Glutaricaciduria II is one of the conditions termed organic acidemias. Individuals with these conditions have a deficiency or absence of an enzyme that prevents them from breaking down certain chenicals in the body, resulting the accumulation of several organic acids in the blood and urine. Two enzymes that may be deficient in glutaricaciduria II are electron transfer flavoprotein (ETF) and ETF-ubiquinone oxidoreductase (ETF:QO). A complete enzyme deficiency causes a severe form of the disorder termed neonatal glutaricaciduria ll that is associated with a short life span and, sometimes, with specific physical birth defects. The less severe form of the disorder is termed late onset glutaricaciduria ll and has an extremely variable age of onset. Symptoms include nausea, vomiting, weakness and low blood sugar (hypoglycemia). Glutaricaciduria II is inherited as an autosomal recessive genetic disorder.
Newborns with the neonatal form of the disorder may have severe hypoglycemia, respiratory distress, low muscle tone, an odor of sweaty feet, liver abnormalities (hepatomegaly) and kidney abnormalities. Physical abnormalities are sometimes present and can include a large head (macrocephaly), high forehead, flat nasal bridge, malformed ears and genital abnormalities.
Symptoms of the late onset form of the disorder are variable and may include hypoglycemia and intermittent periods of vomiting and weakness.
Glutaricaciduria ll is caused by a deficiency or absence of enzymes that break down fats and proteins in the body, resulting in the accumulation of several organic acids in the blood and urine. Two enzymes that have been associated with glutaricaciduria II are electron transfer flavoprotein (ETF) and EFT-ubiquinone oxidoreductase (ETF:QO). Some individuals with glutaricaciduria ll have normal levels of these enzymes and the abnormal enzyme in those patients is not known.
Glutaricaciduria ll is inherited as an autosomal recessive genetic trait. Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.
The diagnosis of glutaricaciduria ll is usually made by examining urine organic acids. The characteristic pattern for glutaricaciduria is an elevation of glutaric, ethylmalonic, adipic and isovaleric acid. Some individuals with this condition are initially identified through newborn blood screening using tandem mass spectrometry for the markers C4, C5, C6, C8 and C10. Some individuals do not have an abnormal pattern of urine organic acids except when they are ill. The definitive diagnosis of glutaricaciduria ll is made by demonstrating abnormalities in ETF or ETF-QO antigens or activity in cultured fibroblast cells obtained from a skin biopsy. Prenatal diagnosis may be possible by measuring glutaric acid in amniotic fluid.
Glutaricaciduria is usually treated with a high carbohydrate, low protein and low fat diet. It is recommended that affected individuals eat often to avoid low blood sugar. Dietary supplementation with riboflavin, glycine and carnitine may be helpful.
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Brusilow SW, Vallee DL. Symptomatic inborn errors of metabolism in the neonate. Current Therapy in Neonatal-Perinatal Medicine. Marcel Decker. 1985;24-27.
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McKusick VA. Online Mendelian Inheritance in Man, 6th ed. Johns Hopkins University Press; 1983:703,735,1038.
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