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Guerrero Cervera B, Donoso Trenado V, Fernández-Sellers C, Vila Clérigues N, Correcher Medina P, Zorio E. Cardiomyopathy associated with primary carnitine deficiency in adults: lack of complete response in patients with delayed treatment initiation. REVISTA ESPANOLA DE CARDIOLOGIA (ENGLISH ED.) 2024; 77:265-267. [PMID: 38469824 DOI: 10.1016/j.rec.2023.08.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/31/2023] [Indexed: 03/13/2024]
Affiliation(s)
- Borja Guerrero Cervera
- Departamento de Cardiología, Hospital Universitario y Politécnico La Fe, Valencia, Spain. https://twitter.com/@BorjaGueCer
| | - Víctor Donoso Trenado
- Departamento de Cardiología, Hospital Universitario y Politécnico La Fe, Valencia, Spain; Unidad de Insuficiencia Cardiaca Avanzada y Trasplante Cardiaco, Servicio de Cardiología, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - Carlos Fernández-Sellers
- Servicio de Patología Forense, Instituto de Medicina Legal y Ciencias Forenses de Valencia, Valencia, Spain
| | | | | | - Esther Zorio
- Departamento de Cardiología, Hospital Universitario y Politécnico La Fe, Valencia, Spain; Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Spain; Unidad de Cardiopatías Familiares y Muerte Súbita, Hospital Universitario y Politécnico La Fe, Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain.
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2
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Abrahamsen RK, Lund AM, Rasmussen J. Patients with primary carnitine deficiency treated with L-carnitine are alive and doing well-A 10-year follow-up in the Faroe Islands. JIMD Rep 2023; 64:453-459. [PMID: 37927485 PMCID: PMC10623095 DOI: 10.1002/jmd2.12383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 07/11/2023] [Indexed: 11/07/2023] Open
Abstract
Primary carnitine deficiency (PCD) can be lethal. Carnitine is essential for the transfer of long-chain fatty acids across the inner mitochondrial membrane for β-oxidation. The reported prevalence of PCD in the Faroe Islands of 1:300 is the highest in the world. The Faroese PCD patient cohort has been closely monitored and we now report results from a 10-year follow-up study of 139 PCD patients. Four patients have died of natural causes since diagnosis. There were no signs of cardiac complications related to PCD. 70.5% reported an effect of L-carnitine treatment. 33.7% reported current symptoms with fatigue and low stamina being the most common. 65.1% had experienced side effects during L-carnitine treatment. Most common side effects were fish odor, abdominal pain, and diarrhea. The overall mean L-carnitine dosage was 66.3 mg/kg/day. Free p-carnitine was similar between male and female patients on L-carnitine-18.6 and 18.8 μmol/L, respectively. L-carnitine supplementation seems to be a safe and effective treatment when suffering from PCD. PCD patients in the Faroe Islands are alive and doing well more than 10 years after diagnosis.
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Affiliation(s)
- Rannvá K. Abrahamsen
- Gastro Unit, Medical DivisionCopenhagen University Hospital‐Amager and HvidovreHvidovreDenmark
- Department of Internal MedicineNational HospitalTórshavnFaroe Islands
| | - Allan M. Lund
- Department of Pediatrics and Clinical Genetics, Centre for Inherited Metabolic DiseasesCopenhagen University Hospital, RigshospitaletCopenhagenDenmark
| | - Jan Rasmussen
- Department of Internal MedicineNational HospitalTórshavnFaroe Islands
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Liepinsh E, Svalbe B, Stelfa G, Grinberga S, Zvejniece L, Schiöth HB, Dambrova M. Knockout of Tmlhe in mice is not associated with autism spectrum disorder phenotypes or motor dysfunction despite low carnitine levels. Mol Autism 2023; 14:29. [PMID: 37553674 PMCID: PMC10410785 DOI: 10.1186/s13229-023-00560-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 07/12/2023] [Indexed: 08/10/2023] Open
Abstract
Deletion of exon 2 of the trimethyllysine hydroxylase epsilon (TMLHE) gene was identified in probands with autism spectrum disorder (ASD). TMLHE encodes the first enzyme in carnitine biosynthesis, N6-trimethyllysine dioxygenase (TMLD). Researchers have suggested that carnitine depletion could be important for the development of ASD and cognitive, locomotor and social dysfunctions, but previous findings have been inconclusive regarding the specific role of endogenous carnitine. We developed a mouse knockout model with constitutive TMLD enzyme inactivation that exhibited a significant decrease in the carnitine by more than 90% compared to wild-type (WT) mice. However, we did not observe any significant social, cognitive, or repetitive-behavior changes associated with ASD in the knockout mice; muscle strength and coordination were also not affected. In addition, the life expectancy of knockout mice was similar to that of WT mice. In conclusion, knockout of Tmlh in mice does not induce an ASD phenotype or motor dysfunction despite extremely low carnitine and gamma-butyrobetaine concentrations. Moreover, inactivation of TMLD does not induce a phenotype similar to previously described primary carnitine deficiency; indeed, our results showed that low levels of carnitine sustained adequate energy production, muscle function and social behavior in mice.
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Affiliation(s)
- Edgars Liepinsh
- Latvian Institute of Organic Synthesis, Riga, Latvia.
- Riga Stradins University, Riga, Latvia.
| | - Baiba Svalbe
- Latvian Institute of Organic Synthesis, Riga, Latvia
| | - Gundega Stelfa
- Latvian Institute of Organic Synthesis, Riga, Latvia
- Latvia University of Life Sciences and Technologies, Jelgava, Latvia
| | | | | | | | - Maija Dambrova
- Latvian Institute of Organic Synthesis, Riga, Latvia
- Riga Stradins University, Riga, Latvia
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Mortensen Ó, Thomsen E, Lydersen LN, Apol KD, Weihe P, Steig BÁ, Andorsdóttir G, Als TD, Gregersen NO. FarGen: Elucidating the distribution of coding variants in the isolated population of the Faroe Islands. Eur J Hum Genet 2023; 31:329-337. [PMID: 36404349 PMCID: PMC9995356 DOI: 10.1038/s41431-022-01227-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 09/30/2022] [Accepted: 10/27/2022] [Indexed: 11/22/2022] Open
Abstract
Here we present results from FarGen Phase I exomes. This dataset is based on the FarGen cohort, which consists of 1,541 individuals from the isolated population of the Faroe Islands. The purpose of this cohort is to serve as a reference catalog of coding variants, and to conduct population genetic studies to better understand the genetic contribution to various diseases in the Faroese population. The first whole-exome data set comprise 465 individuals and a total of 148,267 genetic variants were discovered. Principle Component Analysis indicates that the population is isolated and weakly structured. The distribution of variants in various functional classes was compared with populations in the gnomAD dataset; the results indicated that the proportions were consistent across the cohorts, but probably due to a small sample size, the FarGen dataset contained relatively few rare variants. We identified 19 variants that are classified as pathogenic or likely pathogenic in ClinVar; several of these variants are associated with monogenetic diseases with increased prevalence in the Faroe Islands. The results support previous studies, which indicate that the Faroe Islands is an isolated and weakly structured population. Future studies may elucidate the significance of the 19 pathogenic variants that were identified. The FarGen Phase I dataset is an important step for genetic research in the Faroese population, and the next phase of FarGen will increase the sample size and broaden the scope.
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Affiliation(s)
- Ólavur Mortensen
- The Genetic Biobank of the Faroe Islands, Tórshavn, Faroe Islands
| | - Elisabet Thomsen
- The Genetic Biobank of the Faroe Islands, Tórshavn, Faroe Islands
| | | | - Katrin D Apol
- The Genetic Biobank of the Faroe Islands, Tórshavn, Faroe Islands
| | - Pál Weihe
- Department of Occupational Medicine and Public Health, National Hospital of the Faroe Islands Tórshavn, Tórshavn, Faroe Islands
| | - Bjarni Á Steig
- Medical Department, National Hospital of the Faroe Islands, Tórshavn, Faroe Islands
| | - Guðrið Andorsdóttir
- The Genetic Biobank of the Faroe Islands, Tórshavn, Faroe Islands
- Centre of Health Science, Faculty of Health, University of the Faroe Islands, Tórshavn, Faroe Islands
| | - Thomas D Als
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus, Denmark
- Center for Genomics and Personalized Medicine, Aarhus, Denmark
| | - Noomi O Gregersen
- The Genetic Biobank of the Faroe Islands, Tórshavn, Faroe Islands.
- Centre of Health Science, Faculty of Health, University of the Faroe Islands, Tórshavn, Faroe Islands.
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Louis L, Margaux G, Claire G, Delphine L, Sandrine R, Emmanuel R, Cécile G, Samir M, Isabelle R. Infantile primary carnitine deficiency: A severe cardiac presentation unresponsive to carnitine supplementation. JIMD Rep 2023; 64:35-41. [PMID: 36636599 PMCID: PMC9830015 DOI: 10.1002/jmd2.12346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 10/11/2022] [Accepted: 10/21/2022] [Indexed: 11/11/2022] Open
Abstract
Primary carnitine deficiency (PCD) is an inherited disease of fatty acid beta-oxidation with autosomal recessive inheritance. The disease manifests as metabolic decompensation with hypoketotic hypoglycaemia associated with cardiomyopathy, hepatomegaly, rhabdomyolysis, and seizures. Various outcomes are described from asymptomatic adults to dramatic sudden infant death syndrome cases. We present a severe case of PCD decompensation in an 18-week-old female. She presented with hypotonia, moaning, diarrhea, and vomiting at the pediatric emergency. Initially suspected as intracranial hypertension, the clinical condition evolved rapidly and caused a reversible cardiac arrest with profound hypoglycemia. Despite carnitine supplementation, she succumbed from cardiac arrhythmia and multivisceral failure 4 days after admission. The genetic analyses showed a PCD with biallelic pathogenic variants of SLC22A5 gene. The case report is notable for the severity of the cardiac damage possibly favored by maternal carnitine deficiency during pregnancy. The analysis of previously published PCD cases highlights (i) the importance of having large access to emergency biochemical tests for early therapeutic care although the disease has unpredictable severity and (ii) the fact that the clinical outcome remains unpredictable if carnitine treatment is initiated late.
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Affiliation(s)
- Lebreton Louis
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
| | | | - Guibet Claire
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
| | - Lamireau Delphine
- Hôpital Pédiatrique, Pôle Pédiatrique, CHU de BordeauxBordeauxFrance
| | - Roche Sandrine
- Hôpital Pédiatrique, Pôle Pédiatrique, CHU de BordeauxBordeauxFrance
| | - Richard Emmanuel
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
- INSERM BRIC U1312Université de BordeauxBordeauxFrance
| | - Ged Cécile
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
- INSERM BRIC U1312Université de BordeauxBordeauxFrance
| | - Mesli Samir
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
| | - Redonnet‐Vernhet Isabelle
- Laboratoire de BiochimiePôle de Biologie et Pathologie, CHU de BordeauxBordeauxFrance
- lNSERM MRGM U1211Université de BordeauxBordeauxFrance
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Liammongkolkul S, Boonyawat B, Vijarnsorn C, Tim-Aroon T, Wasant P, Vatanavicharn N. Phenotypic and molecular features of Thai patients with primary carnitine deficiency. Pediatr Int 2023; 65:e15404. [PMID: 36321377 DOI: 10.1111/ped.15404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 09/13/2022] [Accepted: 09/22/2022] [Indexed: 11/07/2022]
Abstract
BACKGROUND Primary carnitine deficiency (PCD) is screened by expanded newborn screening (NBS) using tandem mass spectrometry (MS/MS) that can detect both affected neonates and mothers. This study aimed to delineate the clinical, biochemical, and molecular findings of Thai PCD patients. METHODS Expanded NBS using MS/MS was implemented in Bangkok and 146,757 neonates were screened between 2014 and 2018. PCD was screened by low free carnitine (C0) levels in dried blood spots. Plasma C0 levels and C0 clearance values were measured in neonates and their mothers with positive screening results. Clinically diagnosed cases were described. The coding regions and intron-exon boundaries of the SLC22A5 gene were sequenced in all cases with low plasma C0 levels. RESULTS There were 14 cases with confirmed PCD: two clinically diagnosed cases, and 12 cases identified through NBS including five newborns, six mothers, and one older sibling. Thus, the incidence of PCD in neonates was 1:29,351. All affected neonates and mothers were asymptomatic except one mother with dilated cardiomyopathy. SLC22A5 gene sequencing identified biallelic causative variants in all cases, comprising 10 different variants of which four were novel. c.51C > G (p.Phe17Leu) and c.760C > T (p.Arg254Ter) were the most prevalent variants in this study. Cases with significant clinical features tended to have higher C0 clearance values. CONCLUSIONS Primary carnitine deficiency is a common inherited metabolic disorder (IMD) in Thailand. Our findings broaden the spectrum of SLC22A5 variants. The future national NBS program will shed more light on PCD and other IMDs in Thailand.
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Affiliation(s)
- Somporn Liammongkolkul
- Division of Medical Genetics, Department of Pediatrics, Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Boonchai Boonyawat
- Division of Medical Genetics, Department of Pediatrics, Phramongkutklao Hospital and College of Medicine, Bangkok, Thailand
| | - Chodchanok Vijarnsorn
- Division of Cardiology, Department of Pediatrics, Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Thipwimol Tim-Aroon
- Division of Medical Genetics, Department of Pediatrics, Faculty of Medicine Ramathbodi Hospital, Mahidol University, Bangkok, Thailand
| | - Pornswan Wasant
- Division of Medical Genetics, Department of Pediatrics, Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Nithiwat Vatanavicharn
- Division of Medical Genetics, Department of Pediatrics, Siriraj Hospital, Mahidol University, Bangkok, Thailand
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Wilson C. Metabolic disease in the Pacific: Lessons for indigenous populations. J Inherit Metab Dis 2022; 45:919-925. [PMID: 35267200 DOI: 10.1002/jimd.12495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/02/2022] [Accepted: 03/08/2022] [Indexed: 11/09/2022]
Abstract
Twenty-five percent of the New Zealand population is either Māori or Pacific and are thus indigenous to the region. The New Zealand National Metabolic Service has considerable experience in diagnosing and managing metabolic diseases in this population. The frequencies and phenotypes of inborn errors of metabolism in indigenous people differ from that in Western European populations. Metabolic services need to be aware of these local variations and adapt their screening and treatment protocols accordingly. Likewise, the services themselves need to adopt culturally appropriate practices. This includes an understanding of the language, ideally employment of indigenous people and targeting of the service to meet the needs of the people. Knowledge of the metabolic diseases common within particular ethnic groups is important for the rapid delivery of appropriate management. Newborn screening protocols need to reflect the local populations. With the advent of expanded newborn screening relatively benign forms of fatty acid oxidation disorders have been commonly encountered. This high prevalence may reflect a selective evolutionary advantage as similar conditions have been found in other ethnic groups with traditionally high fat and low carbohydrate diets. HLA haplotypes of indigenous populations are less represented in international stem cell transplant databanks thereby making the option of human stem cell transplant more challenging. The recent discovery that short-chain enoyl-CoA hydratase deficiency is particularly common in New Zealand with nearly a dozen cases identified this year suggests there is still a lot to learn regarding Māori and Pacific and indeed an indigenous metabolic disease.
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Affiliation(s)
- Callum Wilson
- National Metabolic Service, Auckland City Hospital and Starship Children's Hospital, Auckland, New Zealand
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Chen Y, Lin Q, Zeng Y, Qiu X, Liu G, Zhu W. Gene spectrum and clinical traits of 10 patients with primary carnitine deficiency. Mol Genet Genomic Med 2021; 9:e1583. [PMID: 33560599 PMCID: PMC8077093 DOI: 10.1002/mgg3.1583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 10/26/2020] [Accepted: 11/17/2020] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND Rare studies focused on the tandem mass spectrometry (MS/MS) findings for the primary carnitine deficiency (PCD) in the neonates in China mainland. In this study, we aim to analyze the gene mutation spectrum of PCD in Fujian Province in China mainland. METHODS Primary carnitine deficiency (PCD) samples used in this study were selected from 95,453 cases underwent neonatal screening between May 2015 and February 2020. SLC22A5 gene sequencing was performed on the neonates and their parents with C0 level of less than 8.8 μmol/L. RESULTS Ten patients (male: 7; female: 3) were finally included in this study. Among these patients, nine were neonates, and one was maternal decline of C0 of less than 8.8 μmol/L. The maternal case showed two types of mutations of SLC22A5 including c.760C>T(p.R254*) and c.1400C>G(p.S467C). The other nine neonates showed compound mutations involving nine types in 18 sites, among which two mutations [i.e., c.37G>T(p.E13*) and c.694A>G(p.T232A)] were novel that had never been reported before. Bioinformatic analysis indicated that c.37G>T(p.E13*) was a pathogenic mutation, while the c.694A>G (p.T232A) was considered to be likely pathogenic. CONCLUSION MS/MS screening on PCD contributed to the early diagnosis and screening. In addition, SLC22A5 gene mutation analysis contributed to the PCD screening.
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Affiliation(s)
- Yao Chen
- Neonatal Screening Center, Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Qingying Lin
- Neonatal Screening Center, Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Yinglin Zeng
- Neonatal Screening Center, Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Xiaolong Qiu
- Neonatal Screening Center, Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Guanghua Liu
- Department of Pediatrics, Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
| | - Wenbin Zhu
- Neonatal Screening Center, Fujian Maternity and Child Health Hospital, Affiliated Hospital of Fujian Medical University, Fuzhou, China
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Rasmussen J, Dunø M, Lund AM, Steuerwald U, Hansen SH, Joensen HD, Køber L, Nielsen OW. Increased risk of sudden death in untreated primary carnitine deficiency. J Inherit Metab Dis 2020; 43:290-296. [PMID: 31373028 DOI: 10.1002/jimd.12158] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 07/17/2019] [Accepted: 07/29/2019] [Indexed: 12/22/2022]
Abstract
Primary carnitine deficiency (PCD) affects fatty acid oxidation and is associated with cardiomyopathy and cardiac arrhythmia, but the risk of sudden death in PCD is unknown. The Faroe Islands have a high prevalence of PCD, 1:300. This study systematically investigated a possible association between untreated PCD and sudden death in young Faroese subjects. We investigated all medico-legal cases of sudden death between 1979 and 2012 among subjects below the age of 45. Stored biomaterial was examined with molecular genetic analysis to reveal PCD. We compared the prevalence of PCD among sudden death cases with that of the background population (0.23%) to calculate the odds ratio (OR) for sudden death with PCD. Biomaterial was available and genetically analyzed from 53 of 65 sudden death cases (82%) in the Faroe Islands. Six (one male and five females) of the 53 cases were homozygous for the PCD related c.95A>G mutation-a prevalence of 11.3% (95% CI 5%-23%) and an OR of 54.3 (95% CI 21-138, P < .0001) for the association between sudden death and untreated PCD. Only 11 of the 53 sudden death cases were women-of whom five were homozygous for the c.95A>G mutation (45.5%) yielding an OR of 348.8 (95% CI 94-1287, P < .0001) for the association between sudden death and untreated PCD in females. This study showed a strong association between sudden death and untreated PCD, especially in females.
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Affiliation(s)
- Jan Rasmussen
- Department of Internal Medicine, National Hospital, Torshavn, Faroe Islands
- Department of Cardiology, Rigshospitalet University Hospital, Copenhagen, Denmark
| | - Morten Dunø
- Department of Clinical Genetics, Centre for Inherited metabolic Diseases, Copenhagen University Hospital, Copenhagen, Denmark
| | - Allan M Lund
- Department of Clinical Genetics, Centre for Inherited metabolic Diseases, Copenhagen University Hospital, Copenhagen, Denmark
| | - Ulrike Steuerwald
- Department of Occupational and Public Health, Faroese National Health System, Torshavn, Faroe Islands
| | - Steen-Holger Hansen
- Section of Forensic Pathology, Department of Forensic Medicine, University of Copenhagen, Copenhagen, Denmark
| | | | - Lars Køber
- Department of Cardiology, Rigshospitalet University Hospital, Copenhagen, Denmark
| | - Olav W Nielsen
- Department of Cardiology, Bispebjerg University Hospital, Copenhagen, Denmark
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Cardiac function and incidence of unexplained myocardial scarring in patients with primary carnitine deficiency - a cardiac magnetic resonance study. Sci Rep 2019; 9:13909. [PMID: 31558765 PMCID: PMC6763485 DOI: 10.1038/s41598-019-50458-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 09/11/2019] [Indexed: 11/15/2022] Open
Abstract
Primary carnitine deficiency (PCD) not treated with L-Carnitine can lead to sudden cardiac death. To our knowledge, it is unknown if asymptomatic patients treated with L-Carnitine suffer from myocardial scarring and thus be at greater risk of potentially serious arrhythmia. Cardiac evaluation of function and myocardial scarring is non-invasively best supported by cardiac magnetic resonance imaging (CMR) with late gadolinium enhancement (LGE). The study included 36 PCD patients, 17 carriers and 17 healthy subjects. A CMR cine stack in the short-axis plane were acquired to evaluate left ventricle (LV) systolic and diastolic function and a similar LGE stack to evaluate myocardial scarring and replacement fibrosis. LV volumes and ejection fraction were not different between PCD patients, carriers and healthy subjects. However, LV mass was higher in PCD patients with the severe homozygous mutation, c.95 A > G (p = 0.037; n = 17). Among homozygous PCD patients there were two cases of unexplained myocardial scarring and this is in contrast to no myocardial scarring in any of the other study participants (p = 0.10). LV mass was increased in PCD patients. L-carnitine supplementation is essential in order to prevent potentially lethal cardiac arrhythmia and serious adverse cardiac remodeling.
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Zhang Y, Li H, Liu J, Yan H, Liu Q, Wei X, Xi H, Jia Z, Wu L, Wang H. Molecular investigation in Chinese patients with primary carnitine deficiency. Mol Genet Genomic Med 2019; 7:e901. [PMID: 31364285 PMCID: PMC6732302 DOI: 10.1002/mgg3.901] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 07/15/2019] [Accepted: 07/17/2019] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Primary carnitine deficiency (PCD) is an autosomal recessive disorder of carnitine transportation caused by mutations in the SLC22A5 that lead to low serum carnitine levels and decreased intracellular carnitine accumulation. Characteristic clinical findings are hypoketotic hypoglycemia and skeletal and cardiac myopathy. OBJECTIVE To genetically diagnose 24 unrelated Chinese patients with PCD, including 18 infants and six adults. METHODS The entire coding region and the intron-exon boundaries of SLC22A5 were amplified by polymerase chain reaction (PCR). In silico analyses and reverse transcription-polymerase chain reaction (RT-PCR) were used to predict variants' impact on protein structure and function. RESULTS Disease-causing variants in the SLC22A5 were identified in all 24 subjects, and c.288delG, c.495C>A, c.774_775insTCG, c.824+1G>A, and c.1418G>T were novel. The novel variant c.824+1G>A caused a truncated protein p.Phe276Tyrfs*8. CONCLUSIONS We identified 13 variants in the SLC22A5 in 24 PCD patients, and five of these variants are novel mutations. c.824+1G>A was confirmed to alter mRNA splicing by reverse transcription PCR. Furthermore, our findings broaden the mutation spectrum of SLC22A5 and the understanding of the diverse and variable effects of PCD variants.
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Affiliation(s)
- Yanghui Zhang
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Haoxian Li
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Jing Liu
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Huiming Yan
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Qin Liu
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Xianda Wei
- National Research Center for Assisted Reproductive Technology and Reproductive Genetics, Jinan, Shandong, China
| | - Hui Xi
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Zhengjun Jia
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
| | - Lingqian Wu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan, China
| | - Hua Wang
- Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China.,NHC Key Laboratory of Birth Defects Research, Prevention and Treatment (Hunan Provincial Maternal and Child Health Care Hospital), Changsha, Hunan, China
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Guevara-Campos J, González-Guevara L, Guevara-González J, Cauli O. First Case Report of Primary Carnitine Deficiency Manifested as Intellectual Disability and Autism Spectrum Disorder. Brain Sci 2019; 9:brainsci9060137. [PMID: 31200524 PMCID: PMC6628273 DOI: 10.3390/brainsci9060137] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 06/12/2019] [Accepted: 06/12/2019] [Indexed: 12/26/2022] Open
Abstract
Systemic primary carnitine deficiency (PCD) is a genetic disorder caused by decreased or absent organic cation transporter type 2 (OCTN2) carnitine transporter activity, resulting in low serum carnitine levels and decreased carnitine accumulation inside cells. In early life, PCD is usually diagnosed as a metabolic decompensation, presenting as hypoketotic hypoglycemia, Reye syndrome, or sudden infant death; in childhood, PCD presents with skeletal or cardiac myopathy. However, the clinical presentation of PCD characterized by autism spectrum disorder (ASD) with intellectual disability (ID) has seldom been reported in the literature. In this report, we describe the clinical features of a seven-year-old girl diagnosed with PCD who presented atypical features of the disease, including a developmental delay involving language skills, concentration, and attention span, as well as autistic features and brain alterations apparent in magnetic resonance imaging. We aim to highlight the difficulties related to the diagnostic and therapeutic approaches used to diagnose such patients. The case reported here presented typical signs of PCD, including frequent episodes of hypoglycemia, generalized muscle weakness, decreased muscle mass, and physical growth deficits. A molecular genetic study confirmed the definitive diagnosis of the disease (c.1345T>G (p.Y449D)) in gene SLC22A5, located in exon 8. PCD can be accompanied by less common clinical signs, which may delay its diagnosis because the resulting global clinical picture can closely resemble other metabolic disorders. In this case, the patient was prescribed a carnitine-enriched diet, as well as oral carnitine at a dose of 100 mg/kg/day. PCD has a better prognosis if it is diagnosed and treated early; however, a high level of clinical suspicion is required for its timely and accurate diagnosis.
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Affiliation(s)
- José Guevara-Campos
- "Felipe Guevara Rojas" Hospital, Pediatrics Service, University of Oriente, El Tigre-Anzoátegui 6034, Venezuela.
| | - Lucía González-Guevara
- "Felipe Guevara Rojas" Hospital, Epilepsy and Encephalography Unit, El Tigre-Anzoátegui 6034, Venezuela.
| | | | - Omar Cauli
- Department of Nursing, University of Valencia, 46010 Valencia, Spain.
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Mortensen Ó, Lydersen LN, Apol KD, Andorsdóttir G, Steig BÁ, Gregersen NO. Using dried blood spot samples from a trio for linked-read whole-exome sequencing. Eur J Hum Genet 2019; 27:980-988. [PMID: 30765883 PMCID: PMC6777531 DOI: 10.1038/s41431-019-0343-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 12/21/2018] [Accepted: 01/05/2019] [Indexed: 01/22/2023] Open
Abstract
Long-term collection of dried blood spot (DBS) samples through newborn screening may have retrospective and prospective advantages, especially in combination with advanced analytical techniques. This work concerns whether linked-reads may overcome some of the limitations of short-read sequencing of DBS samples, such as performing molecular phasing. We performed whole-exome sequencing of DNA extracted from DBS and corresponding whole blood (WB) reference samples, belonging to a trio with unaffected parents and a proband affected by primary carnitine deficiency (PCD). For the DBS samples we were able to phase >21% of the genes under 100 kb, >40% of the SNPs, and the longest phase block was >72 kb. Corresponding results for the WB reference samples was >85%, >75%, and >915 kb, respectively. Concerning the PCD causing variant (rs72552725:A > G) in the SLC22A5 gene we observe full genotype concordance between DBS and WB for all three samples. Furthermore, we were able to phase all variants within the SLC22A5 gene in the proband’s WB data, which shows that linked-read sequencing may replace the trio information for haplotype detection. However, due to smaller molecular lengths in the DBS data only small phase blocks were observed in the proband’s DBS sample. Therefore, further optimisation of the DBS workflow is needed in order to explore the full potential of DBS samples as a test bed for molecular phasing.
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Affiliation(s)
- Ólavur Mortensen
- FarGen, The Genetic Biobank of the Faroe Islands, Tórshavn, Faroe Islands
| | | | | | | | - Bjarni Á Steig
- General Medical Department, National Hospital of the Faroe Islands, Tórshavn, Faroe Islands
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14
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Wilson C, Knoll D, de Hora M, Kyle C, Glamuzina E, Webster D. The decision to discontinue screening for carnitine uptake disorder in New Zealand. J Inherit Metab Dis 2019; 42:86-92. [PMID: 30740730 DOI: 10.1002/jimd.12030] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
When screening for carnitine uptake disorder (CUD), the New Zealand (NZ) newborn screening (NBS) service identified infants as screen-positive if they had initial and repeat free carnitine (C0) levels of less than 5.0 μmol/L. Since 2006, the NBS service has identified two infants with biochemical and genetic features consistent with neonatal CUD and nine mothers with features consistent with maternal CUD. A review of the literature suggests that these nine women reflect less than half the true prevalence and that CUD is relatively common. However, the NZ results (two infants) suggest a very low sensitivity and positive predictive value of NBS. While patients presenting with significant disease due to CUD are well described, the majority of adults with CUD are asymptomatic. Nonetheless, treatment with high-dose oral L-carnitine is recommended. Compliance with oral L-carnitine is likely to be poor long term. This may represent a specific risk as treatment could repress the usual compensatory mechanisms seen in CUD, such that a sudden discontinuation of treatment may be dangerous. L-carnitine is metabolized to trimethylamine-N-oxide (TMAO) and treated patients have extremely high plasma TMAO levels. TMAO is an independent risk factor for atherosclerosis and, thus, caution should be exercised regarding long-term treatment with high-dose carnitine of asymptomatic patients who may have a biochemical profile without disease. Due to these concerns, the NZ Newborn Metabolic Screening Programme (NMSP) initiated a review via a series of advisory and governance committees and decided to discontinue screening for CUD.
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Affiliation(s)
- Callum Wilson
- National Metabolic Service, Starship Children's Hospital, P.O. Box 92024, Auckland 1142, New Zealand
| | - Detlef Knoll
- Newborn Metabolic Screening Unit, Auckland City Hospital, Auckland, New Zealand
| | - Mark de Hora
- Newborn Metabolic Screening Programme, LabPlus, Auckland City Hospital, Auckland, New Zealand
| | - Campbell Kyle
- LabPlus, Auckland City Hospital, Auckland, New Zealand
| | - Emma Glamuzina
- National Metabolic Service, Starship Children's Hospital, P.O. Box 92024, Auckland 1142, New Zealand
| | - Dianne Webster
- Newborn Metabolic Screening Programme, LabPlus, Auckland City Hospital, Auckland, New Zealand
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15
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Frigeni M, Balakrishnan B, Yin X, Calderon FRO, Mao R, Pasquali M, Longo N. Functional and molecular studies in primary carnitine deficiency. Hum Mutat 2017; 38:1684-1699. [PMID: 28841266 DOI: 10.1002/humu.23315] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 08/13/2017] [Accepted: 08/17/2017] [Indexed: 12/30/2022]
Abstract
Primary carnitine deficiency is caused by a defect in the OCTN2 carnitine transporter encoded by the SLC22A5 gene. It can cause hypoketotic hypoglycemia or cardiomyopathy in children, and sudden death in children and adults. Fibroblasts from affected patients have reduced carnitine transport. We evaluated carnitine transport in fibroblasts from 358 subjects referred for possible carnitine deficiency. Carnitine transport was reduced to 20% or less of normal in fibroblasts of 140 out of 358 subjects. Sequencing of the 10 exons and flanking regions of the SLC22A5 gene in 95 out of 140 subjects identified causative variants in 84% of the alleles. The missense variants identified in our patients and others previously reported (n = 92) were expressed in CHO cells. Carnitine transport was impaired by 73 out of 92 variants expressed. Prediction algorithms (Polyphen-2, SIFT) correctly predicted the functional effects of expressed variants in about 80% of cases. These results indicate that mutations in the coding region of the SLC22A5 gene cannot be identified in about 16% of the alleles causing primary carnitine deficiency. Prediction algorithms failed to determine the functional effects of amino acid substitutions in this transmembrane protein in about 20% of cases. Therefore, functional studies in fibroblasts remain the best strategy to confirm or exclude a diagnosis of primary carnitine deficiency.
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Affiliation(s)
- Marta Frigeni
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah
| | - Bijina Balakrishnan
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah
| | - Xue Yin
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah
| | - Fernanda R O Calderon
- ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Rong Mao
- ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Marzia Pasquali
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah.,ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Nicola Longo
- Division of Medical Genetics/Pediatrics, University of Utah, Salt Lake City, Utah.,ARUP Institute for Clinical and Experimental Pathology®, ARUP Laboratories, Salt Lake City, Utah.,Department of Pathology, University of Utah, Salt Lake City, Utah
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16
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Beaudet AL. Brain carnitine deficiency causes nonsyndromic autism with an extreme male bias: A hypothesis. Bioessays 2017; 39. [PMID: 28703319 DOI: 10.1002/bies.201700012] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Could 10-20% of autism be prevented? We hypothesize that nonsyndromic or "essential" autism involves extreme male bias in infants who are genetically normal, but they develop deficiency of carnitine and perhaps other nutrients in the brain causing autism that may be amenable to early reversal and prevention. That brain carnitine deficiency might cause autism is suggested by reports of severe carnitine deficiency in autism and by evidence that TMLHE deficiency - a defect in carnitine biosynthesis - is a risk factor for autism. A gene on the X chromosome (SLC6A14) likely escapes random X-inactivation (a mixed epigenetic and genetic regulation) and could limit carnitine transport across the blood-brain barrier in boys compared to girls. A mixed, common gene variant-environment hypothesis is proposed with diet, minor illnesses, microbiome, and drugs as possible risk modifiers. The hypothesis can be tested using animal models and by a trial of carnitine supplementation in siblings of probands. Perhaps the lack of any Recommended Dietary Allowance for carnitine in infants should be reviewed. Also see the video abstract here: https://youtu.be/BuRH_jSjX5Y.
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Affiliation(s)
- Arthur L Beaudet
- Departments of Molecular and Human Genetics and Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA
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17
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Rasmussen J, Hougaard DM, Sandhu N, Fjællegaard K, Petersen PR, Steuerwald U, Lund AM. Primary Carnitine Deficiency: Is Foetal Development Affected and Can Newborn Screening Be Improved? JIMD Rep 2017; 36:35-40. [PMID: 28105570 DOI: 10.1007/8904_2016_30] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 11/15/2016] [Accepted: 11/23/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Primary carnitine deficiency (PCD) causes low levels of carnitine in patients potentially leading to metabolic and cardiac symptoms. Newborn screening for PCD is now routine in many countries by measuring carnitine levels in infants. In this study we report Apgar scores, length and weight in newborns with PCD and newborns born to mothers with PCD compared to controls. Furthermore we report how effective different screening algorithms have been to detect newborns with PCD in the Faroe Islands. RESULTS Newborns with PCD and newborns born to mothers with PCD did not differ with regard to Apgar scores, length and weight compared to controls. Newborns with PCD and newborns born to mothers with PCD had significantly lower levels of free carnitine (fC0) than controls. Screening algorithms focusing only on fC0 had a high rate of detection of newborns with PCD. Sample collection 4-9 days after birth seems to result in a higher detection rate than the current 2-3 days. CONCLUSION The clinical status at birth in infants with PCD and infants born to mothers with PCD does not differ compared to control infants. Screening algorithms for PCD should focus on fC0, and blood samples should be taken when the maternal influence on fC0 has diminished.
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Affiliation(s)
- Jan Rasmussen
- Department of Internal Medicine, National Hospital, FO-100, Torshavn, Faroe Islands.
| | - David M Hougaard
- Section of Neonatal Screening and Hormones, Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Noreen Sandhu
- Section of Neonatal Screening and Hormones, Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark
| | - Katrine Fjællegaard
- Department of Internal Medicine, National Hospital, FO-100, Torshavn, Faroe Islands
| | - Poula R Petersen
- Department of Internal Medicine, National Hospital, FO-100, Torshavn, Faroe Islands
| | - Ulrike Steuerwald
- Department of Occupational and Public Health, National Hospital System, Torshavn, Faroe Islands.,Screening-Laboratories Hannover, Hannover, Germany
| | - Allan M Lund
- Centre for Inherited Metabolic Diseases, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
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Wilson C, Knoll D, de Hora M, Kyle C, Glamuzina E, Webster D. The Risk of Fatty Acid Oxidation Disorders and Organic Acidemias in Children with Normal Newborn Screening. JIMD Rep 2016; 35:53-58. [PMID: 27928776 DOI: 10.1007/8904_2016_25] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Revised: 11/13/2016] [Accepted: 11/15/2016] [Indexed: 01/11/2023] Open
Abstract
New Zealand has undertaken expanded newborn screening since 2006. During that period there have been no reported cases of fatty acid oxidation disorders or organic acidemias that have been diagnosed clinically that the screening programme missed. However there may have been patients that presented clinically that were not diagnosed correctly or notified.In order to investigate the false-negative screening rate a case-control study was undertaken whereby the clinical coding data and relevant medical records were reviewed for 150 controls and 525 cases. The cases had normal newborn screening but with key analytes and/or ratios just below the notification level for individual disorders and thus in theory were most at risk of having metabolic disease.Two cases had medical histories suggestive of metabolic disease and thus could represent a false-negative screen. One of these had marginally elevated octanoyl carnitine levels and thus possible medium-chain acyl Co-A dehydrogenase deficiency (MCADD) while the other had elevated isovaleryl carnitine and thus may have been a case of isovaleric acidemia (IVA). However, subsequent molecular analysis revealed that the diagnosis of MCADD and IVA was unlikely.Despite relatively high cut-offs the New Zealand Newborn Metabolic Screening Programme does not appear to have missed any confirmed cases of fatty acid oxidation disorders and organic acidemias in its first 8 years of expanded newborn screening. This would suggest a similar low false-negative screening rate in centres with comparable screening protocols and would indicate that the risk of fatty acid oxidation disorders and classical organic acidemias in children who had normal newborn screening is low.
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Affiliation(s)
- Callum Wilson
- National Metabolic Service, Starship Children's Hospital, PO Box 92024, Auckland, 1142, New Zealand.
| | - Detlef Knoll
- Newborn Metabolic Screening Unit, Auckland City Hospital, Auckland, New Zealand
| | - Mark de Hora
- Newborn Metabolic Screening Programme, LabPlus, Auckland City Hospital, Auckland, New Zealand
| | - Campbell Kyle
- LabPlus, Auckland City Hospital, Auckland, New Zealand
| | - Emma Glamuzina
- National Metabolic Service, Starship Children's Hospital, PO Box 92024, Auckland, 1142, New Zealand
| | - Dianne Webster
- Newborn Metabolic Screening Programme, LabPlus, Auckland City Hospital, Auckland, New Zealand
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Roussel J, Thireau J, Farah C, Le Guennec JY, Babuty D. Reply to the Editor—Carnitine and Ventricular Repolarization: A Complex Link? Heart Rhythm 2016; 13:1760. [DOI: 10.1016/j.hrthm.2016.04.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Indexed: 10/21/2022]
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20
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To the Editor- Carnitine and ventricular repolarization: a complex link? Heart Rhythm 2016; 13:1760. [PMID: 27136696 DOI: 10.1016/j.hrthm.2016.04.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Indexed: 11/21/2022]
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Longo N, Frigeni M, Pasquali M. Carnitine transport and fatty acid oxidation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2422-35. [PMID: 26828774 DOI: 10.1016/j.bbamcr.2016.01.023] [Citation(s) in RCA: 470] [Impact Index Per Article: 58.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/27/2016] [Accepted: 01/28/2016] [Indexed: 12/14/2022]
Abstract
Carnitine is essential for the transfer of long-chain fatty acids across the inner mitochondrial membrane for subsequent β-oxidation. It can be synthesized by the body or assumed with the diet from meat and dairy products. Defects in carnitine biosynthesis do not routinely result in low plasma carnitine levels. Carnitine is accumulated by the cells and retained by kidneys using OCTN2, a high affinity organic cation transporter specific for carnitine. Defects in the OCTN2 carnitine transporter results in autosomal recessive primary carnitine deficiency characterized by decreased intracellular carnitine accumulation, increased losses of carnitine in the urine, and low serum carnitine levels. Patients can present early in life with hypoketotic hypoglycemia and hepatic encephalopathy, or later in life with skeletal and cardiac myopathy or sudden death from cardiac arrhythmia, usually triggered by fasting or catabolic state. This disease responds to oral carnitine that, in pharmacological doses, enters cells using the amino acid transporter B(0,+). Primary carnitine deficiency can be suspected from the clinical presentation or identified by low levels of free carnitine (C0) in the newborn screening. Some adult patients have been diagnosed following the birth of an unaffected child with very low carnitine levels in the newborn screening. The diagnosis is confirmed by measuring low carnitine uptake in the patients' fibroblasts or by DNA sequencing of the SLC22A5 gene encoding the OCTN2 carnitine transporter. Some mutations are specific for certain ethnic backgrounds, but the majority are private and identified only in individual families. Although the genotype usually does not correlate with metabolic or cardiac involvement in primary carnitine deficiency, patients presenting as adults tend to have at least one missense mutation retaining residual activity. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
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Affiliation(s)
- Nicola Longo
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA; Department of Pathology, University of Utah, and ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, USA.
| | - Marta Frigeni
- Division of Medical Genetics, Department of Pediatrics, University of Utah, Salt Lake City, UT, USA
| | - Marzia Pasquali
- Department of Pathology, University of Utah, and ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, USA
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Rasmussen J, Thomsen JA, Olesen JH, Lund TM, Mohr M, Clementsen J, Nielsen OW, Lund AM. Carnitine levels in skeletal muscle, blood, and urine in patients with primary carnitine deficiency during intermission of L-carnitine supplementation. JIMD Rep 2015; 20:103-11. [PMID: 25665836 DOI: 10.1007/8904_2014_398] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 12/04/2014] [Accepted: 12/10/2014] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Primary carnitine deficiency (PCD) is a disorder of fatty acid oxidation with a high prevalence in the Faroe Islands. Only patients homozygous for the c.95A>G (p.N32S) mutation have displayed severe symptoms in the Faroese patient cohort. In this study, we investigated carnitine levels in skeletal muscle, plasma, and urine as well as renal elimination kinetics before and after intermission with L-carnitine in patients homozygous for c.95A>G. METHODS Five male patients homozygous for c.95A>G were included. Regular L-carnitine supplementation was stopped and the patients were observed during five days. Blood and urine were collected throughout the study. Skeletal muscle biopsies were obtained at 0, 48, and 96 h. RESULTS Mean skeletal muscle free carnitine before discontinuation of L-carnitine was low, 158 nmol/g (SD 47.4) or 5.4% of normal. Mean free carnitine in plasma (fC0) dropped from 38.7 (SD 20.4) to 6.3 (SD 1.7) μmol/L within 96 h (p < 0.05). Mean T 1/2 following oral supplementation was approximately 9 h. Renal reabsorption of filtered carnitine following oral supplementation was 23%. The level of mean free carnitine excreted in urine correlated (R (2) = 0.78, p < 0.01) with fC0 in plasma. CONCLUSION Patients homozygous for the c.95A>G mutation demonstrated limited skeletal muscle carnitine stores despite long-term high-dosage L-carnitine supplementation. Exacerbated renal excretion resulted in a short T 1/2 in plasma carnitine following the last oral dose of L-carnitine. Thus a treatment strategy of minimum three daily separate doses of L-carnitine is recommended, while intermission with L-carnitine treatment might prove detrimental.
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Affiliation(s)
- J Rasmussen
- Department of Internal Medicine, National Hospital, Torshavn, The Faroe Islands,
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Abstract
Carnitine is essential for the transfer of long-chain fatty acids from the cytosol into mitochondria for subsequent β-oxidation. A lack of carnitine results in impaired energy production from long-chain fatty acids, especially during periods of fasting or stress. Primary carnitine deficiency (PCD) is an autosomal recessive disorder of mitochondrial β-oxidation resulting from defective carnitine transport and is one of the rare treatable etiologies of metabolic cardiomyopathies. Patients affected with the disease may present with acute metabolic decompensation during infancy or with severe cardiomyopathy in childhood. Early recognition of the disease and treatment with L-carnitine may be life-saving. In this review article, the pathophysiology, clinical presentation, diagnosis, treatment and prognosis of PCD are discussed, with a focus on cardiac involvements.
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Affiliation(s)
- Lijun Fu
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Meirong Huang
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Shubao Chen
- Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, China
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Residual OCTN2 transporter activity, carnitine levels and symptoms correlate in patients with primary carnitine deficiency. Mol Genet Metab Rep 2014; 1:241-248. [PMID: 27896095 PMCID: PMC5121291 DOI: 10.1016/j.ymgmr.2014.04.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 04/25/2014] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The prevalence of primary carnitine deficiency (PCD) in the Faroe Islands is the highest reported in the world (1:300). Serious symptoms related to PCD, e.g. sudden death, have previously only been associated to the c.95A > G/c.95A > G genotype in the Faroe Islands. We report and characterize novel mutations associated with PCD in the Faroese population and report and compare free carnitine levels and OCTN2 transport activities measured in fibroblasts from PCD patients with different genotypes. METHODS Genetic analyses were used to identify novel mutations, and carnitine uptake analyses in cultured skin fibroblasts from selected patients were used to examine residual OCTN2 transporter activities of the various genotypes. RESULTS Four different mutations, including the unpublished c.131C > T (p.A44V), the novel splice mutation c.825-52G > A and a novel risk-haplotype (RH) were identified in the Faroese population. The two most prevalent genotypes were c.95A > G/RH (1:600) and c.95A > G/c.95A > G (1:1300). Patients homozygous for the c.95A > G mutation had both the significantly (p < 0.01) lowest mean free carnitine level at 2.03 (SD 0.66) μmol/L and lowest residual OCTN2 transporter activity (4% of normal). There was a significant positive correlation between free carnitine levels and residual OCTN2 transporter activities in PCD patients (R2 = 0.430, p < 0.01). CONCLUSION There was a significant positive correlation between carnitine levels and OCTN2 transporter activities. The c.95A > G/c.95A > G genotype had the significantly lowest mean free carnitine level and residual OCTN2 transporter activity.
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