What are inborn errors of metabolism, and can newborn infants with these disorders be identified and treated with a favorable outcome? Only three decades ago these were common questions asked by the medical community. Today the basic answers are vaguely familiar even to the layperson.
Screening newborn infants and identifying those with inherited metabolic disorders require a team approach by physician and nonphysician scientists, skilled technologists, and public health workers—a process constituting "laboratory medicine on a mass scale in the public area."1 Newborn screening routinely identifies infants with metabolic disturbances such as phenylketonuria and congenital hypothyroidism. By detecting rare disorders early enough, their associated long-term complications, especially neurological deficits, can be reduced. If affected infants are identified within the first few weeks of life, their quality of life can be dramatically improved by recommended therapeutic interventions. Earlier detection of a larger number of genetic and nongenetic congenital disorders is