Phenylketonuria (PKU) Support Group

Phenylketonuria [PKU] is a human genetic disorder (though it is possible to exist in mice), in which the body lacks phenylalanine hydroxylase, the enzyme necessary to metabolize phenylalanine to tyrosine. Left untreated, the disorder can cause brain damage and progressive mental retardation as a result of the accumulation of phenylalanine and its breakdown products. The incidence of occurrence of PKU is about 1 in 15,000 births, but the incidence varies widely in different human populations from 1 in 4,500 births among the Irish to fewer than one in 100,000 births among the population of Finland.

If the condition is diagnosed early enough, an affected child can grow up with normal brain development, by eating a special diet low in phenylalanine. This requires severely restricting or eliminating foods high in protein, such as meat, nuts, cheese and other dairy products. Starchy foods such as potatoes, bread, pasta, and corn must also be avoided. Supplementary formulas are used in these patients to provide the protein and other necessary nutrients that would otherwise be lacking in a diet free of protein. In those patients with a deficit in BH4 production or PAH has a low affinity for BH4, treatment consists of giving this cofactor as a supplement; this is referred to as BH4 responsive PKU. There are a number of potential other therapies currently under investigation, including gene therapy, and an injectable form of PAH. However, it is likely that it will be many years before these are available for use in affected individuals.