Longitudinal observational study investigating outcome measures for clinical trials in inclusion body myositis.

OBJECTIVE: To describe decline in muscle strength and physical function in patients with sporadic inclusion body myositis (IBM). METHODS: Manual muscle testing (MMT), quantitative muscle testing (QMT) and disability scoring using the IBM Functional Rating Scale (IBMFRS) were undertaken for 181 patients for up to 7.3 years. The relationship between MMT, QMT and IBMFRS composite scores and time from onset were examined using linear mixed effects models adjusted for gender and age of disease onset. Adaptive LASSO regression analysis was used to identify muscle groups that best predicted the time elapsed from onset. Cox proportional hazards regression was used to evaluate time to use of a mobility aid. RESULTS: Multilevel modelling of change in percentage MMT, QMT and IBMFRS score over time yielded an average decline of 3.7% (95% CI 3.1% to 4.3%), 3.8% (95% CI 2.7% to 4.9%) and 6.3% (95% CI 5.5% to 7.2%) per year, respectively. The decline, however, was not linear, with steeper decline in the initial years. Older age of onset was associated with a more rapid IBMFRS decline (p=0.007), but did not influence the rate of MMT/QMT decline. Combination of selected muscle groups allowed for generation of single measures of patient progress (MMT and QMT factors). Median (IQR) time to using a mobility aid was 5.4 (3.6-9.2) years, significantly affected by greater age of onset (HR 1.06, 95% CI 1.04 to 1.09, p<0.001). CONCLUSION: This prospective observational study represents the largest IBM cohort to date. Measures of patient progress evaluated in this study accurately predict disease progression in a reliable and useful way to be used in trial design.

Mobility shift of beta-dystroglycan as a marker of GMPPB gene-related muscular dystrophy.

BACKGROUND: Defects in glycosylation of alpha-dystroglycan (α-DG) cause autosomal-recessive disorders with wide clinical and genetic heterogeneity, with phenotypes ranging from congenital muscular dystrophies to milder limb girdle muscular dystrophies. Patients show variable reduction of immunoreactivity to antibodies specific for glycoepitopes of α-DG on a muscle biopsy. Recessive mutations in 18 genes, including guanosine diphosphate mannose pyrophosphorylase B (GMPPB), have been reported to date. With no specific clinical and pathological handles, diagnosis requires parallel or sequential analysis of all known genes. METHODS: We describe clinical, genetic and biochemical findings of 21 patients with GMPPB-associated dystroglycanopathy. RESULTS: We report eight novel mutations and further expand current knowledge on clinical and muscle MRI features of this condition. In addition, we report a consistent shift in the mobility of beta-dystroglycan (ß-DG) on Western blot analysis of all patients analysed by this mean. This was only observed in patients with GMPPB in our large dystroglycanopathy cohort. We further demonstrate that this mobility shift in patients with GMPPB was due to abnormal N-linked glycosylation of ß-DG. CONCLUSIONS: Our data demonstrate that a change in ß-DG electrophoretic mobility in patients with dystroglycanopathy is a distinctive marker of the molecular defect in GMPPB.

Chronic pain has a strong impact on quality of life in facioscapulohumeral muscular dystrophy.

INTRODUCTION: Earlier small case series and clinical observations reported on chronic pain playing an important role in facioscapulohumeral dystrophy (FSHD). The aim of this study was to determine the characteristics and impact of pain on quality of life (QoL) in patients with FSHD. METHODS: We analyzed patient reported outcome measures collected through the U.K. FSHD Patient Registry. RESULTS: Of 398 patients, 88.6% reported pain at the time of study. The most frequent locations were shoulders and lower back. A total of 203 participants reported chronic pain, 30.4% of them as severe. The overall disease impact on QoL was significantly higher in patients with early onset and long disease duration. Chronic pain had a negative impact on all Individualised Neuromuscular Quality of Life Questionnaire domains and overall disease score. DISCUSSION: Our study shows that pain in FSHD type 1 (FSHD1) is frequent and strongly impacts on QoL, similar to other chronic, painful disorders. Management of pain should be considered when treating FSHD1 patients. Muscle Nerve 57: 380-387, 2018.

Clinical features of the myasthenic syndrome arising from mutations in GMPPB.

BACKGROUND: Congenital myasthenic syndrome (CMS) due to mutations in GMPPB has recently been reported confirming the importance of glycosylation for the integrity of neuromuscular transmission. METHODS: Review of case notes of patients with mutations in GMPPB to identify the associated clinical, neurophysiological, pathological and laboratory features. In addition, serum creatine kinase (CK) levels within the Oxford CMS cohort were retrospectively analysed to assess its usefulness in the differential diagnosis of this new entity. RESULTS: All patients had prominent limb-girdle weakness with minimal or absent craniobulbar manifestations. Presentation was delayed beyond infancy with proximal muscle weakness and most patients recall poor performance in sports during childhood. Neurophysiology showed abnormal neuromuscular transmission only in the affected muscles and myopathic changes. Muscle biopsy showed dystrophic features and reduced α-dystroglycan glycosylation. In addition, myopathic changes were present on muscle MRI. CK was significantly increased in serum compared to other CMS subtypes. Patients were responsive to pyridostigimine alone or combined with 3,4-diaminopyridine and/or salbutamol. CONCLUSIONS: Patients with GMPPB-CMS have phenotypic features aligned with CMS subtypes harbouring mutations within the early stages of the glycosylation pathway. Additional features shared with the dystroglycanopathies include myopathic features, raised CK levels and variable mild cognitive delay. This syndrome underlines that CMS can occur in the absence of classic myasthenic manifestations such as ptosis and ophthalmoplegia or facial weakness, and links myasthenic disorders with dystroglycanopathies. This report should facilitate the recognition of this disorder, which is likely to be underdiagnosed and can benefit from symptomatic treatment.

Mutations in GMPPB cause congenital myasthenic syndrome and bridge myasthenic disorders with dystroglycanopathies.

Congenital myasthenic syndromes are inherited disorders that arise from impaired signal transmission at the neuromuscular junction. Mutations in at least 20 genes are known to lead to the onset of these conditions. Four of these, ALG2, ALG14, DPAGT1 and GFPT1, are involved in glycosylation. Here we identify a fifth glycosylation gene, GMPPB, where mutations cause congenital myasthenic syndrome. First, we identified recessive mutations in seven cases from five kinships defined as congenital myasthenic syndrome using decrement of compound muscle action potentials on repetitive nerve stimulation on electromyography. The mutations were present through the length of the GMPPB, and segregation, in silico analysis, exon trapping, cell transfection followed by western blots and immunostaining were used to determine pathogenicity. GMPPB congenital myasthenic syndrome cases show clinical features characteristic of congenital myasthenic syndrome subtypes that are due to defective glycosylation, with variable weakness of proximal limb muscle groups while facial and eye muscles are largely spared. However, patients with GMPPB congenital myasthenic syndrome had more prominent myopathic features that were detectable on muscle biopsies, electromyography, muscle magnetic resonance imaging, and through elevated serum creatine kinase levels. Mutations in GMPPB have recently been reported to lead to the onset of muscular dystrophy dystroglycanopathy. Analysis of four additional GMPPB-associated muscular dystrophy dystroglycanopathy cases by electromyography found that a defective neuromuscular junction component is not always present. Thus, we find mutations in GMPPB can lead to a wide spectrum of clinical features where deficit in neuromuscular transmission is the major component in a subset of cases. Clinical recognition of GMPPB-associated congenital myasthenic syndrome may be complicated by the presence of myopathic features, but correct diagnosis is important because affected individuals can respond to appropriate treatments.

A multicentre postal survey investigating the contribution of illness perceptions, coping and optimism to quality of life and mood in adults with muscle disease.

OBJECTIVE: To replicate the finding that illness perceptions influence quality of life in adults with muscle disease and to explore the additional influence of coping and optimism on quality of life and mood. DESIGN: A postal survey including questionnaires recording quality of life, mood, illness perceptions, optimism, coping and functional impairment. SETTING: National Health Service muscle clinics in the United Kingdom. PARTICIPANTS: A convenience sample of adults with muscle disease. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Individualised Neuromuscular Quality of Life Questionnaire, Hospital Anxiety and Depression Scale. RESULTS: A total of 226 completed questionnaires were returned. Although functional impairment explained most of the variance in three out of eight quality of life domains, psychological factors explained greater amounts of variance (between 19% and 52% of variance) in all other quality of life domains and in both mood domains (between 45% and 48% of variance). Overall, illness perceptions explained much of the variance in quality of life and mood score (between 5% and 37% of variance), while coping (up to 8% of variance) and optimism (up to 15% of variance) explained smaller amounts of variance. CONCLUSION: The results confirm that illness perceptions are associated with quality of life in muscle disease and suggest that they also influence mood. The addition of optimism and coping variables into the analysis yielded small increases in the proportions of variance in quality of life and mood which were explained. These results have implications for the composition of future psychological interventions.

ANO5 gene analysis in a large cohort of patients with anoctaminopathy: confirmation of male prevalence and high occurrence of the common exon 5 gene mutation.

Limb girdle muscular dystrophy type 2L or anoctaminopathy is a condition mainly characterized by adult onset proximal lower limb muscular weakness and raised CK values, due to recessive ANO5 gene mutations. An exon 5 founder mutation (c.191dupA) has been identified in most of the British and German LGMD2L patients so far reported. We aimed to further investigate the prevalence and spectrum of ANO5 gene mutations and related clinical phenotypes, by screening 205 undiagnosed patients referred to our molecular service with a clinical suspicion of anoctaminopathy. A total of 42 unrelated patients had two ANO5 mutations (21%), whereas 14 carried a single change. We identified 34 pathogenic changes, 15 of which are novel. The c.191dupA mutation represents 61% of mutated alleles and appears to be less prevalent in non-Northern European populations. Retrospective clinical analysis corroborates the prevalently proximal lower limb phenotype, the male predominance and absence of major cardiac or respiratory involvement. Identification of cases with isolated hyperCKaemia and very late symptomatic male and female subjects confirms the extension of the phenotypic spectrum of the disease. Anoctaminopathy appears to be one of the most common adult muscular dystrophies in Northern Europe, with a prevalence of about 20%-25% in unselected undiagnosed cases.

Real-World Data on Access to Standards of Care for People With Spinal Muscular Atrophy in the UK.

Spinal Muscular Atrophy (SMA) is characterized by muscle atrophy and weakness and has an incidence of 1:11. 000 live births which projects an estimated population in the UK of 650-1,300 affected patients. Standards of Care (SoC) were updated in 2017 and they have been widely adopted as a reference for implementation of care in SMA across the globe. The effectiveness of implementation and adherence to these standards across different countries is unclear. The aim of this study is to describe the experience of individuals with SMA regarding their care in the UK. An online anonymised survey was sent out via patient organizations, the UK SMA Patient Registry, professional networks, and social media to reach across the UK. The survey captured demographic profile, professionals involved in a patient's care, Interventions and access to mobility aids and home adaptations. Participants responded about their access to services and to rate how important each professional and intervention was for their health and wellbeing. One hundred and twenty-eight responses were collected with a median age of 34 years (1-81). Seventy-three percent of participants were adults and 60% men. Overall good access to neurologist (>90%) but limited to nurse specialist (48%) and physiotherapist (57%). Good access to respiratory support was reported but limited for interventions for positioning and bracing and exercise. This survey highlights that access to certain professionals for people with SMA is limited in the UK. Striking differences were noted between pediatric and adult populations. Limited access to care were regularly reported, with half of the study population consistently not accessing full multidisciplinary care. Access to interventions for contracture management were recorded to have significant limitations. Mobility aids and home adaptations are widely available and were also reported as the most valued interventions. Access to nutritional support or speech and language therapy appears only to be available for a small proportion of the participants. Access to respiratory care was good especially in severe forms of SMA. We found pockets of good practice in the UK that align with the SoC. However, access is not equal for adults and children and access to certain professionals is significantly limited.

Clinical and pathological heterogeneity in late-onset partial merosin deficiency.

Mutations in the LAMA2 gene result in a complete loss of merosin and underlie a severe congenital type of muscular dystrophy (MDC1A).We investigated the clinical, genetic, and histological basis of late-onset muscular dystrophy in one family. The proband and her affected brother exhibited late-onset predominantly proximal muscle weakness. In addition, the proband experienced seizures. Magnetic resonance imaging of her brain demonstrated white-matter abnormalities. Sequencing of LAMA2 identified two new heterozygous point mutations in the two affected members. Muscle histology demonstrated dystrophic features, rimmed vacuoles, and partial loss of laminin α immunoreactivity. Partial merosin deficiency can present with a mild, late-onset limb-girdle-type pattern of weakness, with or without epilepsy, and pathologically may exhibit features observed in inclusion-body myopathy.

Genetic and phenotypic characterisation of inherited myopathies in a tertiary neuromuscular centre.

Diagnosis of inherited myopathies can be a challenging and lengthy process due to broad genetic and phenotypic heterogeneity. In this study we applied focused exome sequencing to investigate a cohort of 100 complex adult myopathy cases who remained undiagnosed despite extensive investigation. We evaluated the frequency of genetic diagnoses, clinical and pathological factors most likely to be associated with a positive diagnosis, clinical pitfalls and new phenotypic insights that could help to guide future clinical practice. We identified pathogenic/likely pathogenic variants in 32/100 cases. TTN-related myopathy was the most common diagnosis (4/32 cases) but the majority of positive diagnoses related to a single gene each. Childhood onset of symptoms was more likely to be associated with a positive diagnosis. Atypical and new clinico-pathological phenotypes with diagnostic pitfalls were identified. These include the new emerging group of neuromyopathy genes (HSPB1, BICD2) and atypical biopsy findings: COL6A-related myopathy with mitochondrial features, DOK7 presenting as myopathy with minicores and DES-related myopathy without myofibrillar pathology. Our data demonstrates the diagnostic efficacy of broad NGS screening when combined with detailed clinico-pathological phenotyping in a complex neuromuscular cohort. Atypical clinico-pathological features may delay the diagnostic process if smaller targeted gene panels are used.

The Diagnostic Value of MRI Pattern Recognition in Distal Myopathies.

Objective: Distal myopathies are a diagnostically challenging group of diseases. We wanted to understand the value of MRI in the current clinical setting and explore the potential for optimizing its clinical application. Methods: We retrospectively audited the diagnostic workup in a distal myopathy patient cohort, reassessing the diagnosis, whilst documenting the usage of MRI. We established a literature based distal myopathies MRI pattern template and assessed its diagnostic utility in terms of sensitivity, specificity, and potential impact on the diagnostic workup. Results: Fifty-five patients were included; in 38 with a comprehensive set of data the diagnostic work-up was audited. The median time from symptoms onset to diagnosis was 12.1 years. The initial genetic diagnostic rate was 39%; 18% were misdiagnosed as neuropathies and 13% as inclusion body myositis (IBM). Based on 21 publications we established a MRI pattern template. Its overall sensitivity (50%) and specificity (32%) were low. However in some diseases (e.g., MYOT-related myopathy, TTN-HMERF) MRI correctly identified the causative gene. The number of genes suggested by MRI pattern analysis was smaller compared to clinical work up (median 1 vs. 9, p < 0.0001) but fewer genes were correctly predicted (5/10 vs. 7/10). MRI analysis ruled out IBM in all cases. Conclusion: In the diagnostic work-up of distal myopathies, MRI is useful in assisting genetic testing and avoiding misdiagnosis (IBM). The overall low sensitivity and specificity limits its generalized use when traditional single gene test methods are applied. However, in the context of next generation sequencing MRI may represent a valuable tool for interpreting complex genetic results.

Atypical periodic paralysis and myalgia: A novel RYR1 phenotype.

OBJECTIVE: To characterize the phenotype of patients with symptoms of periodic paralysis (PP) and ryanodine receptor (RYR1) gene mutations. METHODS: Cases with a possible diagnosis of PP but additional clinicopathologic findings previously associated with RYR1-related disorders were referred for a tertiary neuromuscular clinical assessment in which they underwent detailed clinical evaluation, including neurophysiologic assessment, muscle biopsy, and muscle MRI. Genetic analysis with next-generation sequencing and/or targeted Sanger sequencing was performed. RESULTS: Three cases with episodic muscle paralysis or weakness and additional findings compatible with a RYR1-related myopathy were identified. The McManis test, used in the diagnosis of PP, was positive in 2 of 3 cases. Genetic analysis of known PP genes was negative. RYR1 analysis confirmed likely pathogenic variants in all 3 cases. CONCLUSIONS: RYR1 mutations can cause late-onset atypical PP both with and without associated myopathy. Myalgia and cramps are prominent features. The McManis test may be a useful diagnostic tool to indicate RYR1-associated PP. We propose that clinicopathologic features suggestive of RYR1-related disorders should be sought in genetically undefined PP cases and that RYR1 gene testing be considered in those in whom mutations in SCN4A, CACNA1S, and KCNJ2 have already been excluded.

Tubular Aggregates and Cylindrical Spirals Have Distinct Immunohistochemical Signatures.

Tubular aggregates and cylindrical spirals are 2 distinct ultrastructural abnormalities observed in muscle biopsies that have similar histochemical staining characteristics on light microscopy. Both are found in a wide range of disorders. Recently, a number of genetic mutations have been reported in conditions with tubular aggregates in skeletal muscle. It is widely accepted that tubular aggregates arise from the sarcoplasmic reticulum, but the origin of cylindrical spirals has been less clearly defined. We describe the histopathological features of myopathies with tubular aggregates, including a detailed immunohistochemical analysis of congenital myasthenic syndromes with tubular aggregates due to mutations in GFPT1 and DPAGT1, and myopathies with cylindrical spirals. Our findings support the notion that cylindrical spirals, like tubular aggregates, derive primarily from the sarcoplasmic reticulum; however, immunohistochemistry indicates that different molecular components of the sarcoplasmic reticulum may be involved and can be used to distinguish between these different inclusions. The immunohistochemical differences may also help to guide genetic testing.

CAV3 mutations causing exercise intolerance, myalgia and rhabdomyolysis: Expanding the phenotypic spectrum of caveolinopathies.

Rhabdomyolysis is often due to a combination of environmental trigger(s) and genetic predisposition; however, the underlying genetic cause remains elusive in many cases. Mutations in CAV3 lead to various neuromuscular phenotypes with partial overlap, including limb girdle muscular dystrophy type 1C (LGMD1C), rippling muscle disease, distal myopathy and isolated hyperCKemia. Here we present a series of eight patients from seven families presenting with exercise intolerance and rhabdomyolysis caused by mutations in CAV3 diagnosed by next generation sequencing (NGS) (n = 6). Symptoms included myalgia (n = 7), exercise intolerance (n = 7) and episodes of rhabdomyolysis (n = 2). Percussion-induced rapid muscle contractions (PIRCs) were seen in five out of six patients examined. A previously reported heterozygous mutation in CAV3 (p.T78M) and three novel variants (p.V14I, p.F41S, p.F54V) were identified. Caveolin-3 immunolabeling in muscle was normal in 3/4 patients; however, immunoblotting showed more than 50% reduction of caveolin-3 in five patients compared with controls. This case series demonstrates that exercise intolerance, myalgia and rhabdomyolysis may be caused by CAV3 mutations and broadens the phenotypic spectrum of caveolinopathies. In our series, immunoblotting was a more sensitive method to detect reduced caveolin-3 levels than immunohistochemistry in skeletal muscle. Patients presenting with muscle pain, exercise intolerance and rhabdomyolysis should be routinely tested for PIRCs as this may be an important clinical clue for caveolinopathies, even in the absence of other "typical" features. The use of NGS may expand current knowledge concerning inherited diseases, and unexpected/atypical phenotypes may be attributed to well-known human disease genes.

Targeting protein homeostasis in sporadic inclusion body myositis.

Sporadic inclusion body myositis (sIBM) is the commonest severe myopathy in patients more than 50 years of age. Previous therapeutic trials have targeted the inflammatory features of sIBM but all have failed. Because protein dyshomeostasis may also play a role in sIBM, we tested the effects of targeting this feature of the disease. Using rat myoblast cultures, we found that up-regulation of the heat shock response with arimoclomol reduced key pathological markers of sIBM in vitro. Furthermore, in mutant valosin-containing protein (VCP) mice, which develop an inclusion body myopathy, treatment with arimoclomol ameliorated disease pathology and improved muscle function. We therefore evaluated arimoclomol in an investigator-led, randomized, double-blind, placebo-controlled, proof-of-concept trial in sIBM patients and showed that arimoclomol was safe and well tolerated. Although arimoclomol improved some IBM-like pathology in the mutant VCP mouse, we did not see statistically significant evidence of efficacy in the proof-of-concept patient trial.

The effects of an intronic polymorphism in TOMM40 and APOE genotypes in sporadic inclusion body myositis.

A previous study showed that, in carriers of the apolipoprotein E (APOE) genotype ε3/ε3 or ε3/ε4, the presence of a very long (VL) polyT repeat allele in "translocase of outer mitochondrial membrane 40" (TOMM40) was less frequent in patients with sporadic inclusion body myositis (sIBM) compared with controls and associated with a later age of sIBM symptom onset, suggesting a protective effect of this haplotype. To further investigate the influence of these genetic factors in sIBM, we analyzed a large sIBM cohort of 158 cases as part of an International sIBM Genetics Study. No significant association was found between APOE or TOMM40 genotypes and the risk of developing sIBM. We found that the presence of at least 1 VL polyT repeat allele in TOMM40 was significantly associated with about 4 years later onset of sIBM symptoms. The age of onset was delayed by 5 years when the patients were also carriers of the APOE genotype ε3/ε3. In addition, males were likely to have a later age of onset than females. Therefore, the TOMM40 VL polyT repeat, although not influencing disease susceptibility, has a disease-modifying effect on sIBM, which can be enhanced by the APOE genotype ε3/ε3.

A novel MYH7 mutation occurring independently in French and Norwegian Laing distal myopathy families and de novo in one Finnish patient.

Laing early-onset distal myopathy is a rare autosomal dominant myopathy and caused by mutations in the MYH7 gene, encoding the slow beta myosin heavy chain. We report the first molecularly verified Laing distal myopathy in a French family caused by a novel p.Glu1508del mutation in the MYH7 gene. Interestingly, we identified the identical mutation in an unrelated Norwegian family and, as a de novo mutation, in one sporadic Finnish patient. Described in detail are the clinical and electrophysiological characteristics of 5 patients from the French family. The phenotype in the Finnish patient and the Norwegian patients is largely similar. This mutation causes a benign myopathy within the range of previously reported Laing myopathy phenotype variations. Onset of weakness in the tibialis anterior (TA) muscles occurred in early childhood in all patients. Finger extensor and neck flexor weakness together with Achilles tendon retractions were other frequent findings. The independent recurrence of the identical mutation without any founder background may reflect a mutational susceptibility of this residue, in accordance with some other MYH7 mutations previously reported. De novo mutations seem to be frequent in Laing distal myopathy. This is of clinical importance since a dominant family history is missing, which may confuse differential diagnostic efforts.