Malonic aciduria

Case report: A novel 5'-UTR-exon1-intron1 deletion in MLYCD in an IVF child with malonyl coenzyme A decarboxylase deficiency and literature review

The subject of the study is an 11-month old IVF baby girl with the typical clinical manifestation of malonyl coenzyme A decarboxylase deficiency, including developmental delay, limb weakness, cardiomyopathy, and excessive excretion of malonic acid and methylmalonic acid. Whole genome sequencing (WGS) revealed a novel heterozygous nonsense mutation (c.672delG, p.Trp224Ter) in the MLYCD gene of the proband and her father and a novel heterozygous deletion in 5'-UTR-exon1-intron1 of the MLYCD gene of the proband and her mother. The patient's cardiac function and limb weakness improved considerably after 3 months of a low-fat diet supplemented with L-carnitine. Furthermore, mapping of gene mutations and clinical manifestations was done by case collection.

Heterogenous Clinical Landscape in a Consanguineous Malonic Aciduria Family

Malonic aciduria is an extremely rare inborn error of metabolism due to malonyl-CoA decarboxylase deficiency. This enzyme is encoded by the MLYCD (Malonyl-CoA Decarboxylase) gene, and the disease has an autosomal recessive inheritance. Malonic aciduria is characterized by systemic clinical involvement, including neurologic and digestive symptoms, metabolic acidosis, hypoglycemia, failure to thrive, seizures, developmental delay, and cardiomyopathy. We describe here two index cases belonging to the same family that, despite an identical genotype, present very different clinical pictures. The first case is a boy with neonatal metabolic symptoms, abnormal brain MRI, and dilated cardiomyopathy. The second case, the cousin of the first patient in a consanguineous family, showed later symptoms, mainly with developmental delay. Both patients showed high levels of malonylcarnitine on acylcarnitine profiles and malonic acid on urinary organic acid chromatographies. The same homozygous pathogenic variant was identified, c.346C > T; p. (Gln116*). We also provide a comprehensive literature review of reported cases. A review of the literature yielded 52 cases described since 1984. The most common signs were developmental delay and cardiomyopathy. Increased levels of malonic acid and malonylcarnitine were constant. Presentations ranged from neonatal death to patients surviving past adolescence. These two cases and reported patients in the literature highlight the inter- and intrafamilial variability of malonic aciduria.

A novel frameshift mutation of malonyl-CoA decarboxylase deficiency: clinical signs and therapy response of a late-diagnosed case

We evaluate the clinical findings and the treatment response of a late‐diagnosed case with a novel homozygous insertion c.13_14insG (p.P6Afs*202) result in a frameshift mutation in MLYCD gene. Both cardiac and neurologic involvements were mild when compared to previously reported cases, and see low‐fat/high‐carbohydrate diet treatment is highly effective.

A new case of malonyl-CoA decarboxylase deficiency with mild clinical features

Malonyl-CoA decarboxylase deficiency is an extremely rare autosomal recessive inborn error of fatty acid metabolism. It usually follows a severe disease course and presents poor prognosis without treatment. Here, we report an affected female juvenile with a mild clinical and biochemical phenotype who mainly featured poor schooling without cardiomyopathy and metabolic acidosis. She was suspected of malonyl-CoA decarboxylase deficiency due to a 57-kb deletion in 16q23.3 encompassing the MLCYD gene revealed by chromosome microarray. Malonyl-CoA decarboxylase deficiency was then confirmed by acylcarnitine analysis and organic acid analysis. Real-time PCR analysis of the patient revealed the first three exon deletion of the MLYCD gene, which was maternally inherited. DNA sequencing of the MLYCD gene of the patient identified a novel heterozygous mutation (c.911G>A, p.G304E) in exon 4 that was paternally inherited. The patient urine malonic acid dissolved and had a better school record in 6 month after initiation of fat-limited diet. At 1 year post treatment, the blood malonylcarnitine level decreased remarkably. Our result expands the phenotype of malonyl-CoA decarboxylase deficiency and suggests attentions should be paid to the mild form of disorders, for example, malonyl-CoA decarboxylase deficiency, which usually present a severe disease course.

Malonyl-CoA decarboxylase deficiency: long-term follow-up of a patient new clinical features and novel mutations

BACKGROUND

Malonyl-CoA decarboxylase (MLYCD, EC 4.1.1.9) deficiency is a rare autosomal recessive disorder that is widely diagnosed by neonatal screening.

METHODS

We report long term follow up of a patient with MLYCD deficiency showing signs of neonatal hypoglycemia, mental retardation, developmental delay and rheumatoid arthritis. Brain MRI revealed patchy, symmetrical hyperintensity of the deep white matter with periventricular white matter and subcortical arcuate fibers being spared. MLCYD gene sequence analysis was done to identify possible mutations. Expression analyses at mRNA and protein levels were also performed. Further, immunocytochemical studies were implemented to check for its subcellular localization.

RESULTS

MLYCD gene sequencing identified a novel compound heterozygous mutation (c.22 T>A, p.M1K, c.454 C>A; pH152N) in our patient and a heterozygous mutation in the healthy mother c.22 T>A; pM1K. Reduced expression of RNA and protein levels was observed. Immunocytochemical analysis showed diffused staining across the cytoplasm with apparent signs of intracellular mislocalization to the nucleus. RESULTS also indicated subcellular colocalization of MLCYD with mitochondria was scant compared to control.

CONCLUSION

Our patient was identified with a novel compound heterozygous MLYCD mutation at the N-terminal helical domain. This study indicates that protein mislocalization is a characteristic feature of MLYCD deficiency in our patient.

A new case of malonic aciduria with a presymptomatic diagnosis and an early treatment

Malonyl-CoA decarboxylase deficiency (MLYCD) is a rare autosomal recessive inborn error of metabolism presenting a variable clinical phenotype. We report an affected Italian male receiving an early diagnosis (8days after birth) and a timely dietary therapy (high carbohydrate, low long chain fatty acid and medium chain triglyceride supplemented diet with l-carnitine supplementation). The boy was born at term and presented normal function of the heart (except for a tricuspid Ebstein-like dysplasia) and neurodevelopmental status. Genomic sequencing of MLYCD gene revealed two point mutations (c.672G>A, c.869C>T) not listed in the Human MLYCD Allelic Variant Database nor in Human Gene Mutation Database, responsible for a deleterious effect on protein structure and function according to a computational analysis (MuPro, SIFT, ConSEQ v1.1). At the age of 2years he only showed a mild language and psychomotor delay, while heart functioning became normal. Brain MRI examination was normal. Thirty-five cases, including our patient, have been described to date. This is the first report concerning a malonic aciduria patient diagnosed on newborn screening and treated in a presymptomatic stage of the disease.

Novel compound heterozygous mutation of MLYCD in a Chinese patient with malonic aciduria

A 3-year-old Chinese boy presented with prominent clinical features of malonic aciduria, including developmental delay, short stature, brain abnormalities and massive excretion of malonic acid and methylmalonic acid. Molecular characterization by DNA sequencing analysis and multiplex ligation-dependent probe amplification of the MLYCD gene revealed a heterozygous mutation (c.920T>G, p.Leu307Arg) in the patient and his father and a heterozygous deletion comprising exon 1 in the patient and his mother. The missense mutation (c.920T>G) was not found in 100 healthy controls and has not been reported previously. Our findings expand the number of reported cases and add a novel entry to the repertoire of MLYCD mutations.

Fatal malonyl CoA decarboxylase deficiency due to maternal uniparental isodisomy of the telomeric end of chromosome 16

Malonic aciduria is a rare autosomal recessive disorder caused by deficiency of malonyl-CoA decarboxylase, encoded by the MLYCD gene. We report on a patient with clinical presentation in the neonatal period. Metabolic investigations led to a diagnosis of malonyl-CoA decarboxylase deficiency, confirmed by decreased activity in cultured fibroblasts. High doses of carnitine and a diet low in lipids led to a reduction in malonic acid excretion, and to an improvement in his clinical conditions, but at the age of 4 months he died suddenly and unexpectedly. No autopsy was performed. Molecular analysis of the MLYCD gene performed on the proband's RNA and genomic DNA identified a previously undescribed mutation (c.772-775delACTG) which was homozygous. This mutation was present in his mother but not in his father; paternity was confirmed by microsatellite analysis. A hypothesis of maternal uniparental disomy (UPD) was investigated using fourteen microsatellite markers on chromosome 16, and the results confirmed maternal UPD. Maternal isodisomy of the 16q24 region led to homozygosity for the MLYCD mutant allele, causing the patient's disease. These findings are relevant for genetic counselling of couples with a previously affected child, since the recurrence risk in future pregnancies is dramatically reduced by the finding of UPD. In addition, since the patient had none of the clinical manifestations previously associated with maternal UPD 16, this case provides no support for the existence of maternally imprinted genes on chromosome 16 with a major effect on phenotype.

Nonezymatic formation of succinate in mitochondria under oxidative stress

The products of the reactions of mitochondrial 2-oxo acids with hydrogen peroxide and tert-butyl hydroperoxide (tert-BuOOH) were studied in a chemical system and in rat liver mitochondria. It was found by HPLC that the decarboxylation of alpha-ketoglutarate (KGL), pyruvate (PYR), and oxaloacetate (OA) by both oxidants results in the formation of succinate, acetate, and malonate, respectively. The two latter products do not metabolize in rat liver mitochondria, whereas succinate is actively oxidized, and its nonenzymatic formation from KGL may shunt the tricarboxylic acid (TCA) cycle upon inactivation of alpha-ketoglutarate dehydrogenase (KGDH) under oxidative stress, which is inherent in many diseases and aging. The occurrence of nonenzymatic oxidation of KGL in mitochondria was established by an increase in the CO(2) and succinate levels in the presence of the oxidants and inhibitors of enzymatic oxidation. H(2)O(2) and menadione as an inductor of reactive oxygen species (ROS) caused the formation of CO(2) in the presence of sodium azide and the production of succinate, fumarate, and malate in the presence of rotenone. These substrates were also formed from KGL when mitochondria were incubated with tert-BuOOH at concentrations that completely inhibit KGDH. The nonenzymatic oxidation of KGL can support the TCA cycle under oxidative stress, provided that KGL is supplied via transamination. This is supported by the finding that the strong oxidant such as tert-BuOOH did not impair respiration and its sensitivity to the transaminase inhibitor aminooxyacetate when glutamate and malate were used as substrates. The appearance of two products, KGL and fumarate, also favors the involvement of transamination. Thus, upon oxidative stress, nonenzymatic decarboxylation of KGL and transamination switch the TCA cycle to the formation and oxidation of succinate.

Succinate causes oxidative damage through N-methyl-d-aspartate-mediated mechanisms

In this study we investigated whether succinate, the accumulating substrate in succinate dehydrogenase (SDH) deficiencies and SDH inhibitor intoxication, causes lipoperoxidation and protein carbonylation, and if NMDA receptors are involved in the succinate-induced oxidative damage. Adult male mice (30-40 g) received an intracerebroventricular injection of succinic acid (0.7, 1.0 and 1.7 micromol/5 microl) or 0.9% NaCl (5 microl) and had their exploratory behavior assessed in an open field for 10 min. Succinate (0.7 and 1.0 micromol/5 microl) decreased locomotor activity behavior and increased thiobarbituric acid reactive substances (TBARS) and protein carbonylation in the forebrain. Conversely, 1.7 micromol of succinate did not alter locomotor activity or oxidative damage parameters. The involvement of NMDA receptors in the succinate-induced increase of total protein carbonylation content and exploratory behavior inhibition was assessed by co-administrating MK-801 (7 nmol/2.5 microl icv), a noncompetitive NMDA receptor antagonist, with succinate (1 micromol/2.5 microl icv). The co-administration of MK-801 protected against succinate-induced increase of total protein carbonylation and decrease of locomotor activity. These results suggest the involvement of NMDA receptors in these effects of succinate, which may of particular relevance for succinate-accumulating conditions, such as SDH inhibitors intoxication and inherited SDH deficiencies.

Intrastriatal malonate administration induces convulsive behaviour in rats

Malonic acidaemia is an inborn error of metabolism that accumulates malonate, a competitive succinate dehydrogenase (SDH; EC 1.3.99.1) inhibitor. The present study investigated the behavioural effects of unilateral intrastriatal administration of malonate (0.6, 1.8 or 6 micromol) in adult male Wistar rats (n=10-13). Low doses of malonate (1.8 micromol) decreased exploratory activity and caused ipsiversive rotational behaviour. High doses of malonate (6 micromol) induced contralateral rotational behaviour and convulsive episodes. Malonate competitively inhibited SDH in mitochondrion-enriched fractions from striatum ( Ki=0.034+/-0.008 mmol/L). Interestingly, methylmalonate, which is a weaker SDH inhibitor than malonate (Ki=4.22+/-1.3 mmol/L), induced more convulsions than malonate at equimolar doses and did not cause ipsiversive rotational behaviour. It is suggested that the potency of SDH inhibition in vitro does not correlate positively with the convulsant potential of these inhibitors in vivo.

Succinate increases neuronal post-synaptic excitatory potentials in vitro and induces convulsive behavior through N-methyl-d-aspartate-mediated mechanisms

Succinate is a dicarboxylic acid that accumulates due to succinate dehydrogenase inhibition by malonate and methylmalonate exposure. These neurotoxins cause increased excitability and excitotoxic damage, which can be prevented by administering high amounts of succinate. In the present study we investigated whether succinate alters hippocampal field excitatory post-synaptic potentials. Bath application of succinate at intermediate concentrations (0.3-1 mM) increased the slope of field excitatory post-synaptic potentials in hippocampal slices, and at high concentrations (above 1 mM) did not alter or decrease field excitatory post-synaptic potentials slope. Succinate-induced enhancement of field excitatory post-synaptic potentials slope was abolished by the addition of d-2-amino-5-phosphonovaleric acid (50 microM) to the perfusate, supporting the involvement of N-methyl-d-aspartate receptors in the excitatory effect of this organic acid. Accordingly, succinate (0.8-7.5 micromol) i.c.v. administration caused dose-dependent convulsive behavior in mice. The i.c.v. co-administration of MK-801 (7 nmol) fully prevented succinate-induced convulsions, further suggesting the involvement of N-methyl-d-aspartate receptors in the convulsant action of succinate. Our data indicate that accumulation of moderate amounts of succinate may contribute to the excitotoxicity induced by succinate dehydrogenase inhibitors, through the activation of N-methyl-d-aspartate receptors.

Genomic organization and characterization of the promoter of rat malonyl-CoA decarboxylase gene

Malonyl-CoA decarboxylase (MCD) catalyzes the decarboxylation of malonyl-CoA, an elongating agent for fatty acid synthesis and also known as a fuel-sensing mediator. In order to elucidate the genome organization, we isolated a 2020 bp rat MCD cDNA from rat brain cDNA library and isolated the corresponding rat genomic clones from the rat genomic PAC library. Sequencing and comparison of these clones showed that the MCD genome consists of five exons and four introns spanning approximately 17 kb. The proximal upstream region is GC-rich, lacks a TATA box, and contains a variety of putative transcriptional regulatory elements within 2 kb. A major transcriptional initiation site was identified by a primer extension at a site 157 nucleotides upstream of the translational initiation site. To investigate the transcriptional regulation of MCD, a series of 5'-deletion constructs of the 5'-flanking region were generated and cloned upstream from the luciferase reporter gene. By comparing promoter activity in CV-1 cells, we suggest that an area of -15 bp 5' from the first exon acted as a basal promoter for MCD and that there are positive cis-regulatory elements in the region from -55 to -325 bp and negative regulator elements in the region -1380 to -2240 bp.

Rat Malonyl-CoA Decarboxylase; Cloning, Expression in E. coli and its Biochemical Characterization

Malonyl-CoA decarboxylase (E.C.4.1.1.9) catalyzes the conversion of malonyl-CoA to acetyl-CoA. Although the metabolic role of this enzyme has not been fully defined, it has been reported that its deficiency is associated with mild mental retardation, seizures, hypotonia, cadiomyopathy, developmental delay, vomiting, hypoglycemia, metabolic acidosis, and malonic aciduria. Here, we isolated a cDNA clone for malonyl CoA decarboxylase from a rat brain cDNA library, expressed it in E. coli, and characterized its biochemical properties. The full-length cDNA contained a single open-reading frame that encoded 491 amino acid residues with a calculated molecular weight of 54, 762 Da. Its deduced amino acid sequence revealed a 65.6% identity to that from the goose uropigial gland. The sequence of the first 38 amino acids represents a putative mitochondrial targeting sequence, and the last 3 amino acid sequences (SKL) represent peroxisomal targeting ones. The expression of malonyl CoA decarboxylase was observed over a wide range of tissues as a single transcript of 2.0 kb in size. The recombinant protein that was expressed in E. coli was used to characterize the biochemical properties, which showed a typical Michaelis-Menten substrate saturation pattern. The Km and Vmax were calculated to be 68 microM and 42.6 micromol/min/mg, respectively.

Malonyl CoA decarboxylase deficiency: C to T transition in intron 2 of the MCD gene

Malonyl CoA decarboxylase (MCD) is an enzyme involved in the metabolism of fatty acids synthesis. Based on reports of MCD deficiency, this enzyme is particular important in muscle and brain metabolism. Mutations in the MCD gene result in a deficiency of MCD activity, that lead to psychomotor retardation, cardiomyopathy and neonatal death. To date however, only a few patients have been reported with defects in MCD. We report here studies of a patient with MCD deficiency, who presented with hypotonia, cardiomyopathy and psychomotor retardation. DNA sequencing of MCD revealed a homozygous intronic mutation, specifically a -5 C to T transition near the acceptor site for exon 3. RT-PCR amplification of exons 2 and 3 revealed that although mRNA from a normal control sample yielded one major DNA band, the mutant mRNA sample resulted in two distinct DNA fragments. Sequencing of the patient's two RT-PCR products revealed that the larger molecular weight fragments contained exons 2 and 3 as well as the intervening intronic sequence. The smaller size band from the patient contained the properly spliced exons, similar to the normal control. Western blotting analysis of the expressed protein showed only a faint band in the patient sample in contrast to a robust band in the control. In addition, the enzyme activity of the mutant protein was lower than that of the control protein. The data indicate that homozygous mutation in intron 2 disrupt normal splicing of the gene, leading to lower expression of the MCD protein and MCD deficiency.

Malonic aciduria in Maltese dogs: normal methylmalonic acid concentrations and malonyl-CoA decarboxylase activity in fibroblasts

A family of Maltese dogs with malonic aciduria is reported. The propositus presented at 3 years of age with episodes of seizures and stupor with hypoglycaemia, acidosis, and ketonuria. Urinary organic acid assays showed elevated malonic acid without elevation of methylmalonic acid. Cultured fibroblasts had normal malonyl-CoA decarboxylase activity. Treatment with frequent feedings of a low-fat diet high in medium-chain triglycerides resulted in normalization of clinical signs and a resolution of the malonic aciduria. Two full siblings of the propositus had died at a young age of undiagnosed metabolic and neurological disease. Urine organic acid assays were performed on other family members. A half-sister showed mild malonic aciduria and other organic acid changes similar to the propositus, while the mother and half-brother showed mildly elevated ketone bodies. This family suggests further genetic and clinical heterogeneity in the malonic acidurias.

Combined malonic and methylmalonic aciduria with normal malonyl-coenzyme A decarboxylase activity: a case supporting multiple aetiologies

We identified a patient who excreted large amounts of methylmalonic acid and malonic acid. In contrast to other patients who have been described with combined methylmalonic and malonic aciduria, our patient excreted much larger amounts of methylmalonic acid than malonic acid. Since most previous patients with this biochemical phenotype have been reported to have deficiency of malonyl-CoA decarboxylase, we assayed malonyl-CoA decarboxylase activity in skin fibroblasts derived from our patient and found the enzyme activity to be normal. We examined four isocaloric (2000 kcal/day) dietary regimes administered serially over a period of 12 days with 3 days devoted to each dietary regimen. These diets were high in carbohydrate, fat or protein, or enriched with medium-chain triglycerides. Diet-induced changes in malonic and methylmalonic acid excretion became evident 24-36 h after initiating a new diet. Total excretion of malonic and methylmalonic acid was greater (p < 0.01) during a high-protein diet than during a high-carbohydrate or high-fat diet. A high-carbohydrate, low-protein diet was associated with the lowest levels of malonic and methylmalonic acid excretion. Perturbations in these metabolites were most marked at night. On all dietary regimes, our patient excreted 3-10 times more methylmalonic acid than malonic acid, a reversal of the ratios reported in patients with malonyl-CoA decarboxylase deficiency. Our data support a previous observation that combined malonic and methylmalonic aciduria has aetiologies other than malonyl-CoA decarboxylase deficiency. The malonic acid to methylmalonic acid ratio in response to dietary intervention may be useful in identifying a subgroup of patients with normal enzyme activity.

Neurological dysfunction in methylmalonic acidaemia is probably related to the inhibitory effect of methylmalonate on brain energy production

Methylmalonic acidaemia is an inherited metabolic disorder caused by a severe deficiency of the activity of the enzyme L-methylmalonyl-CoA mutase or its cofactor 5'-deoxyadenosylcobalamin, resulting in tissue accumulation of large quantities of methylmalonic acid. Among the various clinical features, neurological symptoms are frequently observed. Patients may present cerebral atrophy and basal ganglia abnormalities are common. In the present report, we update the current knowledge on the influence of methylmalonic acid on brain metabolism in the hope of better understanding the neurological dysfunction characteristic of methylmalonic acidaemia. We present evidence showing that the metabolite inhibits brain energy production by various mechanisms and propose that a fall in cellular ATP generation leading to excitotoxicity is crucial for the occurrence of the neurological damage observed in these patients.

Methylmalonic and malonic aciduria in a dog with progressive encephalomyelopathy

A 12 week old female Labrador retriever dog with signs of progressive diffuse degeneration of the brain and spinal cord was found to have methylmalonic and malonic aciduria. Over a 5 month period, the dog developed neurologic signs compatible with disease of the central nervous system with predominant diffuse cerebral and right lateralizing brainstem deficits. Gross pathological examination of the brain showed that the lateral, third, and fourth ventricles of the brain were markedly enlarged and associated with white and grey matter atrophy. Syringomyelia and hydromyelia of the central canal into the dorsal funiculus of the spinal cord beginning at the level of the cervical intumescence and extending to the lumbar intumescence was also present. Significant biochemical abnormalities include methylmalonic and malonic aciduria, mild lactic and pyruvic aciduria. There was also accumulation of citric acid cycle intermediates including succinic, aconitic, and fumaric acids. Disordered fatty acid oxidation was suggested by increased excretion of adipic, ethylmalonic, suberic and sebacic acids. Neither ketoacidosis nor hyperammonemia were present, and serum cobalamin levels were normal. Overall, this dog demonstrates an inborn error of metabolism resulting in abnormal organic acid accumulation associated with a neurodegenerative disease.

CT and MR of the brain in the diagnosis of organic acidemias. Experiences from 107 patients

The results of CT and/or MRI of the brain in 107 patients with different types of organic acidemia are presented. The CSF spaces were wide in more than two-thirds of the patients, in 46 slightly-to-moderately and in 26 markedly-to-severely dilated. Marked widening of the operculae was found in all 5 patients with glutaric acidemia type 1, but open opercula was also found in other organic acidemias. White matter changes were found in about half the patients, in 28 mildly-to-moderately pronounced, in another 28 marked or severe. Basal ganglia or central pathway pathology was seen in a total of 34 patients, i.e. 32%. These changes in 25 patients involved the caudate and/or lentiform nuclei: in 14 cases the T2 signal was increased and volume loss was present, in 9 cases increased T2 signal with preserved volume was found (in one of these the changes were transient). In 2 patients, both with ethylmalonic aciduria (cause unknown), only small high T2 spots were seen in the caudate heads and the putamina. In 4 patients, all suffering from methylmalonic acidemia, only the globus pallidus was affected. In 3 patients, all with beta-ketothiolase deficiency, high T2 intensity changes were seen only in the postero-lateral putamina. The remaining 8 patients represent a variety of different locations of lesions. The CT or MRI findings in many patients with organic acidemias should alert the radiologist that a neurometabolic disorder may be present; in some cases the location and appearance of the lesions may even suggest the correct diagnosis.

A new patient with alpha-ketoglutaric aciduria and progressive extrapyramidal tract disease

A 4.5-year-old boy with chronic progressive encephalopathy is described. The clinical presentation initially included seizures and hypotonia which later evolved into severe extrapyramidal disease and dementia. The gas chromatography/mass spectrometry (GC/MS) analysis of urine indicated that alpha-ketoglutarate was increased 210 times and aconitic acid 80 times. No disturbance of acid/base balance, lactic acid or ammonia metabolism accompanied this clinical picture. The fibroblasts contained 29% of normal alpha-ketoglutarate dehydrogenase activity, while the activity of another mitochondrial marker enzyme, glutamate dehydrogenase, was normal. The neuroimaging studies revealed bilateral striatal necrosis. The clinical and biochemical findings were almost identical to two previously reported patients. Experience with this patient emphasizes the need for detailed organic acid biochemical investigation in any progressive encephalopathy and that extrapyramidal tract signs should evoke the possibility of alpha-ketoglutaric aciduria, among other 'neurologic organic acidemias'.

Neurophysiologic correlates of organic acidemias: a survey of 107 patients

The files of 107 patients with 19 different types of organic acidemia were reviewed retrospectively. Approximately 50% of the patients had abnormal electroencephalogram (EEG) at the time of initial study. In patients who had serial studies, the EEG deteriorated in 38% and improved in 15%. The predominant EEG abnormality encountered was slowing of the background activity in various degrees. Focal or generalized paroxysmal activity occurring in conjunction with slow background activity indicated a poor prognosis. Brainstem auditory evoked potentials (BAEP), visual evoked potentials (VEP), and somatosensory evoked potentials (SEP) were analyzed. The VEP was abnormal in 44%, BAEP in 39%, and SEP in 29% of the patients. Given the magnitude and frequency by which neurophysiological abnormalities occur in organic acidemias, neurophysiology testing provides complementary functional information and has an important place in the clinical work-up of these diseases.