Phenylketonuria

Phenylketonuria (PKU) is a rare, inborn metabolism error resulting from a deficiency of phenylalanine hydroxylase (an enzyme) transmitted by an autosomal (i.e., nonsex chromosome) recessive gene. The incidence of PKU in the United States is approximately 1:15,000, and 1 in 60 persons (generally mothers) is a carrier of the gene.

The most serious outcomes of PKU are moderate to severe mental retardation and behaviors such as hyperactivity, inattention, perceptual–motor problems, aggressiveness, negative mood, and motor difficulties. Children untreated for PKU are normal at birth, but begin to show slowed brain development by four months.

Well-established screening procedures (via blood analysis) are used to test every child for PKU at birth. Managing the disorder via dietary supplements from the first month of life can result in normal development. PKU diets use synthetic foods that provide amino acids with minimal or no phenylalanine. A diet free of phenylalanine must be supplemented with low-protein dietary supplements and measured amounts of fruits, vegetables, and synthetic foods to maintain essential phenylalanine levels. Dietary compliance for both parents and children may be a significant problem. Misunderstanding, mismanagement, or lax attention to the diet may delay development of the child. Instruction in nutrition education is useful for parents of children with PKU. Specific dietary instructions should be shared with educators, babysitters, friends, and family members. As children reach adolescence, more difficulties may develop with peer pressure. [Page 385]School personnel can assist parents and children with PKU in maintaining and monitoring the diet.