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Phenylketonuria (PKU) is a rare genetic condition caused by the buildup of the amino acid phenylalanine, an essential building block of proteins, which is obtained through the diet. For an individual to inherit PKU, they must inherit a genetic defect from both parents that carries instructions for making the enzyme (phenylalanine hydroxylase) that breaks down phenylalanine. The enzyme may work less than normal or not at all. The excess phenylalanine accumulates in the blood and is toxic to the brain. Infants with PKU may not present with symptoms initially, but without treatment could experience severe intellectual disability, seizures, and additional neurologic problems.

Phenylketonuria affects approximately 1 in every 10,000 newborns in the United States (about 20,000 individuals)1. As a result of newborn screening in all 50 states, PKU cases can be detected shortly after birth and promptly treated to minimize the risk of complications.

Signs and symptoms of phenylketonuria include, but are not limited to, the following:

  • Intellectual disability (if un-treated, or not treated consistently)
  • Lighter skin, hair, and eyes than siblings without disease
  • Seizures
  • Hyperactivity
  • Jerking movements of the arms or legs
  • Smaller than normal head size
  • Red skin rash with small pimples
  • Body odor caused by build-up of phenylacetic acid in the urine or sweat
  • Vomiting
  • Irritability

Individuals with PKU must keep a strict low-phenylalanine diet. Women with PKU who have stopped treatment should return to a low-phenylalanine diet before conception and continue throughout pregnancy to prevent exposure of the developing infant to toxic levels of phenylalanine during pregnancy.

Current drug therapy available at Accredo for phenylketonuria includes:

  • Kuvan
    • Kuvan is approved by the US Food and Drug Administration (FDA) for the treatment of high levels of phenylalanine in the blood (hyperphenylalaninemia) due to tetrahydrobiopterin (BH4)-responsive phenylketonuria in conjunction with a phenylalanine restricted diet.

1.    Genetics home reference. (2012) NIH/NLM.  Phenylketonuria.  http://ghr.nlm.nih.gov/condition/phenylketonuria Accessed 07 January 2015

Disclaimer – This information is not intended to replace discussions with your healthcare provider.



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