Prader-Willi syndrome can usually be diagnosed using a series of genetic tests.
Genetic testing can be used to check the chromosomes in a sample of your child's blood for the genetic abnormalities 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.
Read more about the causes of 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, who want to know whether their child may have Prader-Willi syndrome.
1 point is given for each of the following symptoms a child has:
Half a point is given for each of the following symptoms a child has:
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.