Yuval E. Landau

Genomics in Newborn Screening

ewborn screening has substantially changed the geneticmetabolic world and greatly expanded the concept of preventive medicine. This expansion has been marked by two major milestones in the 50-year history of newborn screening: the first, pre-tandem mass spectrometry, included the early detection of phenylketonuria (PKU), galactosemia, homocystinuria, maple syrup urine disease, congenital hypothyroidism, congenital adrenal hyperplasia, sickle cell disease, and biotinidase deficiency; the second, tandem mass spectrometry-based, has seen an explosive increase in information, often instrumental for diagnosis, prevention, and appropriate management of many additional metabolic disorders including the organic acidemias and fatty acidoxidation defects not previously covered. The latter era, however, has also had its share of shortcomings and pitfalls, much of which related to inconclusive diagnosis and incomplete knowledge of natural history. Determining the precise disorder in the identified infant is critical to his/her proper clinical care and treatment as well as to providing accurate information and genetic counseling to the family. There are several possibilities for making a definitive diagnosis. In some diseases, such as tyrosinemia type I, there is a specific analyte, succinylacetone, which defines the disorder. In other disorders, represented most frequently by PKU, the metabolite profile is so abnormal and so characteristic that there is virtually no doubt as to the diagnosis. Many other disorders now included in newborn screening, however, require a determination of clearly reduced activity of the relevant enzyme or finding two pathogenic mutations in the gene that encodes the enzyme to unequivocally establish the diagnosis. Proving reduced enzyme activity can be considered the gold standard but enzyme assays may require tissue not readily accessible or assays not widely available or that sometimes yield equivocal results. Determining the mutations (genotyping) is more widely available and easier to perform but its role has not been clearly formulated. The limited genotyping for 1 or only a very few mutations known to be frequent in a disorder has been implemented in the newborn

Pediatric Neurologic Complications Associated With Influenza A H1N1.

Influenza is associated with a variety of neurologic complications. Although the epidemiologic and clinical characteristics of influenza A H1N1 were reviewed in depth, only brief descriptions of neurologic complications exist. We describe the neurologic complications of children hospitalized with influenza A H1N1 infection. We undertook a retrospective study of all hospitalized children with laboratory-confirmed influenza A H1N1 infection accompanied by neurologic complications during a 4-month winter period. Their demographics and clinical characteristics of neurologic presentations were reviewed. Fourteen of 74 children (19%) with laboratory-confirmed influenza A H1N1 infection presented with neurologic complications. Eleven (11/14, 79%) were previously healthy, and three exhibited chronic conditions. Ten (10/14, 71%) presented with seizures: six were febrile, and four were nonfebrile. Other complications included transverse myelitis, myositis, expressive aphasia, and syncope. Only the child with transverse myelitis required a course of rehabilitation. Neurologic complications associated with influenza A H1N1 in our patients were relatively mild. Seizures (febrile or nonfebrile) were the most common. However, the possibility of influenza A H1N1 infection should be borne in mind when diagnosing children with neurologic signs during the influenza A H1N1 season.

Biallelic Mutations in DNAJC12 Cause Hyperphenylalaninemia, Dystonia, and Intellectual Disability

Phenylketonuria (PKU, phenylalanine hydroxylase deficiency), an inborn error of metabolism, can be detected through newborn screening for hyperphenylalaninemia (HPA). Most individuals with HPA harbor mutations in the gene encoding phenylalanine hydroxylase (PAH), and a small proportion (2%) exhibit tetrahydrobiopterin (BH4) deficiency with additional neurotransmitter (dopamine and serotonin) deficiency. Here we report six individuals from four unrelated families with HPA who exhibited progressive neurodevelopmental delay, dystonia, and a unique profile of neurotransmitter deficiencies without mutations in PAH or BH4 metabolism disorder-related genes. In these six affected individuals, whole-exome sequencing (WES) identified biallelic mutations in DNAJC12, which encodes a heat shock co-chaperone family member that interacts with phenylalanine, tyrosine, and tryptophan hydroxylases catalyzing the BH4-activated conversion of phenylalanine into tyrosine, tyrosine into L-dopa (the precursor of dopamine), and tryptophan into 5-hydroxytryptophan (the precursor of serotonin), respectively. DNAJC12 was undetectable in fibroblasts from the individuals with null mutations. PAH enzyme activity was reduced in the presence of DNAJC12 mutations. Early treatment with BH4 and/or neurotransmitter precursors had dramatic beneficial effects and resulted in the prevention of neurodevelopmental delay in the one individual treated before symptom onset. Thus, DNAJC12 deficiency is a preventable and treatable cause of intellectual disability that should be considered in the early differential diagnosis when screening results are positive for HPA. Sequencing of DNAJC12 may resolve any uncertainty and should be considered in all children with unresolved HPA.

Neuropsychological Outcomes in Fatty Acid Oxidation Disorders: 85 Cases Detected by Newborn Screening

Mitochondrial fatty acid oxidation disorders include conditions in which the transport of activated acyl-Coenzyme A (CoA) into the mitochondria or utilization of these substrates is disrupted or blocked. This results in a deficit in the conversion of fat into energy. Most patients with fatty acid oxidation defects are now identified through newborn screening by tandem mass spectrometry. With earlier identification and preventative treatments, mortality and morbidity rates have improved. However, in the absence of severe health and neurological effects from these disorders, subtle developmental delays or neuropsychological deficits have been noted. Medical records were reviewed to identify outcomes in 85 children with FAODs diagnosed through newborn screening and followed at one metabolic center. Overall, 54% of these children identified through newborn screening experienced developmental challenges. Speech delay or relative weakness in language was noted in 26 children (31%) and motor delays were noted in 24 children (29%). The majority of the 46 children receiving psychological evaluations performed well within the average range, with only 11% scoring <85 on developmental or intelligence tests. These results highlight the importance of screening children with fatty acid oxidation disorders to identify those with language, motor, or cognitive delay. Although expanded newborn screening dramatically changes the health and developmental outcomes in many children with fatty acid oxidation disorders, it also complicates the interpretation of biochemical and molecular findings and raises questions about the effectiveness or necessity of treatment in a large number of cases. Only by systematically evaluating developmental and neuropsychological outcomes using standardized methods will the true implications of newborn screening, laboratory results, and treatments for neurocognitive outcome in these disorders become clear.

Long-term outcome of expanded newborn screening at Boston children’s hospital: benefits and challenges in defining true disease

IntroductionThere is no universal consensus of the disorders included in newborn screening programs. Few studies so far, mostly short-term, have compared the outcome of disorders detected by expanded newborn screening (ENBS) to the outcome of the same disorders detected clinically.MethodsWe compared the clinical and neurodevelopmental outcomes in patients with metabolic disorders detected by ENBS, including biotinidase testing, with those detected clinically and followed at the Metabolism Clinic at Boston Children’s Hospital.ResultsOne hundred eighty-nine patients came to attention from ENBS and 142 were clinically diagnosed. 3-methylcrotonyl-CoA carboxylase, biotinidase, and carnitine deficiencies were exclusively identified by ENBS and medium chain acyl-CoA dehydrogenase (MCADD) and very long chain acyl-CoA dehydrogenase deficiencies (VLCADD) were predominantly identified by ENBS whereas the organic acid disorders more often came to attention clinically. Only 2% of the ENBS-detected cases had clinically severe outcomes compared to 42% of those clinically detected. The mean IQ score was 103 + 17 for the ENBS-detected cases and 77 + 24 for those clinically detected. Those newly included disorders that seem to derive the greatest benefit from ENBS include the fatty acid oxidation disorders, profound biotinidase deficiency, tyrosinemia type 1, and perhaps carnitine deficiency.ConclusionAlthough the NBS-identified and clinically-identified cohorts were not completely comparable, this long-term study shows likely substantial improvement overall in the outcome of these metabolic disorders in the NBS infants. Infants with mild disorders and benign variants may represent a significant number of infants identified by ENBS. The future challenge will be to unequivocally differentiate the disorders most benefitting from ENBS and adjust programs accordingly.

Creatine transporter deficiency: Novel mutations and functional studies.

X-linked cerebral creatine deficiency (MIM 300036) is caused by deficiency of the creatine transporter encoded by the SLC6A8 gene. Here we report three patients with this condition from Israel. These unrelated patients were evaluated for global developmental delays and language apraxia. Borderline microcephaly was noted in one of them. Diagnosis was prompted by brain magnetic resonance imaging and spectroscopy which revealed normal white matter distribution, but absence of the creatine peak in all three patients. Biochemical testing indicated normal plasma levels of creatine and guanidinoacetate, but an increased urine creatine/creatinine ratio. The diagnosis was confirmed by demonstrating absent [14]C-creatine transport in fibroblasts. Molecular studies indicated that the first patient is hemizygous for a single nucleotide change substituting a single amino acid (c.619 C > T, p.R207W). Expression studies in HeLa cells confirmed the causative role of the R207W substitution. The second patient had a three base pair deletion in the SLC6A8 gene (c.1222_1224delTTC, p.F408del) as well as a single base change (c.1254 + 1G > A) at a splicing site in the intron-exon junction of exon 8, the latter occurring de novo. The third patient, had a three base pair deletion (c.1006_1008delAAC, p.N336del) previously reported in other patients with creatine transporter deficiency. These three patients are the first reported cases of creatine transporter deficiency in Israel.

Management of children with nonfebrile seizures in the emergency department.

BACKGROUND Children with seizures are often referred to the emergency department where they are typically evaluated by a physician with limited knowledge of pediatric epileptology and undergo a costly and extensive work-up that contributes little to the final decision. AIM The aim of this study was to examine the medical management of children with nonfebrile seizures in the emergency department and to define the potential role of the neurology clinic in this context. MATERIALS AND METHODS The files of 85 children who made 104 visits to the emergency department of a pediatric tertiary hospital for nonfebrile seizures were retrospectively reviewed. RESULTS Average age was 7.5 years. Blood tests were performed in almost all visits; a minority also involved the use of brain scans and electroencephalography. A neurologist was consulted in about half the visits. Only electroencephalography and neurologic consultation contributed significantly to the final decision. Hospitalization was recommended in 71% of cases, but it was usually short term and not accompanied by significant changes in the management. CONCLUSION In children with nonfebrile seizures, a problem-oriented approach including only the necessary work-up (e.g. electroencephalography) with neurologist consultation can potentially decrease the inpatient load and lower health care costs, while sparing patients unnecessary tests.

Reversal of cystoid macular edema in gyrate atrophy patients

ABSTRACT Purpose: This study reports the presentation of two families with gyrate atrophy (GA). The aim of this study was to characterize the potential effect of therapeutic regimens on macular edema. Methods: Two unrelated patients with GA were studied for the potential effect of low protein diet (≤ 0.8 g/kg/d), and oral administration of pyridoxine (500 mg/day), on serum ornithine levels, best corrected visual acuity (BCVA), slit-lamp, OCT, and auto-fluorescence findings. Blood samples for DNA, mRNA, and exons of the OAT gene were screened for mutations and splicing effect when relevant. Results: At presentation, both patients manifested typical ophthalmic features of GA including cystoid macular edema (CME). One patient also exhibited optic nerve head hamartoma. Following treatment ornithine levels have lessened, BCVA improved, and central macular thickness (CMT) markedly decreased in all four studied eyes. The molecular pathologic features included a novel splice site mutation (c.900+1G>A). Conclusions: We have identified a novel mutation and two formerly described mutations in patients with GA. Of them, one patient comprised an unusual phenotype including bilateral astrocytic hamartomas. We have recognized for the first time improvement in CME following treatment with low protein intake and pyridoxine supplement. This finding may have significance in the understanding of treatment options for macular edema regardless of underlying etiology.

Recurrent unexplained hyperammonemia in an adolescent with arginase deficiency

OBJECTIVES This report investigates the etiology of recurrent episodic elevations in plasma ammonia in an adolescent male with arginase deficiency as there were concerns regarding pre-analytical and analytical perturbations of ammonia measurements. There were repeated discrepancies between the magnitude of his ammonia levels and the severity of his clinical signs of hyperammonemia. PATIENT AND METHODS The patient is a fourteen-year-old arginase-deficient male diagnosed at three years of age. Since 2008 (when he reached 10 years of age), there appeared to be an increase in the frequency of hospitalizations with elevated ammonia. A typical emergency visit with initial ammonia of 105 μmol/L (reference interval: 16-47 μmol/L) is illustrated. Pre-analytical and analytical procedures for the patients sample handling were retrospectively examined. His ammonia levels were compiled since diagnosis. The frequency of his initial or peak ammonia levels greater than two times (94 μmol/L) or four times (188 μmol/L) the upper limit of normal was computed. Student t-test was used to calculate the significance of the differences before 2008 and since 2008. RESULTS One out of eleven and ten out of 19 hospitalizations had initial ammonia greater than two times normal before and after 2008, respectively. Both the patients overall ammonia and peak ammonia levels are significantly higher since 2008 (p value <0.001 for both) than those before 2008. CONCLUSIONS To our knowledge, few adolescent males with arginase deficiency experience recurrent episodes of hyperammonemia requiring intravenous nitrogen scavenging agents. We hope that this study provides new insights into the natural history of arginase deficiency and the management of such patients.

Cardiac failure in very long chain acyl-CoA dehydrogenase deficiency requiring extracorporeal membrane oxygenation (ECMO) treatment: A case report and review of the literature

Fatty acid oxidation (FAO) defects often present with multi-system involvement, including several life-threatening cardiac manifestations, such as cardiomyopathy, pericardial effusion and arrhythmias. We report herein a fatal case of cardiac dysfunction and rapid-onset tamponade following an acute illness in a neonate with molecularly proven very long chain acyl-CoA dehydrogenase (VLCAD) deficiency (harboring the known del799_802 mutation), requiring 15 days of extracorporeal membrane oxygenation (ECMO) treatment. As data regarding the use of ECMO in FAO defects in general, and VLCAD in particular, are scarce, we review the literature and discuss insights from in vitro models and several successful reported cases.