Phenylketonuria

Phenylketonuria (pku) is due to a deficiency of phenylalanine hydroxylase, the enzyme that converts phenylalanine to tyrosine. High levels of phenylala-nine accumulate in the body resulting in severe mental retardation, seizures, and a musty odor. PKU is an autosomal recessive genetic disorder. The incidence is 1 in 10,000 to 1 in 12,000 live births. PKU is detected on newborn screens, which are most sensitive when performed between forty-eight and seventy-two hours of life, and after the infant has been fed a diet containing protein. Phenylalanine levels are easily detected by a few drops of blood, and early treatment prevents complications making it a model disease for screening. Treatment includes a diet low in phenylalanine and frequent monitoring of blood levels. Dietary therapy should begin immediately in the newborn period. The duration of therapy is controversial. It is recommended that children maintain a very restrictive diet through the age of six, and they are encouraged to maintain some restriction throughout life.