Inborn errors of metabolism in infancy and early childhood: an update.

Recent innovations in medical technology have changed newborn screening programs in the United States. The widespread use of tandem mass spectrometry is helping to identify more inborn errors of metabolism. Primary care physicians often are the first to be contacted by state and reference laboratories when neonatal screening detects the possibility of an inborn error of metabolism. Physicians must take immediate steps to evaluate the infant and should be able to access a regional metabolic disorder subspecialty center. Detailed knowledge of biochemical pathways is not necessary to treat patients during the initial evaluation. Nonspecific metabolic abnormalities (e.g., hypoglycemia, metabolic acidosis, hyperammonemia) must be treated urgently even if the specific underlying metabolic disorder is not yet known. Similarly, physicians still must recognize inborn errors of metabolism that are not detected reliably by tandem mass spectrometry and know when to pursue additional diagnostic testing. The early and specific diagnosis of inborn errors of metabolism and prompt initiation of appropriate therapy are still the best determinants of outcome for these patients.