptoms, avoid serious health problems and improve quality of life.

1. Lifestyle and Daily Support

Children and adults with PWS need supportive care in daily life like food access and activity.

Parents need to restrict or lock access to food to prevent overeating.
A well-planned low-calorie diet with balanced nutrition is essential to control weight.
Regular physical activity helps maintain a healthy weight, improves strength and mood.
A structured daily routine reduces anxiety and can prevent behavioural outbursts.

2. Therapies

Therapies is very important in improving development and independence in children:

Speech therapy improves communication, since language skills may develop slowly.
Occupational therapy helps with fine motor skills, coordination and self-care tasks.
Behavioural therapy teaches coping strategies to manage temper tantrums, food-seeking and obsessive behaviours.
Sleep management therapy may be needed for those with sleep apnea or severe daytime sleepiness.

3. Prader-Willi Syndrome Treatment

Treatment of Prader-Willi syndrome depends on many things like the severity of the condition, age of the children, the causes of the condition, etc.

Growth hormone therapy can increase height, improve muscle tone, boost metabolism and reduce body fat.
Hormone replacement therapy may be recommended to support puberty, fertility and bone health.
Medications may be used to treat complications such as diabetes, mood disorders, sleep problems or behavioural challenges.

4. Educational and Emotional Support

Most children with PWS require special education programs adapted to their intellectual ability.

Personalised learning plans to improve their academic performances and competitiveness.
Counselling and psychological support benefit both the child and family in coping with challenges.
Parents offer guidance, emotional support and practical advice from others who face similar challenges.

Prognosis of Prader-Willi Syndrome

Prader-Willi Syndrome is a long term health problem but with early diagnosis, structured care and continuous medical care, children with PWS can achieve good health and development. The outlook largely depends on how well obesity and its related complications are controlled and managed, as uncontrolled weight gain is the biggest threat to long-term health.

With proper diet, growth hormone therapy and supportive care, many children with PWS have achieved growth, attend school and actively participate in family and community life. Adults with PWS may also be able to work and live in supported environments and enjoy meaningful social connections when given consistent guidance and structure.

Because of better awareness, early treatment and specialised care, the Life expectancy of Prader-Willi Syndrome has improved greatly in recent years. Most people can live longer, healthier and more fulfilling lives when they receive proper management and emotional support.

Conclusion

Prader-Willi Syndrome is a rare but complex genetic condition that requires continuous care and support. It is important to determine the symptoms earlier, manage food-related challenges and provide continuous therapies to help children and adults with PWS achieve their best potential. With proper treatment and family support, people with PWS can live healthier and more fulfilling lives.

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