Aciduria Research Articles

Neurological manifestations of organic acidurias.

Organic acidurias (OADs) are inherited neurometabolic diseases largely caused by deficiencies in enzymes involved in amino acid degradation, which result in accumulation of organic acids in the brain and other tissues. Disease presentation usually occurs in infancy, although late-onset variants can emerge during childhood or adulthood. Patients predominantly manifest with acute encephalopathy with life-threatening systemic manifestations (classical OADs) or progressive neurological symptoms (cerebral OADs), leading to permanent cerebral abnormalities. Some OADs are treatable, and early diagnosis and treatment implementation have substantially decreased the mortality and overall morbidity from OADs. However, long-term irreversible cerebral and systemic complications are frequent because the therapeutic options are currently limited. The pathophysiology of brain dysfunction is still unclear in most OADs, andfurther investigation is needed to enable the development of novel therapeutic strategies. ThisReview focuses on current knowledge of the OADs, including epidemiology, short-term and long-term neurological and systemic features, diagnosis and prognosis, and recent advances in therapy and pathophysiology. The goal of the article is to alert neurologists and related health professionals to the existence and importance of these neurometabolic diseases and to stimulate research into the damaging factors that contribute to their neurodegenerative sequelae.

Formation of 3-hydroxyglutaric acid in glutaric aciduria type I: in vitro participation of medium chain acyl-CoA dehydrogenase.

3‐Hydroxyglutaric acid (3‐OH‐GA) in urine has been identified as the most reliable diagnostic marker for glutaric aciduria type I (GA I). We showed that hydratation of glutaconyl‐CoA to 3‐hydroxyglutaryl‐CoA, which is subsequently hydrolyzed to 3‐OH‐GA, is efficiently catalyzed by 3‐methylglutaconyl‐CoA hydratase (3‐MGH). We have now investigated whether mitochondrial acyl‐CoA‐dehydrogenases can convert glutaryl‐CoA to glutaconyl‐CoA. Short‐chain acyl‐CoA dehydrogenase (SCAD), medium‐chain acyl‐CoA dehydrogenase (MCAD), and long‐chain acyl‐CoA dehydrogenase (LCAD) accepted glutaryl‐CoA as a substrate. The highest k cat of glutaryl‐CoA was found for MCAD (0.12 ± 0.01 second−1) and was about 26‐fold and 52‐fold higher than those of LCAD and SCAD, respectively. The turnover of MCAD for glutaryl‐CoA was about 1.5% of that of its natural substrate octanoyl‐CoA. Despite high K m (above 600 μM) and low turnover rate, the oxidation of glutaryl‐CoA by MCAD in combination with 3‐MGH could explain the urinary concentration of 3‐OH‐GA in GA I patients.

Evaluation of mass spectrometric indicators for the differential diagnosis of inherited disorders of organic acid metabolism in children

The objective. To calculate the reference intervals of the content of organic acids in the urine of the children of different age groups based on the results of gas chromatography with mass spectrometry; to find out their diagnostic value as biochemical markers of organic acidemia and other metabolic disorders. Materials and methods. The group consisted of 80 children with suspected organic acidemia. The control group consisted of 443 practically healthy children of different ages. The urine samples were analyzed for the content of 28 organic by gas chromatography with mass spectrometry. The results. The authors established reference intervals of 28 organic urine acids. The differences in the reference intervals defined in this work were isolated from those obtained in other studies. There were identified 37 children with abnormalities in the spectrum of organic acids according to the results of the analysis of the urine samples of patients by gas chromatography-mass spectrometry. 23 patients were diagnosed with various forms of organic acidemia on the basis of characteristic clinical and laboratory data and changes in the indicators of organic acids. The conclusion. The method of gas chromatography with mass spectrometry has proved its effectiveness and reliability for the diagnosis of hereditary diseases from the group of organic acidemias.

A novel missense mutation of Isovaleryl-CoA dehydrogenase gene associated with chronic intermittent Isovaleric acidemia in a Bangladeshi patient

Isovaleric acidemia (IVA) is an organic acidemia characterized by the deficiency of isovaleryl-CoA dehydrogenase (IVD) enzyme, of the third step in the leucine degradation pathway in humans. We present here the case of a 9-year-old patient diagnosed with IVA at 2 years of age using tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GC/MS) analysis, as observed by elevated levels of signature disease markers- isovaleryl (C5)-carnitine and isovalerylglycine (IVG) in blood and urine samples, respectively. Over the ensuing seven year follow-up, his most prominent symptoms were hyperammonemia which peaked at >109 μmol/L complimented by developmental and motor dysfunctions. Delayed intervention using sodium benzoate, levocarnitine, multivitamins and a leucine free-diet appeared to gradually regulate his metabolite levels to normal, improving his overall health, although failed to mitigate his impaired mental status. Sequencing of the IVD gene unearthed a novel point mutation carried as a single allele by each parent, c.969G > T in exon-9 whose pathogenicity was predicted by three bioinformatics tools, SIFT, PolyPhen-2 and PhD-SNP. These bioinformatics investigations revealed a missense mutation imparting an amino acid change from a highly conserved glutamine residue to a histidine at a site proximal to the binding of an essential cofactor, FAD, which was implicated in his chronic intermittent, clinical manifestation.

The Therapeutic Hypothermia in Treatment of Hyperammonemic Encephalopathy due to Urea Cycle Disorders and Organic Acidemias.

Hyperammonemic encephalopathy in newborns with urea cycle disorders and certain organic acidurias can cause severe brain injury, coma and death. Standard therapy includes protein restriction, nitrogen-scavenging drugs, prevention of catabolism and hemodialysis. Neuroprotective hypothermia as part of the treatment has been reported only 3 times. It has been suggested that mild systemic hypothermia can contribute to better neurological outcomes in hyperammonemic encephalopathy. However, the limited experience precludes accurate conclusions on safety and efficacy. Whole body therapeutic hypothermia was included in the standard treatment of hyperammonemic encephalopathy in 4 neonates with urea cycle disorder or organic aciduria. Two patients survived the initial crisis. One patient has a developmental quotient of 0.8, while the other shows severe developmental delay. The cooling protocol had to be discontinued in 3 patients due to the otherwise untreatable complications (hypotension and hemorrhage). The efficacy and safety of therapeutic hypothermia in the treatment of neonatal hyperammonemic encephalopathy depend on various factors, requiring further evaluation.

Efficacy of peritoneal dialysis in neonates presenting with hyperammonaemia due to urea cycle defects and organic acidaemia.

Newborns with inborn errors of metabolism can present with hyperammonaemic coma. In this study, we evaluated the effect of peritoneal dialysis on plasma ammonium levels and on the short-term outcome in neonatal patients with urea cycle defects and organic acidaemia. Data from infants with hyperammonaemia due to urea cycle defects or organic acidaemia treated with dialysis were collected and retrospectively analyzed. The results of patient groups (group I, survived; and group II, died) were compared. Fourteen neonates were enrolled in this study. In group I, plasma ammonium levels before dialysis were median (IQR) 1652 μg/dL (1165-2098 μg/dL); in group II, they were 1289 μg/dL (1070-5550 μg/dL). There was no statistically significant difference. Urea cycle defects were diagnosed in eight, and organic acidaemia in six patients. The duration of a blood ammonia level >200 μg/dL was longer in group II (P = 0.04). A <60.8% decline in the ammonia level from the beginning of dialysis to the 12th hour of dialysis carried a 3.33-fold higher risk of mortality, when compared with a greater decline. Five patients with urea cycle defects, and one with organic acidaemia, died. The mortality risk was 8.33-fold (95% CI = 0.63-90.86) higher for patients with urea cycle defects than for those with organic acidaemia. In patients with hyperammonaemia treated with peritoneal dialysis, the rate of ammonia removal and the underlying aetiology appear to be important prognostic factors. Neonates with organic acidaemia who are admitted to centres without continuous renal replacement therapy facilities can be effectively treated with peritoneal dialysis.

Clinicoradiological Spectrum of L-2-Hydroxy Glutaric Aciduria: Typical and Atypical Findings in an Indian Cohort.

Context:Neurometabolic disorders form an important group of potentially treatable diseases. It is important to recognize the clinical phenotype and characteristic imaging patterns to make an early diagnosis and initiate appropriate treatment. L-2-hydroxy glutaric aciduria (L2HGA) is a rare organic aciduria with a consistent and highly characteristic imaging pattern, which clinches the diagnosis in most cases.Aims:The study aims to describe the clinical profile, magnetic resonance imaging (MRI) patterns, and outcome in a cohort of children with L2HGA and to assess the clinicoradiological correlation.Materials and Methods:This is a retrospective descriptive study done at the Department of Radiodiagnosis and Neurological Sciences of our institution. Clinical and radiological findings of children diagnosed with L2HGA over an 8-year period (2010–2017) were collected and analyzed. Descriptive statistical analysis of clinical and imaging data was performed.Results:There were six girls and four boys. A total of 14 MRI brain studies in 10 patients with the diagnosis were analyzed. MRI of all patients showed a similar pattern with extensive confluent subcortical white-matter signal changes with symmetrical involvement of dentate nuclei and basal ganglia. In two children who presented with acute decompensation, there was asymmetric cortical involvement and restricted diffusion, which are previously unreported. There was no significant correlation between the radiological pattern with the disease duration, clinical features, or course of the disease.Conclusion:MRI findings in L2HGA are highly consistent and diagnostic, which helps in early diagnosis, particularly in resource-constraint settings, where detailed metabolic workup is not possible. The article also describes novel clinical radiological profile of acute encephalopathic clinical presentation.

Evaluation of dietary treatment and amino acid supplementation in organic acidurias and urea-cycle disorders: On the basis of information from a European multicenter registry.

Organic acidurias (OAD) and urea-cycle disorders (UCD) are rare inherited disorders affecting amino acid and protein metabolism. As dietary practice varies widely, we assessed their long-term prescribed dietary treatment against published guideline and studied plasma amino acids levels. We analyzed data from the first visit recorded in the European registry and network for intoxication type metabolic diseases (E-IMD, Chafea no. 2010 12 01). In total, 271 methylmalonic aciduria (MMA) and propionic aciduria (PA) and 361 UCD patients were included. Median natural protein prescription was consistent with the recommended daily allowance (RDA), plasma L-valine (57%), and L-isoleucine (55%) levels in MMA and PA lay below reference ranges. Plasma levels were particularly low in patients who received amino acid mixtures (AAMs-OAD) and L-isoleucine:L-leucine:L-valine (BCAA) ratio was 1.0:3.0:3.2. In UCD patients, plasma L-valine, L-isoleucine, and L-leucine levels lay below reference ranges in 18%, 30%, and 31%, respectively. In symptomatic UCD patients who received AAM-UCD, the median natural protein prescription lay below RDA, while their L-valine and L-isoleucine levels and plasma BCAA ratios were comparable to those in patients who did not receive AAM-UCD. Notably, in patients with ornithine transcarbamylase syndrome (OTC-D), carbamylphosphate synthetase 1 syndrome (CPS1-D) and hyperammonemia-hyperornithinemia-homocitrullinemia (HHH) syndrome selective L-citrulline supplementation resulted in higher plasma L-arginine levels than selective L-arginine supplementation. In conclusion, while MMA and PA patients who received AAMs-OAD had very low BCAA levels and disturbed plasma BCAA ratios, AAMs-UCD seemed to help UCD patients obtain normal BCAA levels. In patients with OTC-D, CPS1-D, and HHH syndrome, selective L-citrulline seemed preferable to selective L-arginine supplementation.

Decreased plasma l-arginine levels in organic acidurias (MMA and PA) and decreased plasma branched-chain amino acid levels in urea cycle disorders as a potential cause of growth retardation: Options for treatment

Background and aimPatients with methylmalonic acidemia (MMA) and propionic acidemia (PA) and urea cycle disorders (UCD), treated with a protein restricted diet, are prone to growth failure. To obtain optimal growth and thereby efficacious protein incorporation, a diet containing the essential and functional amino acids for growth is necessary. Optimal growth will result in improved protein tolerance and possibly a decrease in the number of decompensations. It thus needs to be determined if amino acid deficiencies are associated with the growth retardation in these patient groups. We studied the correlations between plasma L-arginine levels, plasma branched chain amino acids (BCAA: L-isoleucine, L-leucine and L-valine) levels (amino acids known to influence growth), and height in MMA/PA and UCD patients. MethodsWe analyzed data from longitudinal visits made in stable metabolic periods by patients registered at the European Registry and Network for Intoxication Type Metabolic Diseases (E-IMD, Chafea no. 2010 12 01). ResultsIn total, 263 MMA/PA and 311 UCD patients were included, all aged below 18 years of age. In patients with MMA and PA, height z-score was positively associated with patients' natural-protein-to-energy prescription ratio and their plasma L-valine and L-arginine levels, while negatively associated with the amount of synthetic protein prescription and their age at visit. In all UCDs combined, height z-score was positively associated with the natural-protein-to-energy prescription ratio. In those with carbamylphosphate synthetase 1 deficiency (CPS1-D), those with male ornithine transcarbamylase deficiency (OTC-D), and those in the hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome subgroup, height z-score was positively associated with patients' plasma L-leucine levels. In those with argininosuccinate synthetase deficiency (ASS-D) and argininosuccinate lyase deficiency (ASL-D), height was positively associated with patients' plasma L-valine levels. ConclusionPlasma L-arginine and L-valine levels in MMA/PA patients and plasma L-leucine and L-valine levels in UCD patients, as well as the protein-to-energy prescription ratio in both groups were positively associated with height. Optimization of these plasma amino acid levels is essential to support normal growth and increase protein tolerance in these disorders. Consequently this could improve the protein-to-energy intake ratio.

Organic acidemia in pregnancy: Report of case of isovaleric acidemia (IVA) with outline of management principles

Introduction: Isovaleric or organic academia is a rare, but potentially serious metabolic disorder, incidence around 1 in 250,000 children.

Correction to: Carglumic acid in hyperammonaemia due to organic acidurias: a profile of its use in the EU

The article Carglumic acid in hyperammonaemia due to organic acidurias: a profile of its use in the EU, written by Hannah A. Blair

Ammonium accumulation and chemokine decrease in culture media of Gcdh−/− 3D reaggregated brain cell cultures

Glutaric Aciduria type I (GA-I) is caused by mutations in the GCDH gene. Its deficiency results in accumulation of the key metabolites glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in body tissues and fluids. Present knowledge on the neuropathogenesis of GA-I suggests that GA and 3-OHGA have toxic properties on the developing brain.We analyzed morphological and biochemical features of 3D brain cell aggregates issued from Gcdh−/− mice at two different developmental stages, day-in-vitro (DIV) 8 and 14, corresponding to the neonatal period and early childhood. We also induced a metabolic stress by exposing the aggregates to 10 mM l-lysine (Lys).Significant amounts of GA and 3-OHGA were detected in Gcdh−/− aggregates and their culture media. Ammonium was significantly increased in culture media of Gcdh−/− aggregates at the early developmental stage. Concentrations of GA, 3-OHGA and ammonium increased significantly after exposure to Lys. Gcdh−/− aggregates manifested morphological alterations of all brain cell types at DIV 8 while at DIV 14 they were only visible after exposure to Lys. Several chemokine levels were significantly decreased in culture media of Gcdh−/− aggregates at DIV 14 and after exposure to Lys at DIV 8.This new in vitro model for brain damage in GA-I mimics well in vivo conditions. As seen previously in WT aggregates exposed to 3-OHGA, we confirmed a significant ammonium production by immature Gcdh−/− brain cells. We described for the first time a decrease of chemokines in Gcdh−/− culture media which might contribute to brain cell injury in GA-I.

Hereditary diseases of coenzyme A thioester metabolism.

Coenzyme A (CoA) thioesters (acyl-CoAs) are essential intermediates of metabolism. Inborn errors of acyl-CoA metabolism include a large fraction of the classical organic acidemias. These conditions can involve liver, muscle, heart and brain, and can be fatal. These conditions are increasingly detected by newborn screening. There is a renewed interest in CoA metabolism and in developing effective new treatments. Here, we review theories of the pathophysiology in relation to mitochondrial CoA sequestration, toxicity and redistribution (CASTOR).

Carglumic acid in hyperammonaemia due to organic acidurias: a profile of its use in the EU

Carglumic acid (N-carbamylglutamate; Carbaglu®), a structural analog of N-acetylglutamate, is an effective and generally well-tolerated option for the treatment of hyperammonaemia due to propionic, methylmalonic and isovaleric acidurias. These organic acidurias are linked to a group of autosomal recessive inherited disorders that are associated with secondary hyperammonaemia due to the inhibition of the urea cycle. Carglumic acid can be administered orally or through a nasogastric tube. In retrospective, observational studies and case series/reports, carglumic acid rapidly reduced plasma ammonia levels and improved clinical symptoms of hyperammonaemia. Carglumic acid is generally well tolerated, and, based on limited data, may be associated with fewer treatment-emergent adverse events when used in combination with ammonia scavengers than when either therapy is administered alone.

Screening for organic acidurias and aminoacidopathies in high-risk Brazilian patients: Eleven-year experience of a reference center.

Organic acidurias and aminoacidopathies are groups of frequent inborn errors of metabolism (IEMs), which are caused by mutations in specific genes that lead to loss of protein/enzyme or transport function with important deleterious effects to cell metabolism. Since a considerable number of such disorders are potentially treatable when diagnosed at an early stage of life, diagnosis is crucial for the patients. In the present report, we describe symptomatic individuals referred to our service that were diagnosed with these disorders from 2006 to 2016. We used blood and urine samples from 21,800 patients suspected of aminoacidopathies or organic acidemias that were processed by the analytical techniques reverse phase high-performance liquid chromatography for amino acid quantification and gas chromatography coupled to mass spectrometry for organic acid detection. Analysis of dried blood spots by liquid chromatography-tandem mass spectrometry was used in some cases. We detected 258 cases of organic acidurias, and 117 patients with aminoacidopathies were diagnosed. Once diagnosis was performed, patients were promptly submitted to the available treatments with clear reduction of mortality and morbidity. The obtained data may help pediatricians and metabolic geneticists to become aware of these diseases and possibly expand newborn screening programs in the future.

Screening Urinary Methylmalonic Acid by Thin Layer chromatography in children with Suspected inborn Errors of Metabolism

Introduction: Inborn errors of metabolism (IEM) are a group of disorders due to deficiency of the enzyme. The symptoms are due to the accumulation of toxic substances or deficiency of products. Organic aciduria is a group of IEM which is due to errors in the metabolism of branched chain amino acids and lysine. Studies showed that methylmalonicaciduria (MMA), glutaric aciduria, branched chain aminoacidurias are more common organicaciduria. Many methods are used for detection of methylmalonic acid some of them are not affordable by developing countries. Objective: To study the role of thin layer chromatography in detection of methylmalonic aciduria in children with suspected inborn errors of metabolism. Method: Untimed urine samples were collected from 385 children with clinically suspected inborn errors of metabolism and analyzed for MMA by colour reaction and thin layer chromatography (TLC). Bromocresol green and Ortho dianisidine were the dye used for spotting MMA on TLC. Result: Among 385 children who presented with developmental delay, seizures, hypotonia were worked up for underlying inborn errors of metabolism. Of them 52 children showed positive result for MMA by thin layer chromatography. Discussion: Significant number of children showed positive result for MMA by thin layer chromatography hence the method may be useful for screening methylmalonicaciduria. Further studies required to confirm the diagnosis

Patterns, evolution, and severity of striatal injury in insidious- vs acute-onset glutaric aciduria type 1.

Striatal injury in patients with glutaric aciduria type 1 (GA1) results in a complex, predominantly dystonic, movement disorder. Onset may be acute following acute encephalopathic crisis (AEC) or insidious without apparent acute event. We analyzed clinical and striatal magnetic resonance imaging (MRI) findings in 21 symptomatic GA1 patients to investigate if insidious- and acute-onset patients differed in timing, pattern of striatal injury, and outcome. Eleven patients had acute and ten had insidious onset, two with later AEC (acute-on-insidious). The median onset of dystonia was 10 months in both groups, and severity was greater in patients after AEC (n = 8 severe, n = 5 moderate) than in insidious onset (n = 4 mild, n = 3 moderate, n = 1 severe). Deviations from guideline-recommended basic metabolic treatment were identified in six insidious-onset patients. Striatal lesions were extensive in all acute-onset patients and restricted to the dorsolateral putamen in eight of ten insidious-onset patients. After AEC, the two acute-on-insidious patients had extensive striatal changes superimposed on pre-existing dorsolateral putaminal lesions. Two insidious-onset patients with progressive dystonia without overt AEC also had extensive striatal changes, one with sequential striatal injury revealed by diffusion-weighted imaging. Insidious-onset patients had a latency phase of 3.5 months to 6.5 years between detection and clinical manifestation of dorsolateral putaminal lesions. Insidious-onset type GA1 is characterized by dorsolateral putaminal lesions, less severe dystonia, and an asymptomatic latency phase, despite already existing lesions. Initially normal MRI during the first months and deviations from guideline-recommended treatment in a large proportion of insidious-onset patients substantiate the protective effect of neonatally initiated treatment.

Glutaric aciduria type 1: a review of phenotypic and genetic characteristics

Glutaric aciduria type I (GA1) is an inherited metabolic disorder in which excessive levels of the amino acids lysine, hydroxylysine, and tryptophan accumulate in the body as a result of defective glutaryl-CoA dehydrogenase (GCDH) enzyme activity. Excessive metabolites are toxic that can cause damage to the brain, particularly due to the occurrence of basal ganglia and intellectual disability. Missense, splicing, and other deletion mutations in GCDH gene lead to the deficiency of the enzyme activity and are known to cause GA1. The severity of GA1 along with its neurological manifestations and clinical outcome is dependent upon the age at onset and therefore, early definitive diagnosis of GA1 becomes essential. GA1 occurs in approximately 1 of every 30,000-40,000 individuals worldwide that may reach up to 1 in 300 newborn babies in the Amish and Canadian communities. Owing to very high consanguinity rates in Saudi Arabia, it is presumed to be much more common in the Kingdom and is one of the initial disorders that were included in the country's neonatal screening program. In the current study, we have reviewed clinical manifestations, diagnosis, updated management, and mutation spectrum in GA1 with an example of one of our patients with GA1, and highlighted the importance of multipara-metric strategy in the early diagnosis and management of the disease.

Tribute to Linda Joanna DE MEIRLEIR

Tribute to Linda Joanna DE MEIRLEIR

Diagnosis of inherited metabolic disorders by selective metabolite testing: three years' experience at a tertiary care center in Rawalpindi.

To determine the pattern of various inherited metabolic disorders specifically through plasma amino acid and urine organic acid testing in high-risk paediatric population.. The cross-sectional retrospective study was conducted at the Armed Forces Institute of Pathology, Rawalpindi, Pakistan, and comprised data from April 2015 to March 2018 of children referred to the Department of Chemical Pathology and Endocrinology for work-up of suspected inherited metabolic disorders. Complete clinical history, baseline biochemical investigations, plasma amino acid and urine organic acid profiles, where indicated, were collected. Quantitative plasma amino acid and analysis was carried out by Ion Exchange Chromatography on Biochrome 30+ amino acid analyser, and urine organic acid analysis by Gas Chromatography-Mass Spectrometry. Findings were linked to the identified disorders. SPSS 21 was used for data analysis. Of the 805 cases reviewed, 49(6%) had an inherited metabolic disorder. Male:Female ratio of the cases was 1.5:1, and the median age was 240 days (interquartile range: 1-15695 days). The most common presenting symptom was seizures 316(39.3%) followed by lethargy 283(35.2%). Of the diagnosed cases, aminoacidopathies were 28(57%) and in them, non-ketotic hyperglycaemia accounted for 7(25%.). There were 12(24.5%) cases of organic acidurias followed by 9(18.4%) that were other than the two diagnoses. The cases of inherited metabolic disorder detected indicated significant prevalence. Non-ketotic hyperglycinemia was the commonest disorder diagnosed.