Isovaleric academia, also called IVA, is an extremely rare inherited inborn error of metabolism (IEM) of leucine metabolism. It is an autosomal recessive disorder that is caused by a deficiency of isovaleryl-CoA dehydrogenase. It is characterized by a build-up of isovaleric acid in the blood and other biofluids. High levels of isovaleric acid lead to a rancid cheese odour. There are two major phenotypes of IVA: (1) an acute form and (2) a late-onset form. The acute form manifests as catastrophic disease in the newborn period and infants become extremely sick in the first week of life. There is usually a history of poor feeding, vomiting, lethargy, and seizures. In the acute form, metabolic acidosis is present, usually with an elevated anion gap and ketosis. There may be secondary hyperammonemia, thrombocytopenia, neutropenia, and sometimes anemia. The late-onset form is characterized by chronic, intermittent episodes of metabolic decompensation. The degree of isovaleryl-CoA dehydrogenase deficiency and the mutations differ between the two extreme presentations. The acute form of IVA is reasonably treatable. Administration of glycine has been shown to reduce isovaleric acidemia in neonates. Glycine is readily conjugated with isovaleric acid, which leads to urinary excretion of the conjugate. A diet that is also restricted in leucine consumption is also useful in treating the disorder.
Vockley J, Ensenauer R: Isovaleric acidemia: new aspects of genetic and phenotypic heterogeneity. Am J Med Genet C Semin Med Genet. 2006 May 15;142C(2):95-103. doi: 10.1002/ajmg.c.30089.
Tanaka K, Ikeda Y, Matsubara Y, Hyman DB: Molecular basis of isovaleric acidemia and medium-chain acyl-CoA dehydrogenase deficiency. Enzyme. 1987;38(1-4):91-107.
Valine, Leucine, and Isoleucine Degradation References
Lehninger, A.L. Lehninger principles of biochemistry (4th ed.) (2005). New York: W.H Freeman.
Salway, J.G. Metabolism at a glance (3rd ed.) (2004). Alden, Mass.: Blackwell Pub.
Wanders RJ, Duran M, Loupatty FJ: Enzymology of the branched-chain amino acid oxidation disorders: the valine pathway. J Inherit Metab Dis. 2012 Jan;35(1):5-12. doi: 10.1007/s10545-010-9236-x. Epub 2010 Nov 23.
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