1/6/2024 0 Comments Maple syrup urine disease![]() The diagnosis should then be established by plasma amino acid analysis and urine organic acid analysis. Once suspected, the diagnosis may be provisionally confirmed by a rapid screening test, the dinitrophenylhydrazine (DNPH) test, which detects the α-ketoacids that are formed from the isoleucine, leucine, and valine (see Screening Studies under Biochemical Testing). In either case, response to a positive screening result must be rapid.īedside detection of the characteristic odor of maple syrup by an alert parent or nurse might be the first clue to the diagnosis of this disorder. However, a positive newborn screening result might not be received until after the newborn has already become ill and is in the neonatal intensive care unit. The rate of false-positive and false-negative results has been reduced by the use of MS (mass spectrometry)/MS technology, which can concurrently measure the concentrations of isoleucine, leucine, and valine, thereby permitting the use of amino acid ratios to more reliably identify at-risk newborns. There are relatively few false-positive results for healthy full-term infants. ![]() Newborn screening programs for MSUD are based on the detection of hyperleucinemia. If the patient recovers from this initial episode, the disorder can be characterized by growth failure, mental retardation, and recurrent episodes of metabolic decompensation. If untreated, however, it may lead to hypoglycemia and ketoacidosis. The disease does not generally produce metabolic acidosis, lactic acidemia, hypoglycemia, hyperammonemia, ketosis, or abnormal acylcarnitines. Patients with the severe neonatal form of MSUD are generally normal for the first 2 or 3 days of life but then develop lethargy, hypertonia with extreme opisthotonic posturing (even when unconscious), seizures, and progressive encephalopathy, which may lead to death. 116,138 The classical clinical variant of this disorder manifests in the neonatal period and can lead to serious consequences if it is not recognized and treated quickly (i.e., within the first week of life). Maple syrup urine disease is an inborn error of branched-chain amino acid metabolism caused by branched-chain α-ketoacid dehydrogenase deficiency, which impairs isoleucine, leucine, and valine metabolism. Martin MBBS, FRACP, in Fanaroff and Martin's Neonatal-Perinatal Medicine, 2020 Maple Syrup Urine Disease In the era of newborn screening (NBS), the prompt initiation of treatment of asymptomatic infants detected by NBS means that most individuals who would have developed neonatal manifestations of MSUD remain asymptomatic with continued treatment compliance.Richard J. Individuals with intermediate MSUD have partial branched-chain alpha-ketoacid dehydrogenase deficiency that manifests only intermittently or responds to dietary thiamine therapy these individuals can experience severe metabolic intoxication and encephalopathy in the face of sufficient catabolic stress. Severe intoxication culminates in critical cerebral edema, coma, and central respiratory failure. Worsening encephalopathy manifests as lethargy, apnea, opisthotonos, and reflexive "fencing" or "bicycling" movements as the sweet maple syrup odor becomes apparent in urine Seven to ten days. Early and nonspecific signs of metabolic intoxication (i.e., irritability, hypersomnolence, anorexia) are accompanied by the presence of branched-chain alpha-ketoacids, acetoacetate, and beta-hydroxybutyrate in urine Four to six days. Elevated concentrations of branched-chain amino acids (BCAAs leucine, isoleucine, and valine) and alloisoleucine, as well as a generalized disturbance of amino acid concentration ratios, are present in blood and the maple syrup odor can be detected in cerumen Two to three days. Neonates with classic MSUD are born asymptomatic but without treatment follow a predictable course: 12–24 hours. Maple syrup urine disease (MSUD) is categorized as classic (severe), intermediate, or intermittent.
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