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Incidence of medium-chain acyl-CoA dehydrogenase deficiency in Canada using the Canadian Paediatric Surveillance Program: Role of newborn screening.

ABSTRACT: BACKGROUND:The incidence of medium-chain acyl-CoA dehydrogenase deficiency (MCADD) was estimated using the Canadian Paediatric Surveillance Program (CPSP) in Canada over a three-year period. Data regarding mutations associated with MCADD cases were collected wherever available. METHODS:Data were collected over a 36-month period using a monthly mailed questionnaire distributed through the CPSP to more than 2500 Canadian paediatricians, medical geneticists and paediatric pathologists. RESULTS AND CONCLUSIONS:During the three years of MCADD surveillance, 46 confirmed cases out of a total of 71 reported cases were found - an average of approximately 15 cases per year. This rate is lower than the initial estimate of approximately 30 cases per year of MCADD in Canada, based on the reported incidence of MCADD in the literature of approximately one in 10,000 to one in 20,000. All cases ascertained by newborn screening were asymptomatic. There were two deaths, both in jurisdictions without newborn screening for MCADD. The data support population-based newborn screening for MCADD.

SUBMITTER: Prasad C

PROVIDER: S-EPMC3381659 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

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Incidence of medium-chain acyl-CoA dehydrogenase deficiency in Canada using the Canadian Paediatric Surveillance Program: Role of newborn screening.

Prasad Chitra C Speechley Kathy N KN Dyack Sarah S Rupar Charles A CA Chakraborty Pranesh P Kronick Jonathan B JB

Paediatrics & child health 20120401 4

<h4>Background</h4>The incidence of medium-chain acyl-CoA dehydrogenase deficiency (MCADD) was estimated using the Canadian Paediatric Surveillance Program (CPSP) in Canada over a three-year period. Data regarding mutations associated with MCADD cases were collected wherever available.<h4>Methods</h4>Data were collected over a 36-month period using a monthly mailed questionnaire distributed through the CPSP to more than 2500 Canadian paediatricians, medical geneticists and paediatric pathologist ...[more]

PMID: 23543005

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Project description:BACKGROUND: Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common inherited defect in the mitochondrial fatty acid oxidation pathway, resulting in significant morbidity and mortality in undiagnosed patients.Newborn screening (NBS) has considerably improved MCADD outcome, but the risk of complication remains in some patients. The aim of this study was to evaluate the relationship between genotype, biochemical parameters and clinical data at diagnosis and during follow-up, in order to optimize monitoring of these patients. METHODS: We carried out a multicenter study in southwest Europe, of MCADD patients detected by NBS. Evaluated NBS data included free carnitine (C0) and the acylcarnitines C8, C10, C10:1 together with C8/C2 and C8/C10 ratios, clinical presentation parameters and genotype, in 45 patients. Follow-up data included C0 levels, duration of carnitine supplementation and occurrence of metabolic crises. RESULTS: C8/C2 ratio and C8 were the most accurate biomarkers of MCADD in NBS. We found a high number of patients homozygous for the prevalent c.985A?>?G mutation (75%). Moreover, in these patients C8, C8/C10 and C8/C2 were higher than in patients with other genotypes, while median value of C0 was significantly lower (23 ?mol/L vs 36 ?mol/L).The average follow-up period was 43 months. To keep carnitine levels within the normal range, carnitine supplementation was required in 82% of patients, and for a longer period in patients homozygotes for the c.985A>G mutation than in patients with other genotypes (average 31 vs 18 months). Even with treatment, median C0 levels remained lower in homozygous patients than in those with other genotypes (14 ?mol/L vs 22 ?mol/L).Two patients died and another three suffered a metabolic crisis, all of whom were homozygous for the c.985 A>G mutation. CONCLUSIONS: Our data show a direct association between homozygosity for c.985A>G and lower carnitine values at diagnosis, and a higher dose of carnitine supplementation for maintenance within the normal range. This study contributes to a better understanding of the relationship between genotype and phenotype in newborn patients with MCADD detected through screening which could be useful in improving follow-up strategies and clinical outcome.

Project description:BackgroundMonogenetic inborn errors of metabolism cause a wide phenotypic heterogeneity that may even differ between family members carrying the same genetic variant. Computational modelling of metabolic networks may identify putative sources of this inter-patient heterogeneity. Here, we mainly focus on medium-chain acyl-CoA dehydrogenase deficiency (MCADD), the most common inborn error of the mitochondrial fatty acid oxidation (mFAO). It is an enigma why some MCADD patients-if untreated-are at risk to develop severe metabolic decompensations, whereas others remain asymptomatic throughout life. We hypothesised that an ability to maintain an increased free mitochondrial CoA (CoASH) and pathway flux might distinguish asymptomatic from symptomatic patients.ResultsWe built and experimentally validated, for the first time, a kinetic model of the human liver mFAO. Metabolites were partitioned according to their water solubility between the bulk aqueous matrix and the inner membrane. Enzymes are also either membrane-bound or in the matrix. This metabolite partitioning is a novel model attribute and improved predictions. MCADD substantially reduced pathway flux and CoASH, the latter due to the sequestration of CoA as medium-chain acyl-CoA esters. Analysis of urine from MCADD patients obtained during a metabolic decompensation showed an accumulation of medium- and short-chain acylcarnitines, just like the acyl-CoA pool in the MCADD model. The model suggested some rescues that increased flux and CoASH, notably increasing short-chain acyl-CoA dehydrogenase (SCAD) levels. Proteome analysis of MCADD patient-derived fibroblasts indeed revealed elevated levels of SCAD in a patient with a clinically asymptomatic state. This is a rescue for MCADD that has not been explored before. Personalised models based on these proteomics data confirmed an increased pathway flux and CoASH in the model of an asymptomatic patient compared to those of symptomatic MCADD patients.ConclusionsWe present a detailed, validated kinetic model of mFAO in human liver, with solubility-dependent metabolite partitioning. Personalised modelling of individual patients provides a novel explanation for phenotypic heterogeneity among MCADD patients. Further development of personalised metabolic models is a promising direction to improve individualised risk assessment, management and monitoring for inborn errors of metabolism.

Project description:BACKGROUND: Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common inherited disorder of the mitochondrial fatty acid oxidation, caused by mutations in the ACADM gene. Since the introduction of neonatal screening for MCAD deficiency, a subgroup of newborns have been identified with variant ACADM genotypes that had never been identified before in clinically ascertained patients. In vitro residual MCAD enzyme activity has been found to facilitate risk-stratification. In this study we integrated results of in vitro (residual MCAD enzyme activities) and in vivo (clinical fasting tolerance tests, and phenylpropionic acid loading tests) tests in this subgroup of newborns, defining the consequences of variant ACADM genotypes. METHODS: Enzyme analyses were performed in leukocytes with: hexanoyl-CoA (C6-CoA) +/- butyryl-CoA (C4-CoA), and phenylpropionyl-CoA (PP-CoA). In vitro studies were performed in 9 subjects with variant ACADM genotypes, in vivo functional tests in 6 of these subjects. RESULTS: Enzyme analyses with C6-CoA, C6-CoA + C4-CoA, and PP-CoA identified significantly higher residual MCAD enzyme activities in subjects with variant ACADM genotypes when compared to patients with classical ACADM genotypes.After prolonged fasting (range 15-18.5 hours) no hypoglycaemia was observed. Increasing concentrations of free fatty acids indicated lipolysis, and ketone body concentrations were sufficient for blood glucose concentrations in 5 out of 6 subjects. Phenylpropionic acid loading clearly demonstrated in vivo residual MCAD enzyme activity in all studied subjects. CONCLUSIONS: Subjects with variant ACADM genotypes and residual MCAD enzyme activities >10% display residual MCAD enzyme activities in vitro and in vivo. Our findings support the hypothesis that the guidelines on maximal duration of fasting might be abandoned in subjects with residual MCAD enzyme activities >10% under normal conditions. An emergency regimen and parental instructions remain necessary in all subjects with MCAD deficiency, regardless of residual MCAD enzyme activity.

Dataset Information

Incidence of medium-chain acyl-CoA dehydrogenase deficiency in Canada using the Canadian Paediatric Surveillance Program: Role of newborn screening.

Publications

Incidence of medium-chain acyl-CoA dehydrogenase deficiency in Canada using the Canadian Paediatric Surveillance Program: Role of newborn screening.

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