The Rheumatoid Arthritis and MUScle (RAMUS) Study: Protocol for an observational single-arm study of skeletal muscle in patients with rheumatoid arthritis receiving tofacitinib.

People with rheumatoid arthritis (RA) are disproportionately affected by sarcopenia, the generalised loss of muscle strength and mass, consequently facing an increased risk of falls, functional decline and death. Currently, there are no approved pharmacological treatments for sarcopenia. RA patients who start tofacitinib (a Janus kinase inhibitor) develop small increases in serum creatinine that are not explained by renal function changes and could reflect sarcopenia improvement. The RAMUS Study is a proof of concept, single-arm observational study in which patients with RA who commence tofacitinib according to routine care will be offered participation according to eligibility criteria. Participants will undergo lower limb quantitative magnetic resonance imaging, whole-body dual energy x-ray absorptiometry, joint examination, muscle function testing and blood tests at three time points: prior to starting tofacitinib and 1 and 6 months afterwards. Muscle biopsy will be performed before and 6 months after starting tofacitinib. The primary outcome will be lower limb muscle volume changes following treatment initiation. The RAMUS Study will investigate whether muscle health improves following tofacitinib treatment for RA. Identifying a potential pharmacological treatment for sarcopenia could have important implications for individuals with RA and for older people in general. ISRCTN registry ID: 13364395.

Research priorities for mitochondrial disorders: Current landscape and patient and professional views.

Primary mitochondrial disorders encompass a wide range of clinical presentations and a spectrum of severity. They currently lack effective disease-modifying therapies and have a high mortality and morbidity rate. It is therefore essential to know that competitively funded research designed by academics meets the core needs of people with mitochondrial disorders and their clinicians. Priority setting partnerships are an established collaborative methodology that brings patients, carers and families, charity representatives and clinicians together to try to establish the most pressing and unanswered research priorities for a particular disease. We developed a web-based questionnaire, requesting all patients affected by primary mitochondrial disease, their carers and clinicians to pose their research questions. This yielded 709 questions from 147 participants. These were grouped into overarching themes including basic biology, causation, health services, clinical management, social impacts, prognosis, prevention, symptoms, treatment and psychological impact. Following the removal of "answered questions", the process resulted in a list of 42 discrete, answerable questions. This was further refined by web-based ranking by the community to 24 questions. These were debated at a face-to-face workshop attended by a diverse range of patients, carers, charity representatives and clinicians to create a definitive "Top 10 of unanswered research questions for primary mitochondrial disorders". These Top 10 questions related to understanding biological processes, including triggers of disease onset, mechanisms underlying progression and reasons for differential symptoms between individuals with identical genetic mutations; new treatments; biomarker discovery; psychological support and optimal management of stroke-like episodes and fatigue.

Forecasting stroke-like episodes and outcomes in mitochondrial disease.

In this retrospective, multicentre, observational cohort study, we sought to determine the clinical, radiological, EEG, genetics and neuropathological characteristics of mitochondrial stroke-like episodes and to identify associated risk predictors. Between January 1998 and June 2018, we identified 111 patients with genetically determined mitochondrial disease who developed stroke-like episodes. Post-mortem cases of mitochondrial disease (n = 26) were identified from Newcastle Brain Tissue Resource. The primary outcome was to interrogate the clinico-radiopathological correlates and prognostic indicators of stroke-like episode in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome (MELAS). The secondary objective was to develop a multivariable prediction model to forecast stroke-like episode risk. The most common genetic cause of stroke-like episodes was the m.3243A>G variant in MT-TL1 (n = 66), followed by recessive pathogenic POLG variants (n = 22), and 11 other rarer pathogenic mitochondrial DNA variants (n = 23). The age of first stroke-like episode was available for 105 patients [mean (SD) age: 31.8 (16.1)]; a total of 35 patients (32%) presented with their first stroke-like episode ≥40 years of age. The median interval (interquartile range) between first and second stroke-like episodes was 1.33 (2.86) years; 43% of patients developed recurrent stroke-like episodes within 12 months. Clinico-radiological, electrophysiological and neuropathological findings of stroke-like episodes were consistent with the hallmarks of medically refractory epilepsy. Patients with POLG-related stroke-like episodes demonstrated more fulminant disease trajectories than cases of m.3243A>G and other mitochondrial DNA pathogenic variants, in terms of the frequency of refractory status epilepticus, rapidity of progression and overall mortality. In multivariate analysis, baseline factors of body mass index, age-adjusted blood m.3243A>G heteroplasmy, sensorineural hearing loss and serum lactate were significantly associated with risk of stroke-like episodes in patients with the m.3243A>G variant. These factors informed the development of a prediction model to assess the risk of developing stroke-like episodes that demonstrated good overall discrimination (area under the curve = 0.87, 95% CI 0.82-0.93; c-statistic = 0.89). Significant radiological and pathological features of neurodegeneration were more evident in patients harbouring pathogenic mtDNA variants compared with POLG: brain atrophy on cranial MRI (90% versus 44%, P < 0.001) and reduced mean brain weight (SD) [1044 g (148) versus 1304 g (142), P = 0.005]. Our findings highlight the often idiosyncratic clinical, radiological and EEG characteristics of mitochondrial stroke-like episodes. Early recognition of seizures and aggressive instigation of treatment may help circumvent or slow neuronal loss and abate increasing disease burden. The risk-prediction model for the m.3243A>G variant can help inform more tailored genetic counselling and prognostication in routine clinical practice.

Lower urinary tract dysfunction in adult patients with mitochondrial disease.

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 < .001). Limitations include mutational heterogeneity across the patient cohort. CONCLUSIONS: This is the largest study exploring LUT in patients with mitochondrial disease and supports previous smaller studies suggesting LUT dysfunction is underrecognized in patients with mitochondrial disease and impacts considerably on their quality of life. We propose a clinical guideline for identifying mitochondrial disease patients at risk of LUT dysfunction.

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

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.

mtDNA heteroplasmy level and copy number indicate disease burden in m.3243A>G mitochondrial disease.

Mitochondrial disease associated with the pathogenic m.3243A>G variant is a common, clinically heterogeneous, neurogenetic disorder. Using multiple linear regression and linear mixed modelling, we evaluated which commonly assayed tissue (blood N = 231, urine N = 235, skeletal muscle N = 77) represents the m.3243A>G mutation load and mitochondrial DNA (mtDNA) copy number most strongly associated with disease burden and progression. m.3243A>G levels are correlated in blood, muscle and urine (R2 = 0.61-0.73). Blood heteroplasmy declines by ~2.3%/year; we have extended previously published methodology to adjust for age. In urine, males have higher mtDNA copy number and ~20% higher m.3243A>G mutation load; we present formulas to adjust for this. Blood is the most highly correlated mutation measure for disease burden and progression in m.3243A>G-harbouring individuals; increasing age and heteroplasmy contribute (R2 = 0.27, P < 0.001). In muscle, heteroplasmy, age and mtDNA copy number explain a higher proportion of variability in disease burden (R2 = 0.40, P < 0.001), although activity level and disease severity are likely to affect copy number. Whilst our data indicate that age-corrected blood m.3243A>G heteroplasmy is the most convenient and reliable measure for routine clinical assessment, additional factors such as mtDNA copy number may also influence disease severity.

MT-ND5 Mutation Exhibits Highly Variable Neurological Manifestations at Low Mutant Load.

Mutations in the m.13094T>C MT-ND5 gene have been previously described in three cases of Leigh Syndrome (LS). In this retrospective, international cohort study we identified 20 clinically affected individuals (13 families) and four asymptomatic carriers. Ten patients were deceased at the time of analysis (median age of death was 10years (range: 5·4months-37years, IQR=17·9years). Nine patients manifested with LS, one with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), and one with Leber hereditary optic neuropathy. The remaining nine patients presented with either overlapping syndromes or isolated neurological symptoms. Mitochondrial respiratory chain activity analysis was normal in five out of ten muscle biopsies. We confirmed maternal inheritance in six families, and demonstrated marked variability in tissue segregation, and phenotypic expression at relatively low blood mutant loads. Neuropathological studies of two patients manifesting with LS/MELAS showed prominent capillary proliferation, microvacuolation and severe neuronal cell loss in the brainstem and cerebellum, with conspicuous absence of basal ganglia involvement. These findings suggest that whole mtDNA genome sequencing should be considered in patients with suspected mitochondrial disease presenting with complex neurological manifestations, which would identify over 300 known pathogenic variants including the m.13094T>C.

The Spectrum of Mitochondrial Ultrastructural Defects in Mitochondrial Myopathy.

Mitochondrial functions are intrinsically linked to their morphology and membrane ultrastructure. Characterizing abnormal mitochondrial structural features may thus provide insight into the underlying pathogenesis of inherited and acquired mitochondrial diseases. Following a systematic literature review on ultrastructural defects in mitochondrial myopathy, we investigated skeletal muscle biopsies from seven subjects with genetically defined mtDNA mutations. Mitochondrial ultrastructure and morphology were characterized using two complimentary approaches: transmission electron microscopy (TEM) and serial block face scanning EM (SBF-SEM) with 3D reconstruction. Six ultrastructural abnormalities were identified including i) paracrystalline inclusions, ii) linearization of cristae and abnormal angular features, iii) concentric layering of cristae membranes, iv) matrix compartmentalization, v) nanotunelling, and vi) donut-shaped mitochondria. In light of recent molecular advances in mitochondrial biology, these findings reveal novel aspects of mitochondrial ultrastructure and morphology in human tissues with implications for understanding the mechanisms linking mitochondrial dysfunction to disease.

Pseudo-obstruction, stroke, and mitochondrial dysfunction: A lethal combination.

OBJECTIVES: The m.3243A>G MTTL1 mutation is the most common cause of mitochondrial disease; yet there is limited awareness of intestinal pseudo-obstruction (IPO) in this disorder. We aimed to determine the prevalence, severity, and clinical outcome of patients with m.3243A>G-related mitochondrial disease manifesting with IPO. METHODS: In this large, observational cohort study, we assessed the clinical, molecular, and radiological characteristics of patients with genetically determined m.3243A>G-related mitochondrial disease, who presented with severe symptoms suggestive of bowel obstruction in the absence of an occluding lesion. RESULTS: Between January 2009 and June 2015, 226 patients harbouring the m.3243A>G mutation were recruited to the Medical Research Council Centre Mitochondrial Disease Patient Cohort, Newcastle. Thirty patients (13%) presented acutely with IPO. Thirteen of these patients had a preceding history of stroke-like episodes, whereas 1 presented 27 years previously with their first stroke-like episode. Eight patients developed IPO concomitantly during an acute stroke-like episode. Regression analysis suggested stroke was the strongest predictor for development of IPO, in addition to cardiomyopathy, low body mass index and high urinary mutation load. Poor clinical outcome was observed in 6 patients who underwent surgical procedures. INTERPRETATION: Our findings suggest, in this common mitochondrial disease, that IPO is an under-recognized, often misdiagnosed clinical entity. Poor clinical outcome associated with stroke and acute surgical intervention highlights the importance of the neurologist having a high index of suspicion, particularly in the acute setting, to instigate timely coordination of appropriate care and management with other specialists. Ann Neurol 2016;80:686-692.

Prevalence of nuclear and mitochondrial DNA mutations related to adult mitochondrial disease.

OBJECTIVE: The prevalence of mitochondrial disease has proven difficult to establish, predominantly as a result of clinical and genetic heterogeneity. The phenotypic spectrum of mitochondrial disease has expanded significantly since the original reports that associated classic clinical syndromes with mitochondrial DNA (mtDNA) rearrangements and point mutations. The revolution in genetic technologies has allowed interrogation of the nuclear genome in a manner that has dramatically improved the diagnosis of mitochondrial disorders. We comprehensively assessed the prevalence of all forms of adult mitochondrial disease to include pathogenic mutations in both nuclear and mtDNA. METHODS: Adults with suspected mitochondrial disease in the North East of England were referred to a single neurology center from 1990 to 2014. For the midyear period of 2011, we evaluated the minimum prevalence of symptomatic nuclear DNA mutations and symptomatic and asymptomatic mtDNA mutations causing mitochondrial diseases. RESULTS: The minimum prevalence rate for mtDNA mutations was 1 in 5,000 (20 per 100,000), comparable with our previously published prevalence rates. In this population, nuclear mutations were responsible for clinically overt adult mitochondrial disease in 2.9 per 100,000 adults. INTERPRETATION: Combined, our data confirm that the total prevalence of adult mitochondrial disease, including pathogenic mutations of both the mitochondrial and nuclear genomes (≈1 in 4,300), is among the commonest adult forms of inherited neurological disorders. These figures hold important implications for the evaluation of interventions, provision of evidence-based health policies, and planning of future services.

A national perspective on prenatal testing for mitochondrial disease.

Mitochondrial diseases affect >1 in 7500 live births and may be due to mutations in either mitochondrial DNA (mtDNA) or nuclear DNA (nDNA). Genetic counselling for families with mitochondrial diseases, especially those due to mtDNA mutations, provides unique and difficult challenges particularly in relation to disease transmission and prevention. We have experienced an increasing demand for prenatal diagnostic testing from families affected by mitochondrial disease since we first offered this service in 2007. We review the diagnostic records of the 62 prenatal samples (17 mtDNA and 45 nDNA) analysed since 2007, the reasons for testing, mutation investigated and the clinical outcome. Our findings indicate that prenatal testing for mitochondrial disease is reliable and informative for the nuclear and selected mtDNA mutations we have tested. Where available, the results of mtDNA heteroplasmy analyses from other family members are helpful in interpreting the prenatal mtDNA test result. This is particularly important when the mutation is rare or the mtDNA heteroplasmy is observed at intermediate levels. At least 11 cases of mitochondrial disease were prevented following prenatal testing, 3 of which were mtDNA disease. On the basis of our results, we believe that prenatal testing for mitochondrial disease is an important option for couples where appropriate genetic analyses and pre/post-test counselling can be provided.