Diagnosis Of Mitochondrial Diseases Research Articles

Mitochondrial disorders in the Arab Middle East population: the impact of next generation sequencing on the genetic diagnosis.

Mitochondrial disorders are genetic conditions those faces great challenge in the accurate diagnoses due to extensive clinical heterogeneity associated with it. Mitochondria are the only cellular organelles containing their own genome and their functions are governed by both the nuclear and maternally inherited mitochondrial genomes, thus mitochondrial disease could follow all possible modes of inheritance adding to the complexity of diagnosis. Even though the prevalence of the mitochondrial disease has been studied in various parts of the world, the data regarding their prevalence in the Middle East population remains very limited. However, novel mitochondrial disease genes have been identified within the highly consanguineous Arab Middle East population, with the help of novel genetic technologies including the high throughput next-generation sequencing, leading to the identification of important founder mutations underlying several mitochondrial disorders. Furthermore, novel variants in mitochondrial disease genes help in expanding the spectrum of clinical phenotypes studied. The enrichment of reported phenotypes could enhance targeted gene panels leading to a rapid and precise genetic diagnosis facilitating genetic counseling. The aim of this review is to highlight the impact of next-generation sequencing on mitochondrial disease diagnosis in the Middle East population, particularly in identifying novel candidate genes and founder mutations.

Mitochondrial diseases 2018

Mitochondrial diseases are caused by dysfunction of the mitochondrial oxidative phosphorylation system and can be the result of mutations both in mitochondrial DNA and in nuclear DNA. Mitochondrial diseases collectively describe a diverse group of heritable disorders, which may present at any age and have a wide spectrum of clinical manifestations. This leads to highly variable presentations, making the diagnosis of mitochondrial diseases challenging. Recent advances in genetic testing and novel reproductive options hold great promise for improving the clinical identification and treatment of mitochondrial diseases. In this work we discuss what is new in understanding and diagnosis of mitochondrial diseases.

Bioinformatics Tools and Databases to Assess the Pathogenicity of Mitochondrial DNA Variants in the Field of Next Generation Sequencing.

The development of next generation sequencing (NGS) has greatly enhanced the diagnosis of mitochondrial disorders, with a systematic analysis of the whole mitochondrial DNA (mtDNA) sequence and better detection sensitivity. However, the exponential growth of sequencing data renders complex the interpretation of the identified variants, thereby posing new challenges for the molecular diagnosis of mitochondrial diseases. Indeed, mtDNA sequencing by NGS requires specific bioinformatics tools and the adaptation of those developed for nuclear DNA, for the detection and quantification of mtDNA variants from sequence alignment to the calling steps, in order to manage the specific features of the mitochondrial genome including heteroplasmy, i.e., coexistence of mutant and wildtype mtDNA copies. The prioritization of mtDNA variants remains difficult, relying on a limited number of specific resources: population and clinical databases, and in silico tools providing a prediction of the variant pathogenicity. An evaluation of the most prominent bioinformatics tools showed that their ability to predict the pathogenicity was highly variable indicating that special efforts should be directed at developing new bioinformatics tools dedicated to the mitochondrial genome. In addition, massive parallel sequencing raised several issues related to the interpretation of very low mtDNA mutational loads, discovery of variants of unknown significance, and mutations unrelated to patient phenotype or the co-occurrence of mtDNA variants. This review provides an overview of the current strategies and bioinformatics tools for accurate annotation, prioritization and reporting of mtDNA variations from NGS data, in order to carry out accurate genetic counseling in individuals with primary mitochondrial diseases.

Simultaneous determination of lactic acid and pyruvic acid in tissue and cell culture media by gas chromatography after in situ derivatization-ultrasound-assisted emulsification microextraction.

Lactic acid and pyruvic acid are important metabolites in the tricarboxylic acid cycle that can reflect the cytoplasmic redox state and mitochondrial respiratory chain function. The combination of these acids is considered as a screening index for mitochondrial disorders. Due to their biological effects, a derivatization method was developed to simultaneously detect pyruvic acid and lactic acid in tissue and cell culture media using gas chromatography. In this work, the combined derivatization method with methoxyamine hydrochloride and isobutyl chloroformate was first proposed. To improve the efficiency of derivatization, in situ derivatization-ultrasound-assisted emulsification microextraction (USAEME) was used in this study. After optimizing the volume of reagents and reaction times, good linearity values were obtained from 50 to 1000μmol/L and 1 to 100μmol/L for lactic acid and pyruvic acid, respectively. The limits of detection (LODs) were 0.12μmol/L for lactic acid and 0.29μmol/L for pyruvic acid. The recoveries of the two analytes were between 93.60 and 102.80%, and the precisions were less than 6.20%. This method was successfully applied to quantify pyruvic acid and lactic acid in the animal and cellular hypoxia models which provided an auxiliary means for the diagnosis of mitochondrial diseases. Graphical abstract ᅟ.

Height as a Clinical Biomarker of Disease Burden in Adult Mitochondrial Disease.

ContextAbnormal growth and short stature are observed in patients with mitochondrial disease, but it is unclear whether there is a relationship between final adult height and disease severity.ObjectiveTo determine whether patients with genetically confirmed mitochondrial disease are shorter than their peers and whether stature is related to disease severity.DesignAnalysis of final adult height in relation to disease severity as determined by the Newcastle Mitochondrial Disease Adult Scale (NMDAS).SettingUK Mitochondrial Disease Patient Cohort (Mito Cohort).Patients575 patients were identified with recorded height, weight, and molecular genetic diagnosis of mitochondrial disease within the Mito Cohort.Main Outcome MeasuresAdult height, body mass index (BMI), and their association with genetic subgroup and disease severity.ResultsAdults with mitochondrial disease were short, with a mean height of −0.49 SD (95% CI, −0.58 to −0.39; n = 575) compared with UK reference data. Patients were overweight, with a BMI SD of 0.52 (95% CI, 0.37 to 0.67; n = 472). The most common genetic subgroup (m.3243A>G mutation) had a height SD of −0.70 (95% CI, −0.85 to −0.54; n = 234) and a BMI SD of 0.12 (95% CI, −0.10 to 0.34; n = 212). NMDAS scores were negatively correlated with height SD (r = −0.25; 95% CI, −0.33 to −0.17; P < 0.001, n = 533). Rate of disease progression also correlated negatively with adult height (P < 0.001).ConclusionFinal height in mitochondrial disease reflects disease severity and rate of disease progression. Mitochondrial dysfunction and associated subclinical comorbidities affect growth plate physiology.

MITOCHONDRIAL DISEASES (Posters): P.193Unexpected genetic diagnosis of mitochondrial disease in three consanguineous Turkish families

Mitochondrial diseases are a clinically heterogeneous group of disorders caused by dysfunction of the mitochondrial respiratory chain. Some mitochondrial disorders affect a single organ, while many involve multiple systems such as skeletal muscle, brain, heart and liver, leading to diagnostic difficulties. Here we present three patients who were originally suspected to have a primary disease of skeletal muscle, leukodystrophy and brain malformation. Patients were recruited from three paediatric neurology clinics in Turkey: Izmir, Malatya and Diyarbakir. Whole exome sequencing (WES) was performed using Illumina exome capture (38 Mb target). Data analysis was carried out on the RD-Connect Genome-Phenome Analysis Platform (https://platform.rd-connect.eu/). Standard filtering criteria with MAF<1% and high/moderate VEP were used, as well as a list consisting of >5,000 medically interpretable genes. We identified a homozygous frameshift variant (p.Glu41GlyfsTer10) in NDUFA12 and a homozygous missense variant (p.Gln85His) in NDUFS3, both associated with Leigh syndrome due to mitochondrial complex I deficiency (OMIM# 256000). We also identifid a homozygous nonsense variant (p.His158ProfsTer8) in TACO1 associated with mitochondrial complex IV deficiency (OMIM# 220110), the second patient to be described worldwide so far. All the variants were highly pathogenic and were absent in the control population, suggesting they were disease-causing. Critical clinical review and metabolic analysis confirmed the mitochondrial deficiency. Next generation sequencing has the advantage of allowing an unbiased genetic diagnosis. We described three cases that had been initially diagnosed as myopathy, brain malformation and leukodystrophy, and WES resulted in the diagnoses of mitochondrial disorders. Importantly, this will allow for appropriate clinical management of these patients.

Diagnostic and Therapeutic Approaches for Mitochondrial Diseases

Mitochondrial diseases (MD) represent a heterogenous group of disorders and syndromes caused either by mutations of the mitochondrial DNA (mtDNA) or the nuclear DNA (nDNA). They belong to the most frequent neurogenetic diseases. The spectrum of clinical manifestations is very broad ranging from mild subclinical presentations to rapidly progressive debilitating conditions with reduced life expectancy. Mitochondrial dysfunction can affect any organ of the body; the clinical presentation is often most severe in tissues with high energy demands. The most common MD are Leber's Hereditary Optic Neuropathy (LHON), Chronic Progressive External Ophthalmoplegia (CPEO), Kearns-Sayre Syndrome (KSS), Mitochondrial Myopathy (MM) and Mitochondrial Encephalomyopathy, Lactic Acidosis and Strokelike episodes (MELAS). In the last couple of years, genetics have become more and more important for the diagnosis of MD. The majority of syndromes presents with a characteristic combination of clinical and laboratory findings which should guide the selection of tissues (blood cells, fibroblasts, urothelial cells or muscle) and methods for targeted genetic testing. Therapeutic approaches to MD include pharmacological stimulation of mitochondrial metabolism, supplementation, symptomatic treatment, assistive devices and physiotherapy. Moreover, strict anti-epileptic therapy and treatment or prevention of stroke-like episodes are very important to prevent complications. In contrast, some medication should be avoided for its direct or indirect depressing effect on mitochondrial function. This article provides an introduction to mitochondrial diseases, an overview of the most common syndromes and an update on established and new therapeutic approaches.

Advancing genomic approaches to the molecular diagnosis of mitochondrial disease.

Mitochondrial diseases present a diagnostic challenge due to their clinical and genetic heterogeneity. Achieving comprehensive molecular diagnosis via a conventional candidate-gene approach is likely, therefore, to be labour- and cost-intensive given the expanding number of mitochondrial disease genes. The advent of whole exome sequencing (WES) and whole genome sequencing (WGS) hold the potential of higher diagnostic yields due to the universality and unbiased nature of the methods. However, these approaches are subject to the escalating challenge of variant interpretation. Thus, integration of functional 'multi-omics' data, such as transcriptomics, is emerging as a powerful complementary tool in the diagnosis of mitochondrial disease patients for whom extensive prior analysis of DNA sequencing has failed to return a genetic diagnosis.

Small fibre neuropathy in mitochondrial diseases explored with sudoscan

ObjectivePolyneuropathy in mitochondrial diseases (MDs) is relatively common and widely investigated, but few data are instead reported about small fibres involvement. MethodsIn order to investigate the involvement of small fibres in MDs we performed extensive neurophysiological test (nerve conduction studies; sympathetic skin response; sudoscan) in 27 patients with genetic diagnosis of MD (7 m.3243A > G; 4 m.8344A > G; 9 single mtDNA deletion; 7 multiple mtDNA deletions). ResultsNCS showed a polyneuropathy in 11/27 cases (41%). The incidence was very high in POLG1 (100%), m.8344A > G (75%) and m.3243A > G (43%), while only 11% of patients with single deletion had evidence of large fibres involvement. Sympathetic skin response was abnormal only in three patients (one progressive external ophthalmoplegia with single mtDNA deletion; one patient with m.3243A > G mutation; one patient with POLG1 mutation). Sudoscan revealed the presence of an autonomic small fibres dysfunction in 9/27 cases (33%), most of them (7/9) carrying a single mtDNA deletion. Sudoscan data were also confirmed in a sub-group of patients by laser evoked potentials study. Considering only patients with single mtDNA deletion 7/9 (78%) showed abnormal results at sudoscan. ConclusionsSmall fibre neuropathy is another feature to investigate in mitochondrial diseases and seems specifically associated with the presence of single mtDNA deletion. SignificanceThe correct identification through specific neurophysiological tests of small fibres involvement in MDs represents another tile in this challenging diagnosis.

FGF-21 as a Potential Biomarker for Mitochondrial Diseases.

The diagnosis of mitochondrial diseases is still challenging due to clinical and genetical heterogeneity. The development of advanced technologies including Whole-Exome- Sequencing (WES) and Whole-Genome-Sequencing (WGS) has led to improvements in genetic diagnosis. However, a reliable biomarker in serum could enhance and ease the diagnosis and indeed reduce the need for muscle biopsy. Several studies suggest Fibroblast growth factor 21 (FGF-21) as a biomarker for diagnosis in mitochondrial disorders. It is known, that in patients with mitochondrial disorders, the expression of FGF-21 gets elevated in an effort to counteract the underlying metabolic deficiency. The growth and differentiation factor 15 (GDF-15) has been described as a potential biomarker for mitochondrial diseases, too. In the present review, a literature research, using PubMed database about the reliability of FGF-21 as a biomarker for mitochondrial disorders and its comparison with GDF-15 has been performed.

BS01. Facial twitching: Hemifacial spasms or seizures?

Not everything that twitches is a seizure, and isolated hemifacial twitching with no other symptoms can be a diagnostic challenge. We present a case of facial twitching that was initially thought to be hemifacial spasm, only to have the diagnosis changed to focal motor seizures with the aid of EEG-video monitoring. The patient is a 20-year-old man who presented with new episodes of facial twitching. He carried a diagnosis of mitochondrial disease and epilepsy. At the age of 13, he had his first generalized tonic-clonic seizure, and these have been well controlled for over 3 years. He presented with a 5-week history of left facial twitching and was admitted for long term video monitoring to characterize events. Within minutes of EEG being hooked up, patient had mild hemifacial twitching involving both the upper and lower face (corner of the eye and the corner of the lips) on the left side, which spontaneously resolved within 45 s. He continued to have multiple episodes, without any loss of awareness. On EEG, there were no abnormal changes, and there were also no interictal discharges. Initially, this was most suggestive of hemifacial spasms. Overnight, the twitching occurred in sleep (mainly N2 sleep) and became more pronounced, frequent, clearly clonic in nature, and spread to involve the right side of his face. He continued to maintain awareness and was able to talk and follow commands during the events. The EEG still did not reveal epileptiform discharges, ictally or interictally, but showed muscle artifact that evolved in an epileptic pattern. The pattern was rhythmic, with gradual increase in frequency followed by slowing prior to ending abruptly. All these features supported the diagnosis of seizures. This is an example of a complex case of hemifacial twitching that with initial presentation appeared to be hemifacial spasm. It is important to note there were no epileptiform discharges or interictal pattern to suggest a diagnosis of seizures throughout the entire recording, and this is often the case with small, partial, motor seizures. As it is often, video was key as it allowed observation of the evolution, both electrographically (EMG) and clinically, which led to diagnosis of seizures.

Lipidomic profiling of plasma samples from patients with mitochondrial disease

Mitochondrial disease (MD) is a rare mitochondrial respiratory chain disorder with a high mortality and extremely challenging to treat. Although genomic, transcriptomic, and proteomic analyses have been performed to investigate the pathogenesis of MD, the role of metabolomics in MD, particularly of lipidomics remains unclear. This study was undertaken to identify potential lipid biomarkers of MD. An untargeted lipidomic approach was used to compare the plasma lipid metabolites in 20 MD patients and 20 controls through Liquid Chromatography coupled to Mass Spectrometry. Volcano plot analysis was performed to identify the different metabolites. Receiver operating characteristic (ROC) curves were constructed and the area under the ROC curves (AUC) was calculated to determine the potentially sensitive and specific biomarkers. A total of 41 lipids were significantly different in MD patients and controls. ROC curve analysis showed the top 5 AUC values of lipids (phosphatidylinositols 38:6, lysoPC 20:0, 19:0, 18:0, 17:0) are more than 0.99. Multivariate ROC curve based exploratory analysis showed the AUC of combination of top 5 lipids is 1, indicating they may be potentially sensitive and specific biomarkers for MD. We propose combination of these lipid species may be more valuable in predicting the development and progression of MD, and this will have important implications for the diagnosis and treatment of MD.

Targeted next generation sequencing with an extended gene panel does not impact variant detection in mitochondrial diseases

BackgroundSince the advent of next generation sequencing (NGS), several studies have tried to evaluate the relevance of targeted gene panel sequencing and whole exome sequencing for molecular diagnosis of mitochondrial diseases. The comparison between these different strategies is extremely difficult. A recent study analysed a cohort of patients affected by a mitochondrial disease using a NGS approach based on a targeted gene panel including 132 genes. This strategy led to identify the causative mutations in 15.2% of cases. The number of novel genes responsible for respiratory chain deficiency increases very rapidly.MethodsIn order to determine the impact of larger panels used as a first screening strategy on molecular diagnosis success, we analysed a cohort of 80 patients affected by a mitochondrial disease with a first mitochondrial DNA (mtDNA) NGS screening and secondarily a targeted mitochondrial panel of 281 nuclear genes.ResultsPathogenic mtDNA abnormalities were identified in 4.1% (1/24) of children and 25% (14/56) of adult patients. The remaining 65 patients were analysed with our targeted mitochondrial panel and this approach enabled us to achieve an identification rate of 21.7% (5/23) in children versus 7.1% (3/42) in adults.ConclusionsOur results confirm that larger gene panels do not improve diagnostic yield of mitochondrial diseases due to (i) their very high genetic heterogeneity, (ii) the ongoing discovery of novel genes and (iii) mutations in genes apparently not related to mitochondrial function that lead to secondary respiratory chain deficiency.

Diagnostic odyssey of patients with mitochondrial disease: Results of a survey.

ObjectiveTo document the complex “diagnostic odyssey” of patients with mitochondrial disease.MethodsWe analyzed data from 210 Rare Diseases Clinical Research Network Contact Registry participants who were patients with a biochemical deficiency or self-reported diagnosis of mitochondrial disease, or their caregivers.ResultsParticipants saw an average of 8.19 clinicians (SD 8.0, median 5). The first clinician consulted about symptoms was typically a primary care physician (56.7%), although 35.2% of participants initially sought a specialist. Of note, 55.2% of participants received their diagnosis from a neurologist, 18.2% from a clinical geneticist, and 11.8% from a metabolic disease specialist. A majority of the participants (54.6%) received 1 or more nonmitochondrial diagnoses before their final mitochondrial diagnosis. In their pursuit of a diagnosis, 84.8% of participants received blood tests, 71% a muscle biopsy, 60.5% MRI, and 38.6% urine organic acids. In addition, 39.5% of the participants underwent mitochondrial DNA sequencing, 19% sequencing of nuclear gene(s), and 11.4% whole-exome sequencing.ConclusionsThe diagnostic odyssey of patients with mitochondrial disease is complex and burdensome. It features multiple consultations and tests, and, often, conflicting diagnoses. These reflect disease variety, diagnostic uncertainty, and clinician unfamiliarity. The current survey provides an important benchmark. Its replication at appropriate intervals will assist in tracking changes that may accompany increased popularity of exome testing, more rigorous diagnostic criteria, increased patient reported outcome activity, and trials for promising therapies.

Diagnostic des maladies mitochondriales

Mitochondrial diseases, defined as disorders due to a defect in the phosphorylative oxidation chain (OXPHOS), are the most common inherited diseases of metabolism. These diseases have of very large clinical presentation and difficult diagnosis. They are essentially genetic, due to the alteration of very diverse genes located either on the mitochondrial DNA (mtDNA), or on the nuclear genome. Recent technological advances (NGS) with exome sequencing (WES) have allowed the discovery of many new genes and a better understanding of the pathophysiological mechanisms of these diseases. The diagnostic approach is based on the clinical presentation, biochemical explorations, imaging, histopathology and genetics. The genetic investigations concern the entire mtDNA, followed, if negative, by analysis of large panels of nuclear genes. Only the detection of the causal gene allows to affirm the diagnosis of mitochondrial disease ; in the absence of treatment for these diseases, it allows for genetic counseling and the possibility for parents to give birth to unaffected children.

A Case of Mitochondrial Disease First Diagnosed Over 30 Years After Onset

Mitochondrial disease is induced by mutations in both mitochondrial DNA and DNA of nuclear genes that encode mitochondrial proteins, and there is a general lack of genotype-phenotype correlation in many mitochondrial disorders, which makes the diagnosis of mitochondrial disease difficult. We treated a 37-year-old woman with congenital cataract, bilateral sensory deafness, severe bilateral ptosis, oculomotor disorder in all directions and systemic muscular atrophy and weakness. These clinical characteristics made us perform further examinations, and we found ischemic change in brain and remarkable atrophy of extraocular muscles by magnetic resonance imaging (MRI), optic atrophy by fundus examination and high levels of serum lactate and lactate/pyruvate ratio, which confirmed the diagnosis of mitochondrial disease. Finally, she was diagnosed with having mitochondrial disease for over 30 years after onset. J Endocrinol Metab. 2018;8(6):149-152 doi: https://doi.org/10.14740/jem542

A Case of Mitochondrial Disease First Diagnosed Over 30 Years After Onset

Mitochondrial disease is induced by mutations in both mitochondrial DNA and DNA of nuclear genes that encode mitochondrial proteins, and there is a general lack of genotype-phenotype correlation in many mitochondrial disorders, which makes the diagnosis of mitochondrial disease difficult. We treated a 37-year-old woman with congenital cataract, bilateral sensory deafness, severe bilateral ptosis, oculomotor disorder in all directions and systemic muscular atrophy and weakness. These clinical characteristics made us perform further examinations, and we found ischemic change in brain and remarkable atrophy of extraocular muscles by magnetic resonance imaging (MRI), optic atrophy by fundus examination and high levels of serum lactate and lactate/pyruvate ratio, which confirmed the diagnosis of mitochondrial disease. Finally, she was diagnosed with having mitochondrial disease for over 30 years after onset. J Endocrinol Metab. 2018;8(6):149-152 doi: https://doi.org/10.14740/jem542

Variation of Mitochondrial DNA HV1 AND HV2 of the Vietnamese Population.

The sequence polymorphism of mitochondrial DNA (mtDNA) hypervariable segment 1 (HV1) and hypervariable segment 2 (HV2) is studied and applied to genetic diversity and human evolution assessment, forensic genetics, consanguinity determination, and mitochondrial disease diagnosis. The study identified the variations of HV1 and HV2 of 517 unrelated Vietnamese individuals in Kinh, Muong, Cham, and Khmer ethnic. We performed sequencing of two hypervariable segments of mitochondrial DNA: HV1 and HV2. Fifty haplogroups were identified in which F1a haplogroup frequency was highest at 15.7%, followed by B5a (10.8%), M (8.9%), and M7b1 (7.7%). The most frequently encountered SNPs in this study were A263G (100%), A73G (99.6%), 315insC (96%), 309insC (56%), C16223T (41%), and T16189C (39%). The genetic diversity was calculated at 99.83%, and the probability of random match of two individuals sharing the same mtDNA haplotype was 0.37%. We have assessed the genetic polymorphism of mtDNA HV1 and HV2 of 517 Kinh, Muong, Cham, and Khmer ethnic samples. The result will help in better understanding of Vietnamese's mitochondrial genome diversity and aid in population as well as forensic science.

Chapter 10 - Mitochondrial diseases

Mitochondrial diseases collectively describe a diverse group of heritable disorders that invariably affect mitochondrial respiratory chain function and cellular energy production. Together they represent the most common cause of inherited metabolic disease, may present at any age, have a wide spectrum of clinical manifestations, may be insidious in onset, and potentially have high morbidity and mortality. Due to the presence of mitochondria in all nucleated cells, mitochondrial disease can affect many different tissues, with single or multiple systems being involved. This leads to highly variable presentations, making the diagnosis of mitochondrial diseases challenging. Recent advances in biomarker and genetic testing, coupled with emerging treatments and reproductive options, hold great promise for improving the clinical identification and management of this highly mutable disease group.

Revisiting mitochondrial diagnostic criteria in the new era of genomics.

PurposeDiagnosing primary mitochondrial diseases (MDs) is challenging in clinical practice. The mitochondrial disease criteria (MDC) have been developed to quantify the clinical picture and evaluate the probability of an underlying MD and the need for a muscle biopsy. In this new genetic era with next-generation sequencing in routine practice, we aim to validate the diagnostic value of MDC.MethodsWe retrospectively studied MDC in a multicenter cohort of genetically confirmed primary MD patients.ResultsWe studied 136 patients (61 male, 91 nuclear DNA (nDNA) mutations). Forty-five patients (33%) had probable MD and 69 (51%) had definite MD according to the MDC. A muscle biopsy was performed in 63 patients (47%). Patients with nDNA mutations versus mitochondrial DNA mutations were younger (6.4 ± 9.7 versus 19.5 ± 17.3 y) and had higher MDC (7.07 ± 1.12/8 versus 5.69 ± 1.94/8). At a cutoff of 6.5/8, the sensitivity to diagnose patients with nDNA mutations is 72.5% with a positive predictive value of 69.5%. In the nDNA mutation group, whole-exome sequencing could diagnose patients with lower scores (MDC (6.84 ± 1.51/8) compared to Sanger sequencing MDC (7.44 ± 1.13/8, P = 0.025)). Moreover 7/8 patients diagnosed with possible MD by MDC were diagnosed by whole-exome sequencing.ConclusionMDC remain very useful in the clinical diagnosis of MD, in interpreting whole-exome results and deciding on the need for performing muscle biopsy.