maple syrup urine disease


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maple syrup urine disease

 
a genetic disorder involving deficiency of an enzyme necessary in the metabolism of branched-chain amino acids, marked clinically by mental and physical retardation, feeding difficulties, and a characteristic odor of the urine.

ma·ple syr·up u·rine dis·ease

[MIM*248600]
an inborn error of metabolism caused by defective oxidative decarboxylation of α-keto acids of leucine, isoleucine, and valine; these branched-chain amino acids are present in the blood and urine in high concentrations; manifestations of disease include feeding difficulties, physical and mental retardation, and a urine odor similar to that of maple syrup; neonatal death is common. Autosomal recessive inheritance, caused by mutation in the E1, E2 or E3 subunit of the branched-chain α-keto acid dehydrogenase gene (BCKDH) on 19q. There are various forms differentiated by the subunit of BCKDH mutated.
A rare autosomal recessive [MIM 248600] inborn error of metabolism due to decreased branched-chain -keto acid dehydrogenase complex activity, resulting in defective amino acid metabolism, characterised by urine that smells like maple syrup
Frequency General population 1:200,000; in Pennsylvania Mennonites of German descent 1:176
Pathogenesis The defect in oxidative decarboxylation of branched chain amino acids—BCAA—valine, leucine and isoleucine results in accumulation of BCAA
Lab Increased BCAA, decreased threonine, serine, alanine in urine and serum, positive dinitro-phenylhydrazine test for alpha-keto amino acids, which form insoluble hydrazines
Management Dietary decrease of BCAA, plus dietary overload—20-fold excess of thiamine
Prognosis Mortality was 100%, often due to intercurrent infection; with BCAA-free infant formulas, the survival is ±100% and mental retardation completely preventable; since acute decompensation by BCAA and BCKA is due to a breakdown of endogenous proteins resulting in metabolic acidosis, ketosis, anorexia, emesis and potentially fatal encephalopathy, patients may respond to parenteral solutions of BCAA-free amino acids

maple syrup urine disease

Branched chain ketoaciduria Neonatology A rare AR inborn error of metabolism due to ↓ branched-chain α-keto acid dehydrogenase complex activity, resulting in defective amino acid metabolism, characterized by urine that smells like maple syrup Frequency General population 1:200,000; in Pennsylvania Mennonites of German descent 1:176; the defect in oxidative decarboxylation of branched chain amino acids–BCAA, valine, leucine and isoleucine results in accumulation of BCAA Clinical Neonatal onset, ↓ Moro reflex, dyspnea, spasticity, opisthotonos, mental and growth retardation, severe hypotonia, feeding difficulties, hypoglycemia, convulsions, decorticate rigidity Lab ↑ BCAA, ↓ threonine, serine, alanine in urine and serum, a positive dinitro-phenylhydrazine test for α keto amino acids, which form insoluble hydrazines Treatment Dietary ↓ of BCAA, plus dietary overload–20-fold excess of thiamine Prognosis Mortality was formerly 100%, often due to intercurrent infection; with BCAA-free infant formulas, the survival is virtually 100% and mental retardation completely preventable; since acute decompensation by BCAA and BCKA is due to a breakdown of endogenous proteins resulting in metabolic acidosis, ketosis, anorexia, emesis and potentially fatal encephalopathy, Pts may respond to parenteral solutions of BCAA-free amino acids

ma·ple syr·up u·rine dis·ease

(MSUD) (māpĕl sirŭp yūrin di-zēz)
Inborn error of metabolism caused by defective oxidative decarboxylation of α-keto acids of leucine, isoleucine, and valine; manifestations include feeding difficulties, physical and mental retardation, and a urine odor similar to that of maple syrup; neonatal death is common.

maple syrup urine disease

A hereditary defect of protein metabolism in which the breakdown of amino acids is defective because of the absence of an oxidase enzyme. The result is the presence of keto-acids with an odour of maple syrup in the urine. The condition causes serious neurological disturbances and death within a few months of birth.
References in periodicals archive ?
Description of the mutations in 15 subjects with variant forms of maple syrup urine disease. J Inherit Metab Dis 2007; 30:903-909.
Water apparent diffusion coefficient and T2 changes in the acute stage of maple syrup urine disease: evidence of intramyelinic and vasogenic-interstitial edema.
Domino liver transplantation in maple syrup urine disease. Liver Transpl 2006; 12: 876-882, doi: 10.1002/lt.20744.
Two new mutations in the human E1 beta subunit of branched chain alpha-ketoacid dehydrogenase associated with maple syrup urine disease. Biochim Biophys Acta 1997; 1361: 263-271, doi: 10.1016/S0925-4439(97)00046-X.
(29.-) Rodriguez-Pombo P, Navarrete R, Merinero B, Gomez-Puertas P, Ugarte M.Mutational spectrum of maple syrup urine disease in Spain.
Nutrient intakes of adolescents with phenylketonuria and infants and children with maple syrup urine disease on semisynthetic diets.
Dermatitis in treated maple syrup urine disease. Journal of the American Academy of Dermatology, 28(2 Pt.
Maple syrup urine disease: favourable effect of early diagnosis by newborn screening on the neonatal course of the disease.
Rapid diagnosis of maple syrup urine disease in blood spots from newborns by tandem mass spectrometry.
In maple syrup urine disease (MSUD; McKusik 248600), the degradation of the essential branched-chain L-amino acids leucine, valine, and isoleucine and their derived 2-oxoacids is impaired because of an inherited deficiency in branched-chain 2-oxoacid dehydrogenase complex (EC 1.2.4.4) activity.
On the mechanism of the formation of L-alloisoleucine and the 2-hydroxy-3-methylvaleric acid stereoisomers from L-isoleucine in maple syrup urine disease patients and in normal humans.
Soon after Guthrie (1) expanded newborn screening by adding galactosemia, maple syrup urine disease (MSUD), and homocystinuria to the original screening for phenylketonuria (PKU), he realized that screening would be more efficient and comprehensive if a single assay could be used to detect several disorders rather than the system of a separate bacterial assay for each disorder that he had developed.