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Recent progress in understanding glutaric acidemias.

Glutaric acidemia, which is due to inherited deficiency of glutaryl-CoA dehydrogenase, is characterized clinically by progressive dystonia and dyskinesia in childhood, and pathologically by degeneration of the caudate and putamen. Results using newer imaging techniques (computer tomography and magnetic resonance image scanning) suggest that neurological involvement in this condition begins before birth, and that gliosis of the basal ganglia is a relatively late event. Glutaric acidemia type II is usually due to inherited deficiency of electron transfer flavoprotein (ETF) or ETF:ubiquinone oxidoreductase, but some patients with typical disease may have another, to date undefined, abnormality. There may also be a clinical phenotype of glutaric acidemia type II which, like glutaryl-CoA dehydrogenase deficiency, is characterized by a movement disorder and by degeneration of the basal ganglia.

Child, Preschool↗

Nutrition support for glutaric acidemia type I.

Glutaric acidemia type I is a rare, autosomal recessive, inborn error of lysine and tryptophan metabolism. This disorder is caused by a defect in the mitochondrial enzyme glutaryl-coenzyme A dehydrogenase, resulting in permanent or episodic elevations of glutaric acid. Despite clinical variability, untreated children often experience progressive neurologic damage that frequently leads to death. Recent evidence suggests that a lysine- and tryptophan-restricted diet and pharmacologic therapy with oral riboflavin and L-carnitine may arrest the neurologic deterioration. Several cases of normal growth and development have been reported in children diagnosed and treated before neurologic insult. In this article, we review previously published experience with dietary and pharmacologic therapy and provide guidelines for nutrition support based on our experience of treating four affected children. We suggest that dietary restriction of lysine and tryptophan is a safe and potentially effective therapy for individuals with glutaric acidemia type I.

Amino Acid Metabolism, Inborn Errors↗

Biochemical, pathologic and behavioral analysis of a mouse model of glutaric acidemia type I.

Glutaric acidemia type I (GA-I) is an autosomal recessive disorder of amino acid metabolism resulting from a deficiency of glutaryl-CoA dehydrogenase (GCDH). Patients accumulate glutaric acid (GA) and 3-OH glutaric acid (3-OHGA) in their blood, urine and CSF. Clinically, GA-I is characterized by macrocephaly, progressive dystonia and dyskinesia. Degeneration of the caudate and putamen of the basal ganglia, widening of the Sylvian fissures, fronto-temporal atrophy and severe spongiform change in the white matter are also commonly observed. In this report we describe the phenotype of a mouse model of GA-I generated via targeted deletion of the Gcdh gene in embryonic stem cells. The Gcdh-/- mice have a biochemical phenotype very similar to human GA-I patients, including elevations of GA and 3-OHGA at levels similar to those seen in GA-I patients. The affected mice have a mild motor deficit but do not develop the progressive dystonia seen in human patients. Pathologically, the Gcdh-/- mice have a diffuse spongiform myelinopathy similar to that seen in GA-I patients. However, unlike in human patients, there is no evidence of neuron loss or astrogliosis in the striatum. Subjecting the Gcdh-/- mice to a metabolic stress, which often precipitates an encephalopathic crisis and the development of dystonia in GA-I patients, failed to have any neurologic effect on the mice. We hypothesize that the lack of similarity in regards to the neurologic phenotype and striatal pathology of GA-I patients, as compared with the Gcdh-/- mice, is due to intrinsic differences between the striata of mice and men.

Amino Acid Metabolism, Inborn Errors↗

The urinary excretion of glutarylcarnitine is an informative tool in the biochemical diagnosis of glutaric acidemia type I.

Glutaric acidemia type I (GA-1) is a progressive neurodegenerative inborn error of metabolism that typically manifests acutely in infants during an intercurrent illness. The diagnosis is established biochemically by the detection of glutaric acid and 3-hydroxy glutaric acid in urine and glutarylcarnitine in plasma. However, some patients excrete only small amounts of glutaric acid and may be overlooked, especially if the plasma concentration of glutarylcarnitine is not elevated. To test the hypothesis that measuring the excretion of glutarylcarnitine may improve the recognition of GA-1 patients without significant glutaric aciduria, urine glutarylcarnitine was analyzed in 14 cases. Five of them lacked significant glutaric aciduria, 9 (of 10 available) had a normal plasma glutarylcarnitine concentration. As controls, we also evaluated 54 subjects with glutaric aciduria secondary to other causes (16-7509 mmol/mol creatinine; reference range: <15; no significant amounts of 3-hydroxy glutaric acid detectable). The excretion of glutarylcarnitine was significantly elevated in all GA-1 patients (14-522 mmol/mol creatinine; reference range: <5.2) and in none of the controls with glutaric aciduria. These findings suggest that the urinary excretion of glutarylcarnitine is a specific biochemical marker of GA-1 which could be particularly useful in the work up of patients with suggestive clinical manifestations but without glutaric aciduria and with normal plasma acylcarnitine profiles.

Carnitine↗

Glutaric acidemia type 1.

Glutaric acidemias comprise different disorders resulting in an increased urinary excretion of glutaric acid. Glutaric acidemia type 1 (GA-1) is an autosomal recessive disorder of lysine, hydroxylysine, and tryptophan metabolism caused by deficiency of glutaryl-CoA dehydrogenase. It results in the accumulation of 3-hydroxyglutaric and glutaric acid. Affected patients can present with brain atrophy and macrocephaly and with acute dystonia secondary to striatal degeneration in most cases triggered by an intercurrent childhood infection with fever between 6 and 18 months of age. This disorder can be identified by increased glutaryl (C5DC) carnitine on newborn screening. Urine organic acid analysis indicates the presence of excess 3-OH-glutaric acid, and urine acylcarnitine profile shows glutaryl carnitine as the major peak. Therapy consists in carnitine supplementation to remove glutaric acid, a diet restricted in amino acids capable of producing glutaric acid, and prompt treatment of intercurrent illnesses. Early diagnosis and therapy reduce the risk of acute dystonia in patients with GA-1.

Amino Acid Metabolism, Inborn Errors↗

Antenatal diagnosis of glutaric acidemia.

Two pregnancies at risk for glutaric acidemia were monitored. In one, in which the fetus was not affected, glutaric acid was not detected in the amniotic fluid at amniocentesis (15 weeks) and the glutaryl-CoA dehydrogenase activity of cultured amniotic cells was normal. In the other, a marked elevation of glutaric acid in the amniotic fluid, together with deficiency of glutaryl-CoA dehydrogenase in amniotic cells, prompted termination of the pregnancy, and studies on the abortus confirmed the diagnosis of glutaric acidemia. Glutaric acidemia, is, thus, another inborn error of metabolism which can be diagnosed in utero.

Acyl Coenzyme A↗

On the neurotoxicity of glutaric, 3-hydroxyglutaric, and trans-glutaconic acids in glutaric acidemia type 1.

Glutaric acidemia type 1 (GA1) is an autosomal recessively inherited deficiency of glutaryl-CoA dehydrogenase. Accumulating metabolites, 3-hydroxyglutaric (3-OH-GA), glutaric (GA), and trans-glutaconic (TG) acids, have been proposed to be involved in the development of the striatal degeneration seen in children with GA1 via an excitotoxic mechanism. We have studied the extent to which 3-OH-GA, GA, and TG are neurotoxic and whether neurotoxicity is caused by an excitotoxic mechanism in which 3-OH-GA, GA, or TG overactivates N-methyl-D-aspartate (NMDA) receptors. In cultured mouse neocortical neurons, all three compounds were weakly neurotoxic, possibly through activation of NMDA receptors. However, further studies in the rat cortical wedge preparation and with NMDA receptors expressed in Xenopus oocytes could not confirm an interaction of the compounds with NMDA receptors. It is concluded that the metabolites 3-OH-GA, GA, and TG are only weak neurotoxins and that the neurodegenerative cascade destroying the striatum in patients with GA1 involves mainly mechanisms other than excitoxicity.

Animals↗

Recurrent and novel mutations of GCDH gene in Chinese glutaric acidemia type I families.

Glutaric acidemia type I is caused by mutations of the glutaryl-CoA dehydrogenase (GCDH) gene resulting in loss of GCDH enzyme activity. Patients present with progressive dystonia and lesions in basal ganglia. Dietary treatment, when instituted from the early neonatal period, markedly reduces dystonia and morbidity. Early diagnosis and prenatal diagnosis will be facilitated by knowledge of locally prevalent GCDH mutations. Several common GCDH mutations have been found in different ethnic groups. GCDH mutations were studied in 5 Chinese glutaric acidemia type I families. We detected two novel recurrent mutations (A219T and IVS10-2A>C) which were found in two unrelated families. An asymptomatic carrier of IVS10-2A>C was also found on screening of 120 individuals. Other mutations were identified, including two other novel (R386G & IVS3+1G>A) and two known mutations (G178R & R355H). Fibroblasts from patients carrying the novel mutations were confirmed to be deficient for GCDH activity. This is the first report of GCDH mutations describing recurrent mutations in Chinese patients. The carrier rate of IVS10-2A>C may be particularly high in Chinese.

Alternative Splicing↗

Deficiency of electron transfer flavoprotein or electron transfer flavoprotein:ubiquinone oxidoreductase in glutaric acidemia type II fibroblasts.

Glutaric acidemia type II (GA II) is a human genetic disorder. It has been suggested that the primary defect in this disorder is a deficiency of a protein involved in electron transport between the acyl-CoA dehydrogenases and the bc1 complex of the mitochondrial respiratory chain. Antisera were raised to purified porcine electron transfer flavoprotein (ETF) and electron transfer flavoprotein:ubiquinone oxidoreductase (ETF:QO). The antisera were used to detect the two electron transferases in control and GA II fibroblasts by immunoblotting. Fibroblasts from three unrelated GA II patients were deficient in immunologically detectable ETF:QO and extracts from these three fibroblast lines contained no detectable ETF:QO catalytic activity. Fibroblasts from parents of two of these patients had ETF:QO activity intermediate between activities in control fibroblasts and fibroblasts from the patients. These data indicate that the primary defect in these patients is a deficiency of ETF:QO and that the mode of transmission of the gene is autosomal recessive. Fibroblasts from two other patients with severe GA II had normal levels of ETF-QO activity and antigen but were deficient in immunoreactive ETF. These findings show that GA II results from a deficiency of ETF in some patients and ETF:QO in others. In addition, these investigations provide strong evidence for the specificity and physiological function of the iron-sulfur flavoprotein ETF:QO.

Animals↗

Neuropathological, biochemical and molecular findings in a glutaric acidemia type 1 cohort.

Glutaric acidemia type 1 (GA-1) is an autosomal recessive disorder characterized by a deficiency of glutaryl-CoA dehydrogenase (GCDH) activity. GA-1 is often associated with an acute encephalopathy between 6 and 18 months of age that causes striatal damage resulting in a severe dystonic movement disorder. Ten autopsy cases have been previously described. Our goal is to understand the disorder better so that treatments can be designed. Therefore, we present the neuropathological features of six additional cases (8 months-40 years), all North American aboriginals with the identical homozygous mutation. This cohort displays similar pathological characteristics to those previously described. Four had macroencephaly. All had striatal atrophy with severe loss of medium-sized neurons. We present several novel findings. This natural time course study allows us to conclude that neuron loss occurs shortly after the encephalopathical crisis and does not progress. In addition, we demonstrate mild loss of large striatal neurons, spongiform changes restricted to brainstem white matter and a mild lymphocytic infiltrate in the early stages. Reverse transcriptase-PCR to detect the GCDH mRNA revealed normal and truncated transcripts similar to those in fibroblasts. All brain regions demonstrated markedly elevated concentrations of GA (3770-21 200 nmol/g protein) and 3-OH-GA (280-740 nmol/g protein), with no evidence of striatal specificity or age dependency. The role of organic acids as toxic agents and as osmolytes is discussed. The pathogenesis of selective neuronal loss cannot be explained on the basis of regional genetic and/or metabolic differences. A suitable animal model for GA-1 is needed.

Adolescent↗

Glutaric acidemia type II: neuroimaging and spectroscopy evidence for developmental encephalomyopathy.

Glutaric acidemia type II is associated with neonatal hypoketotic hypoglycemia, metabolic acidosis, profound hypotonia, progressive cardiomyopathy, and early death. Deficiency of either electron transfer flavoprotein or electron transport flavoprotein:ubiquinone oxidoreductase leads to intramitochondrial accumulation of metabolites of compounds oxidized by enzymes that transfer electrons to flavoprotein. No detailed results of antemortem neuroimaging or magnetic resonance spectroscopy have been described previously. We investigated a patient with typical neonatal onset glutaric acidemia type II without obvious dysmorphogenesis or renal malformations. Cranial tomographic scan revealed hypoplastic temporal lobes and marked widening of the sylvian fissures ("bat-wing" appearance). Cranial magnetic resonance imaging documented underdeveloped frontal and temporal lobes with delayed myelination and hypoplasia of the corpus callosum. 31P-Magnetic resonance spectroscopy of muscle was grossly abnormal with a very low energy state consistent with mitochondrial dysfunction. 1H-Magnetic resonance spectroscopy of brain revealed elevated intracerebral lactate concentration and abnormally high choline/creatine ratio suggestive of dysmyelination. These findings constitute the first in vivo evidence of a developmental encephalomyopathy in glutaric acidemia type II.

Age of Onset↗

Morphologic studies of the placenta and autopsy findings in neonatal-onset glutaric acidemia type II.

A case of neonatal-onset glutaric acidemia type II with electron-transfer flavoprotein (ETF) deficiency is presented. The morphological pattern of disease in the male infant included hypospadias, cryptorchidism, bilateral 13 ribs, nuclear cataract, cystic dysplasia of kidneys, lipid accumulation in the liver and renal tubular epithelium, and immature brain with white matter gliosis. The morphologic examination of the placenta revealed features of delayed maturation, including large-for-gestational-age size and abundant immature intermediate villi with cellular syncytiotrophoblast, persistent villous cytotrophoblast, and decreased syncytial knots. In addition, immature intermediate villi showed exaggeration of lacunar interstitial spaces consistent with non-hydropic villous edema. Marked lipid accumulation was seen within extravillous trophoblasts of placental septa and cell islands. Light lipid accumulation was also noted within fibroblasts of stem villi. These findings suggest that in glutaric acidemia type II, fatty acid oxidation could also be affected in the placenta.

Abnormalities, Multiple↗

Glutaric acidemia type II: heterogeneity of clinical and biochemical phenotypes.

We have examined 23 fibroblast lines from patients with neonatal and late onset glutaric acidemia type II and fibroblasts from four parents of these patients. Fifteen of these patients are previously unreported. Results of these investigations show deficiency of electron transfer flavoprotein or electron transfer flavoprotein-ubiquinone oxidoreductase activity in all of the patients' fibroblasts. Immunoblots indicate that the steady state levels of the antigens is very low or undetectable in most of the neonatal onset patients; however, cross-reacting antigen without electron transfer activity is observed in several glutaric acidemia type II fibroblast lines. Assay of parental lines confirm the autosomal transmission of deficiencies of proteins. Of particular interest is the clinical heterogeneity among these patients. Patients may present with an extrapyramidal movement disorder as observed in glutaric aciduria type I, without the typical organic aciduria typical of glutaric acidemia type II even in the presence of severe enzyme deficiency, or with renal cystic dysplasia accompanying electron transfer flavoprotein deficiency. Renal cystic dysplasia had previously been reported only in patients with electron transfer flavoprotein-ubiquinone oxidoreductase deficiency.

Cell Line↗

Age at symptom onset predicts severity of motor impairment and clinical outcome of glutaric acidemia type 1.

OBJECTIVES: In patients with glutaric acidemia type 1 (GAI), biochemical and molecular markers fail to predict the course of individual patients; therefore we sought to identify nonbiochemical variables that correlate with severity of motor deficits or overall clinical outcome. STUDY DESIGN: Archival data was collected from 42 published articles describing 115 patients with GA1. A forward, stepwise, multiple regression analysis was used to find predictors for outcome. RESULTS: Analyses show that in patients who did not have a precipitating illness before the first appearance of motor symptoms, the age at onset was significantly associated with the severity of motor impairments and overall clinical outcome. In patients who had a precipitating illness, the age at onset did not predict the outcome. In both groups of patients, basal ganglia degeneration, enlargement of spaces containing cerebrospinal fluid, and white matter abnormalities were indicative of a poorer prognosis. Treatment given after the appearance of symptoms was not associated with a better clinical outcome or fewer motor deficits. CONCLUSION: Because the age at symptom onset can significantly predict the severity of motor deficits and the overall outcome, it is important to identify patients with GA1 as early as possible. Several studies suggest that presymptomatic treatment may prevent or postpone the onset of symptoms.

Age of Onset↗

Outcome of the first 3-years of a DNA-based neonatal screening program for glutaric acidemia type 1 in Manitoba and northwestern Ontario, Canada.

Glutaric acidemia type 1 (GA1) is overrepresented in the aboriginal population of Island Lake, Manitoba, and northwestern Ontario who speak the Ojibway-Cree (Oji-Cree) dialect. The carrier frequency in these communities has been predicted to be as high as 1 in 10 individuals. Prior to beginning newborn screening for GA1 in May 1998, 18 of 20 affected patients diagnosed at this center have been from these high-risk communities. Most have followed an acute encephalopathic course with permanent neurologic sequelae and high mortality. They excrete small amounts of glutaric acid and 3-hydroxyglutaric acid and have significant residual enzyme activity. A single homozygous mutation in glutaryl-CoA-dehydrogenase (GCDH IVS-1 + 5g right arrow t) has been identified in this population. DNA-based newborn screening targeted to our high-risk communities was begun in order to provide presymptomatic detection and treatment of affected patients. Of the first 1176 newborns screened, 4 affected infants were identified and treated with a low-protein diet, carnitine, and riboflavin. All 4 infants have required numerous hospitalizations for treatment of intercurrent illnesses. Eventually, 3 infants presented with acute dystonic encephalopathy and seizures along with permanent neurological sequelae. One of these infants died unexpectedly at home at 18 months of age. The fourth, now 9 months old, has had a gastrostomy tube placed to facilitate fluid replacement in addition to a standard treatment protocol and is doing well. The reasons for our initial disappointing outcomes in the first 3 of 4 affected babies are likely multiple. Based on our early experience and that of other centers screening newborns for GA1, current therapeutic strategies may be insufficient in preventing the occurrence of neurologic sequelae in some children. An incomplete understanding of the neurotoxic mechanisms underlying this devastating disorder hampers effective management.

Canada↗

CT and MR of the brain in glutaric acidemia type I: a review of 59 published cases and a report of 5 new patients.

PURPOSE: To identify a pattern of findings on CT or MR of the brain in glutaric acidemia type I typical enough to permit a correct diagnosis. METHODS: Clinical history and findings and brain CT and MR results in 59 previously reported patients (MR in 12) and in 5 new patients (all examined with MR and 3 also with CT) were reviewed. RESULTS: In half the patients macrocephaly was present, and in half the onset was acute, often following infection and mimicking encephalitis. Although brain atrophy or hypoplasia was found in 61% and white matter changes in 51% of the patients, open opercula (usually very widely open) and often also wide cerebrospinal fluid spaces anterior to the temporal lobes were seen in 93%. Basal ganglia lesions, presenting as volume loss and high T2 signal in the caudate head and often also the lentiform nucleus bilaterally, were found in 44% and extracerebral fluid collections in 7 of 64 patients. CONCLUSION: The finding of very widely open opercula suggests glutaric acidemia type I, and if combined with basal ganglia lesions is almost pathognomonic, especially in a child with macrocephaly.

Atrophy↗

Glutaryl-CoA dehydrogenase mutations in glutaric acidemia (type I): review and report of thirty novel mutations.

Glutaric acidemia type I (GA1) is caused by mutations in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCD). Sixty-three pathogenic mutations identified by several laboratories are presented, 30 of them for the first time, together with data on expression in Escherichia coli and relationship to the clinical and biochemical phenotype. In brief, many GCD mutations cause GA1, but none is common. There is little if any relationship between genotype and clinical phenotype, but some mutations, even when heterozygous, seem especially common in patients with normal or only minimally elevated urine glutaric acid.

Amino Acid Metabolism, Inborn Errors↗

Glutaric acidemia: a metabolic disorder causing progressive choreoathetosis.

A boy with glutaric acidemia had psychomotor retardation first noted at age 6 months, recurrent metabolic acidosis, and a progressive quadriparesis with choreoathetosis. He died at age 3 1/2 years. Cultured skin fibroblasts lacked glutaryl-CoA dehydrogenase activity. There was a biochemical, but not a clinical, response to dietary restriction of lysine and tryptophan. The caudate and putamen of the brain showed severe loss of nerve cells and fibers with proliferation of astrocytes, as well as markedly reduced gamma-aminobutyric acid and glutamate decarboxylase activity.

Acidosis↗