Methylmalonic aciduria and hypoglycemia.
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BACKGROUND: Propionic aciduria (PA) and Methymalonic aciduria (MMA) result from an inherited abnormality of the enzymes propionyl CoA carboxylase and methylmalonyl CoA mutase respectively. This produces marked increases in the amino acids methionine, threonine, valine and isoleucine (MTVI). Their clinical presentation can be neonatal or late onset forms. AIM: To report 23 children with organic acidurias. MATERIAL AND METHODS: Twenty three cases of organic acidurias diagnosed since 1980 (17 PA and 6 MMA) and followed at the Institute of Nutrition and Food Technology, are reported. RESULTS: The average age of diagnosis was 3.9 days for the neonatal form and 8.3 months for the late onset form. The most frequent symptoms were hypotonia, lethargy and vomiting. Neonatal PA had mean ammonemias of 1089 +/- 678.3 micrograms/dl. The figure for MMA was 933 +/- 801.9 micrograms/dl. Seven children were dialyzed and 30% died. 16 children are followed and 81.2% have normal weight for age. Seven children required gastrostomy because of anorexia and failure to thrive. The nutritional treatment is based on natural and artificial proteins without MTVI, with periodical controls, amino acid and ammonia quantification. Some patients were submitted to enzyme assays and molecular studies. CONCLUSIONS: An early diagnosis and a very strict follow up allows a normal development of children with organic acidurias. There is a relationship between prognosis and the presentation form, the nutritional status and the emergency treatment during acute episodes. The importance of the enzymatic and molecular studies is emphasized because they facilitate treatment, accurate diagnosis and allow an adequate genetic counseling.
Two infants have been studied with glutaric aciduria Type II. The clinical presentation was of an overwhelming illness very early in life; both infants died in the neonatal period. One had dysmorphic features. An acrid odor may be a clue to the diagnosis. Neonatal acidosis, hypoglycemia, and hyperammonemia are characteristic. Organic acid analysis revealed massive lactic aciduria and glutaric aciduria. A variety of other dicarboxylic acids and hydroxy acids and amino acids were found in elevated amounts in body fluids, along with elevated concentrations of butyric, isobutyric, 2-methylbutyric, and isovaleric acids. The pattern of metabolites accumulated is consistent with deficient activity of a number of acyl-CoA dehydrogenases.
A patient with argininosuccinc aciduria was charged with 50 grams of protein, which was followed by considerable hyperammonemia. There was no response in further urea formation; but there was a considerable production of orotic acid, a precursor of pyrimidines. This makes orotic acid to an important diagnostic tool for the diagnosis of impaired urea formation. The patient's plasma amino acid pattern led to the suggestion that orotic acid synthesis is initiated by increased de novo formation of carbamyl phosphate in the cytosol and not by deviation of already existing intramitochondrial carbamyl phosphate.
This paper presents experiences encountered with protein-modified diets (PMD) in the management of 67 patients, aged 1 day to 14 years, followed in the Pediatric Nutrition Clinic in the past 5 years. All had inborn errors of amino acid metabolism: maple syrup urine disease (MSUD), 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency, propionic acidemia (PPA), or methylmalonic aciduria (MMA). In early infancy, the diet prescription is frequently adjusted to search for the infant's tolerance level of restricted amino acids. The levels must be established when natural foods other than milk are added to the PMD. The amino acids restricted are leucine, isoleucine, and valine in MSUD; leucine in HMG-CoA lyase deficiency; and isoleucine, methionine, threonine, and valine in PPA and MMA. Efficacy of the PMD depends on accuracy in prediction of the restricted amino acid requirement and the willingness and ability of parents and patients to conform to its demands.
Antenatal diagnosis in a woman previously delivered of a child with arginino-succinic aciduria, due to deficiency of arginino-succinase (EC 4.3.2.1.), showed the fetus to be unaffected. This was confirmed at birth.
Urinary excretion of orotic acid was measured in controls and in subjects homozygous and heterozygous for lysinuric protein intolerance under various conditions of amino nitrogen intake. In all situations, the controls excreted less than 28 microgram/kg/hr. Only one of the two heterozygotes studied differed from the controls, The orotic aciduria of homozygotes was normal in fasting but increased on a self-chosen low-protein diet (log mean, 80; range, 8 to 588 microgram/kg/hr in 24-hr urine), after cow's milk protein 0.5 g/kg (769; 251 to 1747 microgram/kg/hr in 4 to 6-hr urine), oral ammonium lactate, 2.5 mmoles/kg (95; 15 to 1127 microgram/kg/hr in 1.5-hr urine), and IV alanine, 6.6 mmoles/kg (519; 47 to 1831 microgram/kg/hr in 6-hr urine). Giving ornithine or citrulline IV with the infusion of alanine prevented the increase in orotic acid excretion. Given orally, citrulline was more efficient than ornithine or arginine. To prevent the hyperammonemic and orotic aciduric responses with ornithine its plasma concentrations needed to be higher than normal. Orotic aciduria is a reliable indicator of the function of the urea cycle in lysinuric protein intolerance and facilitates monitoring of the treatment of this disease.
A 4 year old girl with mild mental retardation presented with convulsions, coma and hepatomegaly. She died rapidly. The main biochemical findings were hypoglycaemia, metabolic acidosis, generalised aminoaciduria, elevation of the plasma and urine alpha-amino adipic acid, massive urine excretion of glutaric and glutaconic acids with traces of alpha-hydroxyglutaric acid. The diagnosis of glutaric aciduria was confirmed by the low activity of glutaryl CoA dehydrogenase in liver tissue. This diagnosis should be considered in children with progressive neurological disorders (dystonia, choreoathetosis) and in children with an illness similar to Reye's syndrome.
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UNLABELLED: Two cases of hyperinsulinaemic hypoglycaemia associated with persistent hyperammonaemia in unrelated infants of 7 days and 4 months of age are reported. Blood ammonia levels were 100-300 micromol/l (normal values <40 micromol/l). The hyperammonaemia was asymptomatic and not associated with any of the abnormalities of amino acids or organic acids observed in urea cycle enzyme defects. Orotic aciduria was normal. The hyperammonaemia was not influenced by the levels of blood glucose nor by subtotal pancreatectomy. On admission blood glucose was ca. 1.2 mmol/l (21.6 mg/dl) corresponding to blood insulin levels of 35 and 22 mU/l respectively in both infants. Continuous intravenous glucose perfusion was necessary to prevent hypoglycaemia. Furthermore 2-oxoglutaric acid in urine was increased in the second infant to 3.15 mg/mg creatinine (normal 0.41+/-0.12). This may point to mutations in the glutamate dehydrogenase gene. CONCLUSION: 2-Oxoglutaric aciduria may be an important clue to the diagnose in this syndrome.
Liver transplantation was performed in a girl with early-onset ASLD, leading to unrestricted protein intake and no further neurological deterioration.
Although most commonly associated with infancy, the majority of individuals with urea cycle disorders (UCDs) present outside the neonatal period, frequently in childhood. Signs and symptoms are often vague, but recurrent; fulminant presentations associated with acute illness are also common. A disorder of urea cycle metabolism should be considered in children who have recurrent symptoms, especially neurologic abnormalities associated with periods of decompensation. Routine laboratory tests, including measurement of plasma ammonia concentrations, can indicate a potential UCD; however, specific metabolic testing and ultimately enzymatic or molecular confirmation are necessary to establish a diagnosis. Treatment with dietary protein restriction and medications may be challenging in children.
MR spectroscopy in a patient with argininosuccinate lyase deficiency revealed elevated cerebral guanidinoacetate signals, indicating that the phenomenon of increased levels of this compound in brain tissue is not limited to creatine deficiencies.
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