![]() Severe hypoglycemia and mild hyperammonemia may occur, as may pancreatitis. Early manifestations include feeding difficulties, irregular respirations, progressive loss of the Moro reflex, and apnea. Symptoms begin after 3 to 5 days and progress rapidly to death within 2 to 4 weeks if branched-chain amino acid restriction is not implemented. In the classical form of maple syrup urine disease, infants appear well at birth. The genes encoding the proteins that form the complex were subsequently identified.īranched-chain alpha-ketoacid decarboxylaseīranched-chain dihydrolipoamide acyltransferase Dietary therapy was established, and newborn screening programs were implemented ( 101 89). A defect in branched-chain alpha-ketoacid dehydrogenase was then identified ( 22). Novel therapies investigated include hepatocyte transplantation, drugs to counter oxidative stress, norleucine, and phenylbutyrate to prevent the inactivation of the dehydrogenase complex.Ī hereditary encephalopathy with sweet-smelling urine was described in 1954 ( 56), and shortly thereafter elevations in plasma branched-chain amino acids and their keto acids in the urine were noted ( 100 55).The metabolic defect is in the branched-chain keto acid dehydrogenase complex, and dietary branched-chain amino acids (leucine, isoleucine, and valine) should be restricted and monitored.Soon after birth, maple syrup urine disease classically presents with an encephalopathy accompanied by abnormal movements such as pedaling, ketonuria, and urine with a burnt sugar odor.Inborn errors of metabolism should be suspected in newborns and infants with unexplained encephalopathies.In this article, the authors detail novel approaches to the treatment of maple syrup urine disease, such as the experimental use of phenylbutyrate to prevent the inactivation of the implicated dehydrogenase complex. Branched-chain amino acids (leucine, isoleucine, and valine) and their ketoacids are increased in the blood, and the intake of these amino acids must be controlled. Maple syrup urine disease is an inborn error of branched-chain ketoacid metabolism that presents classically with metabolic distress in newborns, although milder presentations exist.
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