RESUMEN
Carnitine transporter defect (CTD) is a potentially life-threatening disorder causing acute metabolic decompensation, cardiac arrhythmia, and cardiac and skeletal myopathies. CTD is included in many newborn screening (NBS) programs. The screening parameter free carnitine, however, is influenced by maternal conditions due to placental transfer. This study reviewed the NBS results for CTD as part of a pilot study in Bavaria, Germany, and the long-term follow-up of the identified patients treated in our center between January 1999 and June 2018. Among 1,816,000 Bavarian NBS samples, six newborns were diagnosed with CTD (incidence of 1:302,667; positive predictive value (PPV) of 1.63% from 2008 to 2018). In the 24 newborns presented to our center for confirmatory testing, we detected four newborns and six mothers with CTD, one newborn and three mothers in whom CTD was presumed but not genetically confirmed, and one mother with glutaric aciduria type I. In 11 newborns, no indication for an inborn error of metabolism was found. The newborns and mothers with CTD had no serious cardiac adverse events or relevant muscular symptoms at diagnosis and during treatment for up to 14 years. Three mothers were lost to follow-up. Revealing a lower incidence than expected, our data confirm that NBS for CTD most likely misses newborns with CTD. It rather produces high numbers of false-positives and a low PPV picking up asymptomatic mothers with a diagnosis of uncertain clinical significance. Our data add to the growing evidence that argues against an implementation of CTD in NBS programs.
RESUMEN
BACKGROUND: Metabolic myopathies are a heterogenous group of muscle diseases typically characterized by exercise intolerance, myalgia and progressive muscle weakness. Effective treatments for some of these diseases are available, but while our understanding of the pathogenesis of metabolic myopathies related to glycogen storage, lipid metabolism and ß-oxidation is well established, evidence linking treatments with the precise causative genetic defect is lacking. OBJECTIVE: The objective of this study was to collate all published evidence on pharmacological therapies for the aforementioned metabolic myopathies and link this to the genetic mutation in a format amenable to databasing for further computational use in line with the principles of the "treatabolome" project. METHODS: A systematic literature review was conducted to retrieve all levels of evidence examining the therapeutic efficacy of pharmacological treatments on metabolic myopathies related to glycogen storage and lipid metabolism. A key inclusion criterion was the availability of the genetic variant of the treated patients in order to link treatment outcome with the genetic defect. RESULTS: Of the 1,085 articles initially identified, 268 full-text articles were assessed for eligibility, of which 87 were carried over into the final data extraction. The most studied metabolic myopathies were Pompe disease (45 articles), multiple acyl-CoA dehydrogenase deficiency related to mutations in the ETFDH gene (15 articles) and systemic primary carnitine deficiency (8 articles). The most studied therapeutic management strategies for these diseases were enzyme replacement therapy, riboflavin, and carnitine supplementation, respectively. CONCLUSIONS: This systematic review provides evidence for treatments of metabolic myopathies linked with the genetic defect in a computationally accessible format suitable for databasing in the treatabolome system, which will enable clinicians to acquire evidence on appropriate therapeutic options for their patient at the time of diagnosis.
Asunto(s)
Glucógeno/metabolismo , Metabolismo de los Lípidos , Errores Innatos del Metabolismo/tratamiento farmacológico , Enfermedad del Almacenamiento de Glucógeno Tipo II/tratamiento farmacológico , Humanos , Deficiencia Múltiple de Acil Coenzima A Deshidrogenasa/tratamiento farmacológico , Debilidad Muscular , MutaciónRESUMEN
Systemic primary carnitine deficiency (SPCD) is an autosomal recessive inborn error of fatty acid metabolism caused by a defect in the transporter responsible for moving carnitine across plasma membrane. The clinical features of SPCD vary widely based on the age of onset and organs involved. During infancy, patients might show episodes of hypoketotic hypoglycemia, hepatomegaly, elevated transaminases, and hyperammonemia. Skeletal myopathy, elevated creatine kinase, and cardiomyopathy are the main manifestations in children with SPCD, while in adults, the disorder is usually manifested as cardiomyopathy, arrhythmias, or fatigability. Here, we report a 5-year-old boy with SPCD that presented as dilated cardiomyopathy with atypical features, such as anemia, respiratory distress, and proximal muscle weakness. This report supports considering carnitine deficiency treatment in the work-up of unexplained pediatric dilated cardiomyopathy.
RESUMEN
Objective To investigate the clinical and biochemical metabolic features of 12 patients with systemic primary carnitine deficiency(CDSP) and to identify the SLC22A5 gene mutation types of the disease. Method The clinical and biochemical data were collected by retrospective analysis. DNA direct sequencing and multiplex ligation dependent probe amplification(MLPA)were applied for SLC22A5 gene analysis. Result Among 12 patients with CDSP, 3 cases had evident infection factors, 6 cases with convulsions, 5 cases manifested liver hypertrophy, 8 cases with hyperammonemia, and 9 cases showed myocardial damage. All CDSP patients were detected biallelic pathogenic mutation in SLC22A5 gene by direct sequencing. The gene types include IVS2+1G>T, c.3G>T(p.Met1Ile), c.760C>T(p.Arg254X), c.1400C>G(p.Ser467Cys), c.844dupc(p.Arg282fs), c.338G>A(p.Cys113Tyr), c.51C>G(p.Phe17Leu), c.659A>T(p.Glu220Val), and c.1365dupC(p.Thr456fs). c.659A>T(p.Glu220Val) and c.1365dupC(p.Thr456fs)are novel mutations. One female patient was maternal CDSP, her child had abnormal newborn screening. The allele frequency of c.760C>T(p.Arg254X) and c.1400C>G(p.Ser467Cys) were 37.5%(9/24)and 29.2%(7/24)respectively. The MLPA test results of all patients were negative. Conclusion The clinical manifestations are complex and various in patients with CDSP. Point and small InDel(insertions/deletions)mutation constitute the major alteration in SLC22A5 gene. c.1400C>G(p.Ser467Cys) might be another prevalence mutation type in Chinese CDSP patient.
RESUMEN
Systemic primary carnitine deficiency (CDSP) is caused by mutations in SLC22A5 gene, which encodes organic cation transporter 2(OCTN2). CDSP leads to skeletal or cardiac myopathy and hepatic encephalopathy. The present study aimed to identify SLC22A5 gene mutations and analyze the potential relationship between genotype and clinical symptoms in 20 Chinese patients with CDSP. The complete coding region of the SLC22A5 gene including intron-exon boundaries were amplified and sequenced in all patients. Eighteen different mutations were found; of which, nine were novel. The mutations clustering in exons 1 and 4 accounted for 66.7% of all mutant alleles (26/39). The c.760C>T (p. R254X) was the most frequent mutation (25.6%, 10/39), suggesting it as an ethnic founder mutation. The relationship between genotype and phenotype was investigated in patients carrying the R254X mutation. Homozygous patients with R254X were late-onset cases who presented with dilated cardiomyopathy and muscle weakness after 1 year of age. Compound heterozygous patients carrying R254X, combined with other missense mutations occurred in very specific positions, dramatically altered OCTN2 protein function. Based on the analysis of case studies, a clear relationship between free carnitine (C0) level in plasma and OCTN2 genotype was not found in the present work, however, the low plasma C0 level could not indicate disease severity or genotype. Further functional studies with a large sample size are required to understand the relationship between R254X mutation and CDSP.