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      Medium chain acyl-CoA dehydrogenase deficiency in a premature infant

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          Abstract

          Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is identified by newborn screening (NBS). The natural history of MCADD includes metabolic decompensation with hypoglycemia, hyperammonemia, seizures, coma, and death. NBS enables expectant management thus severe symptoms are rare in managed patients. We report premature birth of an MCADD affected infant and resultant management challenges. Nutritional support advanced from parenteral nutrition at 24 hours to enteral feeds. A NBS sample was collected day 2, positive results for MCADD was reported day six, and diagnostic tests were performed day seven. Lab results confirmed MCADD; however, representation of pathologic analytes was so extreme that ingestion of medium chain triglycerides was suspected and subsequently confirmed. Diet was adjusted and reflected in moderation of pathologic analytes. This case emphasizes the need for prompt review NBS results in premature infants. Implementing informatic intervention within electronic medical records, when a disorder requiring special nutritional intervention is identified, will protect premature infants in this vulnerable setting. Standard of care management provided premature infants may be contraindicated in the context of a comorbid inborn error of metabolism.

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          Newborn screening.

          The aim of newborn screening is to detect newborns with serious, treatable disorders so as to facilitate appropriate interventions to avoid or ameliorate adverse outcomes. Mass biochemical testing of newborn babies was pioneered in the 1960s with the introduction of screening for phenylketonuria, a rare inborn error of metabolism, tested by using a dried blood spot sample. The next disorder introduced into screening programs was congenital hypothyroidism and a few more much rarer disorders were gradually included. Two recent advances have greatly changed the pace: modification of tandem mass spectrometry and DNA extraction and analysis from newborn screening dried blood spot. These two technologies make the future possibilities of newborn screening seem almost unlimited. Newborn screening tests are usually carried out on a dried blood spot sample, for which there are special analytical considerations. Dried blood spot calibrators and controls, prepared on the same lot number of filter paper, are needed. Methods have a co-efficient of variation of about 10% due to the increased variability of a dried filter paper sample compared with other biochemical samples. The haematocrit is an additional variable not able to be measured. Also of importance is obtaining a balance between the sensitivity and specificity of each assay. Fixing cut-off points for action needs consideration of what is an acceptable percentage of the population to recall for further testing. Few assays are 100% discriminatory. Programs in Australasia currently screen for at least 30 disorders. Detection of these requires not only the assay of a primary marker but often determination of a ratio of that marker with another, or possibly an alternative assay, for example a DNA mutation. The most important disorders screened for are described briefly: phenylketonuria, primary congenital hypothyroidism, cystic fibrosis, the galactosaemias, medium-chain acyl-CoA dehydrogenase deficiency, glutaryl-CoA dehydrogenase deficiency and congenital adrenal hyperplasia, together with several other disorders detectable by tandem mass spectrometry. Newborn screening deals with rare disorders and benefit cannot be shown easily without very large pilot studies. There have been randomised controlled trials of screening for cystic fibrosis, and now several studies are beginning to establish the benefit of tandem mass spectrometry screening for disorders of fatty acid and amino acid metabolism. Two things will influence the new directions for newborn screening: the development of effective treatments for hitherto untreatable disorders, and advancing technology, enabling new testing strategies to be developed. There are novel treatments on the horizon for many discrete disorders. Susceptibility testing has recently been considered for newborn screening application, but is more controversial. Newborn screening has entered a new and exciting phase, with an explosion of new treatments, new technologies, and, possibly in the future, new preventive strategies.
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            Medium-chain acyl-coenzyme A dehydrogenase deficiency: clinical course in 120 affected children.

            Medium-chain acyl-coenzyme A dehydrogenase deficiency is an autosomal recessive disorder of beta-oxidation of fatty acids manifested by episodic hypoglycemia, encephalopathy, apnea, and sudden death. Medical data were obtained on 120 patients with medium-chain acyl-coenzyme A dehydrogenase deficiency referred to Duke University Medical Center for biochemical testing. There were 55 male and 65 female subjects ranging from birth to 19 years of age; 118 subjects were white. Twenty-three children (19%) died before the diagnosis was made. Follow-up data were available in the 97 surviving patients for an average of 2.6 years after diagnosis. Psychodevelopmental data were collected on 73 patients older than 2 years of age. Unexpected morbidity included developmental and behavioral disability, chronic muscle weakness, failure to thrive, and cerebral palsy. We conclude that unidentified patients with this disorder have a significant risk of sudden death in early childhood and that survivors have a significant risk of developmental disability and chronic somatic illness.
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              Medium-chain acyl-CoA dehydrogenase (MCAD) mutations identified by MS/MS-based prospective screening of newborns differ from those observed in patients with clinical symptoms: identification and characterization of a new, prevalent mutation that results in mild MCAD deficiency.

              Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most frequently diagnosed mitochondrial beta-oxidation defect, and it is potentially fatal. Eighty percent of patients are homozygous for a common mutation, 985A-->G, and a further 18% have this mutation in only one disease allele. In addition, a large number of rare disease-causing mutations have been identified and characterized. There is no clear genotype-phenotype correlation. High 985A-->G carrier frequencies in populations of European descent and the usual avoidance of recurrent disease episodes by patients diagnosed with MCAD deficiency who comply with a simple dietary treatment suggest that MCAD deficiency is a candidate in prospective screening of newborns. Therefore, several such screening programs employing analysis of acylcarnitines in blood spots by tandem mass spectrometry (MS/MS) are currently used worldwide. No validation of this method by mutation analysis has yet been reported. We investigated for MCAD mutations in newborns from US populations who had been identified by prospective MS/MS-based screening of 930,078 blood spots. An MCAD-deficiency frequency of 1/15,001 was observed. Our mutation analysis shows that the MS/MS-based method is excellent for detection of MCAD deficiency but that the frequency of the 985A-->G mutant allele in newborns with a positive acylcarnitine profile is much lower than that observed in clinically affected patients. Our identification of a new mutation, 199T-->C, which has never been observed in patients with clinically manifested disease but was present in a large proportion of the acylcarnitine-positive samples, may explain this skewed ratio. Overexpression experiments showed that this is a mild folding mutation that exhibits decreased levels of enzyme activity only under stringent conditions. A carrier frequency of 1/500 in the general population makes the 199T-->C mutation one of the three most prevalent mutations in the enzymes of fatty-acid oxidation.
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                Author and article information

                Journal
                Pediatr Rep
                PR
                Pediatric Reports
                PAGEPress Scientific Publications, Pavia, Italy
                2036-749X
                2036-7503
                21 November 2017
                21 November 2017
                : 9
                : 4
                : 7045
                Affiliations
                [1 ]Department of Pathology
                [2 ]Division of Medical Genetics, Children’s Hospital of Pittsburgh , PA, USA
                Author notes
                Department of Pathology, Children’s Hospital of Pittsburgh, 4401 Penn Avenue, Pittsburgh, PA 15224, USA. +1.412.692.9874. dobrowolskis@ 123456upmc.edu

                Contributions: SFD, biochemical genetic assessments, composition of manuscript; LGG, initial management of patient, contributed to manuscript composition; JV, consultation on management, contributed to manuscript composition.

                Conflict of interest: the authors declare no potential conflict of interest.

                Article
                10.4081/pr.2017.7045
                5733391
                beda9628-0a5d-4ab4-92a2-6b9d57dfa944
                ©Copyright S.F. Dobrowolski et al., 2017

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 11 January 2017
                : 17 August 2017
                : 18 August 2017
                Page count
                Figures: 1, Tables: 1, Equations: 0, References: 10, Pages: 3
                Categories
                Case Report

                Pediatrics
                mcad deficiency,prematurity,nutritional support,decompensation,medium chain triglycerides

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