Home > Encyclopedia of Children's Health > Phenylketonuria

Definition

Phenylketonuria (PKU) is a rare metabolic disorder caused by a deficiency in the production of the hepatic (liver) enzyme phenylalanine hydroxylase (PAH).

Description

PKU is the most serious form of a class of diseases referred to as hyperphenylalaninemia, all of which involve above normal (elevated) levels of phenylalanine in the blood. The primary symptom of untreated PKU, mental retardation, is the result of consuming foods that contain the amino acid phenylalanine, which is toxic to brain tissue.

PKU is an inherited, autosomal recessive disorder. It is the most common genetic disease involving amino acid metabolism. As of 2004, PKU was incurable, but early, effective treatment can...