PKU Definitions

Phenylketonuria (FEN-nil-KEE-toh-NOO-ree-ah)—or PKU—is a genetically inherited disorder that prevents the full breakdown of phenylalanine (FEN-nil-ALA-neen), an amino acid found in many foods that are high in protein. PKU is treatable by following a strict diet consisting of a specially formulated protein drink made up of the essential and non-essential amino acids (minus phenylalanine) and low-protein foods. Here are some other PKU-related terms you may need to know:

PKU: The Metabolic BreakdownAmino acid: a natural chemical that works as a building block for protein.

BH4: chemical symbol for Tetrahydrobiopterin, a naturally occurring chemical compound in the body. PAH needs BH4 to function properly.

Classical PKU: the most common form of PKU where there are two severe mutations of the PAH gene and as a result, there is little or no PAH enzyme active to convert phenylalanine into tyrosine (phe level in blood: above 20mg/dl).

Hyperphenylalanemia (HyperPhe): used to describe those people whose blood phe level is above normal, but still low enough that they may not require dietary treatment (phe level in blood: less than 10 mg/dl).

Kuvan: the first FDA-approved prescription drug for the treatment of Phenylketonuria; a synthetic form of BH4.

Maternal PKU Syndrome: a collection of birth defects that occur in children born to PKU mothers who did not control their blood phenylalanine levels between 2-6 mg/dl before and throughout their pregnancy.

Mg/dl: milligrams per deciliter

Moderate/Mild PKU: anyone with elevated Phe levels that does not have classical PKU (phe level in blood: above 10-20mg/dl).

PAH: short for phenylalanine hydroxylase, an enzyme in the body that breaks down phenylalanine into tyrosine.

Phenylalanine (phe): the amino acid that is found in many foods and unable to be broken down by PKU patients.

Sapropterin: the generic drug name for Kuvan.

Tyrosine (TIE-roh-seen): an amino acid in the body that is used as a building block for several important brain chemicals.



My PKU tool kit: A transitional guide to adult PKU management (2010). Applied Nutrition Press. Retrieved from:

PKU, Kuvan, and You (2009). BioMarin Pharmaceuticals. Retrieved from:

3 responses to “PKU Definitions

  1. Pingback: Spennende blogger som passer for PKUere! |

  2. Mary Priggemeier

    Thank you, these definitions were very helpful to the grandmother of a newly diagnosed grand daughte.

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