Consensus-based care recommendations for adults with myotonic dystrophy type 1

Expert opinion on mexiletine treatment in adult patients with myotonic dystrophy

In France, mexiletine - a class I antiarrhythmic drug - can be prescribed for the symptomatic treatment of myotonia of the skeletal muscles in adult patients with myotonic dystrophy under a compassionate use programme. Mexiletine is used according to its summary of product characteristics, which describes its use for myotonia treatment in adult patients with non-dystrophic myotonia, a different neuromuscular condition without cardiac involvement. A cardiac assessment is required prior to initiation and throughout treatment due to potential proarrhythmic effects. The presence of conduction system disease, the most common cardiac manifestation of myotonic dystrophy, mandates repeated cardiac evaluations in patients with this condition, and becomes even more important when they are given mexiletine. A group of experts, including three neurologists and five cardiologists from French neuromuscular reference centres, were involved in a task force to develop a treatment algorithm to guide mexiletine use in myotonic dystrophy. The recommendations are based on data from a literature review of the safety of mexiletine-treated patients with myotonic dystrophy, the compassionate use protocol for mexiletine and the personal clinical experience of the experts. The main conclusion of the expert group is that, although existing safety data in mexiletine-treated patients with myotonic dystrophy are reassuring, cardiac assessments should be reinforced in such patients compared with mexiletine-treated patients with non-dystrophic myotonia. This expert opinion to guide mexiletine treatment in patients with myotonic dystrophy should help to reduce the risk of severe adverse events and facilitate interactions between specialists involved in the routine care of patients with myotonic dystrophy.

Translation, reliability, and validity of the Norwegian version of the ABILHAND-NMD and the ACTIVLIM for Myotonic Dystrophy type 1

PURPOSE

To translate ABILHAND-NMD and ACTIVLIM into Norwegian and assess their psychometric properties in adults with Myotonic Dystrophy type 1(DM1).

METHODS

ABILHAND-NMD and ACTIVLIM were translated into Norwegian through a standardized translation process. Psychometric properties of the translated questionnaires were tested. Intraclass correlation coefficient (ICC3.1) was used to assess test-retest reliability and Cronbach's α for internal consistency. The validity of the questionnaires was also assessed.

RESULTS

A total of 39 adults with DM1 were included. We found excellent test-retest reliability on ABILHAND-NMD (ICC 0.91) and ACTIVLIM (ICC 0.93). We found a good internal consistency of ABILHAND-NMD with Cronbach's α (95%CI) of 0.80 (0.69-0.88) and ACTIVLIM with Cronbach's α (95%CI) of 0.88 (0.82-0.93) An expert group of healthcare professionals and a pilot group reported good face and content validity. We found a high correlation between ABILHAND-NMD and ACTIVLIM (r = 0.75), p < 0.001 implying good convergent validity. ABILHAND-NMD and ACTIVLIM showed no floor effect, but a potential for ceiling effect.

CONCLUSION

The Norwegian versions of ABILHAND-NMD and ACTIVLIM are reliable and valid patient reported outcome measures for Myotonic Dystrophy type 1. The questionnaires are easy to administer as they take a short time to answer, and the participants reported no problems understanding the questions.

Myotonic dystrophy type 1 in South Korea: a comprehensive analysis of cancer and comorbidity risks

BACKGROUND AND PURPOSE

Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disorder characterized by myotonia and progressive muscle weakness. Beyond the primary symptoms, there is growing concern regarding a higher incidence of certain comorbidities in DM1 patients, including cancer, diabetes, thyroid dysfunction, and cataracts. This study was designed to examine the occurrence of these conditions among patients diagnosed with DM1 in South Korea, using data from the National Health Insurance Service database.

METHODS

The study undertook a comprehensive review of 3,842 patients diagnosed with DM1 between 2012 and 2018. We assessed the incidence of cancer and the prevalence of diabetes, thyroid dysfunction, and cataracts among these patients, comparing their rates to those in the general population.

RESULTS

In the study cohort, 463 out of 3,842 DM1 patients (12.04%) were diagnosed with cancer, indicating a substantial elevation in cancer risk with an overall standard incidence ratio of 1.9 (95% CI = 1.6-2.3, p < 0.01) when compared to the expected rates in the general population. Moreover, the prevalence of diabetes (15.2%) and thyroid dysfunction (17.6%) was noteworthy in the DM1 population. The mean age at which DM1 patients underwent cataract surgery was 55.07 years, noticeably younger than the mean age of 69.25 years for cataract surgery in the general population.

CONCLUSIONS

DM1 patients have a noteworthy occurrence of several comorbidities such as cancer, diabetes, thyroid dysfunction, and earlier cataract surgery. This highlights the importance of a comprehensive and integrative approach to the management and treatment of DM1, going beyond addressing only the primary neuromuscular symptoms. More research is required to understand the underlying mechanisms contributing to these comorbidities in DM1 patients, which may inform preventative measures and guide improvements in patient care.

Diagnosis and Management of Myotonic Dystrophy Type 1

This JAMA Insights discusses the signs and symptoms, diagnosis, and treatment of myotonic dystrophy type 1.

Comprehensive Cardiovascular Management of Myotonic Dystrophy Type 1 Patients: A Report from the Italian Neuro-Cardiology Network

Myotonic dystrophy is a hereditary disorder with systemic involvement. The Italian Neuro-Cardiology Network-"Rete delle Neurocardiologie" (INCN-RNC) is a unique collaborative experience involving neurology units combined with cardio-arrhythmology units. The INCN facilitates the creation of integrated neuro-cardiac teams in Neuromuscular Disease Centers for the management of cardiovascular involvement in the treatment of myotonic dystrophy type 1 (MD1).

Living with Dysphagia: A Survey Exploring the Experiences of Adults Living with Neuromuscular Disease and their Caregivers in the United Kingdom

Background

Dysphagia is common in adults living with neuromuscular disease (NMD). Increased life expectancy, secondary to improvements in standards of care, requires the recognition and treatment of dysphagia with an increased priority. Evidence to support the establishment of healthcare pathways is, however, lacking. The experiences of people living with NMD (pplwNMD) and their caregivers are valuable to guide targeted, value-based healthcare.

Objective

To generate preliminary considerations for neuromuscular dysphagia care and future research in the United Kingdom, based on the experiences of those living with, or caring for, people with NMD.

Methods

Two surveys (one for adults living with NMD and dysphagia, and a second for caregivers) were co-designed with an advisory group of people living with NMD. Surveys were electronically distributed to adults living with NMD and their caregivers between 18th May and 26th July 2020. Distribution was through UK disease registries, charity websites, newsletters, and social media.

Results

Adults living with NMD receive little information or education that they are likely to develop swallowing difficulties. Most respondents report wanting this information prior to developing these difficulties. Difficulties with swallowing food and medication are common in this group, and instrumental assessment is considered a helpful assessment tool. Both adults living with NMD and caregivers want earlier access to neuromuscular swallowing specialists and training in how best to manage their difficulties.

Conclusions

Improvement is needed in the dysphagia healthcare pathway for adults living with NMD to help mitigate any profound physical and psychological consequences that may be caused by dysphagia. Education about swallowing difficulties and early referral to a neuromuscular swallowing specialist are important to pplwNMD and their caregivers. Further research is required to better understand the experiences of pplwNMD and their caregivers to inform the development of dysphagia healthcare pathways.

Peptide-conjugated antimiRs improve myotonic dystrophy type 1 phenotypes by promoting endogenous MBNL1 expression

Myotonic dystrophy type 1 (DM1) is a rare neuromuscular disease caused by a CTG repeat expansion in the DMPK gene that generates toxic RNA with a myriad of downstream alterations in RNA metabolism. A key consequence is the sequestration of alternative splicing regulatory proteins MBNL1/2 by expanded transcripts in the affected tissues. MBNL1/2 depletion interferes with a developmental alternative splicing switch that causes the expression of fetal isoforms in adults. Boosting the endogenous expression of MBNL proteins by inhibiting the natural translational repressors miR-23b and miR-218 has previously been shown to be a promising therapeutic approach. We designed antimiRs against both miRNAs with a phosphorodiamidate morpholino oligonucleotide (PMO) chemistry conjugated to cell-penetrating peptides (CPPs) to improve delivery to affected tissues. In DM1 cells, CPP-PMOs significantly increased MBNL1 levels. In some candidates, this was achieved using concentrations less than two orders of magnitude below the median toxic concentration, with up to 5.38-fold better therapeutic window than previous antagomiRs. In HSALR mice, intravenous injections of CPP-PMOs improve molecular, histopathological, and functional phenotypes, without signs of toxicity. Our findings place CPP-PMOs as promising antimiR candidates to overcome the treatment delivery challenge in DM1 therapy.

Msi2 enhances muscle dysfunction in a myotonic dystrophy type 1 mouse model

BACKGROUND

Myotonic dystrophy type 1 (DM1) is a rare neuromuscular disease caused by a CTG repeat expansion in the 3' untranslated region of the DM1 protein kinase gene. Characteristic degenerative muscle symptoms include myotonia, atrophy, and weakness. We previously proposed an Musashi homolog 2 (MSI2)>miR-7>autophagy axis whereby MSI2 overexpression repressed miR-7 biogenesis that subsequently de-repressed muscle catabolism through excessive autophagy. Because the DM1 HSALR mouse model expressing expanded CUG repeats shows weak muscle-wasting phenotypes, we hypothesized that MSI2 overexpression was sufficient to promote muscle dysfunction in vivo.

METHODS

By means of recombinant AAV murine MSI2 was overexpressed in neonates HSALR mice skeletal muscle to induce DM1-like phenotypes.

RESULTS

Sustained overexpression of the murine MSI2 protein in HSALR neonates induced autophagic flux and expression of critical autophagy proteins, increased central nuclei and reduced myofibers area, and weakened muscle strength. Importantly, these changes were independent of MBNL1, MBNL2, and Celf1 protein levels, which remained unchanged upon Msi2 overexpression.

CONCLUSIONS

Globally, molecular, histological, and functional data from these experiments in the HSALR mouse model confirms the pathological role of MSI2 expression levels as an atrophy-associated component that impacts the characteristic muscle dysfunction symptoms in DM1 patients.

Myotonic dystrophy type 1: 13 years of experience at a tertiary hospital. Clinical and epidemiological study and genotype-phenotype correlation

INTRODUCTION

The incidence of myotonic dystrophy type 1 (DM1), a disease with great phenotypic variety, in our region is unknown. This study aims to estimate the incidence of DM1 at our hospital (a reference centre in Aragon, Spain) and to identify the characteristics of our population (genotype-phenotype correlation).

METHODS

Retrospective, descriptive study of 459 patients classified according to the number of CTG repeats, as follows: normal (5-35), premutation (36-50), protomutation (51-80), small expansions (81-150), intermediate expansions (151-1000), and large expansions (> 1000). Furthermore, according to clinical phenotype, patients were categorised as unaffected (5-50 CTG repeats), mild form or asymptomatic (51-150), classical form (151-1000), and severe form (> 1000).

RESULTS

The incidence of DM1 was 20.61 cases per million person-years (95% CI, 19.59-21.63). An inverse correlation was observed between the number of CTG repeats and the age at genetic diagnosis (ρ = -0.547; 95% CI, -0.610 to -0.375; P < .001). CTG5 was the most frequent polymorphic allele in healthy individuals. Of all patients with DM1, 28.3% presented the mild or asymptomatic form, 59.1% the classical form, and 12.6% the severe form. Inheritance was maternal in 35.1% of cases, paternal in 59.4%, and uncertain in 5.5%. In mild forms, frontal balding in men was the most prevalent phenotypic trait, as well as myotonia and cataracts, while in the classical form, ptosis, facial weakness, voice and pronunciation alterations, myotonia, and fatigue/sleepiness were most frequent.

CONCLUSIONS

The incidence of DM1 in Aragon is significant. Multidisciplinary study of the phenotype of patients with DM1 is key to early diagnosis and personalised management.

Obstructive Sleep Apnea Treatment with Oral Appliance in a Myotonic Dystrophy Type I Subject: A Case Report

Objective  to report a myotonic dystrophy type 1 (MD1) subject with obstructive sleep apnea syndrome treated with oral appliance. Methods  A review of individual's history and records, associated with a photographic register of all diagnostic methods and literature research about the topic were done. Final Statements  This case depicts the therapeutical choices disposable to treat subjects with obstructive sleep apnea and DM1. Although considered an uncommon treatment, the oral appliances, if well indicated in adequately selected cases, can satisfactorily improve respiratory parameters, symptoms and quality of life.

Frequency and type of cancers in myotonic dystrophy: A retrospective cross-sectional study

INTRODUCTION/AIMS

Myotonic dystrophies (DMs) are autosomal dominant diseases in which expression of a mutant expanded repeat mRNA leads to abnormal splicing of downstream effector genes thought to be responsible for their multisystem involvement. Cancer risk and cancer-related deaths are increased in DM patients relative to the general population. We aimed at determining the frequency and type of cancers in both DM1 and DM2 vs a non-DM muscular dystrophy cohort.

METHODS

A retrospective, cross-sectional study was carried out on patients with genetically confirmed DM1, DM2, facioscapulohumeral muscular dystrophy (FSHD), and oculopharyngeal muscular dystrophy (OPMD) at our institutions from 2000 to 2020.

RESULTS

One hundred eighty-five DM1, 67 DM2, 187 FSHD, and 109 OPMD patients were included. Relative to non-DM, DM patients had an increased cancer risk that was independent of age and sex. Specifically, an increased risk of sex-related (ovarian) and non-sex-related (non-melanoma skin, urological, and hematological) cancers was observed in DM1 and DM2, respectively. The length of CTG repeat expansion was not associated with cancer occurrence in the DM1 group.

DISCUSSION

In addition to current consensus-based care recommendations, our findings prompt consideration of screening for skin, urological, and hematological cancers in DM2 patients, and screening of ovarian malignancies in DM1 female patients.

Cardiac Rehabilitation in a Transplanted Person with Emery-Dreifuss Muscular Dystrophy

Emery-Dreifuss muscular dystrophy is a rare hereditary neuromuscular disease. Its manifestations begin primarily in childhood. The most frequent manifestations are progressive muscle weakness, atrophy that usually begins in the scapula-vertebral region, extending later to the pelvic girdle, and spinal stiffness. Patients can also manifest cardiac involvement as palpitations, syncope, exercise intolerance, congestive heart failure, and variable heart rhythm disturbances. 1 - 3 The presence and severity of these manifestations can vary according to the individual and the disease's subtypes. 2 Cardiac involvement is the most worrisome feature of this disease, and there are some reports of the need for heart transplantation in this dystrophy. 4.

Prediction of respiratory impairment in myotonic dystrophies using the 'Respiratory involvement symptom checklist' (Respicheck)

Chronic hypoventilation due to involvement of respiratory muscles is a frequent symptom in autosomal dominant inherited myotonic dystrophies, especially in type 1 (DM1), leading to a severely reduced quality of life, an early need for ventilatory support, or premature death. Thus, early knowledge of respiratory muscle weakness is essential to initiate further diagnostic and therapeutic measures. To get early, simple, and reliable information about respiratory impairment in DM patients, we performed a prospective controlled cohort study with DM1 and DM2 patients analysing the suitability of 'Respiratory involvement symptom checklist (Respicheck) as a clinically meaningful screening questionnaire for ventilatory impairment in patients with DM1 or DM2. Clinical assessments included a one-time pulmonary function test (spirometry and manometry) and the completion of the Respicheck. 172 participants were enrolled in this study (74 DM1, 72 DM2, 26 healthy controls). With a cut-off RespicheckCAT score of 4, the Respicheck can distinguish between patients with and without respiratory impairment with higher sensitivity and positive predictive value for DM1 than DM2 patients (DM1: sensitivity 77-87; positive predictive value 50-94%; DM2: sensitivity 67-80%; positive predictive value 14-38). In summary, our results confirm a clinically meaningful use of the Respicheck to detect respiratory impairments predominantly in DM1 patients.

Specific DMPK-promoter targeting by CRISPRi reverses myotonic dystrophy type 1-associated defects in patient muscle cells

Myotonic dystrophy type 1 (DM1) is a neuromuscular disease that originates from an expansion of CTG microsatellites in the 3' untranslated region of the DMPK gene, thus leading to the expression of transcripts containing expanded CUG repeats (CUGexp). The pathophysiology is explained by a toxic RNA gain of function where CUGexp RNAs form nuclear aggregates that sequester and alter the function of MBNL splicing factors, triggering splicing misregulation linked to the DM1 symptoms. There is currently no cure for DM1, and most therapeutic strategies aim at eliminating CUGexp-DMPK transcripts. Here, we investigate a DMPK-promoter silencing strategy using CRISPR interference as a new alternative approach. Different sgRNAs targeting the DMPK promoter are evaluated in DM1 patient muscle cells. The most effective guides allowed us to reduce the level of DMPK transcripts and CUGexp-RNA aggregates up to 80%. The CUGexp-DMPK repression corrects the overall transcriptome, including spliceopathy, and reverses a physiological parameter in DM1 muscle cells. Its action is specific and restricted to the DMPK gene, as confirmed by genome-wide expression analysis. Altogether, our findings highlight DMPK-promoter silencing by CRISPRi as a promising therapeutic approach for DM1.

Cancer and Myotonic Dystrophy

Myotonic dystrophy (DM) is the most common muscular dystrophy in adults. Dominantly inherited CTG and CCTG repeat expansions in DMPK and CNBP genes cause DM type 1 (DM1) and 2 (DM2), respectively. These genetic defects lead to the abnormal splicing of different mRNA transcripts, which are thought to be responsible for the multiorgan involvement of these diseases. In ours and others' experience, cancer frequency in patients with DM appears to be higher than in the general population or non-DM muscular dystrophy cohorts. There are no specific guidelines regarding malignancy screening in these patients, and the general consensus is that they should undergo the same cancer screening as the general population. Here, we review the main studies that investigated cancer risk (and cancer type) in DM cohorts and those that researched potential molecular mechanisms accounting for DM carcinogenesis. We propose some evaluations to be considered as malignancy screening in patients with DM, and we discuss DM susceptibility to general anesthesia and sedatives, which are often needed for the management of cancer. This review underscores the importance of monitoring the adherence of patients with DM to malignancy screenings and the need to design studies that determine whether they would benefit from a more intensified cancer screening than the general population.

The myotonic dystrophy type 1 drug development pipeline: 2022 edition

The beginning of the 20th decade has witnessed an increase in drug development programs for myotonic dystrophy type 1 (DM1). We have collected nearly 20 candidate drugs with accomplished preclinical and clinical phases, updating our previous drug development pipeline review with new entries and relevant milestones for pre-existing candidates. Three interventional first-in-human clinical trials got underway with distinct drug classes, namely AOC 1001 and DYNE-101 nucleic acid-based therapies, and the small molecule pitolisant, which joins the race toward market authorization with other repurposed drugs, including tideglusib, metformin, or mexiletine, already in clinical evaluation. Furthermore, newly disclosed promising preclinical data for several additional nucleic-acid therapeutic candidates and a CRISPR-based approach, as well as the advent into the pipeline of novel therapeutic programs, increase the plausibility of success in the demanding task of providing valid treatments to patients with DM1.

The current status of medical care for myotonic dystrophy type 1 in the national registry of Japan

INTRODUCTION/AIMS

Myotonic dystrophy (DM) is a systemic disease with multiple organ complications, making the standardization of medical care a challenge. We analyzed data from Japan's national registry to clarify the current treatment patterns and demographic features of Japanese DM patients.

METHODS

Using the Japanese National Registry of Muscular Dystrophy (Remudy), we analyzed medical care practice for the multisystemic issues associated with adult DM type 1 patients, excluding congenital DM.

RESULTS

We included 809 patients with a median age of 44.2 years. Among these patients, 15.8% used ventilators; 31.7% met the index considered at risk for sudden death due to cardiac conduction defects (PR interval over 240 milliseconds or QRS duration over 120 milliseconds) and 2.8% had implanted cardiac devices. Medication for heart failure was prescribed to 9.6% of patients. Overall, 21.2% of patients had abnormal glucose metabolism, of whom 42.9% were treated with oral medications. Among the oral medications, dipeptidyl peptidase-4 inhibitors were the most common. Cancers were observed in 3.7% of the patients, and endometrial and breast cancers were dominant. Mexiletine was prescribed for myotonia in 1.9% of the patients, and only 1% of the patients received medication for daytime sleepiness.

DISCUSSION

This study shows difference in treatment patterns for DM1 in Japan compared with other countries, such as lower rates of use of implantable cardiac devices and higher rates of ventilator use. These data may be useful in discussions aimed at standardizing medical care for patients with DM.

Introducing a Clinical Practice Guideline in Physiotherapy to Address Sexuality in Adults with a Neuromuscular Disorder

Purpose:

We present the development and the key elements of a clinical practice guideline (CPG) in physiotherapy aiming to address sexuality, more specifically impairments and limitations that can interfere with sexual activity in adults with a neuromuscular disorder (NMD).

Method:

The CPG was based on the Rare Knowledge Mining Methodological Framework (RKMMF) and included a literature review, consultation with physiotherapists, and validation by an interdisciplinary team. The EX-PLISSIT (extended, permission, limited information, specific suggestions, intensive therapy) model and the Competency Profile for physiotherapists in Canada were also used as frameworks to divide the CPG into sections. Here, we present the methodology for the CPG development and key elements related to physiotherapy assessment and treatment related to sexual activity in people with NMDs.

Results:

An extensive CPG was developed through a literature review, consultations, and a validation process. A total of 75 articles were included in the review. Twelve physiotherapists and four health professionals reviewed the CPG. Physiotherapists should address the following in their assessment: relationships; assistance required during sexual activity; urinary, vaginal, or anorectal symptoms; erectile dysfunction; pain; fatigue; and the impact of the NMD on sexuality. Interventions can target physical activity, positioning, muscle weakness, fatigue, decreased range of motion, erectile dysfunction, sensitivity disorders, lubrication, pain, incontinence, and cardiorespiratory implications.

Conclusions:

The CPG promotes the importance of addressing sexuality and proposes different interventions that physiotherapists should integrate into their practice.

Myotonic dystrophy type 1: A comparison between the adult- and late-onset subtype

INTRODUCTION/AIMS

Although the extent of muscle weakness and organ complications has not been well studied in patients with late-onset myotonic dystrophy type 1 (DM1), adult-onset DM1 is associated with severe muscle involvement and possible life-threatening cardiac and respiratory complications. In this study we aimed to compare the clinical phenotype of adult-onset vs late-onset DM1, focusing on the prevalence of cardiac, respiratory, and muscular involvement.

METHODS

Data were prospectively collected in the Dutch DM1 registry.

RESULTS

Two hundred seventy-five adult-onset and 66 late-onset DM1 patients were included. Conduction delay on electrocardiogram was present in 123 of 275 (45%) adult-onset patients, compared with 24 of 66 (36%) late-onset patients (P = .218). DM1 subtype did not predict presence of conduction delay (odds ratio [OR] 0.706; confidence interval [CI] 0.405 to 1.230, P = .219). Subtype did predict indication for noninvasive ventilation (NIV) (late onset vs adult onset: OR, 0.254; CI, 0.104 to 0.617; P = .002) and 17% of late-onset patients required NIV compared with 40% of adult-onset patients. Muscular Impairment Rating Scale (MIRS) scores were significantly different between subtypes (MIRS 1 to 3 in 66% of adult onset vs 100% of late onset [P < .001]), as were DM1-activ^C scores (67 ± 21 in adult onset vs 87 ± 15 in late onset; P < .001).

DISCUSSION

Although muscular phenotype was milder in late-onset compared with adult-onset DM1, the prevalence of conduction delay was comparable. Moreover, subtype was unable to predict the presence of cardiac conduction delay. Although adult-onset patients had an increased risk of having an NIV indication, 17% of late-onset patients required NIV. Despite different muscular phenotypes, screening for multiorgan involvement should be equally thorough in late-onset as in adult-onset DM1.

A retrospective study of needs and interventions among patients with myotonic dystrophy type 1 in Denmark referred to rehabilitation in the period 2000-2019

RATIONALE, AIMS AND OBJECTIVES: Myotonic dystrophy type 1 (DM1) is a progressive multisystem disorder that requires a special focus on the delivery of health and rehabilitation. The aim of the study was to identify the needs and interventions in patients with DM1 referred to a national rehabilitation hospital and to illustrate the needs and interventions in relation to predefined subgroups of disease classification.

METHOD

Electronic medical records from the period 2000-2019 of a randomized sample of patients with DM1 (N = 193) were reviewed to identify rehabilitation needs and interventions. The sample was classified into four subgroups of disease classifications. The number of identified needs and interventions were presented as medians and range, and differences between subgroups were illustrated by Kruskal-Wallis one-way analysis of variance. The needs were categorized using the International Classification of Functioning, Disability and Health (ICF).

RESULTS

A total of 2099 needs and 2103 interventions were registered. The most frequent needs were coordination of healthcare services (480) and employment and income (363), while the most frequent interventions were counselling (835) and follow-up (386). Patients with congenital DM1 had the most needs and interventions per person. In relation to the ICF, the most registered needs were environmental factors (880) and activity and participation (848).

CONCLUSION

All subgroups of patients with DM1 had a substantial number of needs and interventions related to coordinating and navigating within the healthcare system. The subgroup of patients with congenital DM1 had the most needs and interventions compared to the other subgroups.

Impact of restricted access to, and low awareness of, mexiletine on people with myotonia: a real-world European survey

Although mexiletine effectively treats myotonia, supply disruptions affected Europe between 2008-2018. MyoPath was a mixed-methods, cross-sectional, market research survey conducted January-June 2018 to evaluate consequences of limited access to/awareness of mexiletine in people with myotonia. Part A: qualitative structured interviews (clinicians; advocates for adult patients); Part B: quantitative online questionnaire completed by people with self-reported history of myotonia. Part A: Interviews (clinicians, n=12; patient advocates, n=5; 12 countries) indicated poor mexiletine awareness among general neurologists. Patients chose between living with myotonia (other treatments were generally unsatisfactory) or importing mexiletine. Part B: Questionnaire respondents, myotonic dystrophy (DM)1, n=213; DM2, n=128; non-dystrophic myotonia (NDM), n=41; other n=8; (11 countries). Of the respondents, 76/390 (20%) people with awareness of/access to mexiletine described profound improvements in myotonia and health-related quality of life following treatment. Respondents with NDM had greatest mexiletine experience (n=28/41). Mexiletine was associated with fewer falls, less muscle stiffness, increased mobility. Treatment interruptions worsened myotonia and were associated with fatigue, pain, dysphagia, breathing difficulty, impaired digestion, poor sleep. However, 36/54 (67%) of currently treated people expressed anxiety about mexiletine's availability: this finding was expected (MyoPath was undertaken before mexiletine's approval in NDM). MyoPath provides the largest European exploration of patients' views regarding impact of mexiletine on myotonia. Anticipated effects of mexiletine differ between people with different myotonic disorders: myotonia is the main symptom in NDM but one of many potential symptoms affecting those with DM. Nevertheless, findings indicate substantial harm caused to people with myotonia when mexiletine awareness/access is limited.

Energy Expenditure, Body Composition, and Skeletal Muscle Oxidative Capacity in Patients with Myotonic Dystrophy Type 1

BACKGROUND

Myotonic dystrophy type 1 (DM1) patients are at risk for metabolic abnormalities and commonly experience overweight and obesity. Possibly, weight issues result from lowered resting energy expenditure (EE) and impaired muscle oxidative metabolism.

OBJECTIVES

This study aims to assess EE, body composition, and muscle oxidative capacity in patients with DM1 compared to age-, sex- and BMI-matched controls.

METHODS

A prospective case control study was conducted including 15 DM1 patients and 15 matched controls. Participants underwent state-of-the-art methodologies including 24 h whole room calorimetry, doubly labeled water and accelerometer analysis under 15-days of free-living conditions, muscle biopsy, full body magnetic resonance imaging (MRI), dual-energy x-ray absorptiometry (DEXA), computed tomography (CT) upper leg, and cardiopulmonary exercise testing.

RESULTS

Fat ratio determined by full body MRI was significantly higher in DM1 patients (56 [49-62] %) compared to healthy controls (44 [37-52] % ; p = 0.027). Resting EE did not differ between groups (1948 [1742-2146] vs (2001 [1853-2425>] kcal/24 h, respectively; p = 0.466). In contrast, total EE was 23% lower in DM1 patients (2162 [1794-2494] vs 2814 [2424-3310] kcal/24 h; p = 0.027). Also, DM1 patients had 63% less steps (3090 [2263-5063] vs 8283 [6855-11485] steps/24 h; p = 0.003) and a significantly lower VO2 peak (22 [17-24] vs 33 [26-39] mL/min/kg; p = 0.003) compared to the healthy controls. Muscle biopsy citrate synthase activity did not differ between groups (15.4 [13.3-20.0] vs 20.1 [16.6-25.8] μM/g/min, respectively; p = 0.449).

CONCLUSIONS

Resting EE does not differ between DM1 patients and healthy, matched controls when assessed under standardized circumstances. However, under free living conditions, total EE is substantially reduced in DM1 patients due to a lower physical activity level. The sedentary lifestyle of DM1 patients seems responsible for the undesirable changes in body composition and aerobic capacity.

Prevalence of urinary incontinence and other pelvic floor disorders in women with myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a neuromuscular disease that can affect the pelvic floor muscles but few studies have investigated pelvic floor disorders, including urinary incontinence. The main purpose of this study was to document the prevalence, characteristics, and impacts of urinary incontinence and other pelvic floor disorders in women with DM1. Associations between pelvic floor disorders and phenotypes, considering age and parity, were explored. Eighty adult women aged 47,1±13,7 years old participated in a cross-sectional study using validated questionnaires, including the International Consultation Incontinence Questionnaire - Urinary Incontinence short form (ICIQ-UI-SF)), the Pelvic Floor Disorder Inventory (PFDI), and the Pelvic Floor Impact Questionnaire short form (PFIQ-SF). The mean score for the ICIQ-UI-SF was 4.3. The mean scores for the subscales of the PFDI were 36.8 for the urinary distress inventory, 74.1 for the colorectal-anal distress inventory, and 43.8 for the pelvic organ prolapse distress inventory. A total of 60% of women reported urinary incontinence and 56.3% anal incontinence. Pelvic prolapse symptoms (>1 symptom) were reported by 25% of women. Findings reveal high prevalence and significant related impacts of these disorders. This provides evidence regarding the importance of screening for these disorders in a clinical setting and the need to explore treatment approaches.

Emergencies cards for neuromuscular disorders 1st Consensus Meeting from UILDM - Italian Muscular Dystrophy Association Workshop report

Acute hospitalisation may be required to support patients with Neuromuscular disorders (NMDs) mainly experiencing respiratory complications, swallowing difficulties, heart failure, urgent surgical procedures. As NMDs may need specific treatments, they should be ideally managed in specialized hospitals. Nevertheless, if urgent treatment is required, patients with NMD should be managed at the closest hospital site, which may not be a specialized centre where local emergency physicians have the adequate experience to manage these patients. Although NMDs are a group of conditions that can differ in terms of disease onset, progression, severity and involvement of other systems, many recommendations are transversal and apply to the most frequent NMDs. Emergency Cards (EC), which report the most common recommendations on respiratory and cardiac issues and provide indications for drugs/treatments to be used with caution, are actively used in some countries by patients with NMDs. In Italy, there is no consensus on the use of any EC, and a minority of patients adopt it regularly in case of emergency. In April 2022, 50 participants from different centres in Italy met in Milan, Italy, to agree on a minimum set of recommendations for urgent care management which can be extended to the vast majority of NMDs. The aim of the workshop was to agree on the most relevant information and recommendations regarding the main topics related to emergency care of patients with NMD in order to produce specific ECs for the 13 most frequent NMDs.

Myotonic Dystrophy

PURPOSE OF REVIEW

Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) are genetic disorders affecting skeletal and smooth muscle, heart, brain, eyes, and other organs. The multisystem involvement and disease variability of myotonic dystrophy have presented challenges for clinical care and research. This article focuses on the diagnosis and management of the disease. In addition, recent advances in characterizing the diverse clinical manifestations and variability of the disease are discussed.

RECENT FINDINGS

Studies of the multisystem involvement of myotonic dystrophy, including the most lethal cardiac and respiratory manifestations and their molecular underpinnings, expand our understanding of the myotonic dystrophy phenotype. Advances have been made in understanding the molecular mechanisms of both types of myotonic dystrophy, providing opportunities for developing targeted therapeutics, some of which have entered clinical trials in DM1.

SUMMARY

Continued efforts focus on advancing our molecular and clinical understanding of DM1 and DM2. Accurately measuring and monitoring the diverse and variable clinical manifestations of myotonic dystrophy in clinic and in research is important to provide adequate care, prevent complications, and find treatments that improve symptoms and life quality.

Multiple Case Study of Changes in Participation of Adults with Myotonic Dystrophy Type 1: Importance of Redesigning Accomplishment and Resilience

Background: Myotonic dystrophy type 1 (DM1) is the most prevalent adult form of neuromuscular disorders, for which a decrease of participation with age is known. However, little is known about facilitators and barriers to participation, especially from the perspective of both patients and caregivers. Objective: This study explored and explained changes in participation post-diagnosis with myotonic dystrophy type 1 from the perspective of six adults, their relatives and nurse case managers. Methods: A multiple case study was carried out with these triads (n =  6) using semi-structured individual interviews, medical charts, and a participation patient-reported outcome measure. The six cases were built around three women and three men (age: 40–56 years; disease duration: 19–39 years). Their “relatives” were mainly family members. Nurse case managers had done annual follow-ups with all the adults for approximately ten years. Changes in participation were characterized generally by: 1) heterogeneity, 2) insidious increase in restrictions, and more specifically by: 3) redesigning accomplishment, 4) progressive social isolation, 5) restrictions in life-space mobility, and 6) increasingly sedentary activities. Results: Important facilitators of participation were the adult’s resilience, highly meaningful activities, social support, living arrangement, and willingness to use technical aids. Barriers were mostly related to symptoms and a precarious social network, and were affected by misfit and potential syndemic interactions between personal (e.g., comorbidities) and environmental (e.g., stigma) factors. Conclusion: This study identified key facilitators and barriers and their underlying processes, which should be integrated into the evaluation and intervention framework to optimize participation over time.

An evaluation of 24 h Holter monitoring in patients with myotonic dystrophy type 1

AIMS

To evaluate the clinical effectiveness of routine 24 h Holter monitoring to screen for conduction disturbances and arrhythmias in patients with myotonic dystrophy type 1 (DM1).

METHODS AND RESULTS

A retrospective two-centre study was conducted including DM1-affected individuals undergoing routine cardiac screening with at least one 24 h Holter monitoring between January 2010 and December 2020. For each individual, the following data were collected: Holter results, results of electrocardiograms (ECGs) performed at the same year as Holter monitoring, presence of cardiac complaints, and neuromuscular status. Holter findings were compared with the results of cardiac screening (ECG + history taking) performed at the same year. Cardiac conduction abnormalities and/or arrhythmias that would have remained undiagnosed based on history taking and ECG alone were considered de novo findings. A total 235 genetically confirmed DM1 patients were included. Abnormal Holter results were discovered in 126 (54%) patients after a mean follow-up of 64 ± 28 months in which an average of 3 ± 1 Holter recordings per patient was performed. Abnormalities upon Holter mainly consisted of conduction disorders (70%) such as atrioventricular (AV) block. Out of 126 patients with abnormal Holter findings, 74 (59%) patients had de novo Holter findings including second-degree AV block, atrial fibrillation/flutter and non-sustained ventricular tachycardia. Patient characteristics were unable to predict the occurrence of de novo Holter findings. In 39 out of 133 (29%) patients with normal ECGs upon yearly cardiac screening, abnormalities were found on Holter monitoring during follow-up.

CONCLUSION

Twenty-four hour Holter monitoring is of added value to routine cardiac screening for all DM1 patients.

Cognitive, neuropsychological and emotional-behavioural functioning in a sample of children with myotonic dystrophy type 1

AIM

An observational longitudinal study to evaluate the feasibility of assessing cognitive, neuropsychological and emotional-behavioural functioning in children with myotonic dystrophy type 1 (DM1), and to estimate prospectively changes in functioning over time.

METHOD

Ten DM1 patients, aged 1.5-16 years (mean 9.1), 5 with congenital DM1, and 5 with childhood DM1, were assessed with standardized measures of intellectual, neuropsychological, and emotional-behavioural functioning. For 6 patients, assessments were repeated 2 years later.

RESULTS

At baseline, intellectual disability was found both in the congenital and the childhood group. A clear-cut reduction of the mean and individual developmental/intelligence quotient after 2 years was demonstrated in re-tested patients. As regards to the neuropsychological aspects, the baseline evaluation identified impairments in visuospatial skills and attentional functions, with no clear trend observed after two years. In executive functions, no significant profile was identified even though impairments were detected in a few patients. At the emotional-behavioural assessment, scores in clinical range were found, but they remained heterogeneous and no trends could be recognized.

CONCLUSION

Several aspects of CNS functions in DM1 children deserve better definition and a longitudinal assessment. A comprehensive protocol should include cognitive, neuropsychological, emotional and behavioural assessment but larger longitudinal studies are needed to better evaluate the trajectories over time and inform practice.

Mapping the current evidence on the anesthetic management of adult patients with neuromuscular disorders-a scoping review

PURPOSE

Patients with neuromuscular disorders (NMDs) are at increased risk of perioperative complications. The objective of this scoping review was to examine emerging evidence from published studies, case reports, and review articles on anesthetic management of patients with NMDs, following the methodological frame for scoping reviews.

SOURCES

We searched PubMed and EMBASE for articles published between 1 January 2000 and 14 July 2021.

PRINCIPAL FINDINGS

Three prospective and 21 retrospective studies on altered pharmacokinetics and pharmacodynamics of neuromuscular blocking agents (NMBA) in NMD patients were included. Furthermore, 168 case reports/series reporting 212 anesthetics in 197 patients were included. These studies showed that preanesthetic neuromuscular monitoring can be used for precise NMBA dosing in myasthenia gravis patients. Sugammadex was associated with fewer postoperative myasthenic crises. Perioperative complications were not associated with specific anesthetic agents. Case reports/series showed that in 32% (67/212) of anesthetics, at least one complication was reported. Unexpected intensive care unit admission was a frequently reported complication. Patients with a complicated disease course may have had a higher use of succinylcholine (unadjusted relative risk, 0.13; 95% confidence interval [CI], 0.20 to 0.86) and volatile anesthetics (adjusted odds ratio [OR], 0.38; 95% CI, 0.20 to 0.73; P = 0.004).

CONCLUSION

Evidence on the anesthetic management and perioperative complications of patients with NMDs is mainly based on small retrospective studies and case reports. Further clinical trials or large retrospective studies are required to investigate the choice of safe anesthetic agents. Main areas of interest are the potential benefits of neuromuscular monitoring and sugammadex and the risks possibly associated with volatile anesthetics and succinylcholine.

Proof of concept of peptide-linked blockmiR-induced MBNL functional rescue in myotonic dystrophy type 1 mouse model

Myotonic dystrophy type 1 is a debilitating neuromuscular disease causing muscle weakness, myotonia, and cardiac dysfunction. The phenotypes are caused by muscleblind-like (MBNL) protein sequestration by toxic RNA in the DM1 protein kinase (DMPK) gene. DM1 patients exhibit a pathogenic number of repetitions in DMPK, which leads to downstream symptoms. Another disease characteristic is altered microRNA (miRNA) expression. It was previously shown that miR-23b regulates the translation of MBNL1 into protein. Antisense oligonucleotide (AON) treatment targeting this miRNA can improve disease symptoms. Here, we present a refinement of this strategy targeting a miR-23b binding site on the MBNL1 3' UTR in DM1 model cells and mice by using AONs called blockmiRs. BlockmiRs linked to novel cell-penetrating peptide chemistry showed an increase in MBNL1 protein in DM1 model cells and HSA^LR mice. They also showed an increase in muscle strength and significant rescue of downstream splicing and histological phenotypes in mice without disturbing the endogenous levels of other miR-23b target transcripts.

Healthcare resource utilization, total costs, and comorbidities among patients with myotonic dystrophy using U.S. insurance claims data from 2012 to 2019

Background

Myotonic dystrophy (DM) is a rare, inherited disorder with multi-systemic effects that impact the skeletal muscles, eyes, heart, skin and gastrointestinal, endocrine, respiratory, and central nervous systems. DM is divided into two subtypes: DM1 can present from early childhood through adulthood and also has a congenital form (cDM) while DM2 typically manifests during mid-adulthood. Both forms are progressive with no approved treatments, and unmet need for disease-modifying therapies remains high. This study interrogated health insurance claims data to explore the clinical experience, healthcare resource utilization (HCRU), and all-cause costs for DM.

Results

A total of 8541 patients with DM and 242 patients with cDM and their matched controls were selected from a database of over 200 million claimants. HCRU and all-cause costs, including pharmacy, outpatient, and inpatient services, were analyzed across four years in 12-month follow-up periods. Mean all-cause costs per DM patient were high in each of the four periods (range $14,640–$16,704) and showed a steady increase from 13 to 23 months on, while the control group mean costs declined from $9671 in the first 12 months after the index event, to approach the US population average ($5193) over time. For cDM, the highest mean costs were in the first 12-months ($66,496 vs. $2818 for controls), and remained high (above $17,944) across all subsequent periods, while control mean costs approached $0. For DM and cDM, HCRU was higher compared to controls across all study periods and all-cause healthcare costs were mostly driven by inpatient and outpatient encounters. Analysis of all diagnosis codes over the study period (comorbidities) demonstrated an elevated comorbidity profile consistent with the clinical profile of DM.

Conclusions

This study is among the first to utilize claims data to increase understanding of the clinical experience and health economic outcomes associated with DM. The markedly elevated HCRU patterns and comorbidity profile presented here add to the broad body of scientific and clinical knowledge on DM. These insights can inform clinical care and support the development of disease modifying and/or symptom-targeting therapies that address the multi-systemic, progressive nature of DM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02241-9.

Brief assessment of cognitive function in myotonic dystrophy: multicenter longitudinal study using computer-assisted evaluation

INTRODUCTION/AIMS

Myotonic dystrophy type 1 (DM1) is known to affect cognitive function, but the best methods to assess CNS involvement in multicenter studies have not been determined. This study's primary aim was to evaluate the potential of computerized cognitive tests to assess cognition in DM1.

METHODS

We conducted a prospective, longitudinal, observational study of 113 adults with DM1 at 6 sites. Psychomotor speed, attention, working memory, and executive functioning were assessed at baseline, 3-months and 12-months using computerized cognitive tests. Results were compared with assessments of muscle function and patient reported outcomes (PROs), including the Myotonic Dystrophy Health Index (MDHI) and EQ-5D-5L.

RESULTS

Based on intra-class correlation coefficients (ICCs), computerized cognitive tests had moderate to good reliability for psychomotor speed (0.76), attention (0.82), working memory speed (0.79), working memory accuracy (0.65), and executive functioning (0.87). Performance at baseline was lowest for working memory accuracy (p < 0.0001). Executive function performance improved from baseline to 3-months (p < 0.0001), without further changes over one year. There was a moderate correlation between poorer executive function and larger CTG repeat size (r = -0.433). There were some weak associations between PROs and cognitive performance.

DISCUSSION

Computerized tests of cognition are feasible in multicenter studies of DM1. Poor performance was exhibited in working memory, which may be a useful variable in clinical trials. Learning effects may have contributed to the improvement in executive functioning. The relationship between PROs and cognitive impairment in DM1 requires further study. This article is protected by copyright. All rights reserved.

Psychopharmacological Treatments for Mental Disorders in Patients with Neuromuscular Diseases: A Scoping Review

Mental disorders are observed in neuromuscular diseases, especially now that patients are living longer. Psychiatric symptoms may be severe and psychopharmacological treatments may be required. However, very little is known about pharmacotherapy in these conditions. We aimed to summarize the current knowledge on the use of psychopharmacological treatments for mental disorders in patients living with a neuromuscular disease. A scoping review was performed using the methodology of the Joanna Briggs Institute. Four databases were searched from January 2000 to July 2021. Articles were screened based on titles and abstracts. Full-text papers published in peer-reviewed journals in English were selected. Twenty-six articles met eligibility criteria, all being case reports/series focusing on the psychopharmacological control of psychiatric symptoms for the following conditions: myasthenia gravis (n = 11), Duchenne (n = 5) and Becker (n = 3) muscular dystrophy, mitochondrial disorders (n = 3), glycogen storage disease (n = 1), myotonic dystrophy (n = 1), hyperkalemic periodic paralysis (n = 1), and congenital myasthenic syndrome (n = 1). None of the articles provided details on the decision-making process to choose a specific drug/regimen or on follow-up strategies to monitor safety and efficacy. Larger studies showing real-world data would be required to guide consensus-based recommendations, thus improving current standards of care and, ultimately, the quality of life of patients and their families.

Deciphering the Complex Molecular Pathogenesis of Myotonic Dystrophy Type 1 through Omics Studies

Omics studies are crucial to improve our understanding of myotonic dystrophy type 1 (DM1), the most common muscular dystrophy in adults. Employing tissue samples and cell lines derived from patients and animal models, omics approaches have revealed the myriad alterations in gene and microRNA expression, alternative splicing, 3′ polyadenylation, CpG methylation, and proteins levels, among others, that contribute to this complex multisystem disease. In addition, omics characterization of drug candidate treatment experiments provides crucial insight into the degree of therapeutic rescue and off-target effects that can be achieved. Finally, several innovative technologies such as single-cell sequencing and artificial intelligence will have a significant impact on future DM1 research.

Rapid Determination of MBNL1 Protein Levels by Quantitative Dot Blot for the Evaluation of Antisense Oligonucleotides in Myotonic Dystrophy Myoblasts

Western blot assays are not adequate for high-throughput screening of protein expression because it is an expensive and time-consuming technique. Here we demonstrate that quantitative dot blots in plate format are a better option to determine the absolute contents of a given protein in less than 48 h. The method was optimized for the detection of the Muscleblind-like 1 protein in patient-derived myoblasts treated with a collection of more than 100 experimental oligonucleotides.

Aurintricarboxylic Acid Decreases RNA Toxicity in a C. elegans Model of Repeat Expansions

Pathologic expansions of DNA nucleotide tandem repeats may generate toxic RNA that triggers disease phenotypes. RNA toxicity is the hallmark of multiple expansion repeat disorders, including myotonic dystrophy type 1 (DM1). To date, there are no available disease-modifying therapies for DM1. Our aim was to use drug repositioning to ameliorate the phenotype of affected individuals in a nematode model of DM1. As the RNA interference pathway plays a key role in mediating RNA toxicity, we investigated the effect of aurintricarboxylic acid. We demonstrated that by perturbing the RNA interference machinery using aurintricarboxylic acid, we could annihilate the RNA toxicity and ameliorate the phenotype. As our approach targets a universal disease mechanism, it is potentially relevant for more expansion repeat disorders.

[Multidisciplinary care of patients with Myotonic Dystrophy type 1 (DM1) in South Aquitaine]

DM1 is characterized by a multisystemic involvement. Our objective was to determine the proportion of adequate follow-up for each affected organ in DM1 patients based on the recently published American and Spanish recommendations. To this end, we conducted a descriptive cross-sectional survey by phone in adult, genetically proven DM1 patients followed in the two French neuromuscular centers of Bayonne and Hendaye located in South Aquitaine, France. The questionnaire selected the most stringent criteria of the two international recommendations for each item of follow-up. Seventy-three patients were included, 55% of which were women (mean age of 48 years) with an average number of 467 CTG repeats. The proportion of patients receiving clinical follow-up in accordance with the recommendations was 90% in cardiology, 60% in neurology, 68% in ophthalmology, 53% in physiotherapy, 23% in pneumology, and 12% in rehabilitation. The high rate of neurological, cardiological, and ophthalmological monitoring might be explained by a locally dense medical demography whereas low rate of respiratory follow up and rehabilitation may reflect an incomplete knowledge of both the disease and the questionnaire. These results should be carefully interpretated as cognitive status may influence such a declarative study. Our study nevertheless disclosed important disparities according to the recommended multidisciplinary follow-up criteria in this French cohort of adult DM1 patients. These results highlight the major role of a multidisciplinary care and monitoring in DM1.

Preclinical characterization of antagomiR-218 as a potential treatment for myotonic dystrophy

Myotonic dystrophy type 1 (DM1) is a rare neuromuscular disease caused by expansion of unstable CTG repeats in a non-coding region of the DMPK gene. CUG expansions in mutant DMPK transcripts sequester MBNL1 proteins in ribonuclear foci. Depletion of this protein is a primary contributor to disease symptoms such as muscle weakness and atrophy and myotonia, yet upregulation of endogenous MBNL1 levels may compensate for this sequestration. Having previously demonstrated that antisense oligonucleotides against miR-218 boost MBNL1 expression and rescue phenotypes in disease models, here we provide preclinical characterization of an antagomiR-218 molecule using the HSA^LR mouse model and patient-derived myotubes. In HSA^LR, antagomiR-218 reached 40–60 pM 2 weeks after injection, rescued molecular and functional phenotypes in a dose- and time-dependent manner, and showed a good toxicity profile after a single subcutaneous administration. In muscle tissue, antagomiR rescued the normal subcellular distribution of Mbnl1 and did not alter the proportion of myonuclei containing CUG foci. In patient-derived cells, antagomiR-218 improved defective fusion and differentiation and rescued up to 34% of the gene expression alterations found in the transcriptome of patient cells. Importantly, miR-218 was found to be upregulated in DM1 muscle biopsies, pinpointing this microRNA (miRNA) as a relevant therapeutic target.

Congenital Myotonic Dystrophy with Combined Heterozygous ATP8B1/ABCB4 Mutation Leading to Progressive Cholestasis and Liver Failure

Myotonic dystrophy (MyoD) is an inherited genetic disorder caused by the expansion of a CTG trinucleotide repeat in the dystrophia myotonica protein kinase gene. It manifests as a multisystem disease affecting not only skeletal muscles, but also heart, lung, eye, gastrointestinal tract, central nervous system, and endocrine system. However, MyoD is rarely associated with a progressive liver disorder. We report a case of congenital MyoD with combined heterozygous ATP8B1/ABCB4 mutation who developed chronic, progressive low gamma-glutamyltransferase cholestatic liver disease at early infancy, and eventually underwent successful liver transplantation.

Immunosuppression and immunization: Vaccination in pediatric patients with neuromuscular diseases treated with steroids or immune-modulating drugs

BACKGROUND

Modulating the immune response has proven to be beneficial in different neurologic diseases, even in those not perceived thus far to be autoimmune.

METHODS

Extensive literature search has been done for available data on vaccine safety, efficacy and immunization recommendations in patients with neuromuscular disease in general and when receiving immune-modulating treatments.

RESULTS

Vaccinations have been associated with some neuromuscular diseases, but these occurrences are very rare and should not influence the general vaccination recommendations for the pediatric population and for the especially vulnerable patient populations, such as neuromuscular disease patients. Specific guidelines for the immunization of children with neuromuscular diseases in general and those on immune-suppressive treatments were not found, but most guidelines and standards of care for specific neuromuscular diseases recognize and stress the importance of vaccinations, some giving more specific instructions.

CONCLUSION

With just a few exceptions, vaccines are safe in this group of patients and they should receive the same immunizations and according to the same schedule, as all children. Live vaccines should not be administered in patients receiving high dose steroid or immune-modulating drugs such as anti-B cell treatments (rituximab), high dose methotrexate, azathioprine or 6-mercaptopurine. Whenever possible, all live vaccines should be administered prior to long term immune-suppressant treatments. Additional vaccines are recommended in this risk population of children (influenza, pneumococcal, varicella).

Outcome measures frequently used to assess muscle strength in patients with myotonic dystrophy type 1: a systematic review

Measurement of muscle strength is fundamental for the management of patients with myotonic dystrophy type 1 (DM1). Nevertheless, guidance on this topic is somewhat limited due to heterogeneous outcome measures used. This systematic literature review aimed to summarize the most frequent outcome measures to assess muscle strength in patients with DM1. We searched on Pubmed, Web of Science and Embase databases. Observational studies using measures of muscle strength assessment in adult patients with DM1 were included. From a total of 80 included studies, 24 measured cardiac, 45 skeletal and 23 respiratory muscle strength. The most common method and outcome measures used to assess cardiac muscle strength were echocardiography and ejection fraction, for skeletal muscle strength were quantitative muscle test, manual muscle test and maximum isometric torque and medical research council and for respiratory muscle strength were manometry and maximal inspiratory and expiratory pressure. We successfully gathered the more consensual methods and measures to evaluate muscle strength in future clinical studies, particularly to test muscle strength response to treatments in patients with DM1. Future consensus on a set of measures to evaluate muscle strength (core outcome set), is important for these patients.

Defined D-hexapeptides bind CUG repeats and rescue phenotypes of myotonic dystrophy myotubes in a Drosophila model of the disease

In Myotonic Dystrophy type 1 (DM1), a non-coding CTG repeats rare expansion disease; toxic double-stranded RNA hairpins sequester the RNA-binding proteins Muscleblind-like 1 and 2 (MBNL1 and 2) and trigger other DM1-related pathogenesis pathway defects. In this paper, we characterize four d-amino acid hexapeptides identified together with abp1, a peptide previously shown to stabilize CUG RNA in its single-stranded conformation. With the generalized sequence cpy(a/t)(q/w)e, these related peptides improved three MBNL-regulated exon inclusions in DM1-derived cells. Subsequent experiments showed that these compounds generally increased the relative expression of MBNL1 and its nuclear-cytoplasmic distribution, reduced hyperactivated autophagy, and increased the percentage of differentiated (Desmin-positive) cells in vitro. All peptides rescued atrophy of indirect flight muscles in a Drosophila model of the disease, and partially rescued muscle function according to climbing and flight tests. Investigation of their mechanism of action supports that all four compounds can bind to CUG repeats with slightly different association constant, but binding did not strongly influence the secondary structure of the toxic RNA in contrast to abp1. Finally, molecular modeling suggests a detailed view of the interactions of peptide-CUG RNA complexes useful in the chemical optimization of compounds.

Current Treatment Options for Patients with Myotonic Dystrophy Type 2

Purpose of the review

Myotonic dystrophy types 1 and 2 are frequent forms of muscular dystrophies in adulthood. Their clinical differences need to be taken into account for the most appropriate treatment of patients. The aim of this article is to provide an overview on the current and upcoming therapeutic options for patients with myotonic dystrophy type 2 (DM2).

Recent findings

At the moment, no disease-modifying therapies are available for DM2; next-generation therapies may however be available in the near future. In the meanwhile, the symptomatic management of patients has greatly improved, thank to the production of consensus-based standards of care and the growing evidence of efficacy of anti-myotonic drugs, promising employment of cannabinoids for symptom’s relief, regular monitoring, and early detection of treatable extra-muscular manifestations.

Summary

The treatment of DM2 is currently symptomatic and relies on the coordinated intervention of a multidisciplinary team. It remains to be determined whether upcoming causal therapies for myotonic dystrophy type 1 will be applicable also in DM2.

Perspectives on hiPSC-Derived Muscle Cells as Drug Discovery Models for Muscular Dystrophies

Muscular dystrophies are a heterogeneous group of inherited diseases characterized by the progressive degeneration and weakness of skeletal muscles, leading to disability and, often, premature death. To date, no effective therapies are available to halt or reverse the pathogenic process, and meaningful treatments are urgently needed. From this perspective, it is particularly important to establish reliable in vitro models of human muscle that allow the recapitulation of disease features as well as the screening of genetic and pharmacological therapies. We herein review and discuss advances in the development of in vitro muscle models obtained from human induced pluripotent stem cells, which appear to be capable of reproducing the lack of myofiber proteins as well as other specific pathological hallmarks, such as inflammation, fibrosis, and reduced muscle regenerative potential. In addition, these platforms have been used to assess genetic correction strategies such as gene silencing, gene transfer and genome editing with clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), as well as to evaluate novel small molecules aimed at ameliorating muscle degeneration. Furthermore, we discuss the challenges related to in vitro drug testing and provide a critical view of potential therapeutic developments to foster the future clinical translation of preclinical muscular dystrophy studies.

Multifocal Noninvasive Magnetic Stimulation of the Primary Motor Cortex in Type 1 Myotonic Dystrophy -A Proof of Concept Pilot Study

BACKGROUND

Repeated neuromuscular electrical stimulation in type 1 Myotonic Dystrophy (DM1) has previously been shown to cause an increase in strength and a decrease in hyperexcitability of the tibialis anterior muscle.

OBJECTIVE

In this proof-of-principle study our objective was to test the hypothesis that noninvasive repetitive transcranial magnetic stimulation of the primary motor cortex (M1) with a new portable wearable multifocal stimulator causes improvement in muscle function in DM1 patients.

METHODS

We performed repetitive stimulation of M1, localized by magnetic resonance imaging, with a newly developed Transcranial Rotating Permanent Magnet Stimulator (TRPMS). Using a randomized within-patient placebo-controlled double-blind TRPMS protocol, we performed unilateral active stimulation along with contralateral sham stimulation every weekday for two weeks in 6 adults. Methods for evaluation of muscle function involved electromyography (EMG), hand dynamometry and clinical assessment using the Medical Research Council scale.

RESULTS

All participants tolerated the treatment well. While there were no significant changes clinically, EMG showed significant improvement in nerve stimulus-evoked compound muscle action potential amplitude of the first dorsal interosseous muscle and a similar but non-significant trend in the trapezius muscle, after a short exercise test, with active but not sham stimulation.

CONCLUSIONS

We conclude that two-week repeated multifocal cortical stimulation with a new wearable transcranial magnetic stimulator can be safely conducted in DM1 patients to investigate potential improvement of muscle strength and activity. The results obtained, if confirmed and extended by future safety and efficacy trials with larger patient samples, could offer a potential supportive TRPMS treatment in DM1.

Guidelines for genetic testing of muscle and neuromuscular junction disorders

Despite recent advances in the understanding of inherited muscle and neuromuscular junction diseases, as well as the advent of a wide range of genetic tests, patients continue to face delays in diagnosis of sometimes treatable disorders. These guidelines outline an approach to genetic testing in such disorders. Initially, a patient's phenotype is evaluated to identify myopathies requiring directed testing, including myotonic dystrophies, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, mitochondrial myopathies, dystrophinopathies, and oculopharyngodistal myopathy. Initial investigation in the remaining patients is generally a comprehensive gene panel by next-generation sequencing. Broad panels have a higher diagnostic yield and can be cost-effective. Due to extensive phenotypic overlap and treatment implications, genes responsible for congenital myasthenic syndromes should be included when evaluating myopathy patients. For patients whose initial genetic testing is negative or inconclusive, phenotypic re-evaluation is warranted, along with consideration of genes and variants not included initially, as well as their acquired mimickers.