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Van Hove JLK, Freehauf CL, Ficicioglu C, Pena LDM, Moreau KL, Henthorn TK, Christians U, Jiang H, Cowan TM, Young SP, Hite M, Friederich MW, Stabler SP, Spector EB, Kronquist KE, Thomas JA, Emmett P, Harrington MJ, Pyle L, Creadon-Swindell G, Wempe MF, MacLean KN. Biomarkers of oxidative stress, inflammation, and vascular dysfunction in inherited cystathionine β-synthase deficient homocystinuria and the impact of taurine treatment in a phase 1/2 human clinical trial. J Inherit Metab Dis 2019; 42:424-437. [PMID: 30873612 DOI: 10.1002/jimd.12085] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 03/11/2019] [Indexed: 11/10/2022]
Abstract
STUDY OBJECTIVE A phase 1/2 clinical trial was performed in individuals with cystathionine β synthase (CBS) deficient homocystinuria with aims to: (a) assess pharmacokinetics and safety of taurine therapy, (b) evaluate oxidative stress, inflammation, and vascular function in CBS deficiency, and (c) evaluate the impact of short-term taurine treatment. METHODS Individuals with pyridoxine-nonresponsive CBS deficiency with homocysteine >50 μM, without inflammatory disorder or on antioxidant therapy were enrolled. Biomarkers of oxidative stress and inflammation, endothelial function (brachial artery flow-mediated dilation [FMD]), and disease-related metabolites obtained at baseline were compared to normal values. While maintaining current treatment, patients were treated with 75 mg/kg taurine twice daily, and treatment response assessed after 4 hours and 4 days. RESULTS Fourteen patients (8-35 years; 8 males, 6 females) were enrolled with baseline homocysteine levels 161 ± 67 μM. The study found high-dose taurine to be safe when excluding preexisting hypertriglyceridemia. Taurine pharmacokinetics showed a rapid peak level returning to near normal levels at 12 hours, but had slow accumulation and elevated predosing levels after 4 days of treatment. Only a single parameter of oxidative stress, 2,3-dinor-8-isoprostaglandin-F2α, was elevated at baseline, with no elevated inflammatory parameters, and no change in FMD values overall. Taurine had no effect on any of these parameters. However, the effect of taurine was strongly related to pretreatment FMD values; and taurine significantly improved FMD in the subset of individuals with pretreatment FMD values <10% and in individuals with homocysteine levels >125 μM, pertinent to endothelial function. CONCLUSION Taurine improves endothelial function in CBS-deficient homocystinuria in patients with preexisting reduced function.
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Miller JS, Thomas RP, Bennett A, Bianconi S, Bruchey A, Davis RJ, Ficicioglu C, Guthrie W, Porter FD, Thurm A. Early Indicators of Creatine Transporter Deficiency. J Pediatr 2019; 206:283-285. [PMID: 30579583 PMCID: PMC6693671 DOI: 10.1016/j.jpeds.2018.11.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 10/05/2018] [Accepted: 11/05/2018] [Indexed: 11/30/2022]
Abstract
Early identification is a goal for creatine transporter deficiency and will be critical for future treatment. Before their first birthday, one-half of this sample showed both a significant feeding/weight gain issue and delayed sitting or crawling. Combined, these early indicators could have alerted providers to conduct a urine screen.
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Huemer M, Diodato D, Martinelli D, Olivieri G, Blom H, Gleich F, Kölker S, Kožich V, Morris AA, Seifert B, Froese DS, Baumgartner MR, Dionisi-Vici C, Martin CA, Baethmann M, Ballhausen D, Blasco-Alonso J, Boy N, Bueno M, Burgos Peláez R, Cerone R, Chabrol B, Chapman KA, Couce ML, Crushell E, Dalmau Serra J, Diogo L, Ficicioglu C, García Jimenez MC, García Silva MT, Gaspar AM, Gautschi M, González-Lamuño D, Gouveia S, Grünewald S, Hendriksz C, Janssen MCH, Jesina P, Koch J, Konstantopoulou V, Lavigne C, Lund AM, Martins EG, Meavilla Olivas S, Mention K, Mochel F, Mundy H, Murphy E, Paquay S, Pedrón-Giner C, Ruiz Gómez MA, Santra S, Schiff M, Schwartz IV, Scholl-Bürgi S, Servais A, Skouma A, Tran C, Vives Piñera I, Walter J, Weisfeld-Adams J. Phenotype, treatment practice and outcome in the cobalamin-dependent remethylation disorders and MTHFR deficiency: Data from the E-HOD registry. J Inherit Metab Dis 2019; 42:333-352. [PMID: 30773687 DOI: 10.1002/jimd.12041] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
AIM To explore the clinical presentation, course, treatment and impact of early treatment in patients with remethylation disorders from the European Network and Registry for Homocystinurias and Methylation Defects (E-HOD) international web-based registry. RESULTS This review comprises 238 patients (cobalamin C defect n = 161; methylenetetrahydrofolate reductase deficiency n = 50; cobalamin G defect n = 11; cobalamin E defect n = 10; cobalamin D defect n = 5; and cobalamin J defect n = 1) from 47 centres for whom the E-HOD registry includes, as a minimum, data on medical history and enrolment visit. The duration of observation was 127 patient years. In 181 clinically diagnosed patients, the median age at presentation was 30 days (range 1 day to 42 years) and the median age at diagnosis was 3.7 months (range 3 days to 56 years). Seventy-five percent of pre-clinically diagnosed patients with cobalamin C disease became symptomatic within the first 15 days of life. Total homocysteine (tHcy), amino acids and urinary methylmalonic acid (MMA) were the most frequently assessed disease markers; confirmatory diagnostics were mainly molecular genetic studies. Remethylation disorders are multisystem diseases dominated by neurological and eye disease and failure to thrive. In this cohort, mortality, thromboembolic, psychiatric and renal disease were rarer than reported elsewhere. Early treatment correlates with lower overall morbidity but is less effective in preventing eye disease and cognitive impairment. The wide variation in treatment hampers the evaluation of particular therapeutic modalities. CONCLUSION Treatment improves the clinical course of remethylation disorders and reduces morbidity, especially if started early, but neurocognitive and eye symptoms are less responsive. Current treatment is highly variable. This study has the inevitable limitations of a retrospective, registry-based design.
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Chen J, Li X, Edmondson A, Meyers GD, Izumi K, Ackermann AM, Morava E, Ficicioglu C, Bennett MJ, He M. Increased Clinical Sensitivity and Specificity of Plasma Protein N-Glycan Profiling for Diagnosing Congenital Disorders of Glycosylation by Use of Flow Injection-Electrospray Ionization-Quadrupole Time-of-Flight Mass Spectrometry. Clin Chem 2019; 65:653-663. [PMID: 30770376 DOI: 10.1373/clinchem.2018.296780] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 01/23/2019] [Indexed: 12/27/2022]
Abstract
BACKGROUND Congenital disorders of glycosylation (CDG) represent 1 of the largest groups of metabolic disorders with >130 subtypes identified to date. The majority of CDG subtypes are disorders of N-linked glycosylation, in which carbohydrate residues, namely, N-glycans, are posttranslationally linked to asparagine molecules in peptides. To improve the diagnostic capability for CDG, we developed and validated a plasma N-glycan assay using flow injection-electrospray ionization-quadrupole time-of-flight mass spectrometry. METHODS After PNGase F digestion of plasma glycoproteins, N-glycans were linked to a quinolone using a transient amine group at the reducing end, isolated by a hydrophilic interaction chromatography column, and then identified by accurate mass and quantified using a stable isotope-labeled glycopeptide as the internal standard. RESULTS This assay differed from other N-glycan profiling methods because it was free of any contamination from circulating free glycans and was semiquantitative. The low end of the detection range tested was at 63 nmol/L for disialo-biantennary N-glycan. The majority of N-glycans in normal plasma had <1% abundance. Abnormal N-glycan profiles from 19 patients with known diagnoses of 11 different CDG subtypes were generated, some of which had previously been reported to have normal N-linked protein glycosylation by carbohydrate-deficient transferrin analysis. CONCLUSIONS The clinical specificity and sensitivity of N-glycan analysis was much improved with this method. Additional CDGs can be diagnosed that would be missed by carbohydrate-deficient transferrin analysis. The assay provides novel biomarkers with diagnostic and potentially therapeutic significance.
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Ahrens-Nicklas RC, Ganetzky RD, Rush PW, Conway RL, Ficicioglu C. Characteristics and outcomes of patients with formiminoglutamic aciduria detected through newborn screening. J Inherit Metab Dis 2019; 42:140-146. [PMID: 30740726 PMCID: PMC6279618 DOI: 10.1002/jimd.12035] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Glutamate formiminotransferase deficiency (FTCD deficiency) or formiminoglutamic aciduria is the second most common of the known inherited disorders of folate metabolism. Initial case reports suggested that patients may have severe intellectual disability and megaloblastic anemia. However, these cases were obtained from screening cohorts of patients with developmental delay. Subsequently, patients with milder clinical phenotypes have been reported. The full phenotypic spectrum of this disorder remains unknown. METHODS In many states, FTCD deficiency can be incidentally detected on tandem mass spectrometry-based newborn screening of dried blood spots. In this work, we report the outcomes of infants identified to have FTCD deficiency through newborn screening. RESULTS During the study period, 18 patients were identified to have FTCD deficiency and were referred and evaluated at one of the two participating metabolic centers. The overall rate of FTCD deficiency detected through the New Jersey screening program over the study time period was 1:58,982. At a mean age of 56 months at last follow-up: 3/18 (16%) had developmental delays requiring individualized education plans, no patients had profound intellectual disability; 4/16 (25%) had mild self-limited anemia, no patients had profound anemia. CONCLUSIONS These data suggest that the majority of individuals with FTCD deficiency detected by newborn screening are asymptomatic.
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Ah Mew N, Cnaan A, McCarter R, Choi H, Glass P, Rice K, Scavo L, Gillespie CW, Diaz GA, Berry GT, Wong D, Konczal L, McCandless SE, Coughlin Ii CR, Weisfeld-Adams JD, Ficicioglu C, Yudkoff M, Enns GM, Lichter-Konecki U, Gallagher R, Tuchman M. Conducting an investigator-initiated randomized double-blinded intervention trial in acute decompensation of inborn errors of metabolism: Lessons from the N-Carbamylglutamate Consortium. ACTA ACUST UNITED AC 2018; 3:157-170. [PMID: 30613471 PMCID: PMC6311376 DOI: 10.3233/trd-180031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Organic acidemias and urea cycle disorders are ultra-rare inborn errors of metabolism characterized by episodic acute decompensation, often associated with hyperammonemia, resulting in brain edema and encephalopathy. Retrospective reports and translational studies suggest that N-carbamylglutamate (NCG) may be effective in reducing ammonia levels during acute decompensation in two organic acidemias, propionic and methylmalonic acidemia (PA and MMA), and in two urea cycle disorders, carbamylphosphate synthetase 1 and ornithine transcarbamylase deficiency (CPSD and OTCD). We established the 9-site N-carbamylglutamate Consortium (NCGC) in order to conduct two randomized double-blind, placebo-controlled trials of NCG in acute hyperammonemia of PA, MMA, CPSD and OTCD. Conducting clinical trials is challenging in any disease, but poses unique barriers and risks in the ultra-rare disorders. As the number of clinical trials in orphan diseases increases, evaluating the successes and opportunities for improvement in such trials is essential. We summarize herein the design, methods, experiences, challenges and lessons from the NCGC-conducted trials.
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Berry SA, Vockley J, Vinks AA, Dong M, Diaz GA, McCandless SE, Smith WE, Harding CO, Zori R, Ficicioglu C, Lichter-Konecki U, Perdok R, Robinson B, Holt RJ, Longo N. Pharmacokinetics of glycerol phenylbutyrate in pediatric patients 2 months to 2 years of age with urea cycle disorders. Mol Genet Metab 2018; 125:251-257. [PMID: 30217721 DOI: 10.1016/j.ymgme.2018.09.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Revised: 07/27/2018] [Accepted: 09/02/2018] [Indexed: 11/16/2022]
Abstract
INTRODUCTION Glycerol phenylbutyrate (GPB) is approved in the US and EU for the chronic management of patients ≥2 months of age with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. GPB is a pre-prodrug, hydrolyzed by lipases to phenylbutyric acid (PBA) that upon absorption is beta-oxidized to the active nitrogen scavenger phenylacetic acid (PAA), which is conjugated to glutamine (PAGN) and excreted as urinary PAGN (UPAGN). Pharmacokinetics (PK) of GPB were examined to see if hydrolysis is impaired in very young patients who may lack lipase activity. METHODS Patients 2 months to <2 years of age with UCDs from two open label studies (n = 17, median age 10 months) predominantly on stable doses of nitrogen scavengers (n = 14) were switched to GPB. Primary assessments included traditional plasma PK analyses of PBA, PAA, and PAGN, using noncompartmental methods with WinNonlin™. UPAGN was collected periodically throughout the study up to 12 months. RESULTS PBA, PAA and PAGN rapidly appeared in plasma after GPB dosing, demonstrating evidence of GPB cleavage with subsequent PBA absorption. Median concentrations of PBA, PAA and PAGN did not increase over time and were similar to or lower than the values observed in older UCD patients. The median PAA/PAGN ratio was well below one over time, demonstrating that conjugation of PAA with glutamine to form PAGN did not reach saturation. Covariate analyses indicated that age did not influence the PK parameters, with body surface area (BSA) being the most significant covariate, reinforcing current BSA based dosing recommendations as seen in older patients. CONCLUSION These observations demonstrate that UCD patients aged 2 months to <2 years have sufficient lipase activity to adequately convert the pre-prodrug GPB to PBA. PBA is then converted to its active moiety (PAA) providing successful nitrogen scavenging even in very young children.
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Dines JN, Golden-Grant K, LaCroix A, Muir AM, Cintrón DL, McWalter K, Cho MT, Sun A, Merritt JL, Thies J, Niyazov D, Burton B, Kim K, Fleming L, Westman R, Karachunski P, Dalton J, Basinger A, Ficicioglu C, Helbig I, Pendziwiat M, Muhle H, Helbig KL, Caliebe A, Santer R, Becker K, Suchy S, Douglas G, Millan F, Begtrup A, Monaghan KG, Mefford HC. TANGO2: expanding the clinical phenotype and spectrum of pathogenic variants. Genet Med 2018; 21:601-607. [PMID: 30245509 PMCID: PMC6752277 DOI: 10.1038/s41436-018-0137-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 07/05/2018] [Indexed: 12/22/2022] Open
Abstract
Purpose TANGO2-related disorders were first described in 2016 and prior to this publication, only 15 individuals with TANGO2-related disorder were described in the literature. Primary features include metabolic crisis with rhabdomyolysis, encephalopathy, intellectual disability, seizures, and cardiac arrhythmias. We assess whether genotype and phenotype of TANGO2-related disorder has expanded since the initial discovery and determine the efficacy of exome sequencing (ES) as a diagnostic tool for detecting variants. Methods We present a series of 14 individuals from 11 unrelated families with complex medical and developmental histories, in whom ES or microarray identified compound heterozygous or homozygous variants in TANGO2. Results The initial presentation of patients with TANGO2-related disorders can be variable, including primarily neurological presentations. We expand the phenotype and genotype for TANGO2, highlighting the variability of the disorder. Conclusion TANGO2-related disorders can have a more diverse clinical presentation than previously anticipated. We illustrate the utility of routine ES data reanalysis whereby discovery of novel disease genes can lead to a diagnosis in previously unsolved cases and the need for additional copy-number variation analysis when ES is performed.
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Lazzara A, Daymont C, Ladda R, Lull J, Ficicioglu C, Cohen JL, Aprile J. Failure to Thrive: An Expanded Differential Diagnosis. J Pediatr Genet 2018; 8:27-32. [PMID: 30775051 DOI: 10.1055/s-0038-1669445] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 07/23/2018] [Indexed: 10/28/2022]
Abstract
The patient is a term 6-month-old male, who presented with failure to thrive since birth. History was remarkable for suspected milk and soy protein allergy, gastroesophageal reflux, constipation, and abdominal distension that was present since birth. He was losing weight despite oral intake of over 100 kcal/kg per day. Prior workup including laboratory studies, abdominal X-ray, upper gastrointestinal series with fluoroscopy, barium enema, and abdominal ultrasound were all within normal limits. The patient's history, diagnostic evaluation, and final diagnosis are revealed. This case highlights a rare condition presenting as failure to thrive, a common problem with a wide differential diagnosis.
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Bruun TUJ, Sidky S, Bandeira AO, Debray FG, Ficicioglu C, Goldstein J, Joost K, Koeberl DD, Luísa D, Nassogne MC, O'Sullivan S, Õunap K, Schulze A, van Maldergem L, Salomons GS, Mercimek-Andrews S. Treatment outcome of creatine transporter deficiency: international retrospective cohort study. Metab Brain Dis 2018; 33:875-884. [PMID: 29435807 DOI: 10.1007/s11011-018-0197-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 01/29/2018] [Indexed: 12/25/2022]
Abstract
To evaluate the outcome of current treatment for creatine transporter (CRTR) deficiency, we developed a clinical severity score and initiated an international treatment registry. An online questionnaire was completed by physicians following patients with CRTR deficiency on a treatment, including creatine and/or arginine, and/or glycine. Clinical severity score included 1) global developmental delay/intellectual disability; 2) seizures; 3) behavioural disorder. Phenotype scored 1-3 = mild; 4-6 = moderate; and 7-9 = severe. We applied the clinical severity score pre- and on-treatment. Seventeen patients, 14 males and 3 females, from 16 families were included. Four patients had severe, 6 patients had moderate, and 7 patients had a mild phenotype. The phenotype ranged from mild to severe in patients diagnosed at or before 2 years of age or older than 6 years of age. The phenotype ranged from mild to severe in patients with mildly elevated urine creatine to creatinine ratio. Fourteen patients were on the combined creatine, arginine and glycine therapy. On the combined treatment with creatine, arginine and glycine, none of the males showed either deterioration or improvements in their clinical severity score, whereas two females showed improvements in the clinical severity score. Creatine monotherapy resulted in deterioration of the clinical severity score in one male. There seems to be no correlation between phenotype and degree of elevation in urine creatine to creatinine ratio, genotype, or age at diagnosis. Combined creatine, arginine and glycine therapy might have stopped disease progression in males and improved phenotype in females.
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Ahrens-Nicklas R, Schlotawa L, Ballabio A, Brunetti-Pierri N, De Castro M, Dierks T, Eichler F, Ficicioglu C, Finglas A, Gaertner J, Kirmse B, Klepper J, Lee M, Olsen A, Parenti G, Vossough A, Vanderver A, Adang LA. Complex care of individuals with multiple sulfatase deficiency: Clinical cases and consensus statement. Mol Genet Metab 2018; 123:337-346. [PMID: 29397290 PMCID: PMC6856873 DOI: 10.1016/j.ymgme.2018.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 01/15/2018] [Accepted: 01/15/2018] [Indexed: 12/11/2022]
Abstract
Multiple sulfatase deficiency (MSD) is an ultra-rare neurodegenerative disorder that results in defective sulfatase post-translational modification. Sulfatases in the body are activated by a unique protein, formylglycine-generating enzyme (FGE) that is encoded by SUMF1. When FGE is absent or insufficient, all 17 known human sulfatases are affected, including the enzymes associated with metachromatic leukodystrophy (MLD), several mucopolysaccharidoses (MPS II, IIIA, IIID, IVA, VI), chondrodysplasia punctata, and X-linked ichthyosis. As such, individuals demonstrate a complex and severe clinical phenotype that has not been fully characterized to date. In this report, we describe two individuals with distinct clinical presentations of MSD. Also, we detail a comprehensive systems-based approach to the management of individuals with MSD, from the initial diagnostic evaluation to unique multisystem issues and potential management options. As there have been no natural history studies to date, the recommendations within this report are based on published studies and consensus opinion and underscore the need for future research on evidence-based outcomes to improve management of children with MSD.
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Guéant JL, Chéry C, Oussalah A, Nadaf J, Coelho D, Josse T, Flayac J, Robert A, Koscinski I, Gastin I, Filhine-Tresarrieu P, Pupavac M, Brebner A, Watkins D, Pastinen T, Montpetit A, Hariri F, Tregouët D, Raby BA, Chung WK, Morange PE, Froese DS, Baumgartner MR, Benoist JF, Ficicioglu C, Marchand V, Motorin Y, Bonnemains C, Feillet F, Majewski J, Rosenblatt DS. Publisher Correction: A PRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients. Nat Commun 2018; 9:554. [PMID: 29396438 PMCID: PMC5797229 DOI: 10.1038/s41467-018-03054-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The original version of this Article contained an error in the title, which was incorrectly given as 'APRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients'. This has now been corrected in both the PDF and HTML versions of the Article to read 'A PRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients'.
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Kwon JM, Matern D, Kurtzberg J, Wrabetz L, Gelb MH, Wenger DA, Ficicioglu C, Waldman AT, Burton BK, Hopkins PV, Orsini JJ. Consensus guidelines for newborn screening, diagnosis and treatment of infantile Krabbe disease. Orphanet J Rare Dis 2018; 13:30. [PMID: 29391017 PMCID: PMC5796396 DOI: 10.1186/s13023-018-0766-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/12/2018] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Krabbe disease is a rare neurodegenerative genetic disorder caused by deficiency of galactocerebrosidase. Patients with the infantile form of Krabbe disease can be treated at a presymptomatic stage with human stem cell transplantation which improves survival and clinical outcomes. However, without a family history, most cases of infantile Krabbe disease present after onset of symptoms and are ineligible for transplantation. In 2006, New York began screening newborns for Krabbe disease to identify presymptomatic cases. To ensure that those identified with infantile disease received timely treatment, New York public health and medical systems took steps to accurately diagnose and rapidly refer infants for human stem cell transplantation within the first few weeks of life. After 11 years of active screening in New York and the introduction of Krabbe disease newborn screening in other states, new information has been gained which can inform the design of newborn screening programs to improve infantile Krabbe disease outcomes. FINDINGS Recent information relevant to Krabbe disease screening, diagnosis, and treatment were assessed by a diverse group of public health, medical, and advocacy professionals. Outcomes after newborn screening may improve if treatment for infantile disease is initiated before 30 days of life. Newer laboratory screening and diagnostic tools can improve the speed and specificity of diagnosis and help facilitate this early referral. Given the rarity of Krabbe disease, most recommendations were based on case series or expert opinion. CONCLUSION This report updates recommendations for Krabbe disease newborn screening to improve the timeliness of diagnosis and treatment of infantile Krabbe disease. In the United States, several states have begun or are considering Krabbe disease newborn screening. These recommendations can guide public health laboratories on methodologies for screening and inform clinicians about the need to promptly diagnose and treat infantile Krabbe disease. The timing of the initial referral after newborn screening, the speed of diagnostic confirmation of infantile disease, and the transplantation center's experience and ability to rapidly respond to a suspected patient with newly diagnosed infantile Krabbe disease are critical for optimal outcomes.
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Guéant JL, Chéry C, Oussalah A, Nadaf J, Coelho D, Josse T, Flayac J, Robert A, Koscinski I, Gastin I, Filhine-Tresarrieu P, Pupavac M, Brebner A, Watkins D, Pastinen T, Montpetit A, Hariri F, Tregouët D, Raby BA, Chung WK, Morange PE, Froese DS, Baumgartner MR, Benoist JF, Ficicioglu C, Marchand V, Motorin Y, Bonnemains C, Feillet F, Majewski J, Rosenblatt DS. APRDX1 mutant allele causes a MMACHC secondary epimutation in cblC patients. Nat Commun 2018; 9:67. [PMID: 29302025 PMCID: PMC5754367 DOI: 10.1038/s41467-017-02306-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 11/17/2017] [Indexed: 12/17/2022] Open
Abstract
To date, epimutations reported in man have been somatic and erased in germlines. Here, we identify a cause of the autosomal recessive cblC class of inborn errors of vitamin B12 metabolism that we name “epi-cblC”. The subjects are compound heterozygotes for a genetic mutation and for a promoter epimutation, detected in blood, fibroblasts, and sperm, at the MMACHC locus; 5-azacytidine restores the expression of MMACHC in fibroblasts. MMACHC is flanked by CCDC163P and PRDX1, which are in the opposite orientation. The epimutation is present in three generations and results from PRDX1 mutations that force antisense transcription of MMACHC thereby possibly generating a H3K36me3 mark. The silencing of PRDX1 transcription leads to partial hypomethylation of the epiallele and restores the expression of MMACHC. This example of epi-cblC demonstrates the need to search for compound epigenetic-genetic heterozygosity in patients with typical disease manifestation and genetic heterozygosity in disease-causing genes located in other gene trios. Inborn errors of vitamin B12 metabolism of the cblC class are caused by mutations in the MMACHC gene. Here, Guéant et al. report epi-cblC, a class of cblC in which patients are compound heterozygous for a genetic mutation and a secondary epimutation at the MMACHC locus.
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Ficicioglu C, Giugliani R, Harmatz P, Mendelsohn NJ, Jego V, Parini R. Intrafamilial variability in the clinical manifestations of mucopolysaccharidosis type II: Data from the Hunter Outcome Survey (HOS). Am J Med Genet A 2017; 176:301-310. [PMID: 29210515 PMCID: PMC5814921 DOI: 10.1002/ajmg.a.38551] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/25/2017] [Accepted: 10/31/2017] [Indexed: 12/21/2022]
Abstract
Several cases of phenotypic variability among family members with mucopolysaccharidosis type II (MPS II) have been reported, but the data are limited. Data from patients enrolled in the Hunter Outcome Survey (HOS) were used to investigate intrafamilial variability in male siblings with MPS II. As of July 2015, data were available for 78 patients aged ≥5 years at last visit who had at least one affected sibling (39 sibling pairs). These patients were followed prospectively (i.e., they were alive at enrollment in HOS). The median age at the onset of signs and symptoms was the same for the elder and younger brothers (2.0 years); however, the younger brothers were typically diagnosed at a younger age than the elder brothers (median age, 2.5 and 5.1 years, respectively). Of the 39 pairs, eight pairs were classified as being discordant (the status of four or more signs and symptoms differed between the siblings); 21 pairs had one, two, or three signs and symptoms that differed between the siblings, and 10 pairs had none. Regression status of the majority of the developmental milestones studied was generally concordant among siblings. Functional classification, a measure of central nervous system involvement, was the same in 24/28 pairs, although four pairs were considered discordant as functional classification differed between the siblings. Overall, this analysis revealed similarity in the clinical manifestations of MPS II among siblings. This information should help to improve our understanding of the clinical presentation of the disease, including phenotype prediction in affected family members.
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Ficicioglu C. New tools and approaches to newborn screening: ready to open Pandora's box? Cold Spring Harb Mol Case Stud 2017; 3:a001842. [PMID: 28487886 PMCID: PMC5411690 DOI: 10.1101/mcs.a001842] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The landscape of newborn screening (NBS) is changing as new tools are developed. We must acknowledge that NBS is a very important and extraordinarily positive initiative especially for rare and serious inherited disorders; however, lessons learned from current NBS should guide the future of NBS as we enter the era of “omics” that will expand NBS for many other genetic disorders. In this article, I will first discuss new tools such as genomics and metabolomics for NBS. I will then turn to assessing how best to take advantage of new technical developments while considering the best interests of patients and the success of newborn screening.
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Berry SA, Longo N, Diaz GA, McCandless SE, Smith WE, Harding CO, Zori R, Ficicioglu C, Lichter-Konecki U, Robinson B, Vockley J. Safety and efficacy of glycerol phenylbutyrate for management of urea cycle disorders in patients aged 2months to 2years. Mol Genet Metab 2017; 122:46-53. [PMID: 28916119 DOI: 10.1016/j.ymgme.2017.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/01/2017] [Accepted: 09/01/2017] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Glycerol phenylbutyrate (GPB) is approved in the US for the management of patients 2months of age and older with urea cycle disorders (UCDs) that cannot be managed with protein restriction and/or amino acid supplementation alone. Limited data exist on the use of nitrogen conjugation agents in very young patients. METHODS Seventeen patients (15 previously on other nitrogen scavengers) with all types of UCDs aged 2months to 2years were switched to, or started, GPB. Retrospective data up to 12months pre-switch and prospective data during initiation of therapy were used as baseline measures. The primary efficacy endpoint of the integrated analysis was the successful transition to GPB with controlled ammonia (<100μmol/L and no clinical symptoms). Secondary endpoints included glutamine and levels of other amino acids. Safety endpoints included adverse events, hyperammonemic crises (HACs), and growth and development. RESULTS 82% and 53% of patients completed 3 and 6months of therapy, respectively (mean 8.85months, range 6days-18.4months). Patients transitioned to GPB maintained excellent control of ammonia and glutamine levels. There were 36 HACs in 11 patients before GPB and 11 in 7 patients while on GPB, with a reduction from 2.98 to 0.88 episodes per year. Adverse events occurring in at least 10% of patients while on GPB were neutropenia, vomiting, diarrhea, pyrexia, hypophagia, cough, nasal congestion, rhinorrhea, rash/papule. CONCLUSION GPB was safe and effective in UCD patients aged 2months to 2years. GPB use was associated with good short- and long-term control of ammonia and glutamine levels, and the annualized frequency of hyperammonemic crises was lower during the study than before the study. There was no evidence for any previously unknown toxicity of GPB.
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Dowsett L, Lulis L, Ficicioglu C, Cuddapah S. Utility of Genetic Testing for Confirmation of Abnormal Newborn Screening in Disorders of Long-Chain Fatty Acids: A Missed Case of Carnitine Palmitoyltransferase 1A (CPT1A) Deficiency. Int J Neonatal Screen 2017; 3:10. [PMID: 28748224 PMCID: PMC5523953 DOI: 10.3390/ijns3020010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
An 18-month-old male was evaluated after presenting with disproportionately elevated liver transaminases in the setting of acute gastroenteritis. He had marked hepatomegaly on physical exam that was later confirmed with an abdominal ultrasound. Given this clinical picture, suspicion for a fatty acid oxidation disorder was raised. Further investigation revealed that his initial newborn screen was positive for carnitine palmitoyltransferase 1A (CPT1A) deficiency-a rare autosomal recessive disorder of long-chain fatty acid oxidation. Confirmatory biochemical testing in the newborn period showed carnitine levels to be unexpectedly low with a normal acylcarnitine profile. Thus, it was considered to be a false-positive newborn screen and metabolic follow-up was not recommended. Repeat biochemical testing during this hospitalization revealed a normal acylcarnitine profile. The only abnormalities noted were a low proportion of acylcarnitine species from plasma, an elevated free-to-total carnitine ratio, and mild hypoketotic medium chain dicarboxylic aciduria on urine organic acids. Gene sequencing of CPT1A revealed a novel homozygous splice site variant that confirmed his diagnosis. CPT1A deficiency has a population founder effect in the Inuit and other Arctic groups, but has not been previously reported in persons of Ashkenazi Jewish ancestry.
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Dai H, Zhang VW, El-Hattab AW, Ficicioglu C, Shinawi M, Lines M, Schulze A, McNutt M, Gotway G, Tian X, Chen S, Wang J, Craigen WJ, Wong LJ. FBXL4 defects are common in patients with congenital lactic acidemia and encephalomyopathic mitochondrial DNA depletion syndrome. Clin Genet 2017; 91:634-639. [PMID: 27743463 DOI: 10.1111/cge.12894] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 10/11/2016] [Accepted: 10/11/2016] [Indexed: 11/30/2022]
Abstract
Mutations in FBXL4 have recently been recognized to cause a mitochondrial disorder, with clinical features including early onset lactic acidosis, hypotonia, and developmental delay. FBXL4 sequence analysis was performed in 808 subjects suspected to have a mitochondrial disorder. In addition, 28 samples from patients with early onset of lactic acidosis, but without identifiable mutations in 192 genes known to cause mitochondrial diseases, were examined for FBXL4 mutations. Definitive diagnosis was made in 10 new subjects with a total of 7 novel deleterious variants; 5 null and 2 missense substitutions. All patients exhibited congenital lactic acidemia, most of them with severe encephalopathic presentation, and global developmental delay. Overall, FBXL4 defects account for at least 0.7% (6 out of 808) of subjects suspected to have a mitochondrial disorder, and as high as 14.3% (4 out of 28) in young children with congenital lactic acidosis and clinical features of mitochondrial disease. Including FBLX4 in the mitochondrial diseases panel should be particularly important for patients with congenital lactic acidosis.
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Ganetzky RD, Bedoukian E, Deardorff MA, Ficicioglu C. Argininosuccinic Acid Lyase Deficiency Missed by Newborn Screen. JIMD Rep 2016; 34:43-47. [PMID: 27515243 DOI: 10.1007/8904_2016_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Revised: 06/10/2016] [Accepted: 06/14/2016] [Indexed: 12/30/2022] Open
Abstract
Argininosuccinic acid lyase (ASL) deficiency, caused by mutations in the ASL gene (OMIM: 608310) is a urea cycle disorder that has pleiotropic presentations. On the mild end, ASL deficiency can manifest as nonspecific neurocognitive abnormalities without readily identifiable signs to differentiate it from other causes of intellectual disability or learning disabilities. Dietary management and arginine supplementation, if initiated early, may ameliorate symptoms.Because of the nonspecific nature of the symptoms and the possibility for therapeutic management, ASL deficiency is part of the recommended uniform screening panel for newborn screening in the USA. We report here a case of ASL deficiency that was missed on newborn screening in the USA.The case reported here has two known pathogenic mutations - one with no residual activity and one with reported 10% residual activity. Review of this newborn screening results showed subtle elevation of citrulline, overlapping the normal range. These findings suggest that newborn screening may be missing other patients with ASL deficiency with at least one hypomorphic allele. This case was diagnosed incidentally, but in retrospect had symptoms best attributed in full or in part to his ASA deficiency, including protein aversion, developmental delay, and seizures. This case highlights the importance of considering ASL deficiency in patients with nonspecific abnormal neurocognitive signs, such as epilepsy and developmental delay, even when newborn screening was normal.
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Peck SH, Casal ML, Malhotra NR, Ficicioglu C, Smith LJ. Pathogenesis and treatment of spine disease in the mucopolysaccharidoses. Mol Genet Metab 2016; 118:232-43. [PMID: 27296532 PMCID: PMC4970936 DOI: 10.1016/j.ymgme.2016.06.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 06/03/2016] [Accepted: 06/03/2016] [Indexed: 12/21/2022]
Abstract
The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Skeletal disease is common in MPS patients, with the severity varying both within and between subtypes. Within the spectrum of skeletal disease, spinal manifestations are particularly prevalent. Developmental and degenerative abnormalities affecting the substructures of the spine can result in compression of the spinal cord and associated neural elements. Resulting neurological complications, including pain and paralysis, significantly reduce patient quality of life and life expectancy. Systemic therapies for MPS, such as hematopoietic stem cell transplantation and enzyme replacement therapy, have shown limited efficacy for improving spinal manifestations in patients and animal models. Therefore, there is a pressing need for new therapeutic approaches that specifically target this debilitating aspect of the disease. In this review, we examine how pathological abnormalities affecting the key substructures of the spine - the discs, vertebrae, odontoid process and dura - contribute to the progression of spinal deformity and symptomatic compression of neural elements. Specifically, we review current understanding of the underlying pathophysiology of spine disease in MPS, how the tissues of the spine respond to current clinical and experimental treatments, and discuss future strategies for improving the efficacy of these treatments.
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Edmondson AC, Salant J, Ierardi-Curto LA, Ficicioglu C. Missed Newborn Screening Case of Carnitine Palmitoyltransferase-II Deficiency. JIMD Rep 2016; 33:93-97. [PMID: 27067077 PMCID: PMC5413452 DOI: 10.1007/8904_2016_528] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 12/02/2015] [Accepted: 12/04/2015] [Indexed: 01/06/2023] Open
Abstract
Carnitine palmitoyltransferase-II (CPT-II) deficiency can be detected through newborn screening with tandem mass spectrometry. We report a 4-year-old patient with rhabdomyolysis due to CPT-II deficiency, which was initially missed by newborn screening. The patient presented with a 2-day history of fevers, upper respiratory infection, diffuse myalgia, and tea-colored urine. Her medical history was notable for frequent diffuse myalgia when ill. She was demonstrated to have homozygous mutation c.338C>T, p. S113L in CPT2, which is typically found in the adult-onset, myopathic form of the disease. An unknown number of CPT-II deficient patients with normal newborn screening have not yet presented to medical care with the adult-onset, myopathic form of disease. We conclude that (1) not all cases of CPT-II deficiency are currently detected through newborn screening, even when blood is appropriately collected on day 2 of life and (2) CPT-II deficiency should be kept on the differential for patients presenting with rhabdomyolysis, even if the newborn screening results were normal.
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Ng BG, Shiryaev SA, Rymen D, Eklund EA, Raymond K, Kircher M, Abdenur JE, Alehan F, Midro AT, Bamshad MJ, Barone R, Berry GT, Brumbaugh JE, Buckingham KJ, Clarkson K, Cole FS, O'Connor S, Cooper GM, Van Coster R, Demmer LA, Diogo L, Fay AJ, Ficicioglu C, Fiumara A, Gahl WA, Ganetzky R, Goel H, Harshman LA, He M, Jaeken J, James PM, Katz D, Keldermans L, Kibaek M, Kornberg AJ, Lachlan K, Lam C, Yaplito-Lee J, Nickerson DA, Peters HL, Race V, Régal L, Rush JS, Rutledge SL, Shendure J, Souche E, Sparks SE, Trapane P, Sanchez-Valle A, Vilain E, Vøllo A, Waechter CJ, Wang RY, Wolfe LA, Wong DA, Wood T, Yang AC, Matthijs G, Freeze HH. ALG1-CDG: Clinical and Molecular Characterization of 39 Unreported Patients. Hum Mutat 2016; 37:653-60. [PMID: 26931382 DOI: 10.1002/humu.22983] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/17/2016] [Indexed: 12/16/2022]
Abstract
Congenital disorders of glycosylation (CDG) arise from pathogenic mutations in over 100 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 required for proper N-linked glycosylation. ALG1 mutations cause a rare autosomal recessive disorder termed ALG1-CDG. To date 13 mutations in 18 patients from 14 families have been described with varying degrees of clinical severity. We identified and characterized 39 previously unreported cases of ALG1-CDG from 32 families and add 26 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 27 patients tested. Our study triples the number of known patients and expands the molecular and clinical correlates of this disorder.
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Weber DR, Coughlin C, Brodsky JL, Lindstrom K, Ficicioglu C, Kaplan P, Freehauf CL, Levine MA. Low bone mineral density is a common finding in patients with homocystinuria. Mol Genet Metab 2016; 117:351-4. [PMID: 26689745 PMCID: PMC4788514 DOI: 10.1016/j.ymgme.2015.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/07/2015] [Accepted: 12/07/2015] [Indexed: 11/17/2022]
Abstract
Homocystinuria (HCU) due to deficiency of cystathionine beta-synthetase is associated with increased plasma levels of homocysteine and methionine and is characterized by developmental delay, intellectual impairment, ocular defects, thromboembolism and skeletal abnormalities. HCU has been associated with increased risk for osteoporosis in some studies, but the natural history of HCU-related bone disease is poorly understood. The objective of this study was to characterize bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA) in a multi-center, retrospective cohort of children and adults with HCU. We identified 19 subjects (9 males) aged 3.5 to 49.2 years who had DXA scans performed as a part of routine clinical care from 2002-2010. The mean lumbar spine (LS) BMD Z-score at the time of first DXA scan in this cohort was -1.2 (± SD of 1.3); 38% of participants had low BMD for age (as defined by a Z-score ≤-2). Homocysteine and methionine were positively associated with LS BMD Z-score in multiple linear regression models. Our findings suggest that low BMD is common in both children and adults with HCU and that routine assessment of bone health in this patient population is warranted. Future studies are needed to clarify the relationship between HCU and BMD.
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Ganetzky RD, Bloom K, Ahrens-Nicklas R, Edmondson A, Deardorff MA, Bennett MJ, Ficicioglu C. ECHS1 Deficiency as a Cause of Severe Neonatal Lactic Acidosis. JIMD Rep 2016; 30:33-37. [PMID: 26920905 DOI: 10.1007/8904_2016_538] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 01/11/2016] [Accepted: 01/13/2016] [Indexed: 12/02/2022] Open
Abstract
Mitochondrial short-chain enoyl-CoA hydratase deficiency (ECHS1D) is caused by mutations in ECHS1 (OMIM 602292) and is a recently identified inborn error of valine and fatty acid metabolism. This defect leads to secondary mitochondrial dysfunction. The majority of previously reported patients had the Leigh syndrome, with a median life expectancy of approximately 2 years. We report two siblings born 3 years apart with prenatal findings including facial dysmorphia, oligohydramnios, intrauterine growth restriction, and premature delivery. They had severe lactic acidosis with onset within the first hours of life, had congenital dilated cardiomyopathy, and died at 16 h of life and 2 days of life, respectively.Biochemical evaluation of these patients showed elevated butyryl-carnitine in the blood and elevated methylmalonyl/succinyl-CoA and decreased hydroxybutyryl-CoA in frozen liver of patient 2, confirming abnormal short-chain fatty acid metabolism. Elevated butyryl-carnitine has been reported only in a single previous case of ECHS1 deficiency, which also had neonatal onset. Pyruvate and lactate levels were both elevated with a normal pyruvate-lactate ratio. This supports the previous hypothesis that lactic acidosis in these patients results from secondary inhibition of the pyruvate dehydrogenase complex. The biomarker 2,3-dihydroxy-2-methylbutyric acid was detected in patient 2, but at lower levels than in previously reported cases.These cases extend our understanding of the severe end of the phenotypic spectrum of ECHS1 deficiency, clarify the range of biochemical abnormalities associated with this new disorder, and highlight the need to suspect this disease in patients presenting with comparable metabolic derangements and dysmorphic features.
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