Prader-Willi syndrome

Overview

Prader-Willi syndrome is a rare genetic condition that causes a wide range of physical symptoms, learning difficulties and behavioural problems. It's usually noticed shortly after birth.

Symptoms of Prader-Willi syndrome

Typical symptoms of Prader-Willi syndrome include::

an excessive appetite and overeating, which can easily lead to dangerous weight gain
restricted growth, (children are much shorter than average)
reduced muscle tone (hypotonia)
learning difficulties
lack of sexual development
behavioural problems, such as emotional outbursts and physical aggression

Causes of Prader-Willi syndrome

Prader-Willi syndrome is caused by some missing genetic material in a group of genes on chromosome number 15.

This leads to a number of problems and is thought to affect part of the brain called the hypothalamus, which produces hormones and regulates growth and appetite.

This may explain some of the typical features of Prader-Willi syndrome, such as delayed growth and persistent hunger.

The genetic cause happens purely by chance, and boys and girls of all ethnic backgrounds can be affected.

It's extremely rare for parents to have more than 1 child with Prader-Willi syndrome.

Diagnosing Prader-Willi syndrome

Prader-Willi syndrome can usually be confirmed by carrying out genetic testing.

Genetic testing may be recommended if a child has the symptoms of Prader-Willi syndrome. Babies who are very floppy at birth may also be tested.

Managing Prader-Willi syndrome

There's no cure for Prader-Willi syndrome, so treatment aims to manage the symptoms and associated difficulties.

This includes managing the child's excessive appetite and behavioural challenges.

One of the most important parts of caring for someone with Prader-Willi syndrome is to try to maintain a normal weight.

They should have a healthy, balanced diet, avoiding sweet treats and high-calorie items right from the start.

If someone with Prader-Willi syndrome is allowed to eat as much as they want, they'll quickly become dangerously overweight.

Someone with the syndrome can eat much more than other people and still feel hungry.

Limiting food intake can be very challenging. People with Prader-Willi syndrome may become frustrated when they want extra food, and their hunger can make them hide or steal food.

Long-term problems caused by Prader-Willi syndrome

Prader-Willi syndrome itself is not life-threatening. But compulsive eating and weight gain can cause young adults with the syndrome to develop obesity-related conditions such as:

type 2 diabetes
heart failure
breathing difficulties

If their diet is well controlled and they do not become overweight, adults can have a good quality of life and probably a normal life expectancy.

Many adults with Prader-Willi syndrome take part in activities such as voluntary or part-time work but it's unlikely they'll be able to live fully independent lives.

The increased appetite also means there is a higher risk of choking on food, so carers are advised to learn what to do if someone is choking.

PWSA UK

The Prader-Willi Syndrome Association UK (PWSA UK) provides information and support for people whose lives are affected by PWS. You can call the PWSA helpline on 01332 365676.

National Congenital Anomaly and Rare Disease Registration Service

If your child has Prader-Willi syndrome, your clinical team will pass information about them on to the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS).

The NCARDRS helps scientists look for better ways to prevent and treat Prader-Willi syndrome. You can opt out of the register at any time.

Symptoms

Prader-Willi syndrome can cause a wide range of symptoms, and affect your child's physical, psychological and behavioural development.

Floppiness

Floppiness caused by weak muscles is usually noticed shortly after birth. The medical name for this is hypotonia.

Hypotonia can mean your baby:

does not have a full range of movement
has a weak cry
has poor reflexes
cannot suck properly, which means they may have feeding difficulties and be underweight until the age of 1, and may need to be fed with a feeding tube.

Sexual development

Baby boys may have an abnormally small penis, and 1 or both testicles may still be inside their abdomen (undescended testicles). Baby girls will also have underdeveloped genitalia.

Children with Prader-Willi syndrome experience puberty later than usual and may not go through full development into an adult. For example:

boys may still have a high-pitched voice, and may not have much facial and body hair
girls will often not start their periods until they're in the 30s, and their breasts will not fully develop – when periods do occur, they're usually irregular and very light

It's almost unknown for either men or women with Prader-Willi syndrome to have children. They're usually infertile because the testicles and ovaries do not develop normally. But sexual activity is usually possible, particularly if sex hormones are replaced.

Distinctive features

Children with Prader-Willi syndrome may also have distinctive features, including:

almond-shaped eyes
eye problems
a narrow forehead at the temples
narrow bridge of the nose
a thin upper lip and a downturned mouth
unusually fair hair, skin and eyes
small hands and feet

These features are usually noticed at or shortly after birth.

Increased appetite

Children with Prader-Willi syndrome develop an increased appetite and eat an excessive amount of food if they have the opportunity. The medical name for this is hyperphagia.

Between the ages of 1 and 4, the child will start to show an increased interest in food, ask for extra food and become frustrated when they cannot get extra food.

Food is a trigger for challenging behaviour in people with Prader-Willi syndrome.

This can include:

angry behaviour to get food
interest in pictures of food, food-related play or discussion of food
hiding or stealing food, or stealing money to get food
eating inappropriate items, frozen or uncooked food, or waste food
very good memory for people who've given food to them in the past or situations where food was available

People with Prader-Willi syndrome can tolerate much larger amounts of food before their body automatically vomits it back up, and they're not as sensitive to pain. Therefore, they can eat objects that would make other people very ill.

This means they're at higher risk of:

food poisoning
choking
a stomach rupture – where the stomach splits open, sometimes causing life-threatening infection

Vomiting and stomach pain are the 2 most common signs of a gastric rupture.

People with Prader-Willi syndrome do not usually vomit or complain about stomach pain, so take these symptoms very seriously if they happen.

Call your care team or GP immediately for advice.

People with Prader-Willi syndrome do not always become obese if their diet and food issues are controlled.

They will not be able to control their food intake themselves and it must be managed for them. They also have a slow metabolism, and require less food and fewer calories than other people.

Reduced muscle tone means they're less physically active and cannot burn off as much energy as other people.

Learning difficulties and delay in development

Most children with Prader-Willi syndrome have mild to moderate learning difficulties with a low IQ.

This means it will take longer for a child with Prader-Willi syndrome to reach important developmental milestones.

For example, a child with the syndrome will typically begin sitting up at around 12 months and start walking at around 24 months.

Many are late to talk and have difficulty saying some sounds.

Most children with Prader-Willi syndrome can attend a mainstream school with extra support, although some will move to a special school at secondary level

They usually have difficulties with short-term memory, although they often have a good long-term memory.

Despite these problems, people with Prader-Willi syndrome tend to be good at solving puzzles, such as word searches and jigsaws.

Short stature

Children with Prader-Willi syndrome are usually much shorter than other children of their own age. This is usually apparent by the time they're 2 years old.

Low levels of human growth hormone (HGH) contribute to the short stature, and they won't go through the typical growth spurt during puberty.

If HGH is not replaced, the average adult height for people with Prader-Willi syndrome is 159cm (5ft 2in) for a man and 149cm (4ft 10in) for a woman.

Children can be prescribed an artificial version of HGH to encourage growth.

Challenging behaviour

Most people with Prader-Willi syndrome go through phases where their behaviour can be challenging.

But these challenges in behaviour vary from person to person and over time, and also depend on their circumstances.

While this behaviour can be challenging for parents to deal with, people with Prader-Willi syndrome are affectionate, kind, caring and funny.

People with Prader-Willi syndrome are more prone to stress and anxiety than others.

Some of the triggers for difficult behaviour include:

unexpected change
frustration
anxiety around food
feeling under pressure
lack of structure
too much stimulation
low mood
other undiagnosed conditions, such as autism

This can cause challenging behaviour such as:

shouting, screaming and crying
acting out physically
difficulty adapting to change, which can cause them to become argumentative
asking the same question over and over again, or frequently returning to the same topic in a conversation

Find out more about positive ways to manage challenging behaviour on the Prader-Willi Syndrome Association UK website

Skin picking

Many people with Prader-Willi syndrome persistently pick their skin, usually their face, hands or arms.

They may scratch, pierce or pull at their skin, sometimes using paper clips or tweezers.

It can result in open sores, scarring and infection.

Some people may pick out pieces of poo from their bottom, which can cause bleeding and infection.

Sleep problems

Many peoplewith Prader-Willi syndrome have problems sleeping.

They can become tired and sleep during the day but then wake during the night or very early in the morning.

Some children have interrupted breathing during sleep (sleep apnoea). These episodes cause excessive sleepiness in the day, which only worsens inactivity and obesity.

Sleep apnoea gets worse as you gain weight, leading to a vicious cycle. It can also be dangerous to have interrupted breathing at night.

It's important to identify sleep apnoea because effective treatment and support is available.

High pain and vomiting tolerance

People with Prader-Willi syndrome have a high tolerance for pain, which can be potentially dangerous.

For example, a serious condition such as appendicitis would cause severe pain in most people but may pass unnoticed or be a minor upset for someone with Prader-Willi syndrome.

Therefore, if someone with Prader-Willi syndrome does complain of pain, it should be taken seriously.

Abnormal curvature of the spine

Poor muscle tone means there is an increased chance of developing a curvature of the spine (scoliosis).

Who can get it

Prader-Willi syndrome is caused by a genetic change on chromosome number 15.

Genes contain the instructions for making a human being. They're made up of DNA and packaged into strands called chromosomes.

A person has 2 copies of all their genes, which means chromosomes come in pairs.

Humans have 46 chromosomes (23 pairs). One of the chromosomes that belongs to pair number 15 is different in Prader-Willi syndrome.

Around 70% of cases of Prader-Willi syndrome are the result of missing genetic information from the copy of chromosome 15 inherited from the father. This defect is referred to as "paternal deletion".

Paternal deletion is thought to happen entirely by chance, so it's practically unheard of to have more than 1 child with Prader-Willi syndrome caused by paternal deletion.

However, if Prader-Willi syndrome is caused by a different type of problem with chromosome 15, there's a very small chance you could have another child with the syndrome.

Effect on the brain

It's thought the problem with chromosome 15 disrupts the normal development and functioning of part of the brain called the hypothalamus.

The hypothalamus plays a role in many of the body's functions, such as producing hormones and helping regulate appetite.

A malfunctioning hypothalamus may explain some of the typical features of Prader-Willi syndrome, such as delayed growth and persistent hunger.

Studies using advanced brain imaging technology have shown that after eating, people with Prader-Willi syndrome have very high levels of electrical activity in a part of the brain known as the frontal cortex.

This part of the brain is associated with physical pleasure and feelings of contentment.

It may be possible that people with Prader-Willi syndrome find the act of eating immensely rewarding.

Another theory is that in Prader-Willi syndrome, the hypothalamus cannot judge the level of food in the body as well as it usually does.

This means that a person with the syndrome always feels hungry no matter how much food they eat.

Diagnosis

Prader-Willi syndrome can usually be diagnosed by running a series of genetic tests.

Genetic testing

Genetic testing can be used to check the chromosomes in a sample of your child's blood for the genetic changes known to cause Prader-Willi syndrome.

As well as confirming the diagnosis, the results should also allow you to determine the likelihood of having another child with the syndrome.

Checklist for diagnosing Prader-Willi syndrome

A checklist of symptoms known to be typical of Prader-Willi syndrome is also used to identify which children should be tested.

The checklist can help parents concerned about their child's development, behaviour and eating habits, and who want to know whether their child may have Prader-Willi syndrome.

Major criteria

1 point is given for each of the following symptoms a child has:

floppiness and weak muscles that becomes apparent during or shortly after birth
feeding problems and failure to grow during the first year of life
rapid weight gain in children aged 1 to 6 years
characteristic facial features, such as almond-shaped eyes and thin upper lips
underactive testicles or ovaries (hypogonadism), resulting in delayed sexual development
delayed physical development or learning difficulties

Minor criteria

Half a point is given for each of the following symptoms a child has:

lack of movement during pregnancy, such as kicking in the womb, or an unusual lack of energy after birth
sleep disturbances such as sleep apnoea
delayed or absent puberty
unusually fair hair, skin and eyes
narrow hands
thick and sticky saliva
a squint or long-sightedness (hyperopia)
problems pronouncing words and sounds properly
frequent skin picking

Total score

If your child is under the age of 3 and scores 5 points, and has at least 4 of the major criteria, Prader-Willi syndrome would be strongly suspected and genetic testing would be recommended.

If your child is over the age of 3 and scores 8 points, and has at least 5 of the major criteria, Prader-Willi syndrome would be strongly suspected and testing would be recommended.

Management

There's no cure for Prader-Willi syndrome, but your child will have support from healthcare professionals who will help you manage the problems.

Support for development will come from your local child development team, and your child will also see a hospital paediatrician or a paediatric endocrinologist.

The treatment plan will be continually reassessed as your child gets older and their needs change.

The Prader-Willi Syndrome Association has detailed information about how the support your child needs will change as they get older.

Treating problems in babies and children

Feeding difficulties

Babies with Prader-Willi syndrome have difficulty feeding at birth, and may need to be fed using a tube that goes into their nose and down their throat into their stomach.

After a few months, it will usually be possible to feed your child normally using breast or bottle milk, although they may be slower to feed than other babies.

Dietitians and speech and language therapists can help with advice about what feeds to give and how to encourage your baby to feed.

Undescended testicles

If you have a baby boy with undescended testicles, surgery is usually recommended to correct this in the 1st or 2nd year of life.

Treatment is recommended because your son:

will have an increased risk of developing testicular cancer if the testicles are not corrected
may have problems with his self-esteem and body image if he's "missing" 1 or both testicles

Read more about treating undescended testicles.

Managing weight and diet

The most important aspect of caring for someone with Prader-Willi syndrome is trying to manage their diet and prevent them gaining too much weight. It's also probably one of the biggest challenges.

People with Prader-Willi syndrome burn up less energy, and need fewer calories and less food than other people.

A dietitian can give you information about what food to give.

Advice about diet:

start to get into good habits with a healthy diet and regular mealtimes as soon as your child starts on solid food – don't wait for them to show signs of an increased appetite
avoid sugary items, sweets and high-calorie snacks
give smaller portions of carbohydrates such as potatoes, rice or pasta
increase the amount of lower-calorie items such as vegetables, salads and fruit
give them a vitamin supplement

It can be difficult for your child to control their food intake themselves, so you need to:

keep to regular mealtimes and do not allow any extra portions
stop them accessing food outside of mealtimes – you may need to lock cupboards and the fridge, or lock the kitchen, and make sure they cannot get food from the bins or freezer
keep food out of their view
make sure there are no times they can access food unsupervised
make sure everyone who's in contact with them (school staff, relatives and friends) knows about the issues with food

It's also important to let relatives, friends, other parents and teachers know about the need to restrict the person's diet.

Some medicines have been used to try to suppress appetites but have all been unsuccessful.

Weight loss surgery is not ecommended for people with Prader-Willi syndrome because they are not able to stick to the strict diet required after surgery.

Exercise

Exercise plays an important part in helping your child maintain a healthy weight. Children should do at least 60 minutes of exercise a day.

Many people with Prader-Willi syndrome have reduced energy levels.

It may be a good idea to break down their exercise into 5- to 10-minute sessions throughout the day to stop them getting tired and discouraged.

Your care team should be able to recommend a suitable exercise plan.

People with Prader-Willi syndrome usually prefer individual activities to team sports, such as:

swimming
walking
exercising in a gym

It's important not to promise food as a reward to encourage your child to participate in exercise because it can encourage unhealthy behaviour.

Hormone treatments

Treatment with an artificial version of the human growth hormone (HGH) is usually recommended for children with Prader-Willi syndrome.

HGH also has a number of other important health benefits.

For example, it:

increases muscle size while lowering the amount of body fat
increases muscle strength, which helps with activities such as walking and running
should increase energy levels, which will help your child become more physically active
helps normalise facial appearance, making the distinctive facial features associated with Prader-Willi syndrome less noticeable

Starting treatment with HGH is usually recommended during early childhood, from 6 months to 2 years of age, and normally continues until the end of growth.

A test looking for breathing problems (a sleep study) is normally done before starting growth hormone.

A type of HGH called somatropin is used to treat children with Prader-Willi syndrome. Somatropin is given by daily injection. Most children tolerate somatropin well and side effects are uncommon.

It's usual to replace female sex hormones (often with the combined oral contraceptive pill) to:

encourage development of secondary sex characteristics (breast development) and periods
improve bone strength and prevent osteoporosis

Replacing male sex hormone (testosterone) is more contentious. Although this will encourage development of puberty and build muscle strength, it's possible that some behavioural challenges could get worse.

Managing challenging behaviour

Structure and routine

Most people with Prader-Willi syndrome cope best if they have a very structured environment and daily routine.

For example, you should:

establish a regular daily routine and give plenty of notice if any changes are planned
not put pressure on a child to speed up to complete a task – give them plenty of warning if they need to complete an activity, such as getting dressed to go out
ensure other people, such as relatives and teachers, know how to interact with your child
avoid eating in front of your child so they do not start to think about food

Dealing with emotional distress

Parents often learn to recognise the warning signs of emotional distress, which some people call a "meltdown".

It can help if you try to understand why it's happening.

People with Prader-Willi syndrome have difficulty managing their emotions and tend to feel more anxious and stressed than others.

It's sometimes possible to manage this behaviour.

For example, you can:

acknowledge the person's feelings by saying things like, "I can see you're upset about this"
encourage them to go to a quiet place for a few minutes and try some deep breathing or listening to soothing music
remain as calm as possible – if the frustration is directed at you, your partner or another carer can take over

After an episode of emotional distress, try to remain as calm as possible.

It's important to be positive afterwards, and to talk about what has happened.

You can do this once the situation has calmed down – for example, later that day.

You should avoid making them angry or frustrated again by talking about what happened too soon.

Taking food

Many children with Prader-Willi syndrome will try to take food if they get the opportunity.

This is because they are not able to control their impulses when it comes to food.

But it still needs to be managed, otherwise they could become severely obese.

Tips to prevent taking food include trying to establish a contract to reward good behaviour.

In younger children, a verbal agreement, such as: "If you stick to your diet then you can play an extra hour with your puzzles", should work.

In older children and teenagers, a written contract may be more appropriate, particularly as children with Prader-Willi syndrome respond well to clear instructions.

Controlling the urge to take food should always be highly praised and persistent good behaviour rewarded.

Prader-Willi Syndrome Association UK has more information about behaviour management in adults and children with Prader-Willi Syndrome

Treatment for skin picking

Frequent skin picking can lead to scarring and skin infections such as cellulitis, an infection of the underlying tissue.

It's very important for cellulitis to be identified early and treated with large doses of antibiotics.

Keep nails as short as possible to help minimise damage to the skin.

Try to keep any affected part of the body covered up and use clothes to limit access if possible.

Make sure you keep any areas of damaged skin as clean as possible.

Antibiotic cream may be prescribed to be used on damaged areas to prevent infection.

Treatments that are moderately effective in helping prevent people with Prader-Willi syndrome from picking their skin are cognitive behavioural therapy (CBT) and medicine.

Cognitive behavioural therapy (CBT)

CBT is a type of talking therapy. It aims to modify unhelpful and unhealthy patterns of behaviour by changing the way people think.

It's thought people with Prader-Willi syndrome pick their skin as a way of coping with situations such as feeling unhappy or bored. CBT can help people understand the thought patterns that drive skin picking and encourage them to find new ways of thinking about and coping with these situations.

Medicine

A type of antidepressant – selective serotonin reuptake inhibitors (SSRIs) – or antipsychotics (medicine usually used to treat psychosis) are sometimes recommended to treat Prader-Willi syndrome.

However, these medicines can cause side effects and are not usually recommended for children under the age of 18.

Medicine is usually only considered if the symptoms of skin picking are severe enough to justify the associated risks of treatment.

Treatment for psychosis

A small number of people with Prader-Willi syndrome develop psychosis, usually during the teenage years or adulthood.

Psychosis is a mental health problem that causes people to perceive or interpret things differently from those around them.

The symptoms of psychosis usually begin abruptly and will cause the person affected to suddenly become very upset and agitated, and act in ways that are uncharacteristic.

Contact your care team if you notice a sudden and unusual change in behaviour.

Psychosis can be treated with CBT or medication such as antipsychotics.

Adults with Prader-Willi syndrome

Most adults with Prader-Willi syndrome are not able to live fully independent lives, such as living in their own home and having a full-time job.

This is because their challenging behaviour and issues with food mean these environments and situations are too demanding.

But adults with Prader-Willi syndrome can have active social lives and become involved in clubs or volunteering.

Adults with the syndrome who do not live with their parents may need residentail care or supported living.

Prader-Willi Syndrome Association UK has more information and advice for adults with Prader-Willi syndrome.

The information on this page has been adapted by NHS Wales from original content supplied by

NHS website nhs.uk