Pku what is it

Mutations in the PAH gene cause phenylketonuria. The PAH gene provides instructions for making an enzyme called phenylalanine hydroxylase.

This enzyme converts the amino acid phenylalanine to other important compounds in the body. If gene mutations reduce the activity of phenylalanine hydroxylase, phenylalanine from the diet is not processed effectively.

As a result, this amino acid can build up to toxic levels in the blood and other tissues. Because nerve cells in the brain are particularly sensitive to phenylalanine levels, excessive amounts of this substance can cause brain damage. Classic PKU, the most severe form of the disorder, occurs when phenylalanine hydroxylase activity is severely reduced or absent.

People with untreated classic PKU have levels of phenylalanine high enough to cause severe brain damage and other serious health problems. Mutations in the PAH gene that allow the enzyme to retain some activity result in milder versions of this condition, such as variant PKU or non-PKU hyperphenylalaninemia.

Changes in other genes may influence the severity of PKU, but little is known about these additional genetic factors. This condition is inherited in an autosomal recessive pattern , which means both copies of the gene in each cell have mutations.

The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

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From Genetics Home Reference. Description Phenylketonuria commonly known as PKU is an inherited disorder that increases the levels of a substance called phenylalanine in the blood. Frequency The occurrence of PKU varies among ethnic groups and geographic regions worldwide.

Causes Mutations in the PAH gene cause phenylketonuria. The blood is collected on a special paper and sent to a lab for testing. This test can check to see if your baby has PKU or if there is another cause for abnormal test results.

Some experts recommend that if your baby was tested within the first 24 hours of life, they should be tested again at 1 to 2 weeks of age. Babies who have PKU seem normal for the first few months of life. But without treatment, they begin to show signs and symptoms of the illness at about 6 months of age. These include:. If your baby has PKU, they may need testing as often as once a week or more often for the first year of life to check their phenylalanine levels.

After that, they may have testing once or twice a month throughout childhood. Your baby needs to follow a special meal plan that is low in phenylalanine. At first, your baby gets a special protein formula that has reduced phenylalanine. Protein is important to help your baby grow and develop. When your baby is ready to eat solid foods, they can eat vegetables, fruits, some grains like low-protein cereals, breads and pasta and other low-phenylalanine foods.

If your baby has PKU, they should not eat:. PKU meal plans are different for each baby and can vary over time depending on how much phenylalanine your baby can tolerate. Health care providers at a medical center or clinic that has a special program to treat PKU can help you create a meal plan for your baby. Your child will follows the PKU meal plan through their whole life. If they eventually get pregnant, they follow their meal plan throughout pregnancy.

Most pregnant and parenting people who have PKU can have healthy pregnancies and healthy babies. The medicine is more likely to work in people with mild or special forms of PKU.

They still need regular blood tests to check phenylalanine levels. See also: Genetic counseling , Newborn screening. Get expert tips and resources from March of Dimes and CDC to increase your chance of having a healthy, fully-term pregnancy and baby. Complications at birth may include:. There is a problem with information submitted for this request.

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Your in-depth digestive health guide will be in your inbox shortly. You will also receive emails from Mayo Clinic on the latest health news, research, and care. To have an autosomal recessive disorder, you inherit two mutated genes, one from each parent.

These disorders are usually passed on by two carriers. Their health is rarely affected, but they have one mutated gene recessive gene and one normal gene dominant gene for the condition. A defective gene genetic mutation causes PKU, which can be mild, moderate or severe. In a person with PKU, this defective gene causes a lack of or deficiency of the enzyme that's needed to process phenylalanine, an amino acid. A dangerous buildup of phenylalanine can develop when a person with PKU eats protein-rich foods, such as milk, cheese, nuts or meat, and even grains such as bread and pasta, or eats aspartame, an artificial sweetener.

This buildup of phenylalanine results in damage to nerve cells in the brain. For a child to inherit PKU, both the mother and father must have and pass on the defective gene.

This pattern of inheritance is called autosomal recessive. It's possible for a parent to be a carrier — to have the defective gene that causes PKU, but not have the disease. If only one parent has the defective gene, there's no risk of passing PKU to a child, but it's possible for the child to be a carrier.