Oculopharyngeal Dystrophy Research Articles

Clarifying Misconceptions About Myoblast Transplantation in Myology

Clarifying Misconceptions About Myoblast Transplantation in Myology

Neglected conditions

Oculopharyngeal muscular dystrophy (OPMD, OMIM 164300) fits the description of a neglected condition as described in the CMAJ editorial by Kelsall.[1][1] This condition has escaped attention in many medical school and resident teaching curricula despite having an unusually high prevalence in those

201st ENMC International Workshop: Autophagy in muscular dystrophies – Translational approach, 1–3 November 2013, Bussum, The Netherlands

The 201st ENMC International Workshop on autophagy in muscular dystrophies (MD) was held in Bussum, The Netherlands, on 1–3 November 2013, and was attended by 20 participants from 10 countries (France, Finland, Germany, Italy, Japan, Sweden, The Netherlands, Turkey, United Kingdom, and USA). Participants included biochemists, biologists, pathologists, molecular geneticists, neurologists, and paediatricians. The first session of the workshop focused on the basic mechanism of autophagy in particular autophagosome formation and regulation, selective types of autophagy (chaperone-assisted and mitophagy), and the role of autophagy in muscle homeostasis. Further sessions concentrated on the current understanding of the role of autophagy in several muscle disorders including Pompe disease, Danon disease, X-linked myopathy with excessive autophagy (XMEA), laminopathies, GNE myopathy, centronuclear myopathies, myofibrillar myopathies, limb-girdle muscular dystrophies, oculopharyngeal muscular dystrophy (OPMD), distal myopathies, inclusion body myopathy associated with Paget’s disease

Ocular, bulbar, limb, and cardiopulmonary involvement in oculopharyngeal muscular dystrophy

To assess skeletal muscle weakness and progression as well as the cardiopulmonary involvement in oculopharyngeal muscular dystrophy (OPMD). Cross-sectional study including symptomatic patients with genetically confirmed OPMD. Patients were assessed by medical history, ptosis, ophthalmoplegia, facial and limb strength, and swallowing capability. Cardiopulmonary function was evaluated using forced expiratory capacity in 1 s (FEV1), electrocardiogram (ECG), Holter monitoring, and echocardiography. We included 13 symptomatic patients (six males, mean age; 64 years (41-80) from 8 families. Ptosis was the first symptom in 8/13 patients followed by limb weakness in the remaining 5 patients Dysphagia was never the presenting symptom. At the time of examination, all affected patients had ptosis or had previously been operated for ptosis, while ophthalmoplegia was found in 9 patients. Dysphagia, tested by cold-water swallowing test, was abnormal in 9 patients (17-116 s, ref <8 s). Six patients could not climb stairs of whom two were wheelchair bound and one used a rollator. Six patients had reduced FEV1 (range 23%-59%). No cardiac involvement was identified. Limiting limb weakness is common in OPMD and can even be the presenting symptom of the disease. In contrast, dysphagia was not the initial symptom in any of our patients, although it was obligatory for diagnosing OPMD before genetic testing became available. Mild respiratory dysfunction, but no cardiac involvement, was detected.

P9 Adeno-associated virus (AAV)-mediated RNA interference to PABPN1 combined with an optimised resistant transgene for rescue of the muscle specific disease oculopharyngeal muscular dystrophy (OPMD)

Background: OPMD is an autosomal dominant, late-onset muscle disorder, caused by a trinucleotide repeat expansion in PABPN1 resulting in an N-terminal expanded polyalanine tract and intracellular inclusions of aggregated expPABPN1. PABPN1 promotes interaction between the poly(A) polymerase and the cleavage and polyadenylation specificity factor and controls the length of mRNA poly(A) tails, mRNA export from the nucleus, and alternative poly(A) site usage. Aims: We ought to design a gene therapy strategy based on RNA interference to silence mutant PABPN1, combined with a codon- modified sequence resistant to degradation using AAV as a vector. Methods: Viral plasmids containing shRNA constructs (pAAV- sh131, pAAV-sh132, pAAV-sh133) and RNA polymerase III promoters were designed in collaboration with BENITEC BIOPHARMA. A viral plasmid expressing a codon-optimised PABPN1 under a muscle specific promoter (pAAV-spc512-OPTPAB) was synthesised by Geneart. Knock-down efficiency was assessed in vitro and in vivo (A17 mice) by western blotting and quantified using ImageJ. Results: pAAV-sh131, pAAV-sh132 and pAAV-sh133 gave 40%, 90% and 95% knock-down of PABPN1 expression, respectively, in vitro. scAAV8 expressing sh133 injected into TA muscles gave 90% knockdown of PABPN1 expression in vivo. Co-transfection studies showed resistance of pAAV-spc512-OPTPAB to sh133 degradation in vitro. Conclusion: PABPN1 can be efficiently knocked-down in vitro and in vivo. Studies are on-going to investigate PABPN1 knock-down and replacement on muscle function in vivo.

Safety of botulinum toxin for dysphagia in oculopharyngeal muscular dystrophy

Despite multiple studies reporting marked benefit of botulinum toxin (BTX) for treatment of cricopharyngeal dysphagia, little is known about its safety for this indication. We examined the safety of cricopharyngeal BTX for dysphagia in oculopharyngeal muscular dystrophy (OPMD). We reviewed records of patients with OPMD who received cricopharyngeal BTX. Twenty-four patients underwent 66 procedures. Overall adverse event frequency was 44%. The most common adverse events were dysphonia (24%) and worsened dysphagia (14%). Logistic regression demonstrated that dose was a significant predictor of worsened dysphagia (P = 0.036) and of the composite event of dysphonia or worsened dysphagia (P = 0.009). There was a nonsignificant trend for dose as a predictor of dysphonia (P = 0.073). 59% of procedures were associated with symptomatic improvement. While BTX appears to be beneficial for treatment of dysphagia in OPMD, caution is warranted when injecting the cricopharyngeus muscle due to dose-related risk of dysphonia or worsened dysphagia.

A Novel Feed-Forward Loop between ARIH2 E3-Ligase and PABPN1 Regulates Aging-Associated Muscle Degeneration

Alanine expansion mutations in poly(A)-binding protein nuclear 1 (PABPN1) cause muscle weakness in the late-onset disorder oculopharyngeal muscular dystrophy. In affected muscles, expanded PABPN1 forms nuclear aggregates, depleting levels of soluble PABPN1 and inducing a genome-wide shift from distal to proximal polyadenylation site usage. PABPN1 protein accumulation is regulated by the ubiquitin proteasome system, which is highly dysregulated in oculopharyngeal muscular dystrophy. We show that ARIH2 E3-ligase regulates PABPN1 protein accumulation and aggregation. Levels of ARIH2 mRNA are regulated by PABPN1 via proximal polyadenylation site usage. We demonstrate that masking the proximal polyadenylation site in ARIH2 3' untranslated region by antisense oligonucleotides elevates the expression of ARIH2 and PABPN1 and restores myogenic defects that are induced by ARIH2 or PABPN1 down-regulation in cell culture. Invivo ARIH2 mRNA levels significantly decrease from midlife in vastus lateralis muscles and highly correlate with muscle degeneration. We suggest that the expression of both genes is maintained by a feed-forward loop between mRNA stability regulated by PABPN1 and protein turnover regulated by ARIH2.

An evolutionary framework for detecting protein conformation defects

In the medical community, the demand for detecting texture abnormalities related to pathological Protein Conformation Diseases (PCD) has been increasing for years. In this paper, we use the value (V) channel of an HSV (Hue, Saturation, Value) image, which provides a measurable Detection Region of the V Channel (DRVC) for isolating muscular Intranuclear Inclusions (INIs) indicative of Oculopharyngeal Muscular Dystrophy (OPMD), one variety of PCD. Derived from the Cumulative Distribution Function (CDF) computation over DRVC (CDF-DRVC), the robust cumulative histogram presents the INIs-texture-carrying intensity data as non-decreasing distributions, leading to an accurate estimation of intensities in the texture feature extraction. Beyond the proposed CDF-DRVC methodology, we introduce a methodology of feature synthesis to enhance the quality of feature representations. The experiments are conducted on irregular microscopic images (where variations in size and shape occur) in the binary classes of healthy and sick cases related to OPMD. The proposed framework achieves a higher accuracy rate for the detection as compared to other methods, and exhibits a detection strategy for other types of PCD in medical applications.

Autologous Myoblast Transplantation for Oculopharyngeal Muscular Dystrophy: a Phase I/Iia Clinical Study

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset autosomal dominant genetic disease mainly characterized by ptosis and dysphagia. We conducted a phase I/IIa clinical study (ClinicalTrials.gov NCT00773227) using autologous myoblast transplantation following myotomy in adult OPMD patients. This study included 12 patients with clinical diagnosis of OPMD, indication for cricopharyngeal myotomy, and confirmed genetic diagnosis. The feasibility and safety end points of both autologous myoblast transplantation and the surgical procedure were assessed by videoendoscopy in addition to physical examinations. Potential therapeutic benefit was also assessed through videoendoscopy and videofluoroscopy of swallowing, quality of life score, dysphagia grade, and a drink test. Patients were injected with a median of 178 million myoblasts following myotomy. Short and long-term (2 years) safety and tolerability were observed in all the patients, with no adverse effects. There was an improvement in the quality of life score for all 12 patients, and no functional degradation in swallowing was observed for 10 patients. A cell dose-dependant improvement in swallowing was even observed in this study. This trial supports the hypothesis that a local injection of autologous myoblasts in the pharyngeal muscles is a safe and efficient procedure for OPMD patients.

Risk factors for osteoporosis, falls and fractures in hereditary myopathies and sporadic inclusion body myositis — A cross sectional survey

BackgroundThe risk of osteoporosis is known in myopathies requiring long-term steroid treatment and Pompe disease, but not in other hereditary myopathies or sporadic inclusion body myositis (sIBM). MethodsRisk factors of osteoporosis, laboratory parameters of bone metabolism, frequency of falls and fractures, walking ability, and pain were surveyed using questionnaires in 89 patients with sIBM and genetically confirmed myopathies facioscapulohumeral muscular dystrophy (FSHD), myotonic dystrophy types 1 and 2 (DM1, DM2), limb girdle muscular dystrophies (LGMD2A, LGMD2B, LGMD2I), MATR3 myopathy, and oculopharyngeal muscular dystrophy (OPMD). Additionally laboratory parameters of bone metabolism were determined. ResultsThe mean age at examination per disease group ranged from 32 years in LGMD2A to 70 years in sIBM. Myopathies with a higher degree of walking impairment had a higher risk of falls (sIBM, LGMD2A, LGMD2B). At the time of examination 3.4% had a history of osteoporosis. The 25-OH D3 level was decreased in 20% of patients (and in 55% of patients with LGMDs), 57% of them were ambulatory. The 25-OH D3 level was significantly lower in patients with myopathies than in other neurological disorders (p<0.001). 2.7 falls per year per person occurred. Fractures were reported in 6.8% of patients within the last year. They involved frequently the tibia bone. The pain score didn't correlate with either the walking disability (WGMS) score or the 25-OH D3 level. ConclusionThe risk for osteoporosis and reduced 25-OH D3 level seems to be increased in wheelchair-bound patients with myopathy but also in patients with DM1 and autosomal-recessive myopathies.

Oculopharyngeal muscular dystrophy: underdiagnosed disease in Hong Kong

Despite the advances in the understanding of the molecular basis for oculopharyngeal muscular dystrophy in the last decade, it remains an underdiagnosed disease, especially among the Chinese. In the presence of a positive family history and late-onset ptosis, dysphagia, and proximal muscle weakness (its cardinal features), we suggest that PABPN1 gene analysis should be the first-line investigation to rule out this condition. Muscle biopsy can be reserved for atypical cases. Non-specific mitochondrial changes in the muscle specimens of these patients should be appreciated, so as to avoid diagnostic confusion. It is hoped that greater awareness among medical professionals and judicious use of PABPN1 gene analysis will lead to earlier diagnosis, better management, and avoidance of unnecessary invasive investigations of affected patients.

The muscular dystrophies.

With transition to the genetic era, the number of muscular dystrophies has grown significantly, but so too has our understanding of their pathogenic underpinnings. Clinical features associated with each muscular dystrophy still guide us to the diagnosis. However, improved diagnostic abilities refine and expand phenotypic and genotypic correlates. This article discusses the epidemiology, clinical features, and diagnosis of these disorders. Some important recent advancements include (1) a much greater understanding of the pathogenetic pathways underlying facioscapulohumeral muscular dystrophy and myotonic dystrophy type 1; (2) the publication of diagnostic and treatment guidelines for Duchenne muscular dystrophy; and (3) further clarification of the many genetic muscle disorders presenting a limb-girdle pattern of weakness. Muscular dystrophies are genetic, progressive, degenerative disorders with the primary symptom of muscle weakness. Duchenne, Becker, facioscapulohumeral, and myotonic muscular dystrophies are most prevalent and tend to have distinctive features helpful in diagnosis. The limb-girdle, Emery-Dreifuss, and oculopharyngeal muscular dystrophies are less common but often may also be diagnosed on the basis of phenotype. Researchers hope to help patients with future discoveries effective in slowing or halting disease progression, reversing or preventing underlying mechanisms, and repairing previously damaged muscle.

Unclassified cardiomyopathies in neuromuscular disorders

Unclassified cardiomyopathies (CMPs) include left ventricular hypertrabeculation or noncompaction (LVHT) and Takotsubo syndrome (TTS). Unclassified CMPs are frequently associated with noncardiac disease, including neuromuscular disorders (NMDs). This review aims at summarizing and discussing recent findings concerning the association of NMDs with unclassified CMPs. Literature search using the database PubMed from 1966 to June 2013 was performed. LVHT has been described in association with dystrophinopathies, myotonic dystrophies, zaspopathies, laminopathies, dystrobrevinopathies, oculopharyngeal muscular dystrophy, tropomyosin-1 mutations, multiminicore disease, Danon disease, mitochondrial disorders, myoadenylate deaminase deficiency, Pompe's disease, glycogen storage disease-IV, fatty acid oxidation disorder, Barth syndrome, ryanodine receptor mutation, inclusion body myopathy, dystrophic epidermolysis bullosa, Charcot-Marie-Tooth neuropathy, hereditary cobolamine deficiency, beta-thalassemia, poliomyelitis, and Friedreich ataxia. Takotsubo syndrome has been described in association with myasthenia gravis, amyotrophic lateral sclerosis, Guillain-Barre syndrome, rhabdomyolysis, mitochondrial disorder, hypokalemia-related myopathy, syndrome malin, hereditary sensorimotor neuropathy, Beals syndrome, polymyalgia rheumatica, and unclassified myopathy. It is important for treating physicians to know about these associations because treatment and outcome of LVHT, including artificial ventilation, are determined by the presence or absence of an NMD. There are also indications that LVHT in NMDs favors the development of TTS. LVHT and TTS may be associated with NMDs. The pathogenetic link between unclassified CMPs and NMDs remains elusive. Outcome of LVHT and treatment of TTS are additionally determined by the presence or absence of an NMD.

Lithium chloride attenuates cell death in oculopharyngeal muscular dystrophy by perturbing Wnt/β-catenin pathway

Expansion of polyalanine tracts causes at least nine inherited human diseases. Among these, a polyalanine tract expansion in the poly (A)-binding protein nuclear 1 (expPABPN1) causes oculopharyngeal muscular dystrophy (OPMD). So far, there is no treatment for OPMD patients. Developing drugs that efficiently sustain muscle protection by activating key cell survival mechanisms is a major challenge in OPMD research. Proteins that belong to the Wnt family are known for their role in both human development and adult tissue homeostasis. A hallmark of the Wnt signaling pathway is the increased expression of its central effector, beta-catenin (β-catenin) by inhibiting one of its upstream effector, glycogen synthase kinase (GSK)3β. Here, we explored a pharmacological manipulation of a Wnt signaling pathway using lithium chloride (LiCl), a GSK-3β inhibitor, and observed the enhanced expression of β-catenin protein as well as the decreased cell death normally observed in an OPMD cell model of murine myoblast (C2C12) expressing the expanded and pathogenic form of the expPABPN1. Furthermore, this effect was also observed in primary cultures of mouse myoblasts expressing expPABPN1. A similar effect on β-catenin was also observed when lymphoblastoid cells lines (LCLs) derived from OPMD patients were treated with LiCl. We believe manipulation of the Wnt/β-catenin signaling pathway may represent an effective route for the development of future therapy for patients with OPMD.

Control of mRNA stability contributes to low levels of nuclear poly(A) binding protein 1 (PABPN1) in skeletal muscle

BackgroundThe nuclear poly(A) binding protein 1 (PABPN1) is a ubiquitously expressed protein that plays critical roles at multiple steps in post-transcriptional regulation of gene expression. Short expansions of the polyalanine tract in the N-terminus of PABPN1 lead to oculopharyngeal muscular dystrophy (OPMD), which is an adult onset disease characterized by eyelid drooping, difficulty in swallowing, and weakness in the proximal limb muscles. Why alanine-expanded PABPN1 leads to muscle-specific pathology is unknown. Given the general function of PABPN1 in RNA metabolism, intrinsic characteristics of skeletal muscle may make this tissue susceptible to the effects of mutant PABPN1.MethodsTo begin to understand the muscle specificity of OPMD, we investigated the steady-state levels of PABPN1 in different tissues of humans and mice. Additionally, we analyzed the levels of PABPN1 during muscle regeneration after injury in mice. Furthermore, we assessed the dynamics of PABPN1 mRNA decay in skeletal muscle compared to kidney.ResultsHere, we show that the steady-state levels of both PABPN1 mRNA and protein are drastically lower in mouse and human skeletal muscle, particularly those impacted in OPMD, compared to other tissues. In contrast, PABPN1 levels are increased during muscle regeneration, suggesting a greater requirement for PABPN1 function during tissue repair. Further analysis indicates that modulation of PABPN1 expression is likely due to post-transcriptional mechanisms acting at the level of mRNA stability.ConclusionsOur results demonstrate that PABPN1 steady-state levels and likely control of expression differ significantly in skeletal muscle as compared to other tissues, which could have important implications for understanding the muscle-specific nature of OPMD.

Genetic diseases affecting the eyelids

The molecular basis of a number of inherited diseases that affect the eyelids has been elucidated over the last two decades. Due to the vast number of these diseases, a clinician may become overwhelmed by the volume of data, making it difficult to incorporate newer information into his or her clinical practice. This article intends to review the recent developments of inherited diseases that affect the eyelids that a typical oculoplastic surgeon will encounter. This review proposes categorizing genetic diseases affecting the eyelids on rarity and whether the disease manifests itself at birth or later in life. Based on this classification system the following 10 diseases (the first five manifesting at birth, the last five later in life) are considered more likely to be encountered by the typical oculoplastic surgeon and reviewed in detail: blepharophimosis-ptosis-epicanthus inversus syndrome, congenital fibrosis of the extraocular muscles, lymphedema-distichiasis syndrome, neurofibromatosis type 1, congenital myasthenic syndrome, oculopharyngeal muscular dystrophy, chronic progressive external ophthalmoplegia, myotonic dystrophy, neurofibromatosis type 2, and basal cell nevus syndrome. The remaining known genetic disorders that affect the eyelids are considered less likely to be encountered by the typical oculoplastic surgeon and are listed in tabular form. It is prudent for the oculoplastic surgeon to be knowledgeable of inherited disorders that affect the eyelids to aid in accurate diagnosis, counseling, and treatment. The development of future therapies may at some point make treatment of these diseases no longer surgical. http://links.lww.com/COOP/A4.

P.16.12 OPMD from the myoblast’s and fibroblast’s point of view

Oculopharyngeal muscular dystrophy (OPMD) is a late onset autosomal dominant inherited dystrophy due to an expansion of GCG repeats in the coding region of the ubiquitously expressed PABPN1 gene. The main muscular targets of OPMD are cricopharyngeal muscle (CPM) and elevator eyelid muscle whose progressive involvement leads to dysphagia and ptosis. We have recently demonstrated that OPMD CPM is characterized by atrophy, fibrosis and increased PAX7-positive cells compared to control CPM and to OPMD non-affected muscles such as quadriceps (QM). These results suggest that the specific involvement of affected muscles in OPMD correlates with an exacerbated fibrosis and a failure of the regenerative response. This led us to further study the skeletal muscle progenitor cells from CPM and their possible deregulation in OPMD. In vitro, primary cultures isolated from CPM biopsies of both OPMD (n = 4) and control (n = 4) subjects were characterized by a rapid fall of their myogenicity, whereas in primary cultures from control QM (n = 3) the myogenicity was maintained throughout the course of the lifespan. Several hypotheses for this drastic loss of myogenicity have been investigated, e.g. proliferative deregulation between resident fibroblasts and myoblasts. In addition, CPM cells regeneration capacity was explored in vivo. Each primary culture was injected into cryodamaged tibialis anterior (TA) muscle of an immunodeficient mouse model. One month after injection, a high number of human PAX7-positive satellite cells were found in TA muscles injected with CPM myoblasts compared to control injected QM myoblasts. Moreover, an elevated number of human cells were revealed in the interstitial space of TA muscle injected by CPM myoblasts. Altogether, these results show that muscle primary cultures represent a good model to further study the deregulations observed in OPMD CPM. Cellular and molecular mechanisms deregulated in both fibroblasts and myoblasts fractions are now being investigated.

P.14.13 Involvement of optineurin as well as TDP-43 in the pathogenesis of inclusion body myositis

Sporadic inclusion body myositis (sIBM) is a progressive inflammatory myopathy characterized by abnormal accumulation of multiple misfolded proteins, including amyloid-beta, phosphorylated tau (p-tau) in the form of paired helical filaments, and others, with ubiquitin immunoreactivity. Transactive response DNA binding protein-43 (TDP-43) was initially found to be one of the major disease proteins in the pathological inclusions of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration. Recently, several studies have shown the abnormal accumulation of TDP-43 in skeletal muscles of patients with sIBM. Thus, increasing evidences suggest a similarity in the pathophysiological mechanisms of neuronal cell death in ALS and myofiber degeneration in sIBM. To elucidate the involvement of ALS-causing proteins in the pathophysiological mechanisms in sIBM, we analyzed the expression and localization of familial ALS-causing proteins, including TDP-43, fused in sarcoma/translocated in liposarcoma (FUS/TLS), Cu/Zn superoxide dismutase (SOD1), and optineurin (OPTN) by immunohistochemistry, using skeletal muscle biopsy specimens of patients with sIBM, oculopharyngeal muscular dystrophy (OPMD), polymyositis (PM), dermatomyositis (DM), neurogenic muscular atrophy, and healthy control subjects. TDP-43, OPTN, and to a lesser extent FUS/TLS were more frequently accumulated in the cytoplasm in patients with sIBM and OPMD than in patients with PM, DM, neurogenic muscular atrophy, or healthy control subjects. SOD1 was accumulated in a small percentage of myofibers in patients with sIBM and OPMD, and to a very small extent in patients with PM and DM. Interestingly, confocal microscopy imaging showed that TDP-43 proteins more often colocalized with OPTN than with FUS/TLS and p-tau. These findings suggest that OPTN in cooperation with TDP-43 might be involved in the pathophysiological mechanisms of skeletal muscular degeneration in myopathy with rimmed vacuoles.

P.16.13 Myopathy with typical OPMD morphology without association with the PABPN1 gene locus

Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disease characterized by progressive ptosis of the eyelids and dysphagia. Intranuclear inclusions of tubulofilamentous (INIs) in skeletal muscle constitute a pathological hallmark for this disease. The filaments are up to 250 nm in length and have external diameter of 8.5 nm and an internal diameter of 3 nm. The only causative mutation described to date is a triplet repeat expansion consisting of 2–7 additional base triplets in a repeat sequence in exon 1 of the polyadenine binding protein nuclear 1 (PABPN1) gene localized on chromosome 14q11.2. This results in an increase in length of a polyalanine tract in the PABPN1 protein from 10 to 12–17 residues. We describe the clinical, histopathological and genetically findings in three individuals from a Swedish family, with a dominantly inherited adult-onset myopathy characterized by ptosis and dysphagia. Muscle histopathological features included rimmed vacuoles and nuclei containing inclusions of unique 8.5 nm filaments and insoluble PABPN1 protein. The PABPN1 gene was excluded as the disease causative gene in this family both by direct DNA sequencing of the gene together with high density single nucleotide polymorphism (SNP) arrays covering the entire genome excluding the locus harbouring the PABPN1 gene.

184th ENMC international workshop: Pain and fatigue in neuromuscular disorders: 20–22 May 2011, Naarden, The Netherlands

This European Neuromuscular Centre (ENMC) care workshop was attended by 19 professionals working in the field of neuromuscular disorders (pediatric and adult), pain or fatigue from 8 different countries (USA, Great Britain, Germany, France, Italy, Sweden, Denmark and the Netherlands), and 3 patient representatives coming from the Netherlands. This ENMC organized workshop aimed to achieve consensus on the definition of pain and fatigue in NMD, to define a core set of measurement instruments for pain and fatigue in NMD, and to discuss possible interventions. Prior to the workshop, all participants received a questionnaire on the assessment instruments and interventions that they regularly used to, respectively, assess and treat pain and fatigue. Two experts on (chronic) pain and fatigue in general (Henriet van Middendorp and Hans Knoop) were invited to present an overview of definitions, mechanisms, and measurement instruments for pain and fatigue. Next to that, several participants presented data on the prevalence of pain and fatigue in the various NMD populations. Through group discussions with all participants, consensus was reached on the definition and core set of measurement instruments (to be used)/for use in future research and clinical practice in NMD.