Prader-Willi Syndrome (PWS) is a complex genetic disorder that typically causes low muscle tone, short stature, incomplete sexual development, cognitive disabilities, problem behaviours, and a chronic feeling of hunger that can lead to excessive eating and life-threatening obesity.
Most cases of PWS are attributed to a spontaneous genetic error that occurs at or near the time of conception for unknown reasons. In 99% of cases it is not inherited. In a very small percentage of cases (2%), a genetic mutation that does not affect the parent is passed on to the child, and in these families more than one child may be affected. A PWS-like disorder can also be acquired after birth if the hypothalamic portion of the brain is damaged through injury or surgery.
The disorder occurs in 1 in 12,000 - 15,000 births, in both sexes and all races. The name of the syndrome is derived from the names of the doctors who first described the disorder in 1956.
PWS babies are born with very low muscle tone, so that it is extremely difficult for them to suck. In most cases they need to be fed initially by tube or special teats, or with a teat that has a larger hole than normal. Babies with PWS do not cry very often and if they do it is a quite a feeble cry. They also sleep a lot. They take longer than usual to reach developmental milestones such as independent sitting.
At about two years of age, or in some cases later, they will start putting on excess weight. This may be accompanied by a compulsion to eat and an obsession with food. Serious weight gain can result in obesity which can cause high blood pressure, respiratory difficulties, diabetes and other problems. Changes in behaviour may also become evident over time with tantrums, stubbornness and mood swings occurring.
There is no cure for Prader Willi syndrome. Early diagnosis will allow parents to manage their child’s diet and avoid the problems resulting from obesity, and will facilitate access to early intervention services and identify areas of need or risk.
People with PWS, from the onset of insatiable appetite, will never have control over their craving. It is not a matter of self control; their brain just doesn't register that they have had enough to eat. They require considerably fewer calories - 30 to 50% less than the average person - so they should never be put in a situation where they are left alone with food. They have a strong need for routine, sameness and consistency in their environment and poor emotional control. People with PWS can tire more easily and may fall asleep during the day.
People with PWS have a range of learning disabilities regardless of their IQ, which is often in the mild to borderline range of intellectual disability. However poor social and emotional skills inhibit the person performing up to that IQ. Rigid behaviour and tantrums are part of the syndrome.
Most children with PWS go to local kindergarten and primary school. Some may go through high school or attend a special school to learn life skills. People with PWS often work in supported employment. Independent living is rarely achieved.
Further Information and Support
National Institutes of Health - USA
Prader-Will Syndrome Assocation - USA
Reviewed by Padraic Grattan-Smith, Sydney Children's Hospital, Australia