ABSTRACT
Phenylketonuria (PKU) is a disorder of aromatic amino acid metabolism in which phenylalanine cannot be converted to tyrosine (Figure 20.1). The defective enzyme, phenylalanine hydroxylase, is expressed only in liver. This disease is a model for a public health approach to the control of inherited disease since dietary treatment is effective in preventing mental retardation. Routine neonatal screening programs have been most effective in the developed countries of the world. For these reasons, the full blown picture of the classic disease is rarely observed today in these countries. Nevertheless, it does occur, and it is important that it be recognized.
