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BACKGROUND: The U.K. 100,000 Genomes Project is in the process of investigating the role of genome sequencing in patients with undiagnosed rare diseases after usual care and the alignment of this research with health care implementation in the U.K. National Health Service. Other parts of this project focus on patients with cancer and infection.METHODS: We conducted a pilot study involving 4660 participants from 2183 families, among whom 161 disorders covering a broad spectrum of rare diseases were present. We collected data on clinical features with the use of Human Phenotype Ontology terms, undertook genome sequencing, applied automated variant prioritization on the basis of applied virtual gene panels and phenotypes, and identified novel pathogenic variants through research analysis.RESULTS: Diagnostic yields varied among family structures and were highest in family trios (both parents and a proband) and families with larger pedigrees. Diagnostic yields were much higher for disorders likely to have a monogenic cause (35%) than for disorders likely to have a complex cause (11%). Diagnostic yields for intellectual disability, hearing disorders, and vision disorders ranged from 40 to 55%. We made genetic diagnoses in 25% of the probands. A total of 14% of the diagnoses were made by means of the combination of research and automated approaches, which was critical for cases in which we found etiologic noncoding, structural, and mitochondrial genome variants and coding variants poorly covered by exome sequencing. Cohortwide burden testing across 57,000 genomes enabled the discovery of three new disease genes and 19 new associations. Of the genetic diagnoses that we made, 25% had immediate ramifications for clinical decision making for the patients or their relatives.CONCLUSIONS: Our pilot study of genome sequencing in a national health care system showed an increase in diagnostic yield across a range of rare diseases. (Funded by the National Institute for Health Research and others.).

Mitochondrial diseases are some of the most common inherited neurometabolic disorders, and major progress has been made in our understanding, diagnosis, and treatment of these conditions in the past 5 years. Development of national mitochondrial disease cohorts and international collaborations has changed our knowledge of the spectrum of clinical phenotypes and natural history of mitochondrial diseases. Advances in high-throughput sequencing technologies have altered the diagnostic algorithm for mitochondrial diseases by increasingly using a genetics-first approach, with more than 350 disease-causing genes identified to date. While the current management strategy for mitochondrial disease focuses on surveillance for multisystem involvement and effective symptomatic treatment, new endeavours are underway to find better treatments, including repurposing current drugs, use of novel small molecules, and gene therapies. Developments made in reproductive technology offer women the opportunity to prevent transmission of DNA-related mitochondrial disease to their children.

Introduction It has become increasingly important to include patient preference information in decision-making processes for drug development. As neuromuscular disorders represent multisystem, debilitating, and progressive rare diseases with few treatment options, this study aimed to explore unmet health care needs and patient treatment preferences for two neuromuscular disorders, myotonic dystrophy type 1 (DM1) and mitochondrial myopathies (MM) to inform early stages of drug development. Methods Fifteen semi-structured interviews and five focus group discussions (FGDs) were held with DM1 and MM adult patients and caregivers. Topics discussed included (1) reasons for study participation; (2) disease signs/symptoms and their impact on daily lives; (3) top desired benefits; and (4) acceptability of risks and tolerance levels for a hypothetical new treatment. Data were analyzed following a thematic ‘code’ approach. Results A total of 52 participants representing a wide range of disease severities participated. ‘Muscle strength’ and ‘energy and endurance’ were the disease-related unmet needs most often mentioned. Additionally, improved ‘balance’, ‘cognition’ and ‘gut function’ were the top desired treatment benefits, while ‘damage to the liver, kidneys or eyes’ was the most concerning risk. Factors influencing their tolerance to risks related to previously having experienced the risk and differentiation between permanent and temporary risks. A few differences were elicited between patients and caregivers. Conclusions This qualitative study provided an open forum to elicit treatment-desired benefits and acceptable risks to be established by patients themselves. These findings can inform decisions for developing new treatments and the design of clinical trials for DM1 and MM.

While >300 disease-causing variants have been identified in the mitochondrial DNA (mtDNA) polymerase γ, no mitochondrial phenotypes have been associated with POLRMT, the RNA polymerase responsible for transcription of the mitochondrial genome. Here, we characterise the clinical and molecular nature of POLRMT variants in eight individuals from seven unrelated families. Patients present with global developmental delay, hypotonia, short stature, and speech/intellectual disability in childhood; one subject displayed an indolent progressive external ophthalmoplegia phenotype. Massive parallel sequencing of all subjects identifies recessive and dominant variants in the POLRMT gene. Patient fibroblasts have a defect in mitochondrial mRNA synthesis, but no mtDNA deletions or copy number abnormalities. The in vitro characterisation of the recombinant POLRMT mutants reveals variable, but deleterious effects on mitochondrial transcription. Together, our in vivo and in vitro functional studies of POLRMT variants establish defective mitochondrial transcription as an important disease mechanism., POLRMT is key for transcription of the mitochondrial genome, yet has not been implicated in mitochondrial disease to date. Here, the authors identify mutations in POLRMT in individuals with mitochondrial disease-related phenotypes and characterise underlying defects in mitochondrial transcription.

Objectives:\ud The objective of this cross‐sectional, observational study was to investigate performance of activities of daily living in patients with myotonic dystrophy type 1 (DM1).\ud \ud Materials and Methods:\ud Adults with genetically confirmed DM1 were recruited from Newcastle University (Newcastle upon Tyne, UK) and University College London Hospitals NHS Foundation Trust (London, UK). Data on activities of daily living were recorded through the DM1‐ActivC (scale scores range between 0 and 100, where a higher/lower score indicates a higher/lower ability).\ud \ud Results:\ud Our sample comprised 192 patients with DM1 (mean age: 46 years; 51% female). Patients reported most difficulties with running, carrying and putting down heavy objects, and standing on one leg, and least difficulties with eating soup, washing upper body, and taking a shower. Irrespective of the disease duration (mean: 20 years), most patients were able to perform basic and instrumental activities of daily living (eg personal hygiene and grooming, showering, eating, cleaning and shopping), with the exception of functional mobility/transfer tasks (eg walking uphill and running). The mean DM1‐ActivC total score was estimated at 71 (95% CI: 68‐74). Estimated progenitor cytosine‐thymine‐guanine repeat length and age explained 27% of the variance in DM1‐ActivC total scores (P < .001).\ud \ud Conclusions:\ud We show that DM1 impairs performance of activities of daily living, in particular those requiring a high degree of muscle strength, stability and coordination. Yet, across the evolution of the disease, the majority of patients will still be able to independently perform most basic and instrumental activities of daily living.

Mitochondrial diseases are clinically heterogeneous disorders caused by a wide spectrum of mutations in genes encoded by either the nuclear or the mitochondrial genome. Treatments for mitochondrial diseases are currently focused on symptomatic management rather than improving the biochemical defect caused by a particular mutation. This review focuses on the latest advances in the development of treatments for mitochondrial disease, both small molecules and gene therapies, as well as methods to prevent transmission of mitochondrial disease through the germline.

Myotonic dystrophy type 1 (DM1) is the most common adult-onset muscular dystrophy, primarily characterized by muscle wasting and weakness. Many biomarkers already exist in the rapidly developing biomarker research field that aim to improve patients’ care. Limited work, however, has been performed on rare diseases, including DM1. We have previously shown that specific microRNAs (miRNAs) can be used as potential biomarkers for DM1 progression. In this report, we aimed to identify novel serum-based biomarkers for DM1 through high-throughput next-generation sequencing. A number of miRNAs were identified that are able to distinguish DM1 patients from healthy individuals. Two miRNAs were selected, and their association with the disease was validated in a larger panel of patients. Further investigation of miR-223-3p, miR-24-3p, and the four previously identified miRNAs, miR-1-3p, miR-133a-3p, miR-133b-3p, and miR-206-3p, showed elevated levels in a DM1 mouse model for all six miRNAs circulating in the serum compared to healthy controls. Importantly, the levels of miR-223-3p, but not the other five miRNAs, were found to be significantly downregulated in five skeletal muscles and heart tissues of DM1 mice compared to controls. This result provides significant evidence for its involvement in disease manifestation., Graphical abstract, Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults. In this study, two novel miRNAs were identified to be elevated in DM1 patients compared to healthy individuals and suggested as potential biomarkers. Additionally, six miRNAs were investigated in tissues and serum of a DM1 mouse model.

OBJECTIVE This observational cohort study aims to quantify disease burden over time, establish disease progression rates, and identify factors that may determine the disease course of Leigh syndrome. METHODS Seventy-two Leigh syndrome children who completed the Newcastle Paediatric Mitochondrial Disease Scale (NPMDS) at baseline at 3.7 years (interquartile range [IQR] = 2.0-7.6) and follow-up assessments at 7.5 years (IQR = 3.7-11.0) in clinics were enrolled. Eighty-two percent of this cohort had a confirmed genetic diagnosis, with pathogenic variants in the MT-ATP6 and SURF1 genes being the most common cause. The total NPMDS scores denoted mild (0-14), moderate (15-25), and severe (>25) disease burden. Detailed clinical, neuroradiological, and molecular genetic findings were also analyzed. RESULTS The median total NPMDS scores rose significantly (Z = -6.9, p

AimsTo define the prevalence of non-sustained tachyarrhythmias and bradyarrhythmias in patients with the m.3243A>G mitochondrial genotype and a previously defined, profile, associated with ‘high sudden-death risk’.Methods and resultsPatients at high risk of sudden death because of combinations of ventricular hypertrophy, mitochondrial encephalopathy, lactic acidosis and stroke-like episodes family phenotype, epilepsy or high mutation load, due to the m.3243A>G mutation, were identified from a mitochondrial cohort of 209 patients. All recruited had serial ECG and echo assessments previously according to schedule, had an ECG-loop recorder implanted and were followed for as long as the device allowed. Devices were programmed to detect non-sustained brady- or tachy-arrhythmias. This provided comprehensive rhythm surveillance and automatic downloads of all detections to a monitoring station for cardiology interpretation. Those with sinus tachycardia were treated with beta-blockers and those with ventricular hypertrophy received a beta-blocker and ACE-inhibitor combination.Nine consecutive patients, approached (37.2±3.9 years, seven males) and consented, were recruited. None died and no arrhythmias longer than 30s duration occurred during 3-year follow-up. Three patients reported palpitations but ECGs correlated with sinus rhythm. One manifest physiological, sinus pauses >3.5 s during sleep and another had one asymptomatic episode of non-sustained ventricular tachycardia.ConclusionsDespite ‘high-risk’ features for sudden death, those studied had negligible prevalence of arrhythmias over prolonged follow-up. By implication, the myocardium in this genotype is not primarily arrhythmogenic. Arrhythmias may not explain sudden death in patients without Wolff-Parkinson-White or abnormal atrioventricular conduction or, it must require a confluence of other, dynamic, proarrhythmic factors to trigger them.

ObjectiveTo determine the prevalence of neuromuscular junction (NMJ) abnormalities in patients with mitochondrial disease.MethodsEighty patients with genetically proven mitochondrial disease were recruited from a national center for mitochondrial disease in the United Kingdom. Participants underwent detailed clinical and neurophysiologic testing including single-fiber electromyography.ResultsThe overall prevalence of neuromuscular transmission defects was 25.6%. The highest prevalence was in patients with pathogenic dominant RRM2B variants (50%), but abnormalities were found in a wide range of mitochondrial genotypes. The presence of NMJ abnormalities was strongly associated with coexistent myopathy, but not with neuropathy. Furthermore, 15% of patients with NMJ abnormality had no evidence of either myopathy or neuropathy.ConclusionsNMJ transmission defects are common in mitochondrial disease. In some patients, NMJ dysfunction occurs in the absence of obvious pre- or post-synaptic pathology, suggesting that the NMJ may be specifically affected.

Autosomal dominant progressive external ophthalmoplegia (adPEO) is a late‐onset, Mendelian mitochondrial disorder characterised by paresis of the extraocular muscles, ptosis, and skeletal‐muscle restricted multiple mitochondrial DNA (mtDNA) deletions. Although dominantly inherited, pathogenic variants in POLG, TWNK and RRM2B are among the most common genetic defects of adPEO, identification of novel candidate genes and the underlying pathomechanisms remains challenging. We report the clinical, genetic and molecular investigations of a patient who presented in the seventh decade of life with PEO. Oxidative histochemistry revealed cytochrome c oxidase‐deficient fibres and occasional ragged red fibres showing subsarcolemmal mitochondrial accumulation in skeletal muscle, while molecular studies identified the presence of multiple mtDNA deletions. Negative candidate screening of known nuclear genes associated with PEO prompted diagnostic exome sequencing, leading to the prioritisation of a novel heterozygous c.547G>C variant in GMPR (NM_006877.3) encoding guanosine monophosphate reductase, a cytosolic enzyme required for maintaining the cellular balance of adenine and guanine nucleotides. We show that the novel c.547G>C variant causes aberrant splicing, decreased GMPR protein levels in patient skeletal muscle, proliferating and quiescent cells, and is associated with subtle changes in nucleotide homeostasis protein levels and evidence of disturbed mtDNA maintenance in skeletal muscle. Despite confirmation of GMPR deficiency, demonstrating marked defects of mtDNA replication or nucleotide homeostasis in patient cells proved challenging. Our study proposes that GMPR is the 19th locus for PEO and highlights the complexities of uncovering disease mechanisms in late‐onset PEO phenotypes.

The profile and trajectory of cognitive impairment in mitochondrial disease are poorly defined. This systematic review sought to evaluate the current literature on cognition in mitochondrial disease, and to determine future research directions. A systematic review was conducted, employing PubMed, Medline, Psycinfo, Embase and Web of Science, and 360‐degree citation methods. English language papers on adult patients were included. The literature search yielded 2421 articles, of which 167 met inclusion criteria. Case reports and reviews of medical reports of patients yielded broad diagnoses of dementia, cognitive impairment and cognitive decline. In contrast, systematic investigations of cognitive functioning using detailed cognitive batteries identified focal cognitive rather than global deficits. Results were variable, but included visuospatial functioning, memory, attention, processing speed and executive functions. Conclusions from studies have been hampered by small sample sizes, variation in genotype and the breadth and depth of assessments undertaken. Comprehensive cognitive research with concurrent functional neuroimaging and physical correlates of mitochondrial disease in larger samples of well‐characterized patients may discern the aetiology and progression of cognitive deficits. These data provide insights into the pattern and trajectory of cognitive impairments, which are invaluable for clinical monitoring, health planning and clinical trial readiness.

Objective:\ud \ud The objective of this cross-sectional, observational study was to investigate the disease burden of myotonic dystrophy type 1 (DM1), a disabling muscle disorder.\ud Methods:\ud \ud Adults with DM1 were recruited as part of the PhenoDM1 study from Newcastle University (Newcastle upon Tyne, UK). Disease burden data were recorded through the Individualized Neuromuscular Quality of Life (INQoL) questionnaire. Results were examined by sex and clinical variables [e.g. the six-minute walk test (6MWT), the Mini Mental State Examination, and estimated progenitor and modal allele CTG repeat length].\ud Results:\ud \ud Our sample consisted of 60 patients with DM1 (mean age: 45 years; 45% female). Muscle weakness and fatigue constituted the two most common disease manifestations, reported by 93% and 90% of patients, respectively, followed by muscle locking (73%). Most patients (> 55%) reported feeling anxious/worried, depressed, frustrated, and/or having low confidence/self-esteem, 23% and 33% indicated substantial impairment of daily and leisure activities, respectively, and 47% did not work as a consequence of the disease. Estimated progenitor CTG length corrected by age correlated surprisingly well with INQoL scores. Differences by sex were generally minor.\ud Conclusion:\ud \ud We show that DM1 is associated with a substantial disease burden resulting in impairment across many different domains of patients’ lives, emphasizing the need for a holistic approach to medical management. Our results also show that the INQoL records relevant information about patients with DM1, but that further investigation of the psychometric properties of the scale is needed for meaningful interpretation of instrument scores.

Objective The objective of this longitudinal, observational study was to investigate change over time in ability to perform activities of daily living in myotonic dystrophy type 1 (DM1). Methods Adults with genetically confirmed DM1 were recruited as part of the PhenoDM1 study in the UK. Data on activities of daily living were recorded through the DM1-ActivC at baseline and a follow-up visit after 12 (± 3) months. A subset of patients had advanced genetic testing to determine the size of the progenitor allele. Results Our sample comprised 150 patients with DM1 (mean age: 45 years; 52% female). Mean follow-up was 383 days. Mean DM1-ActivC total score at baseline was 71.24 (95% confidence interval 67.77–74.71) and at the follow-up visit 69.04 (65.54–72.54). Approximately 43% of patients had a lower score at the follow-up visit (indicating a decreased ability to perform activities of daily living), 24% a higher score (indicating an increased ability), and 33% the same score at baseline and follow-up. The mean annual change in the DM1-ActivC total score, estimated at − 2.06 (− 3.54 to − 0.59), was significantly related to patients’ baseline score, but not sex, disease duration, timed test results, or cytosine-thymine-guanine repeat length. Conclusions Change over time in ability to perform activities of daily living as recorded through the DM1-ActivC varies substantially between patients with DM1. Our data contribute to the understanding of the natural evolution of the disease, and should be helpful to inform the design of future trials based on the DM1-ActivC.

Mitochondrial diseases are a clinically diverse group of genetic disorders that often present to neurologists. Health related quality of life (HRQOL) is increasingly recognised as a fundamental patient based outcome measure in both clinical intervention and research. Generic outcome measures have been extensively validated to assess HRQOL across populations and different disease states. However, due to their inclusive construct, it is acknowledged that not all relevant aspects of a specific illness may be captured. Hence there is a need to develop disease specific HRQOL measures that centre on symptoms characteristic of a specific disease or condition and their impact. This study presents the initial conceptualisation, development and preliminary psychometric assessment (validity and reliability) of a mitochondrial disease specific HRQOL measure (Newcastle Mitochondrial Quality of life measure (NMQ)). NMQ is a valuable assessment tool and consists of 63 items within 16 unidimensional domains, each demonstrating good internal reliability (Cronbach’s α⩾0.83) and construct validity.

AIMS Mitochondrial diseases present with a spectrum of clinical features, usually with multiorgan involvement and are often characterized by a loss of smooth muscle function. Hence, we hypothesized that mitochondrial dysfunction may contribute to lower urinary tract (LUT) dysfunction. METHODS We performed a prospective cohort study at a single, quaternary, mitochondrial disease referral center, enrolling consecutive adult patients with genetically confirmed mitochondrial disease. Data regarding baseline characteristics and disease burden were gathered. LUT dysfunction was assessed using the International Consultation on Incontinence Modular Questionnaire-Lower Urinary Tract Symptoms (ICIQ-LUTS) questionnaire, bladder voiding efficiency (BVE), and bladder diaries. Patients with one or more features of LUT dysfunction were offered urodynamic testing. RESULTS A total of 109 patients were included. Twenty-six percent of patients manifested at least one feature of LUT dysfunction, which was objectively confirmed in all 14 patients who consented to urodynamic investigation. Disease burden, defined by the Newcastle Mitochondrial Disease Adult Scale (NMDAS), demonstrated a linear relationship with ICIQ-LUTS severity (P = .01), with a statistically significant relationship between NMDAS-gastrointestinal scores and LUTS scores (P

Background The World Health Organization (WHO) recommends that people of all ages take regular and adequate physical activity. If unable to meet the recommendations due to health conditions, international guidance advises being as physically active as possible. Evidence from community interventions of physical activity indicate that people living with medical conditions are sometimes excluded from participation in studies. In this review, we considered the effects of activity-promoting interventions on physical activity and well-being in studies, as well as any adverse events experienced by participants living with inherited or acquired neuromuscular diseases (NMDs). OBJECTIVES: To assess the effects of interventions designed to promote physical activity in people with NMD compared with no intervention or alternative interventions. Search methods On 30 April 2020, we searched Cochrane Neuromuscular Specialised Register, CENTRAL, Embase, MEDLINE, and ClinicalTrials.Gov. WHO ICTRP was not accessible at the time. Selection criteria We considered randomised or quasi-randomised trials, including cross-over trials, of interventions designed to promote physical activity in people with NMD compared to no intervention or alternative interventions. We specifically included studies that reported physical activity as an outcome measure. Our main focus was studies in which promoting physical activity was a stated aim but we also included studies in which physical activity was assessed as a secondary or exploratory outcome. Data collection and analysis We used standard Cochrane procedures. Main results The review included 13 studies (795 randomised participants from 12 studies; number of participants unclear in one study) of different interventions to promote physical activity. Most studies randomised a minority of invited participants. No study involved children or adolescents and nine studies reported minimal entry criteria for walking. Participants had one of nine inherited or acquired NMDs. Types of intervention included structured physical activity support, exercise support (as a specific form of physical activity), and behaviour change support that included physical activity or exercise. Only one included study clearly reported that the aim of intervention was to increase physical activity. Other studies reported or planned to analyse the effects of intervention on physical activity as a secondary or exploratory outcome measure. Six studies did not report results for physical activity outcomes, or the data were not usable. We judged 10 of the 13 included studies at high or unclear risk of bias from incomplete physical activity outcome reporting. We did not perform a meta-analysis for any comparison because of differences in interventions and in usual care. We also found considerable variation in how studies reported physical activity as an outcome measure. The studies that reported physical activity measurement did not always clearly report intention-to-treat (ITT) analysis or whether final assessments occurred during or after intervention. Based on prespecified measures, we included three comparisons in our summary of findings. A physical activity programme (weight-bearing) compared to no physical activity programme One study involved adults with diabetic peripheral neuropathy (DPN) and reported weekly duration of walking during and at the end of a one-year intervention using a StepWatch ankle accelerometer. Based on the point estimate and low-certainty evidence, intervention may have led to an important increase in physical activity per week; however, the 95% confidence interval (CI) included the possibility of no difference or an effect in either direction at three months (mean difference (MD) 34 minutes per week, 95% CI -92.19 to 160.19; 69 participants), six months (MD 68 minutes per week, 95% CI -55.35 to 191.35; 74 participants), and 12 months (MD 49 minutes per week, 95% CI -75.73 to 173.73; 70 participants). Study-reported effect estimates for foot lesions and full-thickness ulcers also included the possibility of no difference, a higher, or lower risk with intervention. A sensor-based, interactive exercise programme compared to no sensor-based, interactive exercise programme One study involved adults with DPN and reported duration of walking over 48 hours at the end of four weeks' intervention using a t-shirt embedded PAMSys sensor. It was not possible to draw conclusions about the effectiveness of the intervention from the very low-certainty evidence (MD -0.64 hours per 48 hours, 95% CI -2.42 to 1.13; 25 participants). We were also unable to draw conclusions about impact on the Physical Component Score (PCS) for quality of life (MD 0.24 points, 95% CI -5.98 to 6.46; 35 participants; very low-certainty evidence), although intervention may have made little or no difference to the Mental Component Score (MCS) for quality of life (MD 5.10 points, 95% CI -0.58 to 10.78; 35 participants; low-certainty evidence). A functional exercise programme compared to a stretching exercise programme One study involved adults with spinal and bulbar muscular atrophy and reported a daily physical activity count at the end of 12 weeks' intervention using an Actical accelerometer. It was not possible to draw conclusions about the effectiveness of either intervention (requiring compliance) due to low-certainty evidence and unconfirmed measurement units (MD -8701, 95% CI -38,293.30 to 20,891.30; 43 participants). Functional exercise may have made little or no difference to quality of life compared to stretching (PCS: MD -1.10 points, 95% CI -5.22 to 3.02; MCS: MD -1.10 points, 95% CI -6.79 to 4.59; 49 participants; low-certainty evidence). Although studies reported adverse events incompletely, we found no evidence of supported activity increasing the risk of serious adverse events. Authors' conclusions We found a lack of evidence relating to children, adolescents, and non-ambulant people of any age. Many people living with NMD did not meet randomised controlled trial eligibility criteria. There was variation in the components of supported activity intervention and usual care, such as physical therapy provision. We identified variation among studies in how physical activity was monitored, analysed, and reported. We remain uncertain of the effectiveness of promotional intervention for physical activity and its impact on quality of life and adverse events. More information is needed on the ITT population, as well as more complete reporting of outcomes. While there may be no single objective measure of physical activity, the study of qualitative and dichotomous change in self-reported overall physical activity might offer a pragmatic approach to capturing important change at an individual and population level.

Additional file 4. Review history.

Additional file 2. LostArc Reports.

Additional file 1: Results. Figure S1. Mitochondrial DNA content during the LostArc procedure. Figure S2. Internal controls for validation of the LostArc method. Figure S3. The COX-ve count is poorly explained by deletions in Complex IV genes alone. Figure S4. LostArc Report example #1: weighted mean of three HEK samples. Figure S5. LostArc Report example #2: young Gwt sample M01. Figure S6. Example fits to alternative replication/deletion models. Table S1. Sample list and deletion mapping statistics. Table S2. Patient symptoms and references associated with POLG variant samples [99–104].

Clinical guidance is often sought when prescribing drugs for patients with primary mitochondrial disease. Theoretical considerations concerning drug safety in patients with mitochondrial disease may lead to unnecessary withholding of a drug in a situation of clinical need. The aim of this study was to develop consensus on safe medication use in patients with a primary mitochondrial disease. A panel of 16 experts in mitochondrial medicine, pharmacology, and basic science from six different countries was established. A modified Delphi technique was used to allow the panellists to consider draft recommendations anonymously in two Delphi rounds with predetermined levels of agreement. This process was supported by a review of the available literature and a consensus conference that included the panellists and representatives of patient advocacy groups. A high level of consensus was reached regarding the safety of all 46 reviewed drugs, with the knowledge that the risk of adverse events is influenced both by individual patient risk factors and choice of drug or drug class. This paper details the consensus guidelines of an expert panel and provides an important update of previously established guidelines in safe medication use in patients with primary mitochondrial disease. Specific drugs, drug groups, and clinical or genetic conditions are described separately as they require special attention. It is important to emphasise that consensus‐based information is useful to provide guidance, but that decisions related to drug prescribing should always be tailored to the specific needs and risks of each individual patient. We aim to present what is current knowledge and plan to update this regularly both to include new drugs and to review those currently included. publishedVersion

Additional file 3. Arc Maps.

The development of any novel reproductive technology involving manipulation of human embryos is almost inevitably going to be controversial and evoke sincerely held, but diametrically opposing views. The plethora of scientific, ethical and legal issues that surround the clinical use of such techniques fuels this divergence of opinion. During the policy change that was required to allow the use of mitochondrial donation in the UK, many of these issues were intensely scrutinised by a variety of people and in multiple contexts. This extensive process resulted in the publication of several reports that informed the recommendations made to government. We have been intrinsically involved in the development of mitochondrial donation, from refining the basic technique for use in human embryos through to clinical service delivery, and have taken the opportunity in this article to offer our own perspective on the issues it raises.

Aims Mitochondrial disease refers to an immensely-diverse group of disorders with variable manifestations and age of onset. Childhood-onset mitochondrial disease often involves multiple systems and requires input from several paediatric sub-specialties. We aim to determine the extra-neurological problems encountered by children with genetically-confirmed mitochondrial diseases. Highlighting these features to practicing clinicians is key to providing better holistic health surveillance to these children with this debilitating multi-systemic disorder. Methods Retrospective, observational cohort study of children followed up at the NHS Highly Specialised Service for Rare Mitochondrial Disease in Newcastle, a national referral in the UK. All available medical notes and genetic results were reviewed Results After excluding those without confirmed genetic diagnoses, 52 children with pathogenic mitochondrial-DNA (mt-DNA) and 53 children with nuclear-DNA (n-DNA) mutations were studied. Among them, the m.3243A>G mt-DNA mutation was the most common (19.1%). Male:female ratio was 0.98 with median age of 11 years (range 0–18 years). Nine (8.6%) were asymptomatic and had been diagnosed through family pedigree tracing. Of those 96 clinically-affected children, the three most common extra-neurological problems were bowel dysmotility (29.2%), visual difficulties (29.2%) and fatigue (28.1%). These were followed by ptosis (20.8%), deafness (15.6%), short stature (13.5%) and chronic progressive external ophthalmoplegia (CPEO) (11.5%). Cardiac manifestations were significantly more frequent in mt-DNA defects (15.9% vs 3.8%, p=0.047). Developmental delay was significantly more prevalent in children with n-DNA mutations rather than mt-DNA mutations (44.2% vs 25%, p=0.039). Other systemic involvement includes diabetes, renal and respiratory (range 4.2%–5.2%) Leigh syndrome, the most common syndromic presentation of paediatric neurodegenerative mitochondrial disease, was reported in 27 of 96 children (28.1%) and significantly more often associated n-DNA mutations (p=0.038). In comparison, central nervous system features, such as ataxia (39.6%), myopathic weakness (37.5%) and bulbar dysfunction (34%) were more frequently reported than the extra-neurological features. Although some of these findings mirror adult studies, classic non-neurological mitochondrial disease manifestations in adults are not as common in these children. Conclusions Nearly a third of this paediatric mitochondrial disease cohort manifest extra-neurological features, namely bowel dysmotility, visual difficulties and fatigue. Cardiac manifestations featured prominently in those with mt-DNA mutations.

Our appreciation of mitochondrial disease, in the context of both genetic and phenotypic heterogeneity, has blossomed over recent years with successive epidemiological studies, accrued clinical expertise and scientific advances. Epidemiological studies have encountered numerous obstacles, most importantly the initial recognition and diagnosis of a rare and variable multisystem disorder, but also complex referral pathways, specific and evolving diagnostic techniques, impaired penetrance and heteroplasmic mtDNA mutations, and the potential for ascertainment bias in disease cohorts. These inherent difficulties have contributed to both historical over- and under-representation of specific mtDNA or nuclear DNA-related mitochondrial disease. The last three decades have seen over 250 pathogenic mtDNA mutations identified, and the evolution of whole-genome sequencing is now identifying increasing numbers of pathogenic nuclear disease genes. Only recently has it been possible to estimate the prevalence of disease due to mutations of both the nuclear and mitochondrial genomes. To date, the most detailed prevalence figures available report the number of adults suffering from all forms of mitochondrial disease to be in the region of 12.5 per 100,000 of the population. One in 4300 people (23 per 100,000) carry pathogenic mutations of either nuclear or mtDNA and either have disease or are at risk of disease in the future. The most prevalent single mutation to cause mitochondrial disease is now recognised to be due to the m.3243A>G mutation in the MT-TL1 gene with a disease estimation of 3.5 per 100,000. Childhood-onset mitochondrial disease has been predicted to range from 0.5 to 1.5 cases per 100,000, approximately one-tenth of that seen in adults. Although no true population-based prevalence studies have yet been performed using laborious whole-genome sequencing, most existing studies focus on screening for individual mutations within cohorts felt to represent either the general population or the particular disease-defined cohorts. A small number of specific mtDNA mutations have been identified as causing a proportion of disease in diabetes, deafness and optic neuropathy cohorts. Although often considered a hallmark of mitochondrial disease, the prevalence of diabetes in most forms of mitochondrial disease is no higher than 10–12% as compared with a prevalence in the general population of 4.5%. The recognised association can be mainly attributed to the prevalent m.3243A>G mutation which frequently presents with maternally inherited deafness and diabetes. Deafness is common among many mtDNA mutations, usually as part of a broader phenotype, but can be the sole manifestation in the m.1555A>G mutation, particularly following exposure to aminoglycoside antibiotics. Leber’s hereditary optic neuropathy (LHON) occurs as a result of three common mutations in 90% of affected patients, with the point prevalence of disease standing at 3.7 per 100,000.

Background: The benefit and safety of exercise training for patients with neuromuscular disorders has long been a contentious topic. This is, in part, due to recognised challenges associated with rare diseases including small and heterogenous patient populations. We performed a systematic review and meta-analyses to evaluate the effectiveness and safety of interventional exercise and establish minimal clinically important differences (MCID) in outcome measures in neuromuscular disorders to facilitate clinical interpretation. Methods: For this systematic review and meta-analyses, we searched MEDLINE, Embase, Scopus, Web of science, SportDiscus and Cochrane Library databases for articles on exercise interventions in patients with NMD, published from inception to Mar 26, 2018. Aerobic, strength, and combined (aerobic and strength) exercise intervention studies in NMD were eligible for inclusion. Meta-analyses was performed to compare outcome measures at baseline with those after at least six weeks of exercise training (i.e. before-after exercise training within individuals). A further meta-analysis was performed to compare outcome measures before-after exercise training between groups (exercise training versus usual care). Impact of disease heterogeneity was explored using a random effect model. Study quality was evaluated via The Cochrane risk of bias tool and NIH Quality Assessment Tool. This study was registered with PROSPERO, number CRD42018102183. Interactive online databases were developed to facilitate full interrogations of data. Findings: We identified 130 articles describing 1,805 participants with 35 different forms of neuromuscular disorders (NMD). Of these studies, 76 were suitable for inclusion in the tabular meta-analyses. Within group and between group meta-analyses showed peak aerobic capacity (SMD 0·56 [95% CI 0·20, 1·10]; p=0·04), and peak power (SMD 0·70 [95% CI 0·15, 1·24]; p=0·01) were able to detect objective changes in exercise capacity. Distance walked (6MWT) (SMD 0·29 [95% CI 0·01, 0·57]; p=0·04), sit-to-stand (STS) (repetitions) (SMD 0·63 [95% CI 0·06, 1·21]; p=0·03), STS (seconds) (SMD -0·67 [95% CI -1·31, 0·03]; p=0·04), rise from supine (SMD -0·50 [95% CI -0·87, -0·13]; p=0·008), SF-36 (SMD 0·70 [95% CI 0·32, 1·07]; p=0·0003), fatigue severity scale (SMD -0·65 [95% CI -1·01, -0·29]; p=

Background: Focal-onset seizures and encephalopathy are prominent features of a stroke-like episode, which is a severe neurological manifestation associated with subtypes of mitochondrial disease. Despite more than 30 years of research, the acute treatment of stroke-like episodes remains controversial. Methods: We used the modified Delphi process to harness the clinical expertise of a group of mitochondrial disease specialists from five European countries to produce consensus guidance for the acute management of stroke-like episodes and commonly associated complications. Results: Consensus on a new definition of mitochondrial stroke-like episodes was achieved and enabled the group to develop diagnostic criteria based on clinical features, neuroimaging and/or electroencephalogram findings. Guidelines for the management of strokelike episodes were agreed with aggressive seizure management strongly recommended at the outset of stroke-like episodes. Conclusions: Our consensus statement defines stroke-like episodes in terms of an epileptic encephalopathy and we have used this to revise both diagnostic criteria and guidelines for management. A prospective, multi-centre, randomised controlled trial is required for evaluating the efficacy of any compound on modifying the trajectory of stroke-like episodes.

Mitochondrial diseases are a group of rare neurometabolic disorders that are extremely complex, not least due to their clinical and genetic heterogeneity. The management of these patients remains difficult, because there are currently no interventions that provide a realistic prospect of cure. This represents a compelling unmet need. And while this is recognised as a significant challenge, there remains another significant barrier to robustly assess and measure disease status and progression for each patient and to measure potential effects of any potential intervention. The tools and instruments used to quantify clinical aspects of disease and its impact on someone’s life are referred to as outcome measures. Recent efforts have been made to identify the most appropriate outcome measures that can overcome the inherent challenges of mitochondrial disease characteristics, such as clinical heterogeneity, unpredictability of disease progression rate and the spectrum of ages that may be affected. Still, there is a need for further research in the field. The different paradigms of these outcomes may vary in their nature and purpose, but all should agree in the fact that they reflect clinically relevant aspects of the health and quality of life of those affected by the disease. Certain outcomes may be measured by clinicians or researchers, while others may be scored directly by the patients or their proxies. Other outcomes may assess walking ability, while others may assess perceived fatigue or visual acuity; yet any of these endpoints may be equally valid. Indeed, it is most likely that a concise battery of outcomes would most likely capture the most clinically relevant and patient-centric measures. When designing a clinical trial in patients with mitochondrial diseases, it is imperative that all stakeholders involved should understand the relevance of selecting a valid outcome measure that promises to measure the characteristic(s) of the disease in which the intervention is expected to reflect its benefit. This chapter endeavours to review current constructs around the assessment of outcome measures and quality of life that have been used in patients with mitochondrial disease to date and to discuss their potential benefits and limitations.

Objectives Defining clinically relevant outcome measures for myotonic dystrophy type 1 (DM1) that can be valid and feasible for different phenotypes has proven problematic. The Outcome Measures for Myotonic Dystrophy (OMMYD) group proposed a battery of functional outcomes: 6‐minute walk test, 30 seconds sit and stand test, timed 10 m walk test, timed 10 m walk/run test, and nine‐hole peg test. This, however, required a large‐scale investigation, Methods A cohort of 213 patients enrolled in the natural history study, PhenoDM1, was analyzed in cross‐sectional analysis and subsequently 98 patients were followed for longitudinal analysis. We aimed to assess: (1) feasibility and best practice; (2) intra‐session reliability; (3) validity; and (4) behavior over time, of these tests. Results OMMYD outcomes proved feasible as 96% of the participants completed at least one trial for all tests and more than half (n = 113) performed all three trials of each test. Body mass index and disease severity associate with functional capacity. There was a significant difference between the first and second trials of each test. There was a moderate to strong correlation between these functional outcomes and muscle strength, disease severity and patient‐reported outcomes. All outcomes after 1 year detected a change in functional capacity except the nine‐hole peg test. Conclusions These tests can be used as a battery of outcomes or independently based on the shown overlapping psychometric features and strong cross‐correlations. Due to the large and heterogeneous sample of this study, these results can serve as reference values for future studies.

It has become increasingly important to include patient preference information in decision-making processes for drug development. As neuromuscular disorders represent multisystem, debilitating, and progressive rare diseases with few treatment options, this study aimed to explore unmet health care needs and patient treatment preferences for two neuromuscular disorders, myotonic dystrophy type 1 (DM1) and mitochondrial myopathies (MM) to inform early stages of drug development.Fifteen semi-structured interviews and five focus group discussions (FGDs) were held with DM1 and MM adult patients and caregivers. Topics discussed included (1) reasons for study participation; (2) disease signs/symptoms and their impact on daily lives; (3) top desired benefits; and (4) acceptability of risks and tolerance levels for a hypothetical new treatment. Data were analyzed following a thematic 'code' approach.A total of 52 participants representing a wide range of disease severities participated. 'Muscle strength' and 'energy and endurance' were the disease-related unmet needs most often mentioned. Additionally, improved 'balance', 'cognition' and 'gut function' were the top desired treatment benefits, while 'damage to the liver, kidneys or eyes' was the most concerning risk. Factors influencing their tolerance to risks related to previously having experienced the risk and differentiation between permanent and temporary risks. A few differences were elicited between patients and caregivers.This qualitative study provided an open forum to elicit treatment-desired benefits and acceptable risks to be established by patients themselves. These findings can inform decisions for developing new treatments and the design of clinical trials for DM1 and MM.

ObjectiveRegular cardiac surveillance is advocated for patients with primary mitochondrial DNA disease. However, there is limited information to guide clinical practice in mitochondrial conditions caused by nuclear DNA defects. We sought to determine the frequency and spectrum of cardiac abnormalities identified in adult mitochondrial disease originated from the nuclear genome.MethodsAdult patients with a genetically confirmed mitochondrial disease were identified and followed up at the national clinical service for mitochondrial disease in Newcastle upon Tyne, UK (January 2009 to December 2018). Case notes, molecular genetics reports, laboratory data and cardiac investigations, including serial electrocardiograms and echocardiograms, were reviewed.ResultsIn this cohort-based observational study, we included 146 adult patients (92 women) (mean age 53.6±18.7 years, 95% CI 50.6 to 56.7) with a mean follow-up duration of 7.9±5.1 years (95% CI 7.0 to 8.8). Eleven different nuclear genotypes were identified: TWNK, POLG, RRM2B, OPA1, GFER, YARS2, TYMP, ETFDH, SDHA, TRIT1 and AGK. Cardiac abnormalities were detected in 14 patients (9.6%). Seven of these patients (4.8%) had early-onset cardiac manifestations: hypertrophic cardiomyopathy required cardiac transplantation (AGK; n=2/2), left ventricular (LV) hypertrophy and bifascicular heart block (GFER; n=2/3) and mild LV dysfunction (GFER; n=1/3, YARS2; n=1/2, TWNK; n=1/41). The remaining seven patients had acquired heart disease most likely related to conventional cardiovascular risk factors and presented later in life (14.6±12.8 vs 55.1±8.9 years, pConclusionsOur findings demonstrate that the risk of cardiac involvement is genotype specific, suggesting that routine cardiac screening is not indicated for most adult patients with nuclear gene-related mitochondrial disease.

Solid organ transplants are rarely performed in both adult and pediatric patients with primary mitochondrial disease. Poor outcomes have been described in case reports and small case series. It is unclear whether the underlying genetic disease has a significant impact on post-transplant morbidity and mortality. Data were obtained for 35 patients from 17 Mitochondrial Disease Centers across North America, the United Kingdom and Australia. Patient outcomes were noted after liver, kidney or heart transplantation. Excluding patients with POLG-related disease, post-transplant survival approached or met outcomes seen in non-mitochondrial disease transplant patients. The majority of mitochondrial disease patients did not have worsening of their mitochondrial disease within 90-days post-transplant. Post-transplant complications, including organ rejection, were not a common occurrence and were generally treatable. Many patients did not have a mitochondrial disease considered or diagnosed prior to transplantation. In conclusion, patients with mitochondrial disease in this cohort generally tolerated solid-organ transplantation. Such patients may not need to be excluded from transplant solely for their mitochondrial diagnosis; additional caution may be needed for patients with POLG-related disease. Transplant teams should be aware of mitochondrial disease as an etiology for organ-failure and consider appropriate consultation in patients without a known cause of their symptoms.

Importance Extrapyramidal movement disorders associated with mitochondrial disease are difficult to treat and can lead to considerable disability. Moreover, potential new treatment trials on the horizon highlight the importance of genotype-phenotype associations and deep phenotyping of the movement disorders related to mitochondrial disease. Objective To describe the phenotype, genetic etiology, and investigation of extrapyramidal movement disorders in a large and well-defined mitochondrial disease cohort. Design, Setting, and Participants An observational cohort study at a single national referral center. Among 678 patients (87% adults) followed up at the Newcastle mitochondrial disease specialized referral center between January 1, 2000, and January 31, 2015, 42 patients (12 pediatric, 30 adult) with genetic or biochemical evidence of mitochondrial disease and with 1 or more predefined extrapyramidal movement disorders (parkinsonism, dystonia, tremor, chorea, and restless legs syndrome) were included. Main Outcomes and Measures We investigated the prevalence and genetic causes of dystonia and parkinsonism as well as radiological findings in the context of movement disorders in mitochondrial disease. All patients were interviewed and examined. All available medical notes and clinical, radiological, and genetic investigations were reviewed. Results Forty-two patients (mean [SD] age, 37 [25] years; 38% female) with mitochondrial disease (12 pediatric [age range, 4-14 years], 30 adult [age range, 20-81 years]) with extrapyramidal movement disorders were identified. Dystonia manifested in 11 pediatric patients (92%), often in the context of Leigh syndrome; parkinsonism predominated in 13 adult patients (43%), among whom 5 (38%) harbored either dominant (n = 1) or recessive (n = 4) mutations in POLG . Eleven adult patients (37%) manifested with either generalized or multifocal dystonia related to mutations in mitochondrial DNA, among which the most common were the m.11778G>A mutation and mutations in MT-ATP6 (3 of 11 patients [27%] each). Bilateral basal ganglia lesions were the most common finding in brain magnetic resonance imaging, usually associated with generalized dystonia or Leigh syndrome. Conclusions and Relevance Dystonia, often associated with Leigh syndrome, was the most common extrapyramidal movement disorder among pediatric patients with mitochondrial disease. Parkinsonism was the most prevalent extrapyramidal movement disorder in adults and was commonly associated with POLG mutations; dystonia was predominantly associated with mitochondrial DNA mutations. These findings may help direct genetic screening in a busy neurology outpatient setting.

The reproductive success of men with mitochondrial disease is to date unreported. We compared the age- and era-adjusted reproductive success of 94 British male patients with mitochondrial disease to that of the UK general male population. The reproductive success of men with mitochondrial disease was 65% of that in the general population (95% confidence interval: 53%; 79%), and the effect magnitude was related to the disease severity. This contrasts with the two previous studies finding that the reproductive success of women with mitochondrial DNA disease is not impaired. We conclude that the reproductive health of men with mitochondrial disease merits increased clinical attention.

Mitochondrial methionyl-tRNA formyltransferase (MTFMT) is required for the initiation of translation and elongation of mitochondrial protein synthesisRetrospective cohort study combining new cases and previously published cases.Thirty-eight patients with pathogenic variants inPatients that harbour pathogenic variants in

Bloom syndrome, caused by biallelic mutations in BLM, is characterized by prenatal-onset growth deficiency, short stature, an erythematous photosensitive malar rash, and increased cancer predisposition. Diagnostically, a hallmark feature is the presence of increased sister chromatid exchanges (SCEs) on cytogenetic testing. Here, we describe biallelic mutations in TOP3A in ten individuals with prenatal-onset growth restriction and microcephaly. TOP3A encodes topoisomerase III alpha (TopIIIα), which binds to BLM as part of the BTRR complex, and promotes dissolution of double Holliday junctions arising during homologous recombination. We also identify a homozygous truncating variant in RMI1, which encodes another component of the BTRR complex, in two individuals with microcephalic dwarfism. The TOP3A mutations substantially reduce cellular levels of TopIIIα, and consequently subjects’ cells demonstrate elevated rates of SCE. Unresolved DNA recombination and/or replication intermediates persist into mitosis, leading to chromosome segregation defects and genome instability that most likely explain the growth restriction seen in these subjects and in Bloom syndrome. Clinical features of mitochondrial dysfunction are evident in several individuals with biallelic TOP3A mutations, consistent with the recently reported additional function of TopIIIα in mitochondrial DNA decatenation. In summary, our findings establish TOP3A mutations as an additional cause of prenatal-onset short stature with increased cytogenetic SCEs and implicate the decatenation activity of the BTRR complex in their pathogenesis.

Mitochondrial dysfunction within the pulmonary vessels has been shown to contribute to the pathology of idiopathic pulmonary arterial hypertension (IPAH). We investigated the hypothesis of whether impaired exercise capacity observed in IPAH patients is in part due to primary mitochondrial oxidative phosphorylation (OXPHOS) dysfunction in skeletal muscle. This could lead to potentially new avenues of treatment beyond targeting the pulmonary vessels. Nine clinically stable participants with IPAH underwent cardiopulmonary exercise testing, in vivo and in vitro assessment of mitochondrial function by 31 P-magnetic resonance spectroscopy ( 31 P-MRS) and laboratory muscle biopsy analysis. 31 P-MRS showed abnormal skeletal muscle bioenergetics with prolonged recovery times of phosphocreatine and abnormal muscle pH handling. Histochemistry and quadruple immunofluorescence performed on muscle biopsies showed normal function and subunit protein abundance of the complexes within the OXPHOS system. Our findings suggest that there is no primary mitochondrial OXPHOS dysfunction but raises the possibility of impaired oxygen delivery to the mitochondria affecting skeletal muscle bioenergetics during exercise.

Context Abnormal 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. Objective To determine whether patients with genetically confirmed mitochondrial disease are shorter than their peers and whether stature is related to disease severity. Design Analysis of final adult height in relation to disease severity as determined by the Newcastle Mitochondrial Disease Adult Scale (NMDAS). Setting UK Mitochondrial Disease Patient Cohort (Mito Cohort). Patients 575 patients were identified with recorded height, weight, and molecular genetic diagnosis of mitochondrial disease within the Mito Cohort. Main Outcome Measures Adult height, body mass index (BMI), and their association with genetic subgroup and disease severity. Results Adults 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). Conclusion Final height in mitochondrial disease reflects disease severity and rate of disease progression. Mitochondrial dysfunction and associated subclinical comorbidities affect growth plate physiology., Patients with mitochondrial disease are shorter than the general population, with adult height related to disease severity and rate of disease progression.