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Contains fulltext : 290862.pdf (Publisher’s version ) (Open Access) Congenital disorders of glycosylation (CDG) are a clinically and biochemically heterogeneous subgroup of inherited metabolic disorders. Most CDG with abnormal N-glycosylation can be detected by transferrin screening, however, MOGS-CDG escapes this routine screening. Combined with the clinical heterogeneity of reported cases, diagnosing MOGS-CDG can be challenging. Here, we clinically characterize ten MOGS-CDG cases including six previously unreported individuals, showing a phenotype characterized by dysmorphic features, global developmental delay, muscular hypotonia, and seizures in all patients and in a minority vision problems and hypogammaglobulinemia. Glycomics confirmed accumulation of a Glc(3) Man(7) GlcNAc(2) glycan in plasma. For quantification of the diagnostic Glcα1-3Glcα1-3Glcα1-2Man tetrasaccharide in urine, we developed and validated a liquid chromatography-mass spectrometry method of 2-aminobenzoic acid (2AA) labeled urinary glycans. As an internal standard, isotopically labeled (13) C(6) -2AA Glc(3) Man was used, while labeling efficiency was controlled by use of (12) C(6) -2AA and (13) C(6) -2AA labeled laminaritetraose. Recovery, linearity, intra- and interassay coefficients of variability of these labeled compounds were determined. Furthermore, Glc(3) Man was specifically identified by retention time matching against authentic MOGS-CDG urine and compared with Pompe urine. Glc(3) Man was increased in all six analyzed cases, ranging from 34.1 to 618.0 μmol/mmol creatinine (reference

We report a patient diagnosed with PGM1‐CDG at 11 years of age after two biallelic likely pathogenic variants in PGM1 were found on research genomic sequencing. To our knowledge, he is the first patient with PGM1‐CDG to be reported with a restrictive cardiomyopathy. Other clinical manifestations included cleft palate, asymptomatic elevated transaminases, intellectual disability and myopathy resulting in exercise intolerance. He was trialed on oral galactose therapy in increasing doses for 18 weeks to assess if there was any biochemical and clinical benefit. His galactose was continued for a further 9 months beyond the initial galactose treatment period due to improvements in exercise tolerance and myopathy. Treatment with galactose demonstrated an improvement in liver function and myopathy with improved exercise tolerance. Treatment with galactose for 15 months did not change heart function and exercise stress test results were stable.

Lathosterolosis is a rare autosomal recessive disorder of cholesterol biosynthesis. It is caused by defects in the SC5D (sterol C5‐desaturase) gene which encodes for the 3‐beta‐hydroxysteroid‐delta‐5‐desaturase (also called sterol‐C5‐desaturase or lathosterol dehydrogenase). Only six cases have been described in the literature, but it is possible that a number of patients with milder forms of the condition might have been missed. Lathosterolosis manifests as microcephaly, bilateral cataracts, dysmorphism, limb anomalies, and developmental delay/intellectual disability. Liver involvement is variable and can range from normal liver function tests to portal fibrosis and cirrhosis. Diagnosis is made by demonstration of specific mutations in the SC5D gene and by plasma sterol analysis to confirm elevated lathosterol levels. In this report, we describe a girl with transaminitis in association with developmental delay/intellectual disability, facial dysmorphism, limb anomalies, and bilateral cataracts. Fibroscan showed severe liver fibrosis. Plasma sterol analysis and exome sequencing confirmed the diagnosis of lathosterolosis. Simvastatin treatment resulted in lowering of plasma lathosterol levels, improvement in transaminitis, and liver fibrosis grade, suggesting that children with this condition should be actively treated in order to prevent progression of liver disease.

Pyridine Nucleotide-Disulfide Oxidoreductase Domain 2 (PYROXD2; previously called YueF) is a mitochondrial inner membrane/matrix-residing protein and is reported to regulate mitochondrial function. The clinical importance of PYROXD2 has been unclear, and little is known of the protein’s precise biological function. In the present paper, we report biallelic variants in PYROXD2 identified by genome sequencing in a patient with suspected mitochondrial disease. The child presented with acute neurological deterioration, unresponsive episodes, and extreme metabolic acidosis, and received rapid genomic testing. He died shortly after. Magnetic resonance imaging (MRI) brain imaging showed changes resembling Leigh syndrome, one of the more common childhood mitochondrial neurological diseases. Functional studies in patient fibroblasts showed a heightened sensitivity to mitochondrial metabolic stress and increased mitochondrial superoxide levels. Quantitative proteomic analysis demonstrated decreased levels of subunits of the mitochondrial respiratory chain complex I, and both the small and large subunits of the mitochondrial ribosome, suggesting a mitoribosomal defect. Our findings support the critical role of PYROXD2 in human cells, and suggest that the biallelic PYROXD2 variants are associated with mitochondrial dysfunction, and can plausibly explain the child’s clinical presentation.

Several studies have shown serum fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15) levels are elevated in patients with mitochondrial disease (MD) where myopathy is a feature. In this study we investigated the utility of FGF21 and GDF15 as biomarkers for MD in a phenotypically and genotypically diverse pediatric cohort with suspected MD against a panel of healthy controls and non-mitochondrial disease controls with some overlapping clinical features. Serum was collected from 56 children with MD, 104 children with non-mitochondrial disease (27 neuromuscular, 26 cardiac, 21 hepatic, 30 renal) and 30 pediatric controls. Serum FGF21 and GDF15 concentrations were measured using ELISA, and their ability to detect MD was determined. Median FGF21 and GDF15 serum concentrations were elevated 17-fold and 3-fold respectively in pediatric MD patients compared to the healthy control group. Non-mitochondrial disease controls had elevated serum GDF15 concentrations while FGF21 concentrations were in the normal range. Elevation of GDF15 in a range of non-mitochondrial pediatric disorders limits its use as a MD biomarker. FGF21 was elevated in MD patients with a spectrum of clinical phenotypes, including those without myopathy. Serum FGF21 had an area under the receiver operating characteristic curve of 0.87, indicating good ability to discriminate between pediatric MD and healthy and non-mitochondrial disease controls. Triaging of pediatric MD patients by clinical phenotyping and serum FGF21 testing, followed by massively parallel sequencing, may enable more rapid diagnosis of pediatric MD.

We report two unrelated patients with infantile onset leukoencephalopathy with vanishing white matter (VWM) and hyperinsulinaemic hypoglycaemia. To our knowledge, this association has not been described previously. Both patients had compound heterozygous pathogenic variants in EIF2B4 detected on exome sequencing and absence of other variants which might explain the hyperinsulinism. Hypoglycaemia became apparent at 6 and 8 months, respectively, although in one patient, transient neonatal hypoglycaemia was also documented. One patient responded to diazoxide and the other was managed with continuous nasogastric feeding. We hypothesise that the pathophysiology of hyperinsulinism in VWM may involve dysregulation of transcription of genes related to insulin secretion.

Brown-Vialetto-van Laere syndrome is characterized by a progressive sensorimotor neuropathy, optic atrophy, hearing loss, bulbar dysfunction, and respiratory insufficiency. Mutations in SLC52A2 and SLC52A3, encoding riboflavin transporters RFVT2 and RFVT3, respectively, are the genetic basis of this disorder, often referred to as riboflavin transporter deficiency types 2 and 3, respectively. We present cases of both types of riboflavin transporter deficiency, highlighting the distinguishing clinical features of a rapidly progressive motor or sensorimotor axonal neuropathy, optic atrophy, sensorineural hearing loss, and bulbar dysfunction. One child presented with isolated central apnea and hypoventilation, not previously described in genetically confirmed Brown-Vialetto-van Laere, later complicated by diaphragmatic paralysis secondary to phrenic nerve palsy. Magnetic resonance imaging showed T2 hyperintensity in the dorsal spinal cord in 2 children, as well as previously unreported cervical nerve root enlargement and cauda equina ventral nerve root enhancement in 1 child. Novel homozygous mutations were identified in each gene-a NM_024531.4(SLC52A2):c.505C > T, NP_078807.1(SLC52A2):p.(Arg169Cys) variant in SLC52A2 and NM_033409.3(SLC52A3):c.1316G > A, NP_212134.3(SLC52A3):p.(Gly439Asp) variant in SLC52A3. Both treated children showed improvement on high-dose riboflavin supplementation, highlighting the importance of early recognition of this treatable clinical entity.

RNA sequencing (RNAseq) is emerging as a complementary tool to DNA sequencing, providing utility in diagnosis for disorders such as neuronal ceroid lipofuscinosis CLN2 disease. We describe an individual with a presentation suggestive of an attenuated CLN2 phenotype, including a history of regression, recent-onset microcephaly and spasticity from age five years. Exome sequencing revealed two variants inherited in trans in TPP1, NM_000391.4:c.225A>G; p.(Gln75 = ) and NM_000391.4:c.1012C>G; p.(Gln338Glu), both classified as variants of uncertain significance. TPP1 activity was found to be significantly reduced in fibroblasts of the affected individual. RNAseq was performed to assess the impact of compound heterozygous variants in TPP1 and enabled the identification of three aberrant splicing events. The c.225A>G variant introduces a 5 nucleotide truncation of exon 3 and a loss of reading frame. The majority of CLN2 transcripts exclude either exon 8 or exons 7-8, resulting in large in-frame deletions. Isoform specific RT-PCR confirmed the aberrant splicing events are mutually exclusive, suggesting that the paternal exon 8 c.1012C>G variant results in exon skipping. This case study demonstrates how RNAseq can be used as an orthogonal test to inform the interpretation of some variants of unknown significance and its particular importance in disorders where effective disease management requires early diagnosis.

Mucopolysaccharidosis Type II (MPS II) or Hunter Syndrome is a rare X-linked condition, due to a defect in a lysosomal enzyme involved in the breakdown of glycosaminoglycans. It is a progressive condition with worsening over time; however, symptom severity and progression rates vary. Normal intellectual function has been reported in males with mild MPS II but few studies are available that provide comprehensive cognitive profiles. Enzyme replacement therapy (ERT) can stabilize physical symptoms and has become standard treatment. Whether ERT can influence cognition is currently unknown. Considering this, we conducted cognitive, fine motor, and behavioural assessments with three males (7;6-12;1 years) with mild MPS II before and after ERT. Generally, cognition, fine motor skills, and behaviour were in the normal range; however, specific deficits in attention and executive function were identified. Following ERT, some memory improvements were seen. Executive deficits remained, and processing speed declined over time.

AIM: Late infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease is a rare neurodegenerative disorder presenting in children aged 2-4 years with seizures and loss of motor and language skills, followed by blindness and death in late childhood. Initial presenting features are similar to a range of common epilepsies. We aim to highlight typical clinical and radiological features that may prompt diagnosis of CLN2 disease in early disease stages. METHODS: We present a series of 13 Australian patients with CLN2 disease, describing clinical features, disease evolution, neuroimaging, electroencephalogram, biochemical and genetic results. Expert neuroradiological magnetic resonance imaging (MRI) analysis was retrospectively performed on 10 cases. RESULTS: Twelve patients presented with seizures, with initial seizures being focal (n = 4), generalised tonic-clonic (n = 3), absence (n = 3) and febrile (n = 2). Eleven patients (85%) had a language delay before the onset of seizures. Cerebellar or cerebral atrophy was noted in all patients on centralised MRI review, with abnormalities of the brain-stem, ventricles, corpus callosum and hippocampi. CONCLUSIONS: Early language delay with the onset of seizures at 2-4 years of age is the hallmark of CLN2 disease. MRI findings of early subtle atrophy in the cerebellum or posterior cortical regions should hasten testing for CLN2 disease to enable early initiation of enzyme replacement therapy.

Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over one hundred genes leading to impaired protein or lipid glycosylation. ALG1 encodes a β1,4 mannosyltransferase that catalyzes the addition of the first of nine mannose moieties to form a dolichol-lipid linked oligosaccharide intermediate (DLO) required for proper N-linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1-CDG. To date thirteen mutations in eighteen patients from fourteen families have been described with varying degrees of clinical severity. We identified and characterized thirty-nine previously unreported cases of ALG1-CDG from thirty-two families and add twenty-six new mutations. Pathogenicity of each mutation was confirmed based on its inability to rescue impaired growth or hypoglycosylation of a standard biomarker in an alg1-deficient yeast strain. Using this approach we could not establish a rank order comparison of biomarker glycosylation and patient phenotype, but we identified mutations with a lethal outcome in the first two years of life. The recently identified protein-linked xeno-tetrasaccharide biomarker, NeuAc-Gal-GlcNAc2, was seen in all twenty-seven patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.

Item does not contain fulltext We studied a group of individuals with elevated urinary excretion of 3-methylglutaconic acid, neutropenia that can develop into leukemia, a neurological phenotype ranging from nonprogressive intellectual disability to a prenatal encephalopathy with progressive brain atrophy, movement disorder, cataracts, and early death. Exome sequencing of two unrelated individuals and subsequent Sanger sequencing of 16 individuals with an overlapping phenotype identified a total of 14 rare, predicted deleterious alleles in CLPB in 14 individuals from 9 unrelated families. CLPB encodes caseinolytic peptidase B homolog ClpB, a member of the AAA+ protein family. To evaluate the relevance of CLPB in the pathogenesis of this syndrome, we developed a zebrafish model and an in vitro assay to measure ATPase activity. Suppression of clpb in zebrafish embryos induced a central nervous system phenotype that was consistent with cerebellar and cerebral atrophy that could be rescued by wild-type, but not mutant, human CLPB mRNA. Consistent with these data, the loss-of-function effect of one of the identified variants (c.1222A>G [p.Arg408Gly]) was supported further by in vitro evidence with the mutant peptides abolishing ATPase function. Additionally, we show that CLPB interacts biochemically with ATP2A2, known to be involved in apoptotic processes in severe congenital neutropenia (SCN) 3 (Kostmann disease [caused by HAX1 mutations]). Taken together, mutations in CLPB define a syndrome with intellectual disability, congenital neutropenia, progressive brain atrophy, movement disorder, cataracts, and 3-methylglutaconic aciduria.

Mitochondrial 3-hydroxy-3-methylglutaryl CoA synthase (HMCS2) deficiency results in episodes of hypoglycemia and increases in fatty acid metabolites. Metabolite abnormalities described to date in HMCS2 deficiency are nonspecific and overlap with other inborn errors of metabolism, making the biochemical diagnosis of HMCS2 deficiency difficult. Urinary organic acid profiles from periods of metabolic decompensation were studied in detail in HMCS2-deficient patients from four families. An additional six unrelated patients were identified from clinical presentation and/or qualitative identification of abnormal organic acids. The diagnosis was confirmed by sequencing and deletion/duplication analysis of the HMGCS2 gene. Seven related novel organic acids were identified in urine profiles. Five of them (3,5-dihydroxyhexanoic 1,5 lactone; trans-5-hydroxyhex-2-enoate; 4-hydroxy-6-methyl-2-pyrone; 5-hydroxy-3-ketohexanoate; 3,5-dihydroxyhexanoate) were identified by comparison with synthesized or commercial authentic compounds. We provisionally identified trans-3-hydroxyhex-4-enoate and 3-hydroxy-5-ketohexanoate by their mass spectral characteristics. These metabolites were found in samples taken during periods of decompensation and normalized when patients recovered. When cutoffs of adipic >200 and 4-hydroxy-6-methyl-2-pyrone >20 μmol/mmol creatinine were applied, all eight samples taken from five HMCS2-deficient patients during episodes of decompensation were flagged with a positive predictive value of 80% (95% confidence interval 35-100%). Some ketotic patients had increased 4-hydroxy-6-methyl-2-pyrone. Molecular studies identified a total of 12 novel mutations, including a large deletion of HMGCS2 exon 1 in two families, highlighting the need to perform quantitative gene analyses. There are now 26 known HMGCS2 mutations, which are reviewed in the text. 4-Hydroxy-6-methyl-2-pyrone and related metabolites are markers for HMCS2 deficiency. Detection of these metabolites will streamline the biochemical diagnosis of this disorder.

Clinical whole-exome sequencing (WES) for identification of mutations leading to Mendelian disease has been offered to the medical community since 2011. Clinically undiagnosed neurological disorders are the most frequent basis for test referral, and currently, approximately 25% of such cases are diagnosed at the molecular level. To date, there are approximately 4,000 “known” disease-associated loci, and many are associated with striking dysmorphic features, making genotype-phenotype correlations relatively straightforward. A significant fraction of cases, however, lack characteristic dysmorphism or clinical pathognomonic traits and are dependent upon molecular tests for definitive diagnoses. Further, many molecular diagnoses are guided by recent gene-disease association discoveries. Hence, there is a critical interplay between clinical testing and research leading to gene-disease association discovery. Here, we describe four probands, all of whom presented with hypotonia, intellectual disability, global developmental delay, and mildly dysmorphic facial features. Three of the four also had sleep apnea. Each was a simplex case without a remarkable family history. Using WES, we identified AHDC1 de novo truncating mutations that most likely cause this genetic syndrome.

Two siblings with fatal Leigh disease had increased excretion of S-(2-carboxypropyl)cysteine and several other metabolites that are features of 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency, a rare defect in the valine catabolic pathway associated with Leigh-like disease. However, this diagnosis was excluded by HIBCH sequencing and normal enzyme activity. In contrast to HIBCH deficiency, the excretion of 3-hydroxyisobutyryl-carnitine was normal in the children, suggesting deficiency of short-chain enoyl-CoA hydratase (ECHS1 gene). This mitochondrial enzyme is active in several metabolic pathways involving fatty acids and amino acids, including valine, and is immediately upstream of HIBCH in the valine pathway. Both children were compound heterozygous for a c.473C > A (p.A158D) missense mutation and a c.414+3G>C splicing mutation in ECHS1. ECHS1 activity was markedly decreased in cultured fibroblasts from both siblings, ECHS1 protein was undetectable by immunoblot analysis and transfection of patient cells with wild-type ECHS1 rescued ECHS1 activity. The highly reactive metabolites methacrylyl-CoA and acryloyl-CoA accumulate in deficiencies of both ECHS1 and HIBCH and are probably responsible for the brain pathology in both disorders. Deficiency of ECHS1 or HIBCH should be considered in children with Leigh disease. Urine metabolite testing can detect and distinguish between these two disorders.

Summary Objectives and aims: To document the incidence of difficult airway management and difficult intubation in the era of replacement therapy for Australian children with mucopolysaccharidosis (MPS). Background: Medical treatment for MPS has developed significantly since 1980’s with a large number of patients now being offered either bone marrow transplant or enzyme replacement. The impact of these therapies on the incidence of difficult airway management has not been adequately documented. Similarly, anesthesia techniques and airway devices have been developed, which are thought to have greatly increased the safety of managing these patients under anesthesia but their role in children with MPS has not been systematically described. Methods: A retrospective chart review of 17 patients with MPS who had received anesthetics at the Royal Children’s Hospital during the time frame January 1998–January 2011. The primary outcome was the incidence of difficult or failed intubation. Secondary outcomes were the relationship between the incidence of difficult intubation and treatment with enzyme replacement therapy (ERT) or bone marrow transplantation. Results: Seventeen patients received 141 anesthetics for 214 procedures. Difficult face mask ventilation occurred in 20 anesthetics (14.2%). Difficult intubation occurred in 40 anesthetics (25%). Failed intubation occurred in two cases (1.6%).The incidence of difficult intubation was 12% in MPS I, 35% MPS II, 86.7% in MPS VI, and 0% in MPS III and IV. Conclusions: Hematopoietic stem cell transplantation prior to 2 years of age reduces the incidence of difficult mask ventilation and difficult intubation in children with MPS I. ERT was initiated late in the clinical course of MPS II and VI and induced improvements in upper airway patency but did not reduce the incidence of difficult airway management.

Molybdenum cofactor deficiency (MoCD) is a rare metabolic disorder characterized by severe and rapidly progressive neurologic damage caused by the functional loss of sulfite oxidase, 1 of 4 molybdenum-dependent enzymes. To date, no effective therapy is available for MoCD, and death in early infancy has been the usual outcome. We report here the case of a patient who was diagnosed with MoCD at the age of 6 days. Substitution therapy with purified cyclic pyranopterin monophosphate (cPMP) was started on day 36 by daily intravenous administration of 80 to 160 μg of cPMP/kg of body weight. Within 1 to 2 weeks, all urinary markers of sulfite oxidase (sulfite, S-sulfocysteine, thiosulfate) and xanthine oxidase deficiency (xanthine, uric acid) returned to almost normal readings and stayed constant (>450 days of treatment). Clinically, the infant became more alert, convulsions and twitching disappeared within the first 2 weeks, and an electroencephalogram showed the return of rhythmic elements and markedly reduced epileptiform discharges. Substitution of cPMP represents the first causative therapy available for patients with MoCD. We demonstrate efficient uptake of cPMP and restoration of molybdenum cofactor–dependent enzyme activities. Further neurodegeneration by toxic metabolites was stopped in the reported patient. We also demonstrated the feasibility to detect MoCD in newborn-screening cards to enable early diagnosis.

OBJECTIVE: Tandem mass spectrometry is widely applied to routine newborn screening but there are no long-term studies of outcome. We studied the clinical outcome at six years of age in Australia. METHODS: In a cohort study, we analyzed the outcome at 6 years for patients detected by screening or by clinical diagnosis among >2 million infants born from 1994 to 1998 (1 017 800, all unscreened) and 1998 to 2002 (461 500 screened, 533 400 unscreened) recording intellectual and physical condition, school placement, other medical problems, growth, treatment, diet, and hospital admissions. Results were analyzed separately for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) and other disorders, and grouped patients as those who presented clinically or died in the first 5 days of life; patients presented later or diagnosed by screening, and those with substantially benign disorders. RESULTS: Inborn errors, excluding phenylketonuria, were diagnosed in 116 of 1 551 200 unscreened infants (7.5/100 000 births) and 70 of 461 500 screened infants (15.2/100 000 births). Excluding MCADD, 21 unscreened patients with metabolic disorders diagnosed after 5 days of life died or had a significant intellectual or physical handicap (1.35/100 000 population) compared with 2 of the screened cohort (0.43/100 000; odds ratio: 3.1 [95% CI: 0.73–13.32]). Considering the likely morbidity or mortality among the expected number of never-diagnosed unscreened patients, there would be a significant difference. Growth distribution was normal in all cohorts. CONCLUSION: Screening by tandem mass spectrometry provides a better outcome for patients at 6 years of age, with fewer deaths and fewer clinically significant disabilities.

OBJECTIVES. The goals were to examine the frequency of perinatal manifestations of mitochondrial oxidative phosphorylation disorders within a population-based cohort, to characterize these manifestations, to identify a possible association between these manifestations and diagnoses at a later age, and to identify possible associations between perinatal complications and specific disorders. METHODS. We conducted a retrospective review of clinical and laboratory records for all patients with definitive oxidative phosphorylation disorders who were diagnosed and treated at the Royal Children's Hospital in Melbourne between 1975 and 2006 (N = 107; male/female ratio: 1.41). RESULTS. Neonatal presentation was recorded for 32 of 107 patients (male/female ratio: 1:1), including 19 who presented on day 1 of life. Prematurity (gestational age of G mutation. CONCLUSIONS. Oxidative phosphorylation disorders present commonly in the neonatal period. The combination of nonspecific manifestations such as prematurity and intrauterine growth retardation with early postnatal decompensation or poor feeding or vomiting and persistent lactic acidosis should suggest the possibility of an oxidative phosphorylation disorder.

Arginine is an important, versatile and a conditionally essential amino acid. Besides serving as a building block for tissue proteins, arginine plays a critical role in ammonia detoxification, and nitric oxide and creatine production. Arginine supplementation is an essential component for the treatment of urea cycle defects but recently some reservations have been raised with regards to the doses used in the treatment regimens of these disorders. In recent years, arginine supplementation or restriction has been proposed and trialled in several disorders, including vascular diseases and asthma, mitochondrial encephalopathy lactic acidosis and stroke-like episodes (MELAS), glutaric aciduria type I and disorders of creatine metabolism, both production and transportation into the central nervous system. Herein we present new therapeutic indications and controversies surrounding arginine supplementation or deprivation.

To prospectively evaluate the diagnostic and clinical utility of singleton whole-exome sequencing (WES) as a first-tier test in infants with suspected monogenic disease. Singleton WES was performed as a first-tier sequencing test in infants recruited from a single pediatric tertiary center. This occurred in parallel with standard investigations, including single- or multigene panel sequencing when clinically indicated. The diagnosis rate, clinical utility, and impact on management of singleton WES were evaluated. Of 80 enrolled infants, 46 received a molecular genetic diagnosis through singleton WES (57.5%) compared with 11 (13.75%) who underwent standard investigations in the same patient group. Clinical management changed following exome diagnosis in 15 of 46 diagnosed participants (32.6%). Twelve relatives received a genetic diagnosis following cascade testing, and 28 couples were identified as being at high risk of recurrence in future pregnancies. This prospective study provides strong evidence for increased diagnostic and clinical utility of singleton WES as a first-tier sequencing test for infants with a suspected monogenic disorder. Singleton WES outperformed standard care in terms of diagnosis rate and the benefits of a diagnosis, namely, impact on management of the child and clarification of reproductive risks for the extended family in a timely manner. Genet Med 18 11, 1090–1096.

Four children in three unrelated families (one consanguineous) presented with lethargy, hyperlactatemia, and hyperammonemia of unexplained origin during the neonatal period and early childhood. We identified and validated three different CA5A alterations, including a homozygous missense mutation (c.697T>C) in two siblings, a homozygous splice site mutation (c.555G>A) leading to skipping of exon 4, and a homozygous 4 kb deletion of exon 6. The deleterious nature of the homozygous mutation c.697T>C (p.Ser233Pro) was demonstrated by reduced enzymatic activity and increased temperature sensitivity. Carbonic anhydrase VA (CA-VA) was absent in liver in the child with the homozygous exon 6 deletion. The metabolite profiles in the affected individuals fit CA-VA deficiency, showing evidence of impaired provision of bicarbonate to the four enzymes that participate in key pathways in intermediary metabolism: carbamoylphosphate synthetase 1 (urea cycle), pyruvate carboxylase (anaplerosis, gluconeogenesis), propionyl-CoA carboxylase, and 3-methylcrotonyl-CoA carboxylase (branched chain amino acids catabolism). In the three children who were administered carglumic acid, hyperammonemia resolved. CA-VA deficiency should therefore be added to urea cycle defects, organic acidurias, and pyruvate carboxylase deficiency as a treatable condition in the differential diagnosis of hyperammonemia in the neonate and young child.

Item does not contain fulltext BACKGROUND: Creatine transporter deficiency is a monogenic cause of X-linked intellectual disability. Since its first description in 2001 several case reports have been published but an overview of phenotype, genotype and phenotype-genotype correlation has been lacking. METHODS: We performed a retrospective study of clinical, biochemical and molecular genetic data of 101 males with X-linked creatine transporter deficiency from 85 families with a pathogenic mutation in the creatine transporter gene (SLC6A8). RESULTS AND CONCLUSIONS: Most patients developed moderate to severe intellectual disability; mild intellectual disability was rare in adult patients. Speech language development was especially delayed but almost a third of the patients were able to speak in sentences. Besides behavioural problems and seizures, mild to moderate motor dysfunction, including extrapyramidal movement abnormalities, and gastrointestinal problems were frequent clinical features. Urinary creatine to creatinine ratio proved to be a reliable screening method besides MR spectroscopy, molecular genetic testing and creatine uptake studies, allowing definition of diagnostic guidelines. A third of patients had a de novo mutation in the SLC6A8 gene. Mothers with an affected son with a de novo mutation should be counselled about a recurrence risk in further pregnancies due to the possibility of low level somatic or germline mosaicism. Missense mutations with residual activity might be associated with a milder phenotype and large deletions extending beyond the 3' end of the SLC6A8 gene with a more severe phenotype. Evaluation of the biochemical phenotype revealed unexpected high creatine levels in cerebrospinal fluid suggesting that the brain is able to synthesise creatine and that the cerebral creatine deficiency is caused by a defect in the reuptake of creatine within the neurones.

Congenital disorders of glycosylation (CDG) represent an expanding family of metabolic disorders with a wide range of biochemical, molecular and clinical phenotypes. ALG3-CDG (CDG-Id), due to a defect in endoplasmic reticulum (ER) mannosyltransferase VI, is one of the less common types of CDG-I. We describe two Vietnamese siblings with confirmed ALG3-CDG (CDG-Id) by molecular testing. As far as we are aware, they are the oldest reported patients in the literature at 15 and 21years. They share similar clinical features with previously reported patients including facial dysmorphism, severe psychomotor retardation, microcephaly, seizures, and gastrointestinal symptoms. Furthermore, our sibling pair highlights the intrafamilial variability, the natural clinical course of ALG3-CDG (CDG-Id) and the benefit of reassessing patients with undiagnosed and complex syndromes, particularly when they present with neurological deterioration.

Background SURF1 deficiency, a monogenic mitochondrial disorder, is the most frequent cause of cytochrome c oxidase (COX) deficient Leigh syndrome (LS). We report the first natural history study of SURF1 deficiency. Methods We conducted a multi-centre case notes review of 44 SURF1-deficient patients from ten different UK centres and two Australian centres. Survival data for LRPPRC-deficient LS and nuclear-encoded complex I-deficient LS patients were obtained from previous publications. The survival of SURF1-deficient patients was compared with these two groups using Kaplan- Meier survival analysis and logrank test. Results The majority of patients (32/44, 73%) presented in infancy (median 9.5 months). Frequent symptoms were poor weight gain (95%, median age 10 months), hypotonia (93%, median age 14 months), poor feeding/vomiting (89%, median age 10 months), developmental delay (88%, median age 14 months), developmental regression (71%, median age 19 months), movement disorder (52%, median age 24 months), oculomotor involvement (52%, median age 29 months) and central respiratory failure (78%, median age 31 months). Hypertrichosis (41%), optic atrophy (23%), encephalopathy (20%), seizures (14%) and cardiomyopathy (2%) were observed less frequently. Lactate was elevated in CSF (mean 4.3 mmol/L) in all patients (30/30) and in blood (mean 4.4 mmol/L) in 31/38 (81%). Fibroblast COX activity was universally decreased (25/25). Normal COX histochemistry was noted in 30% of biopsies, whereas muscle COX activity was reduced in 96% (25/26). Neuroimaging demonstrated lesions characteristic of LS in 28/33 (85%) and atypical findings in 3/33 (9%). Peripheral neuropathy was present in 13/16 (81%) (demyelinating 7/16, axonal 2/16). Kaplan-Meier analysis demonstrated that SURF1-deficient patients experience longer survival (median 5.4 years, p < 0.001) compared to LRPPRC deficiency (median 1.8 years) and nuclear-encoded complex I-deficient LS (median 1.6 years). Survival >10 years was observed in 7 patients, 6 of these patients did not experience neurological regression. The most frequent mutation was c.312_320del10insAT. Five novel mutations (c.468_469delTC, c.799_800delCT, c.575G>A (p.Arg192Gln), c.751+5G>A and c.752-2A>G) were identified. Conclusions SURF1-deficient patients have a homogeneous clinical and biochemical phenotype. Early recognition is essential to expedite diagnosis and enable prenatal diagnosis.

BACKGROUND: Urea cycle disorders (UCD) are caused by genetic defects in enzymes that constitute the hepatic ammonia detoxification pathway. Patients may present with variable clinical manifestations and with hyperammonaemia. Liver abnormalities have been associated with UCD, but only a few reports on the histopathological findings in the liver of UCD patients have been published. METHODS: We conducted a retrospective review of liver biopsies, ex-planted livers and livers at post-mortem of patients with UCD. A single pathologist reviewed all specimens. RESULTS: There were 18 liver samples from 13 patients with confirmed UCD: four ex-planted livers from patients with Ornithine Transcarbamylase (OTC) (n=3) and Carbamoyl Phosphate Synthetase 1 (CPS 1) (n=1) deficiencies, eight post-mortem samples from patients with CPS 1 (n=2), OTC (n=4), Argininosuccinate Synthetase (ASS) (n=1) and Argininosuccinate Lyase (ASL) (n=1) deficiencies, and six liver biopsies, three of which came from one patient with ASL deficiency. The other three liver biopsies were from patients who subsequently received liver transplantation. Histopathological findings in samples from neonates were non-specific. Samples from three late onset OTC deficient and one ASL deficient patients showed thin fibrous septa with portal to portal bridging fibrosis and focal marked enlargement and pallor of the hepatocytes due to accumulation of glycogen particles, resembling glycogenosis and resulting in a prominent nodular pattern. Serial liver biopsies in four UCD patients with interval between samples ranging from 1 year 2 months to 17 years showed progression in fibrosis in one OTC and one ASL deficient patients. Moderate fatty changes to no progression in liver disease were noted in the two patients (OTC=1 and CPS=1). A variety of non-specific features such as fatty change, mild inflammation, cholestasis and focal necrosis were seen in the other UCD patients. CONCLUSIONS: Histopathological changes in livers from neonates with UCD are non-specific. Older patients with UCD seem to show variable hepatic fibrosis compared to those who died early. Some of these patients also show focal and superficial resemblance to a glycogen storage disorder and cirrhosis. However, progression of these changes seems to be slow. To clarify the long term consequence of these changes, more extensive periods of follow up in a larger population series is needed.

Between October 2001 and September 2007, a total number of 391,651 neonates were screened in Victoria using Tandem Mass Spectrometry and 6 newborns were diagnosed as having GA I, giving an incidence of 1:65,275 (CI: 1:29,988=1:177,861). Another patient was diagnosed through cascade screening of children born before the implementation of the expanded newborn screening program. Patients were treated by mild protein restriction (2-2.5 g/kg/day) and carnitine supplementation when well, focussing on the aggressive management of intercurrent illnesses (temporary cessation of protein intake, increase in calorie intake, IV carnitine, aggressive anti febrile and anti infectious treatment), including prophylactic admissions to hospital. Overall, our patients had 35 admissions to hospital, of which 15 were in the first year of life. None had a post infectious dystonic syndrome. Neuropsychological examinations revealed normal to high cognitive and gross motor function in all patients but one, with some deficiencies in fine motor activities and different levels of speech abnormalities in all patients. Since therapeutic approaches for GA I, although not uniform, are well established and have been documented to be effective, newborn screening for this disorder should prove justified. A therapeutic approach of dietary modification, IV carnitine and aggressive treatment of intercurrent illness seems to prevent the severe neurological complications of GA I. More in-depth consideration of speech and language function is necessary to document specific deficits in children with GA I and plan proactive interventions.

Beta-ureidopropionase deficiency (McKusick 606673) is an autosomal recessive condition caused by mutations in the UPB1 gene. To date, five patients have been reported, including one putative case detected through newborn screening. Clinical presentation includes neurological and developmental problems. Here, we report another case of beta-ureidopropionase deficiency who presented with congenital anomalies of the urogenital and colorectal systems and with normal neurodevelopmental milestones. Analysis of a urine sample, because of the suspicion of renal stones on ultrasound, showed strongly elevated levels of the characteristic metabolites, N-carbamyl-beta-amino acids. Subsequent analysis of UPB1 identified a novel mutation 209 G>C (R70P) in exon 2 and a previously reported splice receptor mutation IVS1-2A>G. Expression studies of the R70P mutant enzyme showed that the mutant enzyme did not possess any residual activity. Long-term follow-up is required to determine the clinical significance of the beta-ureidopropionase deficiency in our patient

Objective To determine the frequency, type, and severity of cardiac involvement in pediatric patients with oxidative phosphorylation (OXPHOS) disorders. Study design Retrospective review of clinical and laboratory records of all patients with definitive OXPHOS disorders diagnosed and treated at the Royal Children’s Hospital in Melbourne between 1984 and 2005. Results Of a total of 89 patients (male:female ratio 1.5:1) 29 (33%) had cardiac involvement: 9 as presenting symptoms, 9 developing on follow-up, and 11 with subclinical cardiac findings. Leigh or Leigh-like syndrome and complex I and combined complex I, III, and IV deficiencies were the most common clinical and laboratory diagnoses, respectively. Clinically symptomatic patients had hypertrophic cardiomyopathy (5 patients), dilated cardiomyopathy (4 patients), combined ventricular hypertrophy and systolic dysfunction (3 patients), and left ventricular noncompaction (3 patients) at first assessment. A change in the type of cardiomyopathy was noted on follow-up in 2 patients. Conduction and rhythm abnormalities were present in 7 symptomatic patients. Conclusions Cardiac assessment in children with OXPHOS disorders may reveal subclinical abnormalities of cardiac function. Patients who present with primary cardiac features have a poor prognosis. OXPHOS disorders should be considered in the differential diagnosis of children presenting with otherwise unexplained cardiomyopathy.

We diagnosed six newborn babies with very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) through newborn screening in three years in Victoria (prevalence rate: 1:31,500). We identified seven known and two new mutations in our patients (2/6 homozygotes; 4/6 compound heterozygotes). Blood samples taken at age 48-72 h were diagnostic whereas repeat samples at an older age were normal in 4/6 babies. Urine analysis was normal in 5/5. We conclude that the timing of blood sampling for newborn screening is important and that it is important to perform mutation analysis to avoid false-negative diagnoses of VLCADD in asymptomatic newborn babies. In view of the emerging genotype-phenotype correlation in this disorder, the information derived from mutational analysis can be helpful in designing the appropriate follow-up and therapeutic regime for these patients.