Publications by authors named "Ivo Barić"

78 Publications

NBAS Variants Are Associated with Quantitative and Qualitative NK and B Cell Deficiency.

J Clin Immunol 2021 Aug 13. Epub 2021 Aug 13.

Division of Neuropediatrics and Pediatric Metabolic Medicine, Center for Pediatric and Adolescent Medicine, University Hospital Heidelberg, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany.

Purpose: Biallelic pathogenic NBAS variants manifest as a multisystem disorder with heterogeneous clinical phenotypes such as recurrent acute liver failure, growth retardation, and susceptibility to infections. This study explores how NBAS-associated disease affects cells of the innate and adaptive immune system.

Methods: Clinical and laboratory parameters were combined with functional multi-parametric immunophenotyping methods in fifteen NBAS-deficient patients to discover possible alterations in their immune system.

Results: Our study revealed reduced absolute numbers of mature CD56 natural killer (NK) cells. Notably, the residual NK cell population in NBAS-deficient patients exerted a lower potential for activation and degranulation in response to K562 target cells, suggesting an NK cell-intrinsic role for NBAS in the release of cytotoxic granules. NBAS-deficient NK cell activation and degranulation was normalized upon pre-activation by IL-2 in vitro, suggesting that functional impairment was reversible. In addition, we observed a reduced number of naïve B cells in the peripheral blood associated with hypogammaglobulinemia.

Conclusion: In summary, we demonstrate that pathogenic biallelic variants in NBAS are associated with dysfunctional NK cells as well as impaired adaptive humoral immunity.
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http://dx.doi.org/10.1007/s10875-021-01110-7DOI Listing
August 2021

Inborn Errors of Metabolism Associated With Autism Spectrum Disorders: Approaches to Intervention.

Front Neurosci 2021 28;15:673600. Epub 2021 May 28.

Department of Paediatrics, University Hospital Center Zagreb and University of Zagreb School of Medicine, Zagreb, Croatia.

Increasing evidence suggests that the autism spectrum disorder (ASD) may be associated with inborn errors of metabolism, such as disorders of amino acid metabolism and transport [phenylketonuria, homocystinuria, S-adenosylhomocysteine hydrolase deficiency, branched-chain α-keto acid dehydrogenase kinase deficiency, urea cycle disorders (UCD), Hartnup disease], organic acidurias (propionic aciduria, L-2 hydroxyglutaric aciduria), cholesterol biosynthesis defects (Smith-Lemli-Opitz syndrome), mitochondrial disorders (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes-MELAS syndrome), neurotransmitter disorders (succinic semialdehyde dehydrogenase deficiency), disorders of purine metabolism [adenylosuccinate lyase (ADSL) deficiency, Lesch-Nyhan syndrome], cerebral creatine deficiency syndromes (CCDSs), disorders of folate transport and metabolism (cerebral folate deficiency, methylenetetrahydrofolate reductase deficiency), lysosomal storage disorders [Sanfilippo syndrome, neuronal ceroid lipofuscinoses (NCL), Niemann-Pick disease type C], cerebrotendinous xanthomatosis (CTX), disorders of copper metabolism (Wilson disease), disorders of haem biosynthesis [acute intermittent porphyria (AIP)] and brain iron accumulation diseases. In this review, we briefly describe etiology, clinical presentation, and therapeutic principles, if they exist, for these conditions. Additionally, we suggest the primary and elective laboratory work-up for their successful early diagnosis.
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http://dx.doi.org/10.3389/fnins.2021.673600DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8193223PMC
May 2021

Current Status of Newborn Screening in Southeastern Europe.

Front Pediatr 2021 7;9:648939. Epub 2021 May 7.

University Children's Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia.

Significant part of Southeastern Europe (with a population of 76 million) has newborn screening (NBS) programs non-harmonized with developed European countries. Initial survey was conducted in 2013/2014 among 11 countries from the region (Albania, Bulgaria, Bosnia and Herzegovina (BIH), Croatia, Kosovo, Macedonia, Moldova, Montenegro, Romania, Serbia, and Slovenia) to assess the main characteristics of their NBS programs and their future plans. Their cumulative population at that time was ~52,5 million. At that time, none of the countries had an expanded NBS program, while phenylketonuria screening was not introduced in four and congenital hypothyroidism in three of 11 countries. We repeated the survey in 2020 inviting the same 11 countries, adding Cyprus, Greece, Hungary, and Malta (due to their geographical position in the wider region). The aims were to assess the current state, to evaluate the change in the period, and to identify the main obstacles impacting the implementation of expanded NBS and/or reaching a wider population. Responses were collected from 12 countries (BIH-Federation of BIH, BIH-Republic of Srpska, Bulgaria, Croatia, Greece, Hungary, Kosovo, North Macedonia, Malta, Montenegro, Romania, Serbia, Slovenia) with a population of 68.5 million. The results of the survey showed that the regional situation regarding NBS only modestly improved in this period. All of the surveyed countries except Kosovo screened for at least congenital hypothyroidism, while phenylketonuria was not screened in four of 12 countries. Croatia and Slovenia implemented an expanded NBS program using tandem mass spectrometry from the time of last survey. In conclusion, the current status of NBS programs in Southeastern Europe is very variable and is still underdeveloped (or even non-existent) in some of the countries. We suggest establishing an international task-force to assist with implementation and harmonization of basic NBS services where needed.
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http://dx.doi.org/10.3389/fped.2021.648939DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8138576PMC
May 2021

Early initiation of ambroxol treatment diminishes neurological manifestations of type 3 Gaucher disease: A long-term outcome of two siblings.

Eur J Paediatr Neurol 2021 May 31;32:66-72. Epub 2021 Mar 31.

Department of Pediatrics, University Hospital Centre Zagreb, Zagreb, Croatia; University of Zagreb, School of Medicine, Zagreb, Croatia. Electronic address:

Gaucher disease type 3 (GD3) is a severely debilitating disorder characterized by multisystemic manifestations and neurodegeneration. Enzyme replacement therapy alleviates visceral signs and symptoms but has no effect on neurological features. Ambroxol has been suggested as an enzyme enhancement agent. Some studies have confirmed its effectiveness in preventing the progression of neurological manifestations of neuronopathic Gaucher disease. In this study, we report two GD3 siblings in whom ambroxol combined with enzyme replacement therapy was initiated at different stages of the disease. We demonstrate the enzyme enhancement effect of ambroxol on L444P/H225Q;D409H glucocerebrosidase activity through results of fibroblast studies and long-term clinical outcomes of the two patients. The sibling diagnosed at the age of four-and-a-half years with significant neurological involvement manifested relatively rapid improvement on ambroxol treatment, followed by stabilization of further course. The younger sibling, in whom the treatment was started at seven weeks, displayed attention deficit and low average cognitive functioning at the age of seven years, but did not manifest other neurological symptoms. The difference in neurological outcomes indicates that ambroxol delayed or even halted the evolution of neurological manifestations in the younger sibling. This observation suggests that early initiation of ambroxol treatment may arrest neurological involvement in some GD3 patients.
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http://dx.doi.org/10.1016/j.ejpn.2021.03.013DOI Listing
May 2021

ATP synthase deficiency due to m.8528T>C mutation - a novel cause of severe neonatal hyperammonemia requiring hemodialysis.

J Pediatr Endocrinol Metab 2021 Mar 13;34(3):389-393. Epub 2020 Nov 13.

Department of Pediatrics, University Hospital Centre Zagreb, Zagreb, Croatia.

Objectives: Hyperammonemia in a newborn is a serious condition, which requires prompt intervention as it can lead to severe neurological impairment and death if left untreated. The most common causes of hyperammonemia in a newborn are acute liver failure and inherited metabolic disorders. Several mitochondrial disorders have been described as a cause of severe neonatal hyperammonemia.

Case Presentation: Here we describe a new case of adenosine-triphosphate (ATP) synthase deficiency due to m.8528T>C mutation as a novel cause of severe neonatal hyperammonemia. So far six patients with this mutation have been described but none of them was reported to need hemodialysis in the first days of life.

Conclusion: This broadens the so far known differential diagnosis of severe neonatal hyperammonemia requiring hemodialysis.
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http://dx.doi.org/10.1515/jpem-2020-0396DOI Listing
March 2021

Defining clinical subgroups and genotype-phenotype correlations in NBAS-associated disease across 110 patients.

Genet Med 2020 03 25;22(3):610-621. Epub 2019 Nov 25.

Pediatric Gastroenterology, University of Minnesota Medical School, Minneapolis, MN, USA.

Purpose: Pathogenic variants in neuroblastoma-amplified sequence (NBAS) cause an autosomal recessive disorder with a wide range of symptoms affecting liver, skeletal system, and brain, among others. There is a continuously growing number of patients but a lack of systematic and quantitative analysis.

Methods: Individuals with biallelic variants in NBAS were recruited within an international, multicenter study, including novel and previously published patients. Clinical variables were analyzed with log-linear models and visualized by mosaic plots; facial profiles were investigated via DeepGestalt. The structure of the NBAS protein was predicted using computational methods.

Results: One hundred ten individuals from 97 families with biallelic pathogenic NBAS variants were identified, including 26 novel patients with 19 previously unreported variants, giving a total number of 86 variants. Protein modeling redefined the β-propeller domain of NBAS. Based on the localization of missense variants and in-frame deletions, three clinical subgroups arise that differ significantly regarding main clinical features and are directly related to the affected region of the NBAS protein: β-propeller (combined phenotype), Sec39 (infantile liver failure syndrome type 2/ILFS2), and C-terminal (short stature, optic atrophy, and Pelger-Huët anomaly/SOPH).

Conclusion: We define clinical subgroups of NBAS-associated disease that can guide patient management and point to domain-specific functions of NBAS.
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http://dx.doi.org/10.1038/s41436-019-0698-4DOI Listing
March 2020

The Therapeutic Hypothermia in Treatment of Hyperammonemic Encephalopathy due to Urea Cycle Disorders and Organic Acidemias.

Klin Padiatr 2019 Mar 14;231(2):74-79. Epub 2019 Mar 14.

Klinika za pedijatriju, Sveuciliste u Zagrebu Medicinski fakultet, Zagreb, Croatia.

Background: Hyperammonemic encephalopathy in newborns with urea cycle disorders and certain organic acidurias can cause severe brain injury, coma and death. Standard therapy includes protein restriction, nitrogen-scavenging drugs, prevention of catabolism and hemodialysis. Neuroprotective hypothermia as part of the treatment has been reported only 3 times. It has been suggested that mild systemic hypothermia can contribute to better neurological outcomes in hyperammonemic encephalopathy. However, the limited experience precludes accurate conclusions on safety and efficacy.

Methods: Whole body therapeutic hypothermia was included in the standard treatment of hyperammonemic encephalopathy in 4 neonates with urea cycle disorder or organic aciduria.

Results: Two patients survived the initial crisis. One patient has a developmental quotient of 0.8, while the other shows severe developmental delay. The cooling protocol had to be discontinued in 3 patients due to the otherwise untreatable complications (hypotension and hemorrhage).

Conclusion: The efficacy and safety of therapeutic hypothermia in the treatment of neonatal hyperammonemic encephalopathy depend on various factors, requiring further evaluation.
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http://dx.doi.org/10.1055/a-0855-4001DOI Listing
March 2019

Newborn screening for homocystinurias: Recent recommendations versus current practice.

J Inherit Metab Dis 2019 01;42(1):128-139

Unidad de Metabolismo, Hospital Infantil Miguel Servet, Zaragoza, Spain.

Purpose: To assess how the current practice of newborn screening (NBS) for homocystinurias compares with published recommendations.

Methods: Twenty-two of 32 NBS programmes from 18 countries screened for at least one form of homocystinuria. Centres provided pseudonymised NBS data from patients with cystathionine beta-synthase deficiency (CBSD, n = 19), methionine adenosyltransferase I/III deficiency (MATI/IIID, n = 28), combined remethylation disorder (cRMD, n = 56) and isolated remethylation disorder (iRMD), including methylenetetrahydrofolate reductase deficiency (MTHFRD) (n = 8). Markers and decision limits were converted to multiples of the median (MoM) to allow comparison between centres.

Results: NBS programmes, algorithms and decision limits varied considerably. Only nine centres used the recommended second-tier marker total homocysteine (tHcy). The median decision limits of all centres were ≥ 2.35 for high and ≤ 0.44 MoM for low methionine, ≥ 1.95 for high and ≤ 0.47 MoM for low methionine/phenylalanine, ≥ 2.54 for high propionylcarnitine and ≥ 2.78 MoM for propionylcarnitine/acetylcarnitine. These decision limits alone had a 100%, 100%, 86% and 84% sensitivity for the detection of CBSD, MATI/IIID, iRMD and cRMD, respectively, but failed to detect six individuals with cRMD. To enhance sensitivity and decrease second-tier testing costs, we further adapted these decision limits using the data of 15 000 healthy newborns.

Conclusions: Due to the favorable outcome of early treated patients, NBS for homocystinurias is recommended. To improve NBS, decision limits should be revised considering the population median. Relevant markers should be combined; use of the postanalytical tools offered by the CLIR project (Collaborative Laboratory Integrated Reports, which considers, for example, birth weight and gestational age) is recommended. tHcy and methylmalonic acid should be implemented as second-tier markers.
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http://dx.doi.org/10.1002/jimd.12034DOI Listing
January 2019

Evaluation of dietary treatment and amino acid supplementation in organic acidurias and urea-cycle disorders: On the basis of information from a European multicenter registry.

J Inherit Metab Dis 2019 11 27;42(6):1162-1175. Epub 2019 Feb 27.

Department of Pediatrics, Center for Lysosomal and Metabolic Diseases, Erasmus MC University Medical Center, Rotterdam, The Netherlands.

Organic acidurias (OAD) and urea-cycle disorders (UCD) are rare inherited disorders affecting amino acid and protein metabolism. As dietary practice varies widely, we assessed their long-term prescribed dietary treatment against published guideline and studied plasma amino acids levels. We analyzed data from the first visit recorded in the European registry and network for intoxication type metabolic diseases (E-IMD, Chafea no. 2010 12 01). In total, 271 methylmalonic aciduria (MMA) and propionic aciduria (PA) and 361 UCD patients were included. Median natural protein prescription was consistent with the recommended daily allowance (RDA), plasma L-valine (57%), and L-isoleucine (55%) levels in MMA and PA lay below reference ranges. Plasma levels were particularly low in patients who received amino acid mixtures (AAMs-OAD) and L-isoleucine:L-leucine:L-valine (BCAA) ratio was 1.0:3.0:3.2. In UCD patients, plasma L-valine, L-isoleucine, and L-leucine levels lay below reference ranges in 18%, 30%, and 31%, respectively. In symptomatic UCD patients who received AAM-UCD, the median natural protein prescription lay below RDA, while their L-valine and L-isoleucine levels and plasma BCAA ratios were comparable to those in patients who did not receive AAM-UCD. Notably, in patients with ornithine transcarbamylase syndrome (OTC-D), carbamylphosphate synthetase 1 syndrome (CPS1-D) and hyperammonemia-hyperornithinemia-homocitrullinemia (HHH) syndrome selective L-citrulline supplementation resulted in higher plasma L-arginine levels than selective L-arginine supplementation. In conclusion, while MMA and PA patients who received AAMs-OAD had very low BCAA levels and disturbed plasma BCAA ratios, AAMs-UCD seemed to help UCD patients obtain normal BCAA levels. In patients with OTC-D, CPS1-D, and HHH syndrome, selective L-citrulline seemed preferable to selective L-arginine supplementation.
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http://dx.doi.org/10.1002/jimd.12066DOI Listing
November 2019

Metabolic follow-up of a Croatian patient with gyrate atrophy and a new mutation in the gene: a case report.

Biochem Med (Zagreb) 2018 Oct;28(3):030801

Department of Pediatrics, University Hospital Center Zagreb, Zagreb, Croatia.

Gyrate atrophy (GA) of the choroid and retina is a rare autosomal recessive disorder that occurs due to deficiency of the mitochondrial enzyme ornithine aminotransferase (OAT). Hyperornithinemia causes degeneration of the retina with symptoms like myopia, reduced night vision and progressive vision loss. Our patient is a 10-year-old girl with impaired vision and strabismus. As part of the metabolic work-up, plasma amino acid analysis revealed significantly increased concentration of ornithine (1039 μmol/L; reference interval 20 - 155 μmol/L). Molecular genetic analysis revealed homozygous mutation in exon 7 of the gene that has not been reported previously (c.868_870delCTT p.(Leu290del)). This in frame deletion was predicted to be deleterious by software analysis. Our patient was treated with pyridoxine (vitamin B in a dose of 2 x 100 mg/day), low-protein diet (0.6 g/kg/day) and L-lysine supplementation which resulted in a significant reduction in plasma ornithine concentrations to 53% of the initial concentration and the ophthalmologic findings showed significant improvement. We conclude that low protein diet and lysine supplementation can lead to long-term reduction in plasma ornithine concentrations and, if started at an early age, notably slow the progression of retinal function loss in patients with GA. The effect of therapy can be reliably monitored by periodical measurement of plasma ornithine concentration. To our knowledge, this is the first report of OAT deficiency in Croatia.
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http://dx.doi.org/10.11613/BM.2018.030801DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6214690PMC
October 2018

Hypogammaglobulinemia and imaging features in a patient with infantile free sialic acid storage disease (ISSD) and a novel mutation in the SLC17A5 gene.

J Pediatr Endocrinol Metab 2018 Oct;31(10):1155-1159

Department of Pediatrics, University Hospital Center Zagreb, Zagreb, Croatia.

Background Infantile free sialic acid storage disease (ISSD) is a severe multisystemic disorder characterized by the accumulation of free sialic acid in lysosomes. Case presentation The patient presented prenatally with fetal ascites and large scrotal hernias, without pleural or pericardial effusion. During the infantile period, he was diagnosed with permanent isolated immunoglobulin G (IgG) hypogammaglobulinemia, which thus far has rarely been associated with ISSD. The analysis of the SLC17A5 gene revealed a novel homozygous 94 bp gene deletion. We further provide a detailed description of pre- and postnatal clinical and radiographic findings. Conclusions Fetal ascites could be the first sign of several lysosomal storage diseases (LSDs), including ISSD. The analysis of LSD gene panels is an effective approach to diagnosis in the case of non-specific symptoms and when specific biochemical tests are not easily available.
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http://dx.doi.org/10.1515/jpem-2017-0397DOI Listing
October 2018

Attention deficit/hyperactivity disorder as an associated feature in OCTN2 deficiency with novel deletion (p.T440-Y449).

Clin Case Rep 2018 04 9;6(4):585-591. Epub 2018 Feb 9.

Division of Neurology Department of Pediatrics, and Genetics and Genome Biology Program The Research Institute The Hospital for Sick Children University of Toronto Toronto Ontario M5G 1X8 Canada.

This boy presented with ADHD at 3 years and at 8 years was hyperactive with no documented hypoglycemia and had myopathy, cardiomyopathy, and very low serum carnitine. L-carnitine improved his exercise intolerance, cardiomyopathy, and behavior. Analysis of revealed a premature stop codon (p.R282*) and a novel in-frame deletion (p.T440-Y449).
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http://dx.doi.org/10.1002/ccr3.1316DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5889263PMC
April 2018

A novel mutation in a Croatian boy with brachytelephalangy and a thin corpus callosum.

Hum Genome Var 2018 8;5:18005. Epub 2018 Mar 8.

Department of Pediatrics, University Hospital Centre Zagreb, Zagreb, Croatia.

Biallelic mutations in the post-GPI attachment to proteins 3 () gene cause hyperphosphatasia with mental retardation syndrome 4 (HPMRS4), which is characterized by elevated serum alkaline phosphatase, severe psychomotor developmental delay, seizures, and facial dysmorphism. To date, 15 mutations have been reported in humans. Here we report a novel homozygous mutation (c.314C>A, p.Pro105Gln) in a Croatian patient and fully describe the clinical features.
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http://dx.doi.org/10.1038/hgv.2018.5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5842148PMC
March 2018

The genotypic and phenotypic spectrum of MTO1 deficiency.

Mol Genet Metab 2018 01 15;123(1):28-42. Epub 2017 Nov 15.

Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.

Background: Mitochondrial diseases, a group of multi-systemic disorders often characterized by tissue-specific phenotypes, are usually progressive and fatal disorders resulting from defects in oxidative phosphorylation. MTO1 (Mitochondrial tRNA Translation Optimization 1), an evolutionarily conserved protein expressed in high-energy demand tissues has been linked to human early-onset combined oxidative phosphorylation deficiency associated with hypertrophic cardiomyopathy, often referred to as combined oxidative phosphorylation deficiency-10 (COXPD10).

Material And Methods: Thirty five cases of MTO1 deficiency were identified and reviewed through international collaboration. The cases of two female siblings, who presented at 1 and 2years of life with seizures, global developmental delay, hypotonia, elevated lactate and complex I and IV deficiency on muscle biopsy but without cardiomyopathy, are presented in detail.

Results: For the description of phenotypic features, the denominator varies as the literature was insufficient to allow for complete ascertainment of all data for the 35 cases. An extensive review of all known MTO1 deficiency cases revealed the most common features at presentation to be lactic acidosis (LA) (21/34; 62% cases) and hypertrophic cardiomyopathy (15/34; 44% cases). Eventually lactic acidosis and hypertrophic cardiomyopathy are described in 35/35 (100%) and 27/34 (79%) of patients with MTO1 deficiency, respectively; with global developmental delay/intellectual disability present in 28/29 (97%), feeding difficulties in 17/35 (49%), failure to thrive in 12/35 (34%), seizures in 12/35 (34%), optic atrophy in 11/21 (52%) and ataxia in 7/34 (21%). There are 19 different pathogenic MTO1 variants identified in these 35 cases: one splice-site, 3 frameshift and 15 missense variants. None have bi-allelic variants that completely inactivate MTO1; however, patients where one variant is truncating (i.e. frameshift) while the second one is a missense appear to have a more severe, even fatal, phenotype. These data suggest that complete loss of MTO1 is not viable. A ketogenic diet may have exerted a favourable effect on seizures in 2/5 patients.

Conclusion: MTO1 deficiency is lethal in some but not all cases, and a genotype-phenotype relation is suggested. Aside from lactic acidosis and cardiomyopathy, developmental delay and other phenotypic features affecting multiple organ systems are often present in these patients, suggesting a broader spectrum than hitherto reported. The diagnosis should be suspected on clinical features and the presence of markers of mitochondrial dysfunction in body fluids, especially low residual complex I, III and IV activity in muscle. Molecular confirmation is required and targeted genomic testing may be the most efficient approach. Although subjective clinical improvement was observed in a small number of patients on therapies such as ketogenic diet and dichloroacetate, no evidence-based effective therapy exists.
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http://dx.doi.org/10.1016/j.ymgme.2017.11.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5780301PMC
January 2018

Molecular basis and clinical presentation of classic galactosemia in a Croatian population.

J Pediatr Endocrinol Metab 2018 Jan;31(1):71-75

Metabolism and Genetics Group, Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal.

Background: Classic galactosemia is an autosomal recessive disorder of galactose metabolism caused by severely decreased activity of galactose-1-phosphate uridylyltransferase (GALT) due to pathogenic mutations in the GALT gene. To date more than 330 mutations have been described, with p.Q188R and p.K285N being the most common in Caucasian populations. Although acute manifestations can be fully avoided by a galactose-restricted diet, chronic complications, such as neurological ones, cannot be prevented in a significant number of patients despite compliance with the dietary treatment.

Methods: A cohort of 16 galactosemic Croatian patients, including one pair of siblings, was studied. Molecular characterization was performed by direct sequence analysis of the GALT gene.

Results: Sixteen patients were analyzed and only four different mutations were detected. As expected, p.Q188R and p.K285N were common, accounting for 40% and 37% of unrelated alleles, respectively. The third mutation accounting for 20% of mutant alleles was p.R123X causing a premature stop codon, is thus considered to be severe, which is in accordance with the phenotype presented by the homozygous patient described here. The fourth mutation p.E271D was found in a single allele. More than half of our patients manifested some chronic neurological complications.

Conclusions: This is the first report on mutational and phenotypic spectra of classic galactosemia in Croatia that expands the knowledge on the mutational map of the GALT gene across Europe and reveals the genetic homogeneity of the Croatian population.
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http://dx.doi.org/10.1515/jpem-2017-0302DOI Listing
January 2018

Correction to: Impact of age at onset and newborn screening on outcome in organic acidurias.

J Inherit Metab Dis 2018 Jul;41(4):741-742

Department of General Pediatrics, Division of Neuropediatrics and Inherited Metabolic Diseases, University Children's Hospital, Heidelberg, Im Neuenheimer Feld 430, D-69120, Heidelberg, Germany.

Due to an unfortunate error during the typesetting process, the collaborators were presented incorrectly.
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http://dx.doi.org/10.1007/s10545-017-0116-5DOI Listing
July 2018

Progressive deafness-dystonia due to SERAC1 mutations: A study of 67 cases.

Ann Neurol 2017 Dec;82(6):1004-1015

Pediatric Neurology, Brussels University Hospital, Brussels, Belgium.

Objective: 3-Methylglutaconic aciduria, dystonia-deafness, hepatopathy, encephalopathy, Leigh-like syndrome (MEGDHEL) syndrome is caused by biallelic variants in SERAC1.

Methods: This multicenter study addressed the course of disease for each organ system. Metabolic, neuroradiological, and genetic findings are reported.

Results: Sixty-seven individuals (39 previously unreported) from 59 families were included (age range = 5 days-33.4 years, median age = 9 years). A total of 41 different SERAC1 variants were identified, including 20 that have not been reported before. With the exception of 2 families with a milder phenotype, all affected individuals showed a strikingly homogeneous phenotype and time course. Severe, reversible neonatal liver dysfunction and hypoglycemia were seen in >40% of all cases. Starting at a median age of 6 months, muscular hypotonia (91%) was seen, followed by progressive spasticity (82%, median onset = 15 months) and dystonia (82%, 18 months). The majority of affected individuals never learned to walk (68%). Seventy-nine percent suffered hearing loss, 58% never learned to speak, and nearly all had significant intellectual disability (88%). Magnetic resonance imaging features were accordingly homogenous, with bilateral basal ganglia involvement (98%); the characteristic "putaminal eye" was seen in 53%. The urinary marker 3-methylglutaconic aciduria was present in virtually all patients (98%). Supportive treatment focused on spasticity and drooling, and was effective in the individuals treated; hearing aids or cochlear implants did not improve communication skills.

Interpretation: MEGDHEL syndrome is a progressive deafness-dystonia syndrome with frequent and reversible neonatal liver involvement and a strikingly homogenous course of disease. Ann Neurol 2017;82:1004-1015.
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http://dx.doi.org/10.1002/ana.25110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5847115PMC
December 2017

Clinically Distinct Phenotypes of Canavan Disease Correlate with Residual Aspartoacylase Enzyme Activity.

Hum Mutat 2017 05 14;38(5):524-531. Epub 2017 Feb 14.

Department of Clinical Chemistry, Metabolic Unit, VU University Medical Center, Amsterdam Neuroscience, Amsterdam, The Netherlands.

We describe 14 patients with 12 novel missense mutations in ASPA, the gene causing Canavan disease (CD). We developed a method to study the effect of these 12 variants on the function of aspartoacylase-the hydrolysis of N-acetyl-l-aspartic acid (NAA) to aspartate and acetate. The wild-type ASPA open reading frame (ORF) and the ORFs containing each of the variants were transfected into HEK293 cells. Enzyme activity was determined by incubating cell lysates with NAA and measuring the released aspartic acid by LC-MS/MS. Clinical data were obtained for 11 patients by means of questionnaires. Four patients presented with a non-typical clinical picture or with the milder form of CD, whereas seven presented with severe CD. The mutations found in the mild patients corresponded to the variants with the highest residual enzyme activities, suggesting that this assay can help evaluate unknown variants found in patients with atypical presentation. We have detected a correlation between clinical presentation, enzyme activity, and genotype for CD.
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http://dx.doi.org/10.1002/humu.23181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5412892PMC
May 2017

The ethical framework for performing research with rare inherited neurometabolic disease patients.

Eur J Pediatr 2017 Mar 16;176(3):395-405. Epub 2017 Jan 16.

Fondazione Per la Ricerca Farmacologica Gianni Benzi Onlus, Via Abate Eustasio 30, 70010, Valenzano, BA, Italy.

The need for performing clinical trials to develop well-studied and appropriate medicines for inherited neurometabolic disease patients faces ethical concerns mainly raising from four aspects: the diseases are rare; include young and very young patients; the neurological impairment may compromise the capability to provide 'consent'; and the genetic nature of the disease leads to further ethical implications. This work is intended to identify the ethical provisions applicable to clinical research involving these patients and to evaluate if these cover the ethical issues. Three searches have been performed on the European regulatory/legal framework, the literature and European Union-funded projects. The European legal framework offers a number of ethical provisions ruling the clinical research on paediatric, rare, inherited diseases with neurological symptoms. In the literature, relevant publications deal with informed consent, newborn genetic screenings, gene therapy and rights/interests of research participants. Additional information raised from European projects on sharing patients' data from different countries, the need to fill the gap of the regulatory framework and to improve information to stakeholders and patients/families.

Conclusion: Several recommendations and guidelines on ethical aspects are applicable to the inherited neurometabolic disease research in Europe, even though they suffer from the lack of a common ethical approach. What is Known: • When planning and conducting clinical trials, sponsors and researchers know that clinical trials are to be performed according to well-established ethical rules, and patients should be aware about their rights. • In the cases of paediatric patients, vulnerable patients unable to provide consent, genetic diseases' further rules apply. What is New: • This work discusses which ethical rules apply to ensure protection of patient's rights if all the above-mentioned features coexist. • This work shows available data and information on how these rules have been applied.
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http://dx.doi.org/10.1007/s00431-017-2852-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321701PMC
March 2017

The Slavic NBN Founder Mutation: A Role for Reproductive Fitness?

PLoS One 2016 9;11(12):e0167984. Epub 2016 Dec 9.

Cologne Center for Genomics, University of Cologne, Köln, Germany.

The vast majority of patients with Nijmegen Breakage Syndrome (NBS) are of Slavic origin and carry a deleterious deletion (c.657del5; rs587776650) in the NBN gene on chromosome 8q21. This mutation is essentially confined to Slavic populations and may thus be considered a Slavic founder mutation. Notably, not a single parenthood of a homozygous c.657del5 carrier has been reported to date, while heterozygous carriers do reproduce but have an increased cancer risk. These observations seem to conflict with the considerable carrier frequency of c.657del5 of 0.5% to 1% as observed in different Slavic populations because deleterious mutations would be eliminated quite rapidly by purifying selection. Therefore, we propose that heterozygous c.657del5 carriers have increased reproductive success, i.e., that the mutation confers heterozygote advantage. In fact, in our cohort study of the reproductive history of 24 NBS pedigrees from the Czech Republic, we observed that female carriers gave birth to more children on average than female non-carriers, while no such reproductive differences were observed for males. We also estimate that c.657del5 likely occurred less than 300 generations ago, thus supporting the view that the original mutation predated the historic split and subsequent spread of the 'Slavic people'. We surmise that the higher fertility of female c.657del5 carriers reflects a lower miscarriage rate in these women, thereby reflecting the role of the NBN gene product, nibrin, in the repair of DNA double strand breaks and their processing in immune gene rearrangements, telomere maintenance, and meiotic recombination, akin to the previously described role of the DNA repair genes BRCA1 and BRCA2.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167984PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5148078PMC
July 2017

Consensus recommendations for the diagnosis, treatment and follow-up of inherited methylation disorders.

J Inherit Metab Dis 2017 01 26;40(1):5-20. Epub 2016 Sep 26.

Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics Adolescent Medicine and Neonatology, University Medical Centre Freiburg, Freiburg, Germany.

Inherited methylation disorders are a group of rarely reported, probably largely underdiagnosed disorders affecting transmethylation processes in the metabolic pathway between methionine and homocysteine. These are methionine adenosyltransferase I/III, glycine N-methyltransferase, S-adenosylhomocysteine hydrolase and adenosine kinase deficiencies. This paper provides the first consensus recommendations for the diagnosis and management of methylation disorders. Following search of the literature and evaluation according to the SIGN-methodology of all reported patients with methylation defects, graded recommendations are provided in a structured way comprising diagnosis (clinical presentation, biochemical abnormalities, differential diagnosis, newborn screening, prenatal diagnosis), therapy and follow-up. Methylation disorders predominantly affect the liver, central nervous system and muscles, but clinical presentation can vary considerably between and within disorders. Although isolated hypermethioninemia is the biochemical hallmark of this group of disorders, it is not always present, especially in early infancy. Plasma S-adenosylmethionine and S-adenosylhomocysteine are key metabolites for the biochemical clarification of isolated hypermethioninemia. Mild hyperhomocysteinemia can be present in all methylation disorders. Methylation disorders do not qualify as primary targets of newborn screening. A low-methionine diet can be beneficial in patients with methionine adenosyltransferase I/III deficiency if plasma methionine concentrations exceed 800 μmol/L. There is some evidence that this diet may also be beneficial in patients with S-adenosylhomocysteine hydrolase and adenosine kinase deficiencies. S-adenosylmethionine supplementation may be useful in patients with methionine adenosyltransferase I/III deficiency. Recommendations given in this article are based on general principles and in practice should be adjusted individually according to patient's age, severity of the disease, clinical and laboratory findings.
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http://dx.doi.org/10.1007/s10545-016-9972-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5203850PMC
January 2017

NAXE Mutations Disrupt the Cellular NAD(P)HX Repair System and Cause a Lethal Neurometabolic Disorder of Early Childhood.

Am J Hum Genet 2016 Oct 8;99(4):894-902. Epub 2016 Sep 8.

Institute of Human Genetics, Technische Universität München, 81675 München, Germany; Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany. Electronic address:

To safeguard the cell from the accumulation of potentially harmful metabolic intermediates, specific repair mechanisms have evolved. APOA1BP, now renamed NAXE, encodes an epimerase essential in the cellular metabolite repair for NADHX and NADPHX. The enzyme catalyzes the epimerization of NAD(P)HX, thereby avoiding the accumulation of toxic metabolites. The clinical importance of the NAD(P)HX repair system has been unknown. Exome sequencing revealed pathogenic biallelic mutations in NAXE in children from four families with (sub-) acute-onset ataxia, cerebellar edema, spinal myelopathy, and skin lesions. Lactate was elevated in cerebrospinal fluid of all affected individuals. Disease onset was during the second year of life and clinical signs as well as episodes of deterioration were triggered by febrile infections. Disease course was rapidly progressive, leading to coma, global brain atrophy, and finally to death in all affected individuals. NAXE levels were undetectable in fibroblasts from affected individuals of two families. In these fibroblasts we measured highly elevated concentrations of the toxic metabolite cyclic-NADHX, confirming a deficiency of the mitochondrial NAD(P)HX repair system. Finally, NAD or nicotinic acid (vitamin B3) supplementation might have therapeutic implications for this fatal disorder.
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http://dx.doi.org/10.1016/j.ajhg.2016.07.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5065653PMC
October 2016

Unravelling 5-oxoprolinuria (pyroglutamic aciduria) due to bi-allelic OPLAH mutations: 20 new mutations in 14 families.

Mol Genet Metab 2016 09 22;119(1-2):44-9. Epub 2016 Jul 22.

Centre for Molecular Medicine and Therapeutics, Vancouver, BC, Canada; Department of Pediatrics, BC Children's Hospital, University of British Columbia, Vancouver, BC, Canada; Child and Family Research Institute, Vancouver, BC, Canada.

Primary 5-oxoprolinuria (pyroglutamic aciduria) is caused by a genetic defect in the γ-glutamyl cycle, affecting either glutathione synthetase or 5-oxoprolinase. While several dozens of patients with glutathione synthetase deficiency have been reported, with hemolytic anemia representing the clinical key feature, 5-oxoprolinase deficiency due to OPLAH mutations is less frequent and so far has not attracted much attention. This has prompted us to investigate the clinical phenotype as well as the underlying genotype in patients from 14 families of various ethnic backgrounds who underwent diagnostic mutation analysis following the detection of 5-oxoprolinuria. In all patients with 5-oxoprolinuria studied, bi-allelic mutations in OPLAH were indicated. An autosomal recessive mode of inheritance for 5-oxoprolinase deficiency is further supported by the identification of a single mutation in all 9/14 parent sample sets investigated (except for the father of one patient whose result suggests homozygosity), and the absence of 5-oxoprolinuria in all tested heterozygotes. It is remarkable, that all 20 mutations identified were novel and private to the respective families. Clinical features were highly variable and in several sib pairs, did not segregate with 5-oxoprolinuria. Although a pathogenic role of 5-oxoprolinase deficiency remains possible, this is not supported by our findings. Additional patient ascertainment and long-term follow-up is needed to establish the benign nature of this inborn error of metabolism. It is important that all symptomatic patients with persistently elevated levels of 5-oxoproline and no obvious explanation are investigated for the genetic etiology.
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http://dx.doi.org/10.1016/j.ymgme.2016.07.008DOI Listing
September 2016

Hyperinsulinism-hyperammonemia syndrome: a de novo mutation of the GLUD1 gene in twins and a review of the literature.

J Pediatr Endocrinol Metab 2016 Sep;29(9):1083-8

Hyperinsulinism-hyperammonemia (HI/HA) syndrome is a rare autosomal dominant disease characterized by recurrent hypoglycemia and persistent mild elevation of plasma ammonia. HI/HA syndrome is one of the more common forms of congenital hyperinsulinism (CHI), caused by activating mutations within the GLUD1 gene that encodes the mitochondrial enzyme glutamate dehydrogenase (GDH). We report here on monozygotic twin girls presented with fasting- and protein-induced hypoglycemia and mild persistent hyperammonemia. Genetic analysis revealed that both girls were heterozygous for a novel missense mutation within exon 11 [c.1499A>T, p.(R443W)] of the GLUD1 gene. Despite early treatment with diazoxide and a low protein diet, they both developed non-hypoglycemic seizures in early childhood followed by cognitive impairment. In addition to their clinical course, a review of the literature on HI/HA syndrome is provided.
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http://dx.doi.org/10.1515/jpem-2016-0086DOI Listing
September 2016

Glycine N-Methyltransferase Deficiency: A Member of Dysmethylating Liver Disorders?

JIMD Rep 2017 21;31:101-106. Epub 2016 May 21.

Department of Laboratory Diagnostics, University Hospital Center Zagreb, Zagreb, Croatia.

Glycine N-methyltransferase deficiency is an inherited disorder of methionine metabolism, reported so far in only four patients and characterised by permanent hypermethioninemia. This disorder has been considered as probably benign because moderate hepatomegaly in two patients was the only obvious symptom and mild to moderate elevation of aminotransferases the only laboratory abnormality. Our experience with the current novel patient points out that this disease, due to very high hypermethioninemia, is not harmless and that there may be diagnostic pitfalls in interpretation of biochemical hallmarks of the disease. Since the first description of glycine N-methyltransferase deficiency, other disorders of this metabolic pathway affecting the liver have been reported pointing to dysmethylation as the common pathogenetic mechanism. Therefore, we suggest the whole group to be named dysmethylating liver diseases.
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http://dx.doi.org/10.1007/8904_2016_543DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5388635PMC
May 2016

Respiratory chain deficiency in nonmitochondrial disease.

Neurol Genet 2015 Jun 27;1(1):e6. Epub 2015 Apr 27.

Wellcome Trust Centre for Mitochondrial Research (A.P., H.J.N., H.G., K.D., M.S.-K., P.F.C., R.H.), Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom; Medical Genetics Center (A.A., L.F., B.C., S.K., E.H.-F.), Munich, Germany; Division of Neuropediatrics and Muscle Disorders (J.K.), University Medical Center, Freiburg, Germany; Department of Paediatrics (I.B., M.C.), University Hospital Center Zagreb & University of Zagreb, School of Medicine, Zagreb, Croatia; Department of Paediatrics (M.K.), Hospital Baden-Baden, Germany; and Department of Molecular Genetics and Diagnostics (V.K.), NIEH, Budapest, Hungary.

Objective: In this study, we report 5 patients with heterogeneous phenotypes and biochemical evidence of respiratory chain (RC) deficiency; however, the molecular diagnosis is not mitochondrial disease.

Methods: The reported patients were identified from a cohort of 60 patients in whom RC enzyme deficiency suggested mitochondrial disease and underwent whole-exome sequencing.

Results: Five patients had disease-causing variants in nonmitochondrial disease genes ORAI1, CAPN3, COLQ, EXOSC8, and ANO10, which would have been missed on targeted next-generation panels or on MitoExome analysis.

Conclusions: Our data demonstrate that RC abnormalities may be secondary to various cellular processes, including calcium metabolism, neuromuscular transmission, and abnormal messenger RNA degradation.
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http://dx.doi.org/10.1212/NXG.0000000000000006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4821083PMC
June 2015

Abnormal Hypermethylation at Imprinting Control Regions in Patients with S-Adenosylhomocysteine Hydrolase (AHCY) Deficiency.

PLoS One 2016 14;11(3):e0151261. Epub 2016 Mar 14.

Institute of Human Genetics, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.

S-adenosylhomocysteine hydrolase (AHCY) deficiency is a rare autosomal recessive disorder in methionine metabolism caused by mutations in the AHCY gene. Main characteristics are psychomotor delay including delayed myelination and myopathy (hypotonia, absent tendon reflexes etc.) from birth, mostly associated with hypermethioninaemia, elevated serum creatine kinase levels and increased genome wide DNA methylation. The prime function of AHCY is to hydrolyse and efficiently remove S-adenosylhomocysteine, the by-product of transmethylation reactions and one of the most potent methyltransferase inhibitors. In this study, we set out to more specifically characterize DNA methylation changes in blood samples from patients with AHCY deficiency. Global DNA methylation was increased in two of three analysed patients. In addition, we analysed the DNA methylation levels at differentially methylated regions (DMRs) of six imprinted genes (MEST, SNRPN, LIT1, H19, GTL2 and PEG3) as well as Alu and LINE1 repetitive elements in seven patients. Three patients showed a hypermethylation in up to five imprinted gene DMRs. Abnormal methylation in Alu and LINE1 repetitive elements was not observed. We conclude that DNA hypermethylation seems to be a frequent but not a constant feature associated with AHCY deficiency that affects different genomic regions to different degrees. Thus AHCY deficiency may represent an ideal model disease for studying the molecular origins and biological consequences of DNA hypermethylation due to impaired cellular methylation status.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151261PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4790936PMC
August 2016

Review and evaluation of the methodological quality of the existing guidelines and recommendations for inherited neurometabolic disorders.

Orphanet J Rare Dis 2015 Dec 30;10:164. Epub 2015 Dec 30.

Neurology, gastroenterology pathology and clinical biochemistry Departments, IRP-HSJD and CIBERER, Barcelona, Spain.

Background: Inherited neurometabolic disorders (iNMDs) represent a group of almost seven hundred rare diseases whose common manifestations are clinical neurologic or cognitive symptoms that can appear at any time, in the first months/years of age or even later in adulthood. Early diagnosis and timely treatments are often pivotal for the favorable course of the disease. Thus, the elaboration of new evidence-based recommendations for iNMD diagnosis and management is increasingly requested by health care professionals and patients, even though the methodological quality of existing guidelines is largely unclear. InNerMeD-I-Network is the first European network on iNMDs that was created with the aim of sharing and increasing validated information about diagnosis and management of neurometabolic disorders. One of the goals of the project was to determine the number and the methodological quality of existing guidelines and recommendations for iNMDs.

Methods: We performed a systematic search on PubMed, the National Guideline Clearinghouse (NGC), the Guidelines International Network (G-I-N), the Scottish Intercollegiate Guideline Network (SIGN) and the National Institute for Health and Care Excellence (NICE) to identify all the published guidelines and recommendations for iNMDs from January 2000 to June 2015. The methodological quality of the selected documents was determined using the AGREE II instrument, an appraisal tool composed of 6 domains covering 23 key items.

Results: A total of 55 records met the inclusion criteria, 11 % were about groups of disorders, whereas the majority encompassed only one disorder. Lysosomal disorders, and in particular Fabry, Gaucher disease and mucopolysaccharidoses where the most studied. The overall methodological quality of the recommendation was acceptable and increased over time, with 25 % of the identified guidelines strongly recommended by the appraisers, 64 % recommended, and 11 % not recommended. However, heterogeneity in the obtained scores for each domain was observed among documents covering different groups of disorders and some domains like 'stakeholder involvement' and 'applicability' were generally scarcely addressed.

Conclusions: Greater efforts should be devoted to improve the methodological quality of guidelines and recommendations for iNMDs and AGREE II instrument seems advisable for new guideline development. The elaboration of new guidelines encompassing still uncovered disorders is badly needed.
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http://dx.doi.org/10.1186/s13023-015-0376-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4696316PMC
December 2015

Impact of age at onset and newborn screening on outcome in organic acidurias.

J Inherit Metab Dis 2016 05 21;39(3):341-353. Epub 2015 Dec 21.

Department of General Pediatrics, Division of Neuropediatrics and Inherited Metabolic Diseases, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, D-69120, Heidelberg, Germany.

Background And Aim: To describe current diagnostic and therapeutic strategies in organic acidurias (OADs) and to evaluate their impact on the disease course allowing harmonisation.

Methods: Datasets of 567 OAD patients from the E-IMD registry were analysed. The sample includes patients with methylmalonic (MMA, n = 164), propionic (PA, n = 144) and isovaleric aciduria (IVA, n = 83), and glutaric aciduria type 1 (GA1, n = 176). Statistical analysis included description and recursive partitioning of diagnostic and therapeutic strategies, and odds ratios (OR) for health outcome parameters. For some analyses, symptomatic patients were divided into those presenting with first symptoms during (i.e. early onset, EO) or after the newborn period (i.e. late onset, LO).

Results: Patients identified by newborn screening (NBS) had a significantly lower median age of diagnosis (8 days) compared to the LO group (363 days, p < 0.001], but not compared to the EO group. Of all OAD patients 71 % remained asymptomatic until day 8. Patients with cobalamin-nonresponsive MMA (MMA-Cbl(-)) and GA1 identified by NBS were less likely to have movement disorders than those diagnosed by selective screening (MMA-Cbl(-): 10 % versus 39 %, p = 0.002; GA1: 26 % versus 73 %, p < 0.001). For other OADs, the clinical benefit of NBS was less clear. Reported age-adjusted intake of natural protein and calories was significantly higher in LO patients than in EO patients reflecting different disease severities. Variable drug combinations, ranging from 12 in MMA-Cbl(-) to two in isovaleric aciduria, were used for maintenance treatment. The effects of specific metabolic treatment strategies on the health outcomes remain unclear because of the strong influences of age at onset (EO versus LO), diagnostic mode (NBS versus selective screening), and the various treatment combinations used.

Conclusions: NBS is an effective intervention to reduce time until diagnosis especially for LO patients and to prevent irreversible cerebral damage in GA1 and MMA-Cbl(-). Huge diversity of therapeutic interventions hampers our understanding of optimal treatment.
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http://dx.doi.org/10.1007/s10545-015-9907-8DOI Listing
May 2016
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