APA Dictionary of Psychology

n. an inherited metabolic disease transmitted as an autosomal recessive trait and marked by a deficiency of an enzyme (phenylalanine hydroxylase) needed to utilize the amino acid phenylalanine. Unless it is diagnosed in early infancy and treated by a restricted dietary intake of phenylalanine, phenylketonuria leads to intellectual and developmental disabilities. Women who have been treated for the disease must adopt a restricted diet during pregnancy to prevent neurological damage to their children (see maternal PKU).