Phenylalanine is an essential amino acid which means the body needs it to maintain health, however, the body cannot make it on its own. Mutations in the PAH gene results in low levels of the enzyme phenylalanine hydroxylase. This enzyme is needed to break down phenylalanine. An individual with PKU can experience a dangerous build up phenylalanine if they eat foods high in protein. This can eventually lead to health complications. Individuals that have PKU must limit the amount of phenylalanine from their diets. In the United States and many other countries, newborns are tested for PKU soon after birth.
According to NCBI, “Most forms of PKU and hyperphenylalaninaemia (HPA) are caused by mutations in the PAH gene on chromosome 12q23.2″ (NCBI).
PKU 