Prader-Willi syndrome can cause a wide range of symptoms, and affect your child's physical, psychological and behavioural development.
Floppiness caused by weak muscles is usually noticed shortly after birth. The medical name for this is hypotonia.
Hypotonia can mean your baby:
Baby boys may have an abnormally small penis, and one 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:
It's almost unknown for either men or women with Prader-Willi syndrome to have children. They are usually infertile because the testicles and ovaries do not develop normally. However, sexual activity is usually possible, particularly if sex hormones are replaced.
Children with Prader-Willi syndrome have several distinctive features, including:
These features are usually noticed at or shortly after birth.
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 behave badly to get extra food. This behaviour increases during childhood and is seen in all children with Prader-Willi syndrome. It can include:
Children 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:
Vomiting and stomach pain are the two most common signs of a gastric rupture. People with Prader-Willi syndrome don't usually vomit or complain about stomach pain, so take these symptoms very seriously if they happen to your child. Call your care team or GP immediately for advice.
Children with Prader-Willi syndrome don't always become obese and can remain slim if diet and food issues are controlled. They will never learn 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 children of the same age. Reduced muscle tone means they are less physically active and don't burn off as much energy as other children.
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 pronouncing 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
Their short-term memory is usually poor, although they often have a good long-term memory.
Despite these problems, children with Prader-Willi syndrome tend to be good at solving puzzles, such as word searches and jigsaws.
Read more about learning disability.
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 isn't 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 (see managing Prader-Willi syndrome).
Most children with Prader-Willi syndrome have difficult behaviour traits such as tantrums and stubbornness. Typical behavioural problems include:
While these behavioural problems can be challenging for parents to deal with, children with Prader-Willi syndrome also have many positive aspects to their personality, such as being affectionate, kind, caring and funny.
As many as 4 out of 5 children 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 children may pick out pieces of poo from their bottom. As well as causing embarrassment for children and parents, this can result in bleeding and infection.
Many children with 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.
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. Read more about treating sleep apnoea.
Children 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 a child with Prader-Willi syndrome.
Therefore, if a child with Prader-Willi syndrome does complain of pain, it should be taken seriously.
Poor muscle tone means there is an increased chance of developing a curvature of the spine (scoliosis).
Children with Prader-Willi syndrome can develop: