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Diseases

Genetic and Rare Diseases Information Center (GARD)

Phenylketonuria


Other Names for this Disease
  • PKU
  • Phenylalanine hydroxylase deficiency
  • Oligophrenia phenylpyruvica
  • Folling disease
  • PAH deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

Is it true that PKU testing became a test for all babies in the 1960's? If both parents have the gene, why aren't they affected by PKU early in or later in their lives? What is the chance of false positives/false negatives on the first PKU test taken at the hospital for an infant?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is phenylketonuria (PKU)?

Phenylketonuria (PKU) is an inherited disorder that increases the levels of phenylalanine in the blood. Phenylalanine is a building block of proteins (an amino acid) that is obtained through the diet. If PKU is not treated, phenylalanine can build up to harmful levels in the body. The signs and symptoms of PKU vary from mild to severe. The most severe form of this disorder is known as classic PKU. Without treatment, these children develop permanent intellectual disability. Light skin and hair, seizures, delayed development, behavioral problems, and psychiatric disorders are also common. Less severe forms of this condition, sometimes called variant PKU and non-PKU hyperphenylalaninemia, have a smaller risk of brain damage. Babies born to mothers with PKU and women who no longer follow a low-phenylalanine diet have a risk of intellectual disability because they are exposed to very high levels of phenylalanine before birth. PKU is caused by changes (mutations ) in the PAH gene. It is inherited in an autosomal recessive manner. Because PKU can be detected by a simple blood test and is treatable, newborn screening is available for this disorder.[1][2] The best treatment for PKU is a diet of low-protein foods.[3]
Last updated: 12/28/2015

When did newborn screening for phenylketonuria (PKU) begin?

Dr. Robert Guthrie developed the first newborn screening test for phenylketonuria, which became widely used in the 1960's.[4] The methods he devised for collecting and transporting blood samples on filter paper proved to be easy and cost effective. In honor of Dr. Guthrie, newborn blood samples are collected on Guthrie cards.
Last updated: 7/19/2013

If both parents carry the gene for phenylketonuria (PKU), why don't they have this disorder?

Phenylketonuria (PKU) is inherited in an autosomal recessive manner. In order to have PKU, a person must have genetic changes (mutations) in both copies of the gene that causes this disorder, PAH.[1] A person who has PKU inherits one mutated gene for PKU from each parent. The parents of an individual with PKU are usually unaffected because they only carry one copy of the gene mutation.
Last updated: 7/19/2013

What is the chance of a false positive or false negative result on the first phenylketonuria (PKU) test taken at the hospital?

The false positive and false negative rates may vary from laboratory to laboratory. We recommend that you contact your state's newborn screening program for information on their false positive and negative rates. Click here for the contact information of newborn screening programs listed by state.
Last updated: 7/19/2013

References
Other Names for this Disease
  • PKU
  • Phenylalanine hydroxylase deficiency
  • Oligophrenia phenylpyruvica
  • Folling disease
  • PAH deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.