Mutations of ACADS gene associated with short-chain acyl-coenzyme A dehydrogenase deficiency

Short-chain acyl-coenzyme A dehydrogenase deficiency (SCADD) is an autosomal recessive disorder of mitochondrial fatty acid oxidation associated with mutations in the ACADS gene (Acyl-CoA Dehydrogenase, Short-chain, OMIM #606885). SCADD is a heterogeneous condition that has been associated with various clinical phenotypes ranging from fetal metabolic decompensation in infancy to asymptomatic individuals. Here, the first Korean neonate diagnosed with SCADD by biochemical and genetic findings is reported. The patient has remained asymptomatic by avoiding hypoglycemia. An increased concentration of butylcarnitine was detected on newborn screening. Subsequent urine organic acid analysis showed increased urinary excretion of ethylmalonic acid. To confirm the presence of the genetic abnormality, all the coding exons of the ACADS gene and flanking introns were amplified by the polymerase chain reaction (PCR). Sequence analysis of the ACADS gene revealed novel homozygous missence mutations, c. 1031A>G (p.E344G) in exon 9. In summary, the first Korean patient with confirmed SCADD by genetic analysis is reported with novel mutation.     

Sudden death in medium chain acyl-coenzyme a dehydrogenase deficiency (MCADD) despite newborn screening

IntroductionMedium chain acyl-CoA dehydrogenase deficiency (MCADD) is the most frequent of the fatty acid oxidation disorders (FAOD), a group caused by defects in the mitochondrial B-oxidation of fatty acids. Fatty acid oxidation is critical in supplying energy during periods when glucose is limited or when energy needs are increased beyond the availability of glucose. In MCADD, this energy shortage can result in acute metabolic episodes or sudden death. The prevention of sudden death from MCADD served as the primary impetus to expand newborn screening. However, we have experienced sudden death in four children with MCADD despite their detection by newborn screening. The purpose of this report is to alert others to the danger of sudden death in MCADD even when it is detected by newborn screening, to identify the clinical symptoms that precede sudden death, and to examine the relationship between the newborn screening result and the risk for sudden death.MethodsWe describe these children and their metabolic findings with emphasis on their newborn screening octanoylcarnitine (C8) level, the primary marker for newborn detection of MCADD. We also performed a literature search of cases of sudden death in MCADD in which the clinical status preceding death is described.ResultsThe newborn screening C8 levels in our four cases were markedly elevated, ranging from 8.4 to 24.8 μmol/L (cut off < 0.8 μmol/L). Only two of the children were homozygous for the common c.985A>G MCAD mutation; the other two were heterozygous for this mutation. Similarly, among the eight reported cases which included MCAD genotypes, five were homozygous for the c.985A>G mutation, while two were heterozygous and one was homozygous for a splice site mutation. Vomiting 12–24 h before sudden death was present in all four of our cases, and the review of reported cases of sudden death in MCADD disclosed vomiting as a frequent symptom.ConclusionWe suggest that in MCADD (1) a newborn screening C8 level of 6 μmol/L or greater represents particular risk of sudden death; (2) that MCAD genotypes other than homozygosity for the c.985A>G mutation are also associated with sudden death; (3) that vomiting is a frequent symptom preceding sudden death; and (4) social support and medical follow-up of these families are crucial in reducing the occurrence of sudden death.     

Medium chain acyl-CoA dehydrogenase deficiency detected among Hispanics by New Jersey newborn screening

In the follow-up of New Jersey newborn screens suggestive of medium chain acyl-CoA dehydrogenase deficiency (MCADD) during a 30-month period, we identified five patients of Hispanic American ethnicity. With information provided by the New Jersey Department of Health and Human Services Newborn Screening program we calculated an overall cumulative incidence of approximately 7.20/100,000 for MCADD; 7.58/100,000 among Hispanic Americans and 7.08/100,000 among non-Hispanic Americans. Among the five Hispanic American infants who screened positive, a common variant (c.443G>A [p.R148K]) was identified which accounted for 30% of the alleles; c.799G>A (p.G267R) and c.985A>G (p.K329E) each accounted for an additional 20%; and a novel variant c.302G>A (p.G101E) was identified in one patient. Although treated prospectively during interim illnesses to prevent unwanted sequelae; till date, none of the patients carrying the c.443G>A variant have been symptomatic. ? 2012 Wiley Periodicals, Inc.     

Diagnosis of a patient with a kinetic variant of medium and short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency by newborn screening

Medium and short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is a rare cause of impaired mitochondrial fatty acid oxidation. We present a case report of a patient with hyperinsulinism and homozygosity for a novel mutation causing a kinetic variant of the enzyme. The diagnosis was initially inferred by abnormal newborn screening acylcarnitine analysis with elevated C4-hydroxyacylcarnitine.     

Maternal medium-chain acyl-CoA dehydrogenase deficiency identified by newborn screening

Prior to the advent of expanded newborn screening, sudden and unexplained death was often the first and only symptom of medium-chain acyl-CoA dehydrogenase deficiency (MCADD). With the use of tandem mass spectrometry, infants can now be identified and treated before a life threatening metabolic decompensation occurs. Newborn screening has also been shown to detect previously undiagnosed maternal inborn errors of metabolism. We have now diagnosed two women with MCADD following the identification of low free carnitine in their newborns. While one of the women reported prior symptoms of fasting intolerance, neither had a history of metabolic decompensation or other symptoms consistent with a fatty acid oxidation disorder. These cases illustrate the importance of including urine organic acid analysis and an acylcarnitine profile as part of the confirmatory testing algorithm for mothers when low free carnitine is identified in their infants.     

Argininosuccinate lyase deficiency: Longterm outcome of 13 patients detected by newborn screening

Argininosuccinate lyase deficiency is a urea cycle disorder which can present in the neonatal period with hyperammonemic encephalopathy, or later in childhood with episodic vomiting, growth and developmental delay. Abnormal hair, hepatomegaly, and hepatic fibrosis are unique features of this disorder. Twelve patients with argininosuccinate lyase deficiency were ascertained between 4 and 6 weeks of age by urine amino acid screening. One infant in a previously identified family was diagnosed shortly after birth. Diagnosis was confirmed by enzyme assay in red blood cells and/or skin fibroblasts. At the time of last follow-up, patients had been followed for 13–33 years. All patients were asymptomatic at detection, 7 had slightly increased blood ammonia, and all were initially treated with low-protein diet. Utilization of ¹⁴C-citrulline by intact skin fibroblasts measured by ¹⁴C incorporation into macromolecules was 74–135% of the control mean for 7 of the 8 patients studied. Nine patients had normal development, 4 had learning disability, 6 had EEG abnormalities, 3 had seizure disorder. None had any episodes of hyperammonemic coma. None had hepatomegaly. Patients detected by screening had higher enzyme activity measured by the ¹⁴C-citrulline incorporation assay than comparison groups of patients with neonatal-onset and with late-onset detected by clinical disease. The ability to utilize ¹⁴C-citrulline by intact fibroblasts seems to correlate with clinical outcome and may have prognostic value. It is likely that early diagnosis and treatment contributed to the relatively mild clinical course of the study group.     

Follow-up of patients with short-chain acyl-CoA dehydrogenase and isobutyryl-CoA dehydrogenase deficiencies identified through newborn screening: one center's experience

PurposeTo evaluate the growth, development, and medical histories of children with short-chain acyl-CoA dehydrogenase and isobutyryl-CoA dehydrogenase deficiencies identified through newborn screening.MethodsChart review of patients diagnosed with short-chain acyl-CoA dehydrogenase or isobutyryl-CoA dehydrogenase deficiency at our center.ResultsThere were 16 children with short-chain acyl-CoA dehydrogenase deficiency, including 10 with two pathogenic mutations, and 8 with isobutyryl-CoA dehydrogenase deficiency. All but one patient has had normal growth and development, and that patient also had the 22q deletion syndrome.ConclusionOur data and previous reports suggest that the majority of individuals with short-chain acyl-CoA dehydrogenase or isobutyryl-CoA dehydrogenase deficiencies have normal growth and development.Genet Med 2012:14(3):342–347     

Alternative DNA-based newborn screening for glucose-6-phosphate dehydrogenase deficiency

Newborn screening for G6PD deficiency has been carried out in several countries for more than 25 years. A semi-quantitative enzymatic assay has been used in most laboratories, however, heat inactivation during the summer can cause a significant increase in the false positive rate for this assay. We have developed an alternative DNA-based newborn screening assay for the detection of common mutations within the G6PD gene. The panel of mutations includes the common African A- mutation (G202A;A376G), the common Mediterranean mutation (C563T), and two common Chinese mutations (G1376T and G1388A). A parallel study was performed through screening a total of 4245 neonatal specimens using both the enzymatic and the DNA-based assays. In this population, 49 newborns were identified as hemizygous or homozygous for the A- mutation with an average enzyme activity of 59 microM, 323 were identified as a carrier or unaffected with an average enzyme activity of 208 microM, and no mutation was detected for the remaining 3873 specimens with an average enzyme activity of 234 microM. With this panel of mutations, more than 90% of all affected infants can be identified in our population.     

Successful outcomes of older adolescents and adults with profound biotinidase deficiency identified by newborn screening

PurposeWe began screening newborns for biotinidase deficiency disorder in 1984, and now all states in the United States and many countries perform this screening. The purpose of this study was to determine the outcomes of older adolescent and adult individuals with the disorder identified by newborn screening.Subjects and methodsWe located and surveyed, by questionnaire and telephone interviews, 44 individuals with profound biotinidase deficiency identified by newborn screening with a mean age of 23.1 years.ResultsAll individuals had successfully completed high school, and many were attending or had completed college or graduate school. Compliance in using biotin has been excellent. Several individuals developed a variety of symptoms when they discontinued biotin for days or weeks. These features readily resolved when biotin was resumed. In addition, five treated women had nine uneventful pregnancies and deliveries.ConclusionsNewborn screening for profound biotinidase deficiency and early treatment with biotin result in excellent outcomes for older adolescents and adults with the disorder. In addition, mothers with profound biotinidase deficiency who were treated with biotin had pregnancies with good outcomes. These outcome results indicate that newborn screening for biotinidase deficiency is one of the most successful newborn screening programs.Genet Med 19 4, 396–402.     

Liver disease in alpha1-antitrypsin deficiency detected by screening of 200,000 infants.

We prosepctively studied 200,000 newborns to determine the frequency and clinical characteristics of alpha1-antitrypsin deficiency. One hundred and twenty Pi Z, 48 Pi SZ, two PI Z-and one Pi S-infants were identified and followed to the age of six months. Fourteen of 120 Pi Z infants had prolonged obstructive jaundice, nine with severe clinical and laboratory evidence of liver disease. Five had only laboratory evidence of liver disease. Eight other Pi Z infants had minimal abnormalities in serum bilirubin and hepatic enzyme activity and variable hepatosplenomegaly. All 22 Pi Z infants with hepatic abnormalities, two thirds of whom were made, appeared healthy at six months of age. Ninety-eight Pi Z infants did not have clinical liver disease, but liver-function tests gave abnormal results in 44 of 84 at three months, and in 36 of 60 at six months of age. The number of small-for-gestational-age infants was greater (P less than 0.001) among those with clinical liver disease. None of the 48 Pi SZ infants had clinical liver disease, but 10 of 42 at three months and one of 22 at six months of age had abnormal liver function. The Pi Z and Pi SZ phenotypes are associated with covert or readily apparent hepatic dysfunction in the first three months of life.     

Clinical and biochemical outcomes of patients with medium-chain acyl-CoA dehydrogenase deficiency

BackgroundMedium-Chain Acyl-CoA Dehydrogenase (MCAD) deficiency is a fatty acid oxidation disorder that can have variable clinical severity. There is still limited information on its clinical presentation and longitudinal history by genotype, and effectiveness of newborn screening (NBS).MethodsRetrospective data were collected from 90 patients (44 female, 46 male) to compare biochemical data with clinical outcomes. The frequency of adverse events (number of hypoglycemia-related ER visits and admissions) was assessed by genotype (homozygosity or not for the common pathogenic variant, p.Lys329Glu, in the ACADM gene), and method of diagnosis (NBS vs. clinical).ResultsMCAD deficiency in Utah was more frequent compared to the United States average (1: 9266 versus 1:17,759 newborns). With age, C8-carnitine did not change significantly whereas C2-carnitine decreased (p < .001), possibly reflecting reduced carnitine supplementation typically seen with age. Children with MCAD deficiency had normal growth. p.Lys329Glu homozygotes had higher NBS C8-carnitine (23.4 ± 19.6 vs. 6.6 ± 3.0 μmol/L) and lifetime plasma C8-carnitine levels (6.2 ± 5 vs. 3.6 ± 1.9 μmol/L) compared to patients with at least one other pathogenic variant (p < .001 for both) and higher transaminases compared to compound heterozygotes (ALT 41.9 ± 6.2 vs. 31.5 ± 3.7 U/L, AST 63.9 ± 5.8 vs. 45.7 ± 1.8 U/L, p < .05 for both). On average, p.Lys329Glu homozygotes had more hypoglycemic events than compound heterozygotes (1.44 versus 0.49 events/patient) as did patients diagnosed clinically compared to those diagnosed by NBS (2.15 versus 0.62 events/patient), though these differences were not statistically significant. Neonatal death was observed before results of newborn screening were available in one patient homozygous for the common p.Lys329Glu pathogenic variant, but severe neonatal complications (hypoglycemia, cardiac arrhythmia) were also seen in patients with other mutations. No irreversible complications were observed after diagnosis in any patient with MCAD deficiency.DiscussionHomozygosity for the common ACADM p.Lys329Glu pathogenic variant was associated with increased levels of C8-carnitine and transaminases. Newborn screening provides the opportunity to reduce morbidity and post-neonatal mortality in all patients with MCAD deficiency, regardless of genotype.     

Outcomes of four patients with homocysteine remethylation disorders detected by newborn screening

PurposeWe evaluated the clinical outcome in homocysteine remethylation disorders following newborn screening (NBS) and initiation of early specific treatment.MethodsFive patients with remethylation disorders were included in this study.ResultsTwo asymptomatic patients (one with cblG and one with cblE) were identified by NBS using an approach that combines a postanalytical interpretive tool (available on the Region 4 Stork (R4S) collaborative project website, http://www.clir-r4s.org) and a second-tier test for total homocysteine determination. Both the initial screening and the second-tier test are performed on the same blood spot, with no additional patient contact, resulting in no false-positive outcomes. Two additional patients with methylenetetrahydrofolate reductase deficiency were detected by NBS using low methionine as a marker. Although already symptomatic despite the early diagnosis, the latter two patients greatly improved with treatment and their outcomes are compared with that of another patient with methylenetetrahydrofolate reductase deficiency and significant morbidity who was diagnosed clinically at 3 months of age.ConclusionEarly detection by NBS and timely and specific treatment considerably improve at least short-term outcomes of homocysteine remethylation disorders. When a remethylation disorder is suspected, group-specific treatment could be started prior to the completion of in vitro confirmatory testing because all disorders from this group require similar intervention.     

Proteomic investigation of cultivated fibroblasts from patients with mitochondrial short-chain acyl-CoA dehydrogenase deficiency

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is a rare inherited autosomal recessive disorder with not yet well established mechanisms of disease. In the present study, the mitochondrial proteome of five symptomatic patients homozygous for missense variations in the SCAD gene ACADS was investigated in an extensive large-scale proteomic study to map protein perturbations linked to the disease.Fibroblast cultures of patient cells homozygous for either c.319C>T/p.Arg107Cys (n = 2) or c.1138C>T/p.Arg380Trp (n = 3) in ACADS, and healthy controls (normal human dermal fibroblasts), were studied. The mitochondrial proteome derived from these cultures was analyzed by label free proteomics using high mass accuracy nanoliquid chromatography tandem mass spectrometry (nanoLC–MS/MS).More than 300 mitochondrial proteins were identified and quantified. Thirteen proteins had significant alteration in protein levels in patients carrying variation c.319C>T in ACADS compared to controls and they belonged to various pathways, such as the antioxidant system and amino acid metabolism. Twenty-two proteins were found significantly altered in patients carrying variation c.1138C>T which included proteins associated with fatty acid β-oxidation, amino acid metabolism and protein quality control system. Three proteins were found significantly regulated in both patient groups: adenylate kinase 4 (AK4), nucleoside diphosphate kinase A (NME1) and aldehyde dehydrogenase family 4 member A1 (ALDH4A1). Proteins AK4 and NME1 deserve further investigation because of their involvement in energy reprogramming, cell survival and proliferation with relevance for SCAD deficiency and related metabolic disorders.     

Development of a newborn screening follow-up algorithm for the diagnosis of isobutyryl-CoA dehydrogenase deficiency.

PURPOSE: Isobutyryl-CoA dehydrogenase deficiency is a defect in valine metabolism and was first reported in a child with cardiomyopathy, anemia, and secondary carnitine deficiency. We identified 13 isobutyryl-CoA dehydrogenase-deficient patients through newborn screening due to an elevation of C4-acylcarnitine in dried blood spots. Because C4-acylcarnitine represents both isobutyryl- and butyrylcarnitine, elevations are not specific for isobutyryl-CoA dehydrogenase deficiency but are also observed in short-chain acyl-CoA dehydrogenase deficiency. To delineate the correct diagnosis, we have developed a follow-up algorithm for abnormal C4-acylcarnitine newborn screening results based on the comparison of biomarkers for both conditions. METHODS: Fibroblast cultures were established from infants with C4-acylcarnitine elevations, and the analysis of in vitro acylcarnitine profiles provided confirmation of either isobutyryl-CoA dehydrogenase or short-chain acyl-CoA dehydrogenase deficiency. Isobutyryl-CoA dehydrogenase deficiency was further confirmed by molecular genetic analysis of the gene encoding isobutyryl-CoA dehydrogenase (ACAD8). Plasma acylcarnitines, urine acylglycines, organic acids, and urine acylcarnitine results were compared between isobutyryl-CoA dehydrogenase- and short-chain acyl-CoA dehydrogenase-deficient patients. RESULTS: Quantification of C4-acylcarnitine in plasma and urine as well as ethylmalonic acid in urine allows the differentiation of isobutyryl-CoA dehydrogenase-deficient from short-chain acyl-CoA dehydrogenase-deficient cases. In nine unrelated patients with isobutyryl-CoA dehydrogenase deficiency, 10 missense mutations were identified in ACAD8. To date, 10 of the 13 isobutyryl-CoA dehydrogenase-deficient patients remain asymptomatic, two were lost to follow-up, and one patient required frequent hospitalizations due to emesis and dehydration but is developing normally at 5 years of age. CONCLUSION: Although the natural history of isobutyryl-CoA dehydrogenase deficiency must be further defined, we have developed an algorithm for rapid laboratory evaluation of neonates with an isolated elevation of C4-acylcarnitine identified through newborn screening.