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Genetic and Rare Diseases Information Center (GARD)


Other names people use for this condition
  • PKU
  • Phenylalanine hydroxylase deficiency
  • Oligophrenia phenylpyruvica
  • Folling disease
Home > Genetic & Rare Diseases Information Center (GARD) > Phenylketonuria > Questions and Answers


Phenylketonuria
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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?



  • What is phenylketonuria (PKU)? (Back to Top)

  • Phenylketonuria (PKU) is an inherited condition that is caused by toxic levels of phenylalanine in the body. If left untreated, this buildup of phenylalanine can cause severe intellectual disabilities.  Because PKU can be detected by a simple blood test and is treatable, newborn screening is available for this disorder.[2]
  • Last Reviewed: 11/30/2009

  • When did newborn screening for phenylketonuria (PKU) begin? (Back to Top)

  • Dr. Robert Guthrie developed the first newborn screening test for phenylketonuria, which became widely used in the 1960's.[1]  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 Reviewed: 3/3/2008

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

  • Phenylketonuria (PKU) is inherited in an autosomal recessive manner.[3]  In order to have PKU, a person must have genetic changes (mutations) in both copies of the gene that causes this disorder.  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 Reviewed: 3/3/2008

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

  • 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 Reviewed: 3/4/2008


References  (Back)
  1. Overview: Newborn screening. National Newborn Screening and Resource Center. Available at: http://genes-r-us.uthscsa.edu/resources/newborn/overview.htm. Accessed March 3, 2008.
  2. Phenylketonuria. MedlinePlus Web site. October 10, 2007 Available at: http://www.nlm.nih.gov/medlineplus/phenylketonuria.html. Accessed March 3, 2008.
  3. Phenylketonuria. Genetics Home Reference Web site. January 2008 Available at: http://ghr.nlm.nih.gov/condition=phenylketonuria. Accessed March 3, 2008.

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