MCAD deficiency caused by compound heterozygous pathogenic variants in ACADM

Medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency is an autosomal recessive disease caused by biallelic pathogenic ACADM variants. We report a case of an asymptomatic Japanese girl with MCAD deficiency caused by compound heterozygous pathogenic variants (NM_000016.5:c.1040G > T (p.Gly347Val) and c.449_452delCTGA (p.Thr150ArgfsTer4)). Because the MCAD residual activity in lymphocytes of the patient was below the limit of quantification, both variants are likely to cause complete loss of MCAD enzymatic activity.

Diagnostic potential of stored dried blood spots for inborn errors of metabolism: a metabolic autopsy of medium-chain acyl-CoA dehydrogenase deficiency

AimIt is estimated that 1–5% of sudden infant death syndrome (SIDS) cases might be caused by undiagnosed inborn errors of metabolism (IEMs); however, the postmortem identification of IEMs remains difficult. This study aimed to evaluate the usefulness of dried blood spots (DBSs) stored after newborn screening tests as a metabolic autopsy to determine the causes of death in infants and children who died suddenly and unexpectedly.MethodsInfants or toddlers who had suddenly died without a definite diagnosis between July 2008 and December 2012 at Kyushu University Hospital in Japan were enrolled in this study. Their Guthrie cards, which had been stored for several years at 4–8°C, were used for an acylcarnitine analysis by tandem mass spectrometry to identify inborn errors of metabolism.ResultsFifteen infants and children who died at less than 2 years of age and for whom the cause of death was unknown were enrolled for the study. After correcting the C0 and C8 values assuming the hydrolysation of acylcarnitine in the stored DBSs, the corrected C8 value of one case just exceeded the cut-off level for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency screening. Genetic and biochemical analyses confirmed this patient to have MCAD deficiency.ConclusionDBSs stored after newborn screening tests are a promising tool for metabolic autopsy. The appropriate compensation of acylcarnitine data and subsequent genetic and biochemical analyses are essential for the postmortem diagnosis of inborn errors of metabolism.

Medium-chain acyl-CoA dehydrogenase deficiency: Two novel ACADM mutations identified in a retrospective screening

Objective The aim of this study was to determine whether an expanded newborn screening programme, which is not yet available in Slovenia, would have detected the first two patients with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in the country. Two novel ACADM mutations are also described. Methods Both patients were diagnosed clinically; follow-up involved analysis of organic acids in urine, acylcarnitines in dried blood spots, and genetic analysis of ACADM. Cut-off values of acylcarnitines in newborns were established using analysis of 10,000 newborns in a pilot screening study. Results In both patients, analysis of the organic acids in urine showed a possible β-oxidation defect, while the specific elevation of acylcarnitines confirmed MCAD deficiency. Subsequent genetic analysis confirmed the diagnosis; both patients were compound heterozygotes, each with one novel mutation (c.861 + 2T > C and c.527_533del). The results from a retrospective analysis of newborn screening cards clearly showed major elevations of MCAD-specific acylcarnitines in the patients. Conclusions An expanded newborn screening programme would be beneficial because it would have detected MCAD deficiency in both patients before the development of clinical signs. Our study also provides one of the first descriptions of ACADM mutations in Southeast Europe.