Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Phenylketonuria, or PKU, is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase, rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine to the amino acid tyrosine. When PAH activity is reduced, phenylalanine accumulates and is converted into phenylpyruvate. Untreated PKU can lead to mental retardation, seizures, and other serious medical problems. The mainstream treatment for classic PKU patients is a strict PHE-restricted diet supplemented by a medical formula containing amino acids and other nutrients. Learn more about the Haemophilia, its causes and management in this book.