How is pku inherited

Phenylalanine comes from a person's diet and is used by the body to make proteins. Phenylalanine is found in all food proteins and in some artificial sweeteners.

Without dietary treatment, phenylalanine can build up to harmful levels in the body, causing mental retardation and other serious problems. Women who have high levels of phenylalanine during pregnancy are at high risk for having babies born with mental retardation, heart problems, small head size microcephaly and developmental delay. This is because the babies are exposed to their mother's very high levels of phenylalanine before they are born.

Newborn screening has been used to detect PKU since the 's. As a result, the severe signs and symptoms of PKU are rarely seen. Symptoms of PKU range from mild to severe. Infants born with classic PKU appear normal for the first few months after birth. However, without treatment with a low-phenylalanine diet, these infants will develop mental retardation and behavioral problems. Other common symptoms of untreated classic PKU include seizures, developmental delay, and autism.

Boys and girls who have classic PKU may also have eczema of the skin and lighter skin and hair than their family members who do not have PKU. Most often, PKU is passed to children by two parents who are carriers of the disorder, but don't know it. Untreated PKU can lead to complications in infants, children and adults with the disorder. When mothers with PKU have high blood phenylalanine levels during pregnancy, fetal birth defects or miscarriage can occur.

Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview Phenylketonuria fen-ul-key-toe-NU-ree-uh , also called PKU, is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body.

Email address. First Name let us know your preferred name. Last Name. Thank you for subscribing Your in-depth digestive health guide will be in your inbox shortly. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry. Request an Appointment at Mayo Clinic. Autosomal recessive inheritance pattern Open pop-up dialog box Close. Autosomal recessive inheritance pattern To have an autosomal recessive disorder, you inherit two mutated genes, one from each parent.

Share on: Facebook Twitter. Show references National Library of Medicine. Genetics Home Reference. Accessed Oct. National Organization for Rare Disorders. Learning about phenylketonuria PKU. National Human Genome Research Institute. Women with PKU and uncontrolled phenylalanine levels also have an increased risk of pregnancy loss. The occurrence of PKU varies among ethnic groups and geographic regions worldwide.

Most cases of PKU are detected shortly after birth by newborn screening, and treatment is started promptly. As a result, the severe signs and symptoms of classic PKU are rarely seen. 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. Genetics Home Reference has merged with MedlinePlus.

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