What is Phenylketonuria (PKU)?
PKU is an inherited disorder, caused by a faulty gene. People with PKU are born with a deficiency of a liver enzyme called phenylalanine hydroxylase (PAH). PAH is needed to process an amino acid called phenylalanine (Phe), found in foods containing protein. (Protein is made up of around 20 separate building blocks called amino acids). High protein foods include dairy products, red meat, chicken, fish, eggs, nuts, beans and lentils.
Usually, when we eat protein, it is broken down into different amino acids and used for growth, functioning and repair of the body. Because people with PKU can’t break down phenylalanine in the usual way, it builds up in the blood and damages the brain. People with PKU need phenylalanine, but only a small amount.
People with PKU cannot break down foods containing protein in the usual way. When PKU is detected early and treated with a special diet, children are able to reach their full potential.
Finding out your child has PKU always happens suddenly and unexpectedly. The news of the diagnosis is a shock. Most parents have never heard of PKU, so receiving the diagnosis can be frightening and confusing.
All babies born in most countries in Europe are tested for PKU soon after birth, usually the second or third day. A blood sample is taken from a needle prick on the heel, and the phenylalanine level is measured. If it is high, more tests are done to confirm that the baby has PKU. As soon as the diagnosis is made, the baby is given a special formula (also called a supplement) to lower the phenylalanine to a safe level.
Maintaining the diet in childhood is essential to prevent damage to the growing brain. It is recommended that the diet is continued for life.