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An intestinal obstruction in an eight-month-old child suffering from mevalonic aciduria.

UNLABELLED: This report describes a case of mevalonate kinase deficiency diagnosed at 1 mo of age. Soon after delivery, symptoms were suggestive of congenital infection. An intestinal occlusion occurred towards the age of 8 mo. CONCLUSION: Mevalonate kinase deficiency has variable clinical and biological signs which can lead to a delay in diagnosis. This is the first reported occurrence of bowel obstruction in this disease and the resemblance to a congenital infection in the neonatal period must be emphasized.

Amino Acid Metabolism, Inborn Errors↗

A combined defect of three mitochondrial carboxylases presenting as biotin-responsive 3-methylcrotonyl glycinuria and 3-hydroxyisovaleric aciduria.

A child with a history of episodes of metabolic acidosis was found to excrete 3-hydroxyisovaleric acid and 3-methylcrotonylglycine. These metabolites disappeared following the administration of biotin. The specific activities of propionyl CoA carboxylase, 3-methylcrotonyl CoA carboxylase and pyruvate carboxylase were found to be low in skin fibroblasts cultured in the absence of added biotin. With the addition of biotin, the specific activity of all three carboxylases returned to normal, that of 3-methylcrotonyl CoA carboxylase ahowing the greatest sensitivity to biotin.

Acidosis↗

Mitochondrial 2-methylacetoacetyl-CoA thiolase deficiency: an inborn error of isoleucine and ketone body metabolism.

A review is presented of 22 published cases of verified or probable mitochondrial 2-methylacetoacetyl-CoA thiolase deficiency, a disorder of isoleucine and ketone body metabolism. The clinical expression, characterized by ketoacidosis, vomiting and lethargy, is highly variable. Typical age of onset is between 6 and 24 months. The disorder, which has been observed in several ethnic groups, is apparently inherited as an autosomal, recessive trait. The prognosis is relatively good if acute episodes of ketoacidosis and dehydration are adequately treated. There is abnormal urinary excretion of 2-methyl-3-hydroxybutyric acid, tiglylglycine, and in some instances also 2-methyl-acetoacetic acid. However, such a pattern of organic aciduria has also been found in cases with normal thiolase activity. Genetic complementation analyses have demonstrated considerable heterogeneity. The cDNA for human methyl-acetoacetyl-CoA thiolase has been cloned and sequenced. Studies in one patient showed a G-to-A substitution at position 1138 of the mRNA, causing 347Ala to Thr change in the mature enzyme. Studies in other patients have shown variable enzyme amount and/or stability.

Acetyl-CoA C-Acyltransferase↗

Prenatal diagnosis of 3-hydroxy-3-methylglutaric aciduria by GC-MS and enzymology on cultured amniocytes and chorionic villi.

This paper reports the prenatal diagnosis of HMG CoA lyase deficiency at 16 weeks' gestation by direct chemical analysis of cell-free amniotic fluid and by measurement of HMG CoA lyase activity in cultured amniocytes. Termination of an affected fetus allowed study of chorionic villus tissue, the results providing the basis for future first trimester prenatal diagnoses of this condition. An abstract report of this work has appeared elsewhere.

Amino Acid Metabolism, Inborn Errors↗

3-Oxothiolase activities and [14C]-2-methylbutanoic acid incorporation in cultured fibroblasts from 13 cases of suspected 3-oxothiolase deficiency.

Cultured fibroblasts from 13 patients with organic aciduria suggesting 3-oxothiolase deficiency were studied by measuring first the capacity of the isoleucine degradative pathways in whole cells, as the incorporation of 1-[14C]-2-methylbutanoic acid into macromolecules, and, second, the activity of 3-oxothiolase in cell homogenates using specific 3-oxoacyl-CoA substrates to identify the different enzymes. Nine patients showed low incorporation by the macromolecular labeling assay, as well as deficiency of 2-methylacetoacetyl-CoA thiolase. In this group of patients, low activity by the macromolecular labeling assay was associated with clinically severe symptoms, and vice versa. Two patients showed reduced macromolecular labeling, but apparently normal 3-oxothiolase. Finally, two patients showed normal activities by either test, the reason for their particular organic aciduria being unknown. In conclusion, occurrence of urinary 2-methyl-3-hydroxybutyric acid and/or tiglyglycine is not an unequivocal indicator of the absence of the thiolase that metabolizes 2-methylacetoacetyl-CoA. Measurement of 1-[14C]-2-methylbutanoic acid incorporation in cultured fibroblasts adds important information in studying possible defects of the isoleucine catabolic pathway.

Acetyl-CoA C-Acyltransferase↗

Secondary carnitine deficiency.

For any given tissue the normal carnitine content is that which is necessary for an optimal rate of long-chain fatty acid oxidation. Tissues especially rich in carnitine are liver, muscle and heart. The endogenous rate of carnitine biosynthesis from lysine and methionine is not known to be influenced by fluctuations in the levels of the parent amino acids, as exemplified by hypermethioninaemic patients. Inadequate dietary supply of carnitine, leading to a deficiency, may occur in vegetarians and especially in subjects on total parenteral nutrition. Premature babies are especially at risk in this respect, and this has led to the addition of carnitine to solutions for intravenous alimentation. It has been suggested that carnitine plays an important role in the intramitochondrial regulations of coenzyme A homeostasis by expelling short-chain and medium-chain acyl groups from the mitochondrion in the form of acylcarnitines. These esters are preferentially excreted into the urine and thus result in a depletion of the body's carnitine stores. Important conditions in this respect are the inherited organic acidurias and disorders of fatty acid oxidation. Urinary acylcarnitines can be identified by indirect gas chromatographic or direct mass spectrometric methods. Patients on haemodialysis treatment will lose carnitine in the dialysis fluid, whereas excessive urinary losses of free and acetylated carnitine occur in the Fanconi syndrome. Secondary carnitine deficiency may be accompanied by a moderate degree of muscular dysfunction. Reassuringly, however, no signs of hepatic or cardiac involvement, as often seen in primary carnitine deficiency, have been observed.

Adolescent↗

Diagnosis of urea cycle disorders.

Hyperammonemia in pediatrics can be due to a number of causes (defects of urea cycle enzymes or transport of its metabolites, organic acidurias, acyl-CoA dehydrogenase or carnitine deficiency, liver bypass or nonspecific insufficiency) requiring differentiated rapid treatment for a satisfactory prognosis. The specific diagnosis cannot be established by clinical means. Thus the work-up rests on biochemical analyses. The methods used are detailed and their interpretation discussed. An algorithm for the interpretation of the data which can easily be computerized is presented. The procedure has proven practicable in 126 patients with urea cycle disorders.

Algorithms↗

N-acetylaspartic aciduria due to aspartoacylase deficiency--a new aetiology of childhood leukodystrophy.

We describe a male infant with psychomotor retardation and leukodystrophy who excretes large quantities of N-acetylaspartate in his urine. A high CSF/plasma concentration ratio of N-acetylaspartate indicates that this substance originates in the brain. Fibroblasts from the patient are deficient in aspartoacylase activity. It is proposed that the dysmyelination in the patient may be due to failure of N-acetylaspartate to serve as a carrier of acetyl groups from mitochondria to the cytosol for lipogenesis.

Amidohydrolases↗

Mild variant of argininosuccinic aciduria.

A 7 and one half-year-old boy with a massive excretion of argininosuccinic acid is described. He exhibited only moderate mental retardation, cerebellar ataxia and both abnormal hair and skin. Argininosuccinate lyase activity in the erythrocytes of his parents and his sister was in the range expected for heterozygotes. The patient was put on a low protein diet with arginine supplementation and improved clinically and biochemically on this regime. The variability of the phenotypic expression of argininosuccinate lyase deficiency is stressed.

Abnormalities, Multiple↗

Therapeutic intervention in mice deficient for succinate semialdehyde dehydrogenase (gamma-hydroxybutyric aciduria).

Therapeutic intervention for human succinic semialdehyde dehydrogenase (SSADH) deficiency (gamma-hydroxybutyric aciduria) has been limited to vigabatrin (VGB). Pharmacologically, VGB should be highly effective due to 4-aminobutyrate-transaminase (GABA-transaminase) inhibition, lowering succinic semialdehyde and, thereby, gamma-hydroxybutyric acid (GHB) levels. Unfortunately, clinical efficacy has been limited. Because GHB possesses a number of potential receptor interactions, we addressed the hypothesis that antagonism of these interactions in mice with SSADH deficiency could lead to the development of novel treatment strategies for human patients. SSADH-deficient mice have significantly elevated tissue GHB levels, are neurologically impaired, and die within 4 weeks postnatally. In the current report, we compared oral versus intraperitoneal administration of VGB, CGP 35348 [3-aminopropyl(diethoxymethyl)phosphinic acid, a GABA(B) receptor antagonist], and the nonprotein amino acid taurine in rescue of SSADH-deficient mice from early death. In addition, we assessed the efficacy of the specific GHB receptor antagonist NCS-382 (6,7,8,9-tetrahydro-5-[H]benzocycloheptene-5-ol-6-ylideneacetic acid) using i.p. administration. All interventions led to significant lifespan extension (22-61%), with NCS-382 being most effective (50-61% survival). To explore the limited human clinical efficacy of VGB, we measured brain GHB and gamma-aminobutyric acid (GABA) levels in SSADH-deficient mice receiving VGB. Whereas high-dose VGB led to the expected elevation of brain GABA, we found no parallel decrease in GHB levels. Our data indicate that, at a minimum, GHB and GABA(B) receptors are involved in the pathophysiology of SSADH deficiency. We conclude that taurine and NCS-382 may have therapeutic relevance in human SSADH deficiency and that the poor clinical efficacy of VGB in this disease may relate to an inability to decrease brain GHB concentrations.

Aldehyde Oxidoreductases↗

3-Hydroxy-3-methylglutaric aciduria, combined with 3-methylglutaconic aciduria.

1. A baby with severe metabolic acidosis was found to excrete abnormal amounts of 3-methylcrotonic acid, 3-methylglutaconic acid and 3-hydroxy-3-methylglutaric acid in urine. 2. Several other abnormal constitutents appear to be products of side-reactions and include 3-hydroxy-3-methylbutyric acid and 3-methylglutaric acid. 3. The profile of acids in urine indicates a blockage in the sixth step of leucine catabolism, the cleavage of 3-hydroxy-3-methylglutaryl-CoA to acetoacetic acid and acetyl-CoA.

Acidosis↗

Glutaric aciduria in progressive choreo-athetosis.

The clinical symptoms in a 10-year-old girl with progressive dystonic cerebral palsy are described. The biochemical findings were dominated by large amounts of glutaric acid in the urine. The disorder is caused by impairment of the degradation of glutaryl-CoA. A survey is given of the clinical and biochemical symptoms, based on the five cases reported so far. It is concluded that patients with progressive dystonic palsy should be examined for disorders in the metabolism of organic acids.

Acyl Coenzyme A↗

Genetic defects of folate and cobalamin metabolism.

Deficient activity of an enzyme can result from a defect in the conversion of the vitamin to a co-enzyme as well from an abnormal apo-enzyme or disturbed binding of coenzyme to enzyme. Conversion of dietary vitamin to intracellular active co-enzyme can be complex and require many physiological and biochemical processes including stomach release of bound vitamin, intestinal uptake, carriers/transport, blood transport, cellular uptake, intracellular release and intracellular compartmentalisation. Disorders of malabsorption (food cobalamin malabsorption, intrinsic factor deficiency and abnormal enterocyte cobalamin processing) and transport proteins (transcobalamin II deficiency, R-binder deficiency) mostly lead to disturbed function of the two cobalamin requiring enzymes, methylmalonyl CoA mutase and methionine synthase. Defects of early steps of intracellular cobalamin (cblF, cbl C/D) result in marked deficiencies of both cobalamin co-enzymes and homocystinuria combined with methylmalonic aciduria. Defective synthesis of adenosyl cobalamin in the cbl A/B defects leads to methylmalonyl CoA mutase. Isolated methionine synthase deficiency is also classified as a cobalamin disorder due to its associated deficient formation of methylcobalamin. Folate disorders include methylene-tetrahydrofolate reductase deficiency and glutamate formimino-transferase deficiency. In addition a hereditary disorder of intestinal folate transport has been described. Less well established are disorders of dihydrofolate reductase, methenyl-tetrahydrofolate cyclohydrolase, and defects of cellular folate uptake.

Absorption↗

The synthesis and characterisation of 2-methylacetoacetyl coenzyme A and its use in the identification of the site of the defect in 2-methylacetoacetic and 2-methyl-3-hydroxybutyric aciduria.

(1) 2-Methylacetoacetyl coenzyme A was prepared, purified by ion exchange chromatography as judged by TLC and HPLC and a number of its properties characterised. (2) An assay of 3-oxothiolase in homogenates of cultured human fibroblasts using 2-methylacetoacetyl CoA as substrate is described. (3) This enzyme activity was shown to be absent in fibroblasts from two patients with 2-methylacetoacetic and 2-methyl-3-hydroxybutyric aciduria. (4) These patients also showed decreased activity (42% normal) with acetoacetyl CoA, and indicated that the defective thiolase could also utilize this substrate in normals. The residual activity with acetoacetyl CoA in the patients' fibroblasts resembled the cytosolic acetoacetyl CoA-specific thiolase in properties. We suggest that the enzyme defective in the patients was the mitochondrial acetoacetyl CoA thiolase involved in ketone body utilization in extrahepatic tissues.

Acetoacetates↗

Mutation analysis of the MCM gene in Israeli patients with mut(0) disease.

Three novel mutations (IVS8+3a --> g, N219Y, and E414X) were identified in 6 unrelated patients with mut(0) methylmalonic aciduria. The presence of a wild-type along with rearranged fragments in homozygotes for the IVS8+3a --> g mutation may contribute to their later age of onset (3-11 months of age). Nonetheless, delayed onset was not associated with better neurological outcome and prolonged survival. The large number of undiagnosed dead sibs in most families suggests that the disease is largely underdiagnosed in this region.

Amino Acid Metabolism, Inborn Errors↗

Effects of cysteamine therapy in nephropathic cystinosis.

We studied the effects of cysteamine in five children with nephropathic cystinosis who were treated for up to 30 months. Cysteamine caused a decline in leukocyte cystine levels to the range seen in clinically unaffected heterozygotes; both plasma and urinary cystine diminished by more than half. Therapy had no effect on progressively declining creatinine clearance in three patients, but improvement occurred in the other two. Phosphaturia, glycosuria, aminociduria, and organic aciduria did not improve in any of the patients. Both blood lactate and the lactate pyruvate ratio were diminished. Growth velocity, which was abnormal in four of the five children, did not improve. No major side effects were noted. Therapy with cysteamine caused a consistent, dose-related decline in levels of cystine in leukocytes and in extracellular fluid, caused no improvement so far in renal tubular function or growth velocity, and improved creatinine clearance in some patients.

Amino Acids↗

Type III 3-methylglutaconic aciduria (optic atrophy plus syndrome, or Costeff optic atrophy syndrome): identification of the OPA3 gene and its founder mutation in Iraqi Jews.

Type III 3-methylglutaconic aciduria (MGA) (MIM 258501) is a neuro-ophthalmologic syndrome that consists of early-onset bilateral optic atrophy and later-onset spasticity, extrapyramidal dysfunction, and cognitive deficit. Urinary excretion of 3-methylglutaconic acid and of 3-methylglutaric acid is increased. The disorder has been reported in approximately 40 patients of Iraqi Jewish origin, allowing the mapping of the disease to chromosome 19q13.2-q13.3, by linkage analysis. To isolate the causative gene, OPA3, we sequenced four genes within the critical interval and identified, in the intronic sequence of a gene corresponding to cDNA clone FLJ22187, a point mutation that segregated with the type III MGA phenotype. The FLJ22187-cDNA clone, which we identified as the OPA3 gene, consists of two exons and encodes a peptide of 179 amino acid residues. Northern blot analysis revealed a primary transcript of approximately 5.0 kb that was ubiquitously expressed, most prominently in skeletal muscle and kidney. Within the brain, the cerebral cortex, the medulla, the cerebellum, and the frontal lobe, compared to other parts of the brain, had slightly increased expression. The intronic G-->C mutation abolished mRNA expression in fibroblasts from affected patients and was detected in 8 of 85 anonymous Israeli individuals of Iraqi Jewish origin. Milder mutations in OPA3 should be sought in patients with optic atrophy with later onset, even in the absence of additional neurological abnormalities.

Amino Acid Sequence↗

Analysis of acylcarnitines in maternal urine for prenatal diagnosis of glutaric aciduria type 2.

The urinary acylcarnitine profiles of two mothers whose first children were diagnosed to have glutaric aciduria type 2 (multiple acyl-CoA dehydrogenation deficiency, electron transfer flavoprotein (ETF) deficiency) were analysed in the second pregnancy. Large volumes of tigrylcarnitine and isovalerylcarnitine and a little glutarylcarnitine were detected. Each fetus was also diagnosed to be abnormal by enzyme activity and immunoassay of ETF protein. The acylcarnitines in the mothers' urine disappeared in 1 week after labour or artificial abortion. Acylcarnitines were never detected in the urine of controls.

Abortion, Induced↗