Isovaleric Acidemia
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What is isovaleric acidemia?Isovaleric acidemia is a rare disorder in which the body is unable to process certain proteins properly. People with this disorder have inadequate levels of an enzyme that helps break down the amino acid leucine, a building block of proteins. A characteristic feature of isovaleric acidemia is a distinctive odor of sweaty feet. This odor is caused by the buildup of a compound called isovaleric acid in affected individuals. In about half of cases, the signs and symptoms of this disorder become apparent within a few days after birth and include poor feeding, vomiting, seizures, and lack of energy (lethargy) that can progress to coma. These medical problems are typically severe and can be life-threatening. In the other half of cases, the signs and symptoms of the disorder appear during childhood and may come and go over time. They are often triggered by an infection or by eating an increased amount of protein-rich foods. How common is isovaleric acidemia?Isovaleric acidemia is estimated to affect at least 1 in 250,000 births in the United States. What genes are related to isovaleric acidemia?Mutations in the IVD gene cause isovaleric acidemia. The enzyme made by the IVD gene plays an essential role in breaking down proteins from the diet. Specifically, the enzyme is responsible for the third step in processing leucine, an amino acid that is part of many proteins. If a mutation in the IVD gene reduces or eliminates the activity of this enzyme, the body is unable to break down leucine properly. As a result, a molecule called isovaleric acid and related compounds build up to harmful levels, damaging the brain and nervous system. How do people inherit isovaleric acidemia?This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder.
Source: National Institutes of Health
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New data from China Medical University, Department of Medical Research illuminate research in metabolism
2007 MAR 20 -- A report, "Genetic mutation profile of isovaleric acidemia patients in Taiwan," is newly published data in Molecular Genetics and Metabolism. "Isovaleric acidemia (IVA), a rare recessive autosomal disorder, is caused by isovaleryl-CoA dehydrogenase (IVD) deficiency. IVA may present with symptoms during the acute stage of severe metabolic acidosis, ketosis, vomiting, and altered mental status," scientists writing in the journal Molecular Genetics and Metabolism report. "With the help of newborn screening (NBS) by tandem mass spectrometry (MS/MS), IVA can now be diagnosed presymptomatically. According to statistic data, the incidence of IVA in Taiwan was about 1/365,000. In this study, six IVA patients from five families were investigated and followed-up clinically. As for the timing, two patients were found before MS technique introduced to Taiwan, the others were identified after MS/MS applied to NBS. The blood level of C5-carnitine in our patients was 7.43-18.96 microM (with upper limit in our laboratory <0.51 microM) and all of their urines contained raised amounts of 3-hydroxyisovaleric acid and isovalerylglycine. Molecular analysis of their IVD gene revealed six mutation profiles, among which the 149G-- >A (Arg21His) and 1174 C-- >T (Arg363Cys) mutations have been reported previously, while the other four mutations, 386A-- >G (His100Arg), 347C-- >T (Ser87Phe), 1007G-- >A (Cys307Tyr) and 1199A-- >G (Tyr371Cys), were first reported," wrote W.D. Lin and colleagues, China Medical University, Department of Medical Research. The researchers concluded: "Specially, we found 1199A-- >G (Tyr371Cys) mutated was a common recurring missense mutation in our population (4 in 10 mutant alleles)." Lin and colleagues published their study in Molecular Genetics and Metabolism (Genetic mutation profile of isovaleric acidemia patients in Taiwan. Molecular Genetics and Metabolism, 2007;90(2):134-9). Additional information can be obtained by contacting W.D. Lin, China Medical University Hospital, Dept. of Medical Research, Taichung, Taiwan. The publisher of the journal Molecular Genetics and Metabolism can be contacted at: Academic Press Inc. Elsevier Science, 525 B St., Ste. 1900, San Diego, CA 92101-4495, USA. Keywords: Taiwan, Taichung, Genetics, Metabolism. This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2007, Life Science Weekly via NewsRx.com.
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