Medium-chain acyl-CoA Dehydrogenase Deficiency Research Articles

Oxidized phosphatidylcholines suggest oxidative stress in patients with medium-chain acyl-CoA dehydrogenase deficiency

Inborn errors of metabolism encompass a large group of diseases caused by enzyme deficiencies and are therefore amenable to metabolomics investigations. Medium chain acyl-CoA dehydrogenase deficiency (MCADD) is a defect in β-oxidation of fatty acids, and is one of the most well understood disorders. We report here the use of liquid chromatography–mass spectrometry (LC–MS) based untargeted metabolomics and targeted flow injection analysis–tandem mass spectrometry (FIA–TMS) that lead to discovery of novel compounds of oxidative stress. Dry blood spots of controls (n=25) and patient samples (n=25) were extracted by methanol/water (1/1, v/v) and these supernatants were analyzed by LC–MS method with detection by an Orbitrap Elite MS. Data were processed by XCMS and CAMERA followed by dimension reduction methods. Patients were clearly distinguished from controls in PCA. S-plot derived from OPLS-DA indicated that medium-chain acylcarnitines (octanoyl, decenoyl and decanoyl carnitines) as well as three phosphatidylcholines (PC(16:0,9:0(COOH))), PC(18:0,5:0(COOH)) and PC(16:0,8:0(COOH)) were important metabolites for differentiation between patients and healthy controls. In order to biologically validate these discriminatory molecules as indicators for oxidative stress, a second cohort of individuals were analyzed, including MCADD (n=25) and control (n=250) samples. These were measured by a modified newborn screening method using FIA–TMS (API 4000) in MRM mode. Calculated p-values for PC(16:0,9:0(COOH)), PC(18:0,5:0(COOH)) and PC(16:0,8:0(COOH)) were 1.927×10−14, 2.391×10−15 and 3.354×10−15 respectively. These elevated oxidized phospholipids indeed show an increased presence of oxidative stress in MCADD patients as one of the pathophysiological mechanisms of the disease.

Medium-chain acyl-CoA dehydrogenase deficiency

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is an autosomal recessive disorder of fatty acid oxidation with an incidence in the UK of more than 1:10,000. The majority of patients are homozygous for a missense mutation c.985A > G. Newborn screening for this condition was implemented in England and Northern Ireland in 2009 in Scotland in 2010 and in Wales in 2012. Patients with MCADD are at risk during periods of fasting stress, particularly during intercurrent infections, of developing an encephalopathy associated with hypoketotic hypoglycaemia. These episodes can be prevented by giving high calorie drinks (the emergency regimen) during periods of illness but hospital admission is required for intravenous dextrose if the emergency regimen is not tolerated. No specific treatment is required at other times. This review highlights the pathogenesis, the presentation and management of MCADD.

Recurrent Ventricular Tachycardia in Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency.

We report a baby with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency who presented on day 2 with poor feeding and lethargy. She was floppy with hypoglycaemia (1.8mmol/l) and hyperammonaemia (182μmol/l). Despite correction of these and a continuous intravenous infusion of glucose at 4.5-6.2mg/kg/min, she developed generalised tonic clonic seizures on day 3. She also suffered two episodes of pulseless ventricular tachycardia, from which she was resuscitated successfully. Unfortunately, she died on day 5, following a third episode of pulseless ventricular tachycardia. Arrhythmias are generally thought to be rarer in MCAD deficiency than in disorders of long-chain fatty acid oxidation. This is, however, the sixth report of ventricular tachyarrhythmias in MCAD deficiency. Five of these involved neonates and it may be that patients with MCAD deficiency are particularly prone to ventricular arrhythmias in the newborn period. Three of the patients (including ours) had normal blood glucose concentrations at the time of the arrhythmias and had been receiving intravenous glucose for many hours. These cases suggest that arrhythmias can be induced by medium-chain acylcarnitines or other metabolites accumulating in MCAD deficiency. Ventricular tachyarrhythmias can occur in MCAD deficiency, especially in neonates.

Intermediate MCAD Deficiency Associated with a Novel Mutation of the ACADM Gene: c.1052C>T.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is an autosomal recessive disorder that leads to a defect in fatty acid oxidation. ACADM is the only candidate gene causing MCAD deficiency. A single nucleotide change, c.985A>G, occurring at exon 11 of the ACADM gene, is the most prevalent mutation. In this study, we report a Caucasian family with multiple MCADD individuals. DNA sequence analysis of the ACADM gene performed in this family revealed that two family members showing mild MCADD symptoms share the same novel change in exon 11, c.1052C>T, resulting in a threonine-to-isoleucine change. The replacement is a nonconservative amino acid change that occurs in the C-terminal all-alpha domain of the MCAD protein. Here we report the finding of a novel missense mutation, c.1052C>T (p.Thr326Ile), in the ACADM gene. To our knowledge, c.1052C>T has not been previously reported in the literature or in any of the current databases we utilize. We hypothesize that this particular mutation in combination with p.Lys304Glu results in an intermediate clinical phenotype of MCADD.

Medium-Chain Acyl-CoA Dehydrogenase Deficiency: Evaluation of Genotype-Phenotype Correlation in Patients Detected by Newborn Screening.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is included in many newborn screening programmes worldwide. In addition to the prevalent mutation c.985A>G in the ACADM gene, potentially mild mutations like c.199T>C are frequently found in screening cohorts. There is ongoing discussion whether this mutation is associated with a clinical phenotype. In 37 MCADD patients detected by newborn screening, biochemical phenotype (octanoylcarnitine (C8), ratios of C8 to acetylcarnitine (C2), decanoylcarnitine (C10) and dodecanoylcarnitine (C12) at screening and confirmation) and clinical phenotype (inpatient emergency treatment, metabolic decompensations, clinical assessments, psychometric tests) were assessed in relation to genotype. 16 patients were homozygous for c.985A>G (group 1), 11 compound heterozygous for c.199T>C and c.985A>G/another mutation (group 2) and 7 compound heterozygous for c.985A>G and mutations other than c.199T>C (group 3) and 3 carried neither c.985A>G nor c.199T>C but other known homozygous mutations (group 4). At screening C8/C2 and C8/C10, at confirmation C8/C2, C8/C10 and C8/C12 differed significantly between patients compound heterozygous for c.199T>C (group 2) and other genotypes. C8, C10 and C8/C2 at screening were strongly associated with time of sampling in groups 1 + 3 + 4, but not in group 2. Clinical phenotype did not differ between genotypes. Two patients compound heterozygous for c.199T>C and a severe mutation showed neonatal decompensation with hypoglycaemia. Biochemical phenotype differs between MCADD patients compound heterozygous for c.199T>C with a severe mutation and other genotypes. In patients detected by newborn screening, clinical phenotype does not differ between genotypes following uniform treatment recommendations. Neonatal decompensation can also occur in patients with the presumably mild mutation c.199T>C prior to diagnosis.

Targeted metabolomics in the expanded newborn screening for inborn errors of metabolism.

Inborn errors of metabolism are genetic disorders due to impaired activity of enzymes, transporters, or cofactors resulting in accumulation of abnormal metabolites proximal to the metabolic block, lack of essential products or accumulation of by-products. Many of these disorders have serious clinical consequences for affected neonates, and an early diagnosis allows presymptomatic treatment which can prevent severe permanent sequelae and in some cases death. Expanded newborn screening for these diseases is a promising field of targeted metabolomics. Here we report the application, between 2007 and 2014, of this approach to the identification of newborns in southern Italy at risk of developing a potentially fatal disease. The analysis of amino acids and acylcarnitines in dried blood spots by tandem mass spectrometry revealed 24 affected newborns among 45,466 infants evaluated between 48 and 72 hours of life (overall incidence: 1 : 1894). Diagnoses of newborns with elevated metabolites were confirmed by gas chromatography-mass spectrometry, biochemical studies, and genetic analysis. Five infants were diagnosed with medium-chain acyl CoA dehydrogenase deficiency, 1 with methylmalonic acidemia with homocystinuria type CblC, 2 with isolated methylmalonic acidemia, 1 with propionic acidemia, 1 with isovaleric academia, 1 with isobutyryl-CoA dehydrogenase deficiency, 1 with beta ketothiolase deficiency, 1 with short branched chain amino acid deficiency, 1 with 3-methlycrotonyl-CoA carboxylase deficiency, 1 with formimino-transferase cyclodeaminase deficiency, and 1 with cystathionine-beta-synthase deficiency. Seven cases of maternal vitamin B12 deficiency and 1 case of maternal carnitine uptake deficiency were detected. This study supports the widespread application of metabolomic-based newborn screening for these genetic diseases.

Abnormal Newborn Screening in a Healthy Infant of a Mother with Undiagnosed Medium-Chain Acyl-CoA Dehydrogenase Deficiency.

A neonate with low blood free carnitine level on newborn tandem mass spectrometry screening was evaluated for possible carnitine transporter defect (CTD). The plasma concentration of free carnitine was marginally reduced, and the concentrations of acylcarnitines (including C6, C8, and C10:1) were normal on confirmatory tests. Organic acids in urine were normal. In addition, none of the frequent Faroese SLC22A5 mutations (p.N32S, c.825-52G>A) which are common in the Danish population were identified. Evaluation of the mother showed low-normal free carnitine, but highly elevated medium-chain acylcarnitines (C6, C8, and C10:1) consistent with medium-chain acyl-CoA dehydrogenase deficiency (MCADD). The diagnosis was confirmed by the finding of homozygous presence of the c.985A>G mutation in ACADM.

Inborn Errors of Metabolism in the United Arab Emirates: Disorders Detected by Newborn Screening (2011-2014).

This study reports on the inborn errors of metabolism (IEM) detected by our national newborn screening between 2011 and 2014. One hundred fourteen patients (55 UAE citizens and 59 residents) were diagnosed during this period. The program was most comprehensive (tested 29 IEM) and universally applied in 2013, giving an incidence of 1 in 1,787 citizens. This relatively high prevalence resulted from the frequent consanguineous marriages (81.5%) among affected families. The following eight disorders accounted for 80% of the entities: biotinidase deficiency (14 of 55), phenylketonuria (11 of 55), 3-methylcrotonyl glycinuria (9 of 55), medium-chain acyl-CoA dehydrogenase deficiency (4 of 55), argininosuccinic aciduria, glutaric aciduria type 1, glutaric aciduria type 2, and methylmalonyl-CoA mutase deficiency (2 of 55 each). Mutation analysis was performed in 48 (87%) of the 55 patients, and 33 distinct mutations were identified. Twenty-nine (88%) mutations were clinically significant and, thus, could be included in our premarital screening. Most mutations were homozygous, except for the biotinidase deficiency. The BTD mutations c.1207T>G (found in citizens) and c.424C>A (found in Somalians) were associated with undetectable biotinidase activity. Thus, the high prevalence of IEM in our region is amenable to newborn and premarital screening, which is expected to halt most of these diseases.

Inherent lipid metabolic dysfunction in glycogen storage disease IIIa

We studied two patients from a nonconsanguineous family with life-long abnormal liver function, hepatomegaly and abnormal fatty acid profiles. Abnormal liver function, hypoglycemia and muscle weakness are observed in various genetic diseases, including medium-chain acyl-CoA dehydrogenase (MCAD) deficiency and glycogen storage diseases. The proband showed increased free fatty acids, mainly C8 and C10, resembling fatty acid oxidation disorder. However, no mutation was found in ACADM and ACADL gene. Sequencing of theamylo-alpha-1, 6-glucosidase, 4-alpha-glucanotransferase (AGL) gene showed that both patients were compound heterozygotes for c.118C>T (p.Gln40X) and c.753_756 del CAGA (p.Asp251Glufsx29), whereas their parents were each heterozygous for one of these mutations. The AGL protein was undetectable in EBV-B cells from the two patients. Transcriptome analysis demonstrated a significant different pattern of gene expression in both of patients’ cells, including genes involving in the PPAR signaling pathway, fatty acid biosynthesis, lipid synthesis and visceral fat deposition and metabolic syndrome. This unique gene expression pattern is probably due to the absence of AGL, which potentially accounts for the observed clinical phenotypes of hyperlipidemia and hepatocyte steatosis in glycogen storage disease type IIIa.

Newborn screening for medium chain acyl-CoA dehydrogenase deficiency: Performance improvement by monitoring a new ratio

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is a fatty acid oxidation disorder included on newborn screening (NBS) panels in many regions that have expanded to using tandem mass spectrometry for acylcarnitine screening. False positive (FP) screening results for MCAD deficiency have previously been linked to very low birth weight (VLBW) infants and those who are heterozygous for the common mutation, p.K324E. Previous studies have identified these causes of FP screens by sequencing residual dried blood spots. From our cohort of FP screens in Georgia, we identified an elevation at the same mass as octenoylcarnitine (C8:1) causing elevations of octanoylcarnitine (C8) not due to MCAD deficiency. We reviewed biochemical results from 2011 to 2013 for all newborn screens positive for MCAD deficiency in Georgia to identify screening criteria to allow these cases to be identified prospectively, thus saving families the stress of additional testing on their newborn and reducing healthcare costs while improving screening performance for the screening program. We identified the C8/C8:1 ratio as an effective marker, and developed criteria that will reduce FP screening results due to this interfering substance.

The epidemiology and health service impact of medium-chain acyl-CoA dehydrogenase deficiency among affected children and those with false positive newborn screening results in Ontario

The epidemiology and health service impact of medium-chain acyl-CoA dehydrogenase deficiency among affected children and those with false positive newborn screening results in Ontario

Systematic review and meta-analysis to estimate the birth prevalence of five inherited metabolic diseases.

Many newborn screening programmes now use tandem mass spectrometry in order to screen for a variety of diseases. However, countries have embraced this technology with a differing pace of change and for different conditions. This has been facilitated by the ability of this diagnostic method to limit analysis to specific metabolites of interest, enabling targeted screening for particular conditions. MS/MS was introduced in 2009 in England to implement newborn bloodspot screening for medium chain acyl-CoA dehydrogenase deficiency (MCADD) raising the possibility of screening for other inherited metabolic disorders. Recently, a pilot screening programme was conducted in order to evaluate the health and economic consequences of screening for five additional inherited metabolic disorders in England. As part of this study we conducted a systematic review and meta-analysis to estimate the birth prevalence of these conditions: maple syrup urine disease, homocystinuria (pyridoxine unresponsive), glutaric aciduria type I, isovaleric acidaemia and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency including trifunctional protein deficiency. We identified a total of 99 studies that were able to provide information on the prevalence of one or more of the disorders. The vast majority of studies were of screening programmes with some reporting on clinically detected cases.

Synthesis framework estimating prevalence of MCADD and sensitivity of newborn screening programme in the absence of direct evidence

Background and ObjectivesSeveral countries have included medium-chain acyl-CoA dehydrogenase deficiency (MCADD) in their newborn screening programs. However, the sensitivity of the programs cannot be estimated directly as only individuals with a positive result undergo a definitive diagnostic test. We propose a framework to overcome this limitation and estimate the prevalence of disease, sensitivity of screening, and its yield relative to no screening. Study Design and SettingA Bayesian model simultaneously combined available prevalence data on the most common mutation of MCADD (c.985A>G) in screened and nonscreened populations using the relationship between true and apparent prevalence of disease. Data originated from screening pilots in England, disease surveillance studies, and published literature. Model validity and consistency were formally checked. ResultsTrue prevalence of c.985A>G homozygotes in England was 6.2 per 100,000 individuals, and the sensitivity of the screening program was 94% (95% confidence interval [CI]: 74, 100%) compared with a detection rate in nonscreened areas of 48% (95% CI: 30, 68%) by age of 5 years. Hence, the screening program detected 47% (95% CI: 30, 60%) additional cases compared with no screening. ConclusionThe sensitivity of the screening program in England was high and our estimation approach could be adapted to inform other jurisdictions, rare diseases, and newborn screening programs.

Functional studies of 18 heterologously expressed medium-chain acyl-CoA dehydrogenase (MCAD) variants.

Medium-chain acyl-coenzyme-A dehydrogenase (MCAD) catalyzes the first step of mitochondrial beta-oxidation for medium-chain acyl-CoAs. Mutations in the ACADM gene cause MCAD deficiency presenting with life-threatening symptoms during catabolism. Since fatty-acid-oxidation disorders are part of newborn screening (NBS), many novel mutations with unknown clinical relevance have been identified in asymptomatic newborns. Eighteen of these mutations were separately cloned into the human ACADM gene, heterologously overexpressed in Escherichia coli and functionally characterized by using different substrates, molecular chaperones, and measured at different temperatures. In addition, they were mapped to the three-dimensional MCAD structure, and cross-link experiments were performed. This study identified variants that only moderately affect the MCAD protein in vitro, such as Y42H, E18K, and R6H, in contrast to the remaining 15 mutants. These three mutants display residual octanoyl-CoA oxidation activities in the range of 22% to 47%, are as temperature sensitive as the wild type, and reach 100% activity with molecular chaperone co-overexpression. Projection into the three-dimensional protein structure gave some indication as to possible reasons for decreased enzyme activities. Additionally, six of the eight novel mutations, functionally characterized for the first time, showed severely reduced residual activities < 5% despite high expression levels. These studies are of relevance because they classify novel mutants in vitro on the basis of their corresponding functional effects. This basic knowledge should be taken into consideration for individual management after NBS.

Novel biomarkers for diagnosing and understanding pathophysiology of metabolic diseases

BackgroundTandem mass spectrometric analysis of simultaneously measuredblood spot acylcarnitines and amino acids is a widely accepted andapplied method for the early detection of a number of disorders offatty acid, organic acid and amino acid metabolism. Adaptation of thisapproach has led to vastly improved clinical outcomes for a number ofdisorders including medium chain acyl-CoA dehydrogenase (MCAD)deficiency [1], very long-chain acyl-CoA dehydrogenase (VLCAD)deficiency, glutaric acidemia type 1 and maple syrup urine disease.Outcome data for other conditions are awaited but, intuitively, mostinvestigators believe that these conditions should also result in betteroutcomes if diagnosed presymptomatically [2]. The sensitivity andspecificity of the current process are very high for disorders such asMCAD deficiency but there are numerous examples where sensitivityis not sufficiently high such that positive cases may be missed. Thereis a significant literature documenting missed cases of subsequentlyfatal VLCAD deficiency that was not diagnosed in the newborn perioddespite screening for the disorder [3]. We are lookingfor analternativescreening method to reduce this false negative rate.MethodAcylcarnitinemeasurementinbody fluidsrepresentsbiomarkeraccu-mulation that is several steps away from the primary accumulating me-tabolites. For fatty acid oxidation and many organic acid defects theprimary accumulating metabolite is an intra-mitochondrial coenzyme Aspecies. This species is then converted to an acylcarnitine which exitsthe mitochondria, may be further metabolized elsewhere in the cytosol(peroxisomes, microsomes) and eventually reaches the circulationthrough unknown mechanisms. For VLCAD deficiency for instance, theprimaryaccumulatingmetabolitesshouldbeC16:0,C18:1andC18:2spe-cies but the diagnostic measurands ar e unsaturated C14 species suggest-ing extensive modification of the primary species. Presently, mostpublished acyl-CoA assays require a chromatographic separation stepwhich is generally regarded as too time consuming for screening pur-poses. To address this issue we have developed a flow injection tandemmass spectrometric protocol which can analyze all species of acyl-CoA'sin a Multiple Reaction Mode (MRM) [4]. Acyl-CoA's are intracellular bio-markers and would not be expected to accumulate outside of a cellulardomain so the method was developed initially for tissue analysis for val-idation purposes.ResultsWe analyzed normal mouse tissues and those from both the short-chain acyl-CoA dehydrogenase (SCAD) mouse and the short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD) knockout mouse. A normalprofile from the wild-type mouse liver demonstrated the expectedspecies including C16, C18:1 and C18:1 in addition to acetyl-CoA andfree CoA. There was little intermediate species accumulation. TheSCAD knockout mouse liver demonstrated the expected accumulationof butyryl-CoA whilst the SCHAD knockout mouse demonstrated accu-mulation of medium-chain species consistent with the known chain-length specificity of the enzyme which includes medium chain species.Future directionsWearenowworkingonincreasingthesensitivityoftheassayinorderto be able to analyze acyl-CoA's in the cellular component of a wholeblood sample, a requisite for newborn screening. Initial work withwhitebloodcellssuggeststhatthisisfeasibleandmaybecomeapplicableas mass spectrometers continue to evolve in terms of sensitivity.WehavebeenabletoutilizetheassaytostudyfattyacidoxidationinthegastrointestinaltractandhaverecentlydeterminedthattheGItractcan generate energy from long-chain fatty acids derived fromthedietandshortchainfattyacidsthataregeneratedbythemicrobiomeinapathwaythatappearstobeindependentofmalonyl-CoAregulation.References

The Domain-Specific and Temperature-Dependent Protein Misfolding Phenotype of Variant Medium-Chain acyl-CoA Dehydrogenase

The implementation of expanded newborn screening programs reduced mortality and morbidity in medium-chain acyl-CoA dehydrogenase deficiency (MCADD) caused by mutations in the ACADM gene. However, the disease is still potentially fatal. Missense induced MCADD is a protein misfolding disease with a molecular loss-of-function phenotype. Here we established a comprehensive experimental setup to analyze the structural consequences of eight ACADM missense mutations (p.Ala52Val, p.Tyr67His, p.Tyr158His, p.Arg206Cys, p.Asp266Gly, p.Lys329Glu, p.Arg334Lys, p.Arg413Ser) identified after newborn screening and linked the corresponding protein misfolding phenotype to the site of side-chain replacement with respect to the domain. With fever being the crucial risk factor for metabolic decompensation of patients with MCADD, special emphasis was put on the analysis of structural and functional derangements related to thermal stress. Based on protein conformation, thermal stability and kinetic stability, the molecular phenotype in MCADD depends on the structural region that is affected by missense-induced conformational changes with the central β-domain being particularly prone to structural derangement and destabilization. Since systematic classification of conformational derangements induced by ACADM mutations may be a helpful tool in assessing the clinical risk of patients, we scored the misfolding phenotype of the variants in comparison to p.Lys329Glu (K304E), the classical severe mutation, and p.Tyr67His (Y42H), discussed to be mild. Experiments assessing the impact of thermal stress revealed that mutations in the ACADM gene lower the temperature threshold at which MCAD loss-of-function occurs. Consequently, increased temperature as it occurs during intercurrent infections, significantly increases the risk of further conformational derangement and loss of function of the MCAD enzyme explaining the life-threatening clinical courses observed during fever episodes. Early and aggressive antipyretic treatment thus may be life-saving in patients suffering from MCADD.

Experimental evidence for protein oxidative damage and altered antioxidant defense in patients with medium‐chain acyl‐CoA dehydrogenase deficiency

The objective of this study was to test whether macromolecule oxidative damage and altered enzymatic antioxidative defenses occur in patients with medium-chain acyl coenzyme A dehydrogenase (MCAD) deficiency. We performed a cross-sectional observational study of in vivo parameters of lipid and protein oxidative damage and antioxidant defenses in asymptomatic, nonstressed, MCAD-deficient patients and healthy controls. Patients were subdivided into three groups based on therapy: patients without prescribed supplementation, patients with carnitine supplementation, and patients with carnitine plus riboflavin supplementation. Compared with healthy controls, nonsupplemented MCAD-deficient patients and patients receiving carnitine supplementation displayed decreased plasma sulfhydryl content (indicating protein oxidative damage). Increased erythrocyte superoxide dismutase (SOD) activity in patients receiving carnitine supplementation probably reflects a compensatory mechanism for scavenging reactive species formation. The combination of carnitine plus riboflavin was not associated with oxidative damage. These are the first indications that MCAD-deficient patients experience protein oxidative damage and that combined supplementation of carnitine and riboflavin may prevent these biochemical alterations. Results suggest involvement of free radicals in the pathophysiology of MCAD deficiency. The underlying mechanisms behind the increased SOD activity upon carnitine supplementation need to be determined. Further studies are necessary to determine the clinical relevance of oxidative stress, including the possibility of antioxidant therapy.

Resuscitation of a Neonate With Medium Chain Acyl-Coenzyme A Dehydrogenase Deficiency Using Extracorporeal Life Support

We report a neonate with medium chain acyl-coenzyme A dehydrogenase deficiency (MCAD) who had a cardiac arrest due to ventricular tachycardia and fibrillation. Extracorporeal life support (ECLS) was deployed, from which the baby was subsequently separated and discharged from hospital. This case was a rare neonatal presentation of MCAD and an uncommon indication for ECLS. We discuss the presentations of patients with MCAD and the use of ECLS for patients with possible inborn errors of metabolism and other unknown primary diagnoses.

Disorders associated with abnormal acylcarnitine profile among high risk Egyptian children

Acylcarnitine profile (ACP) is a useful tool in the biochemical diagnosis and monitoring of many acquired and inherited metabolic disorders. In the present study, acylcarnitines (ACs) were quantified in dried blood spot samples collected from 150 high risk Egyptian newborns and children using LC/MS/MS technique. They were referred to the Biochemical Genetics department in the National Research Center. Their age ranged from 1 to 36 months. Thirty seven patients had abnormal ACP diagnostic of some inherited metabolic disorders and other acquired conditions. The study revealed 5 (13.5%) with medium chain acyl CoA dehydrogenase deficiency (MCADD), 1 (2.7%) with long chain hydroxyacyl CoA dehydrogenase deficiency (LCHADD), 1 (2.7%) with multiple acyl CoA dehydrogenase deficiency (MADD), 28 (75.7%) with secondary carnitine deficiency (SCD), 1 (2.7%) with glutaric aciduria type I (GA I), and 1 (2.7%) with methylmalonic aciduria (MMA) (Tab. 8, Ref. 39).

Present Status of Expanded Newborn Screening Project for Inborn Errors of Metabolism by Tandem Mass Spectrometry

In Japan, screening for six diseases including four inborn errors of metabolism has been performed since 1977 for all neonates to prevent severe mental handicaps or death. A rapid screening procedure for analysis of several amino acids and acylcarnitines in blood spots by tandem mass spectrometry was developed by Millington DS et al. in the early 1990s. Although it is called expanded (or extended) newborn screening, the procedure is insufficiently sensitive to or specific for several diseases. Screening for all diseases that can be screened using this procedure is suggested to be cost-ineffective. Many European countries target only two diseases: medium-chain acyl-CoA dehydrogenase deficiency and phenylketonuria; their prevalence in Caucasian populations is very high, but some countries target more than twenty diseases and others an intermediate number. A pilot study targeting 22 diseases suggests that the combined incidence is one per 9,000 (0.01%) in Japan. This primary screening requires secondary screening to confirm the disease using urine, and either organic acids with solvent extraction or metabolome without fractionation are analyzed by gas chromatography-mass spectrometry. There is no need for primary or secondary screening tests to be performed at the same laboratory because the skills required are quite different. Understanding of the methodological problems of tandem mass screening and amelioration of variation and false positivity rate of this screening method among laboratories are critical to the success of the screening system in Japan. GC/MS-based urine metabolomics is expected to become one of the primary screening methodologies for neonates/infants who are already ill.