PKU is caused by a biochemical abnormality which is inherited by a child from both parents. At birth the baby appears to be quite normal, but the condition will be discovered before the age of 1 month by a screening blood test which is taken from all babies born in the UK. If this special test is positive and a further blood test shows the baby to have PKU, treatment is started as soon as possible.
A positive blood test shows that there is too much of a substance called phenylalanine in the baby’s blood. Before early screening and treatment became available and high levels of phenylalanine were allowed to continue in the blood, the normal growth and development of the baby’s brain was affected and in some cases the children became severely mentally abnormal.
Phenylalanine is a natural part of all protein foods and is essential in any normal diet. In PKU, the aim of treatment is to stop the build up of phenylalanine by using a special diet. When the diet is monitored carefully, it will allow the baby’s brain to grow and develop so that a normal lifestyle, apart from the dietary restrictions, can be expected.
Treatment for phenylketonuria has only been available since the late 1950’s so that, even today, doctors, dietitians, biochemists and other health professionals are still learning about PKU, particularly the way it is inherited and the long term outlook for treated adults with the condition. There are likely to be many questions you will want to have answered and the people looking after your baby will be able to answer most of them but there may be some which at the moment, cannot be answered with any certainty due to our incomplete understanding of PKU.