Falls and resulting fractures in Myotonic Dystrophy: Results from a multinational retrospective survey

Awareness of bone strength in patients with neuromuscular disorders: ERN EURO-NMD clinician survey and European patient survey

Bone strength is reduced In various neuromuscular disorders (NMDs). We aimed to assess the awareness and practice of bone strength management in NDMs among clinicians and patients. We performed two online surveys; among health care providers (HCPs) of the European Reference Network for Neuromuscular Disorders (ERN EURO-NMD) and among patients. The survey among 52 HCPs showed that awareness of potentially impaired bone strength in people with NMDs was reasonable to good: the vast majority of HCPs asked often or almost always about bone fractures during history-taking (81 %). Bone strength was less often assessed: often or almost always at diagnosis (50 %) and at follow-up (58 %). Medical training on this topic was considered poor to very poor in 50 % of HCPs. Prevention and treatment of reduced bone strength was variable and multidisciplinary care was sub-optimal. The survey among 581 patients provided important additional insights. Many patients were followed-up outside ERN EURO-NMD centers and treatment was variable. These parallel surveys provided a broad view on the awareness and management of bone strength in people with NMDs. The findings are expected to increase the appreciation of this important aspect of NMD care, and direct future research foci and care guidelines.

Multiorgan Involvement and Mortality in Individuals With Adult-Onset Myotonic Dystrophy (DM1)-A Danish Register-Based Study I

BACKGROUND AND PURPOSE

Adult-onset myotonic dystrophy type 1 (DM1) is characterized by a diagnostic delay due to milder symptoms than the infantile and juvenile forms. Despite this, there is a risk of negative biopsychosocial consequences, particularly due to the cognitive impact. Individuals with adult-onset DM1 may receive less attention and have lower adherence to hospital follow-ups, which increases the risk of adverse events and early death. The aim of this study was to provide knowledge on the time of diagnosis, multiorgan involvement, and mortality in a national cohort of individuals with adult-onset DM1.

METHODS

Data from individuals with DM1 were extracted from the Danish National Health and administrative registers in the period 1994-2022; each individual with DM1 was paired with 10 reference individuals from the general Danish population.

RESULTS

Analyses were based on 949 individuals with DM1 and 9427 controls. The median age at diagnosis was 43 years; 40% of individuals had a parent-child relationship. Respiratory insufficiency and cataracts were the most common involvements among individuals with DM1. The average age at death was 58 years; risk of mortality was 5.87 times higher than controls (p < 0.001) and individuals with DM1 and cardiovascular disease had a higher mortality rate compared to controls (HR: 2.63, CI: 2.14-3.23, p < 0.001). The risk of mortality tended to decline in the later years of the study period.

CONCLUSION

Despite adult-onset DM1 often being characterized as mild, comorbidities and an excess risk of death are major concerns. This calls for attention from health professionals to improve rehabilitation and survival for this population.

Fractures in Hereditary Neuromuscular Disorders: Frequency, Risk Factors, and Implications

BACKGROUND

Hereditary neuromuscular disorders (NMD) are associated with compromised bone health and elevated fracture risk, though data are largely lacking.

OBJECTIVE

This study aimed to assess the prevalence and risk factors of fractures in hereditary NMD.

METHODS

We conducted a retrospective study in a cohort of adult patients with diverse hereditary NMD, using data from electronic medical records.

RESULTS

Among 469 patients, 505 fractures were recorded, with 5.5% of patients experiencing a fracture within the past year. In the 10 years preceding study inclusion, 31.1% of all patients sustained at least one fracture. The fracture rate was 47.3/1000 patient-years. Fracture incidence was highest in the second decade of life and the first five years after symptom onset. Fracture recurrence occurred in 25.6% over the next two years. Fractures were most prevalent in patients with Duchenne muscular dystrophy, myotonic dystrophy type 1/2, and spinal muscular atrophy. Patients with Vignos scale 5-6 had the highest fracture risk. Major osteoporotic fractures accounted for 28.6%, and 71.3% were caused by low-energy trauma. Long-term complications of a fracture were present in 44.2%, with 9.0% losing ambulation. Osteoporosis was confirmed in 47.5% of DXA scans. In patients with a normal DXA scan, 66.7% experienced a subsequent fracture. Hip T-scores declined with increasing Vignos scale (r = -0.27, p = 0.001). Fracture risk factors included glucocorticoid use, alcohol abuse, recent falls, and previous emergency visits for falls (all p < 0.05).

CONCLUSION

This cohort exhibited a high prevalence of fractures and osteoporosis, emphasizing the need for regular bone health assessment and fracture prevention in hereditary NMD patients.

274th ENMC international workshop: recommendations for optimizing bone strength in neuromuscular disorders. Hoofddorp, The Netherlands, 19-21 January 2024

The 274th ENMC workshop for optimizing bone strength in neuromuscular disorders (NMDs) was held on January 19-21, 2024. The group of participants included experts in the fields of bone health and neuromuscular medicine along with the patient voice. Bone strength represents a crucial aspect of the management of pediatric and adult patients with NMDs. Bone strength may be compromised due to different pathophysiologic mechanisms, including disrupted bone-muscle "cross-talk", loss of biomechanical loading, nutritional insufficiency, inadequate weight-bearing physical activity, muscle weakness and/or immobility, and drug treatment. While for Duchenne muscular dystrophy recommendations for evaluation and treatment of bone strength have been published, evidence on bone strength in other hereditary and acquired NMDs is scarce. Enhanced knowledge is needed to understand the development and maintenance of bone strength in patients with NMDs. This workshop aimed to develop a strategy to improve bone strength and thus prevent fractures in patients with NMDs.

Common Characteristics Between Frailty and Myotonic Dystrophy Type 1: A Narrative Review

Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disorder often considered a model of accelerated aging due to the early appearance of certain age-related clinical manifestations and cellular and molecular aging markers. Frailty, a state of vulnerability related to aging, has been recently studied in neurological conditions but has received considerably less attention in neuromuscular disorders. This narrative review aims to describe 1) the common characteristics between Fried's frailty phenotype criteria (muscular weakness, slow gait speed, weight loss, exhaustion/fatigue, and low physical activity) and DM1, and 2) the psychological and social factors potentially contributing to frailty in DM1. This review gathered evidence suggesting that DM1 patients meet four of the five frailty phenotype criteria. Additionally, longitudinal studies report the deterioration of these criteria over time in DM1. Patients also exhibit psychological/cognitive and social factors that might contribute to frailty. Monitoring frailty criteria in the DM1 population could help to implement timely preventions and interventions to reduce the disease burden and severity of frailty symptoms.

Prevalence of co-morbidity and history of recent infection in patients with neuromuscular disease: A cross-sectional analysis of United Kingdom primary care data

BACKGROUND

People with neuromuscular disease (NMD) experience a broader range of chronic diseases and health symptoms compared to the general population. However, no comprehensive analysis has directly quantified this to our knowledge.

METHODS

We used a large UK primary care database (Clinical Practice Research Datalink) to compare the prevalence of chronic diseases and other health conditions, including recent infections between 23,876 patients with NMD ever recorded by 2019 compared to 95,295 age-sex-practice matched patients without NMD. Modified Poisson regression estimated Prevalence Ratios (PR) to summarise the presence of the disease/condition ever (or for infections in 2018) in NMD patients versus non-NMD patients.

RESULTS

Patients with NMD had significantly higher rates for 16 of the 18 conditions routinely recorded in the primary care Quality and Outcomes Framework (QOF). Approximately 1-in-10 adults with NMD had ≥4 conditions recorded (PR = 1.39, 95%CI 1.33-1.45). Disparities were more pronounced at younger ages (18-49). For other (non-QOF) health conditions, significantly higher recorded levels were observed for rarer events (pulmonary embolism PR = 1.96 95%CI 1.76-2.18, hip fractures PR = 1.65 95%CI 1.47-1.85) as well as for more common primary care conditions (constipation PR = 1.52 95%CI 1.46-1.57, incontinence PR = 1.52 95%CI 1.44-1.60). The greatest co-morbidity burden was in patients with a myotonic disorder. Approximately 1-in-6 (17.1%) NMD patients had an infection recorded in the preceding year, with the risk of being hospitalised with an infection nearly double (PR = 1.92, 95%CI 1.79-2.07) compared to non-NMD patients.

CONCLUSION

The burden of chronic co-morbidity among patients with NMD is extremely high compared to the general population, and they are also more likely to present in primary and secondary care for acute events such as infections.

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.

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.

Endocrine Dysfunction in Patients With Myotonic Dystrophy

Myotonic dystrophy is a dominantly inherited multisystem disorder that results from increased CTG repeats in the 3' region of the myotonic dystrophy protein kinase gene (DMPK). The mutant DMPK mRNA remains in the nucleus and sequesters RNA-binding proteins, including regulators of mRNA splicing. Myotonic dystrophy is characterized by a highly variable phenotype that includes muscle weakness and myotonia, and the disorder may affect the function of many endocrine glands. DMPK mRNA is expressed in muscle, testis, liver, pituitary, thyroid, and bone; the mutated form leads to disruption of meiosis and an increase in fetal insulin receptor-A relative to adult insulin receptor-B, resulting in adult primary testicular failure and insulin resistance predisposing to diabetes, respectively. Patients with myotonic dystrophy are also at increased risk for hyperlipidemia, nonalcoholic fatty liver disease, erectile dysfunction, benign and malignant thyroid nodules, bone fractures, miscarriage, preterm delivery, and failed labor during delivery. Circulating parathyroid hormone and adrenocorticotropic hormone levels may be elevated, but the mechanisms for these associations are unclear. This review summarizes what is known about endocrine dysfunction in individuals with myotonic dystrophy.

What Happened with Muscle Force, Dynamic Stability And Falls? A 10-Year Longitudinal Follow-Up in Adults with Myotonic Dystrophy Type 1

BACKGROUND

Individuals with myotonic dystrophy type 1 (DM1) are known to stumble and fall, but knowledge is scarce regarding dynamic stability in this disorder.

OBJECTIVE

To describe disease progress regarding muscle force, dynamic stability and patient reported unintentional falls during a ten-year period, in individuals with DM1.

METHODS

Quantification of isometric muscle force in four leg muscle groups and assessment of Timed 10-meter-walk in maximum speed (T10max), Timed Up&Go (TUG) and Step test (STEP) were performed at three occasions in a DM1 cohort, together with self-reported falls.

RESULTS

Thirty-four people (m/f:11/23, age:50.2 + /-9.4) participated. The muscle force loss after ten years was large in the distal ankle muscles. A steeper force decrease was seen in most muscles between year five and ten compared to the former five-year period. Males reported more falls than females, 91%vs 35%had fallen last year. A positive correlation, ρ= 0.633, p < 0.001, was shown between walking time (T10max) and number of falls. Frequent fallers were only seen among those with slower walk (T10max > 10seconds), and fewer steps in the STEP test (STEP≤5 steps).

CONCLUSIONS

A diminishing leg muscle strength and worse dynamic stability were seen in the group, with a steeper decrease in the latter five years. Weak ankle dorsiflexors, a slower walk and difficulties to lift the forefoot were related to frequent falls.

[Adult myotonic dystrophy type 1: an update]

Myotonic dystrophy type 1 (DM1) or Steinert's disease (CIE-9-C: 359.21; CIE-10-ES: G71.11, ORPHA: 273) is a rare autosomal dominant inherited myopathy with almost complete penetrance and multisystemic consequences (neurological, cardiological, respiratory, endocrinological, and gastrointestinal). It is one of the clinical most variable diseases. The most bothersome symptoms for the patients (mobility problems, fatigue, hypersomnia, or gastrointestinal symptoms) and their families (apathy, lack of initiative) are not necessarily the most dangerous. Respiratory problems and cardiac arrhythmias shorten life expectancy. There is no specific treatment. The role of the Primary Care physician is crucial in the follow-up of DM1, either by coordinating the different professionals or detecting treatable complications. This work addresses the latter.

Validity of the Mini-BESTest in adults with myotonic dystrophy type 1

INTRODUCTION

Myotonic dystrophy type 1 (DM1) is a multisystemic neuromuscular disease that causes balance problems. The objective of this study was to assess the construct validity of the Mini-BESTest among adults with DM1.

METHODS

Fifty-nine individuals with late-onset or adult phenotypes of DM1 were recruited. Participants performed the Mini-BESTest, 10-Meter Walk Test (10mWT), 6-Minute Walk Test (6MWT), and Timed Up & Go (TUG) and were questioned on their tendency to lose balance and whether they fell in the past month.

RESULTS

Scores on the Mini-BESTest were significantly different between phenotypes and CTG repeat numbers (P < .02). Significant correlations were found with the 10mWT, 6MWT, and the TUG (r = 0.77-0.84; P < .001). A cutoff score of 21.5 was found to identify fallers with 90% posttest accuracy.

DISCUSSION

The Mini-BESTest demonstrates evidence of construct validity when assessing balance in the DM1 population.

DM1 Phenotype Variability and Triplet Repeat Instability: Challenges in the Development of New Therapies

Myotonic dystrophy type 1 (DM1) is a complex neuromuscular disease caused by an unstable cytosine thymine guanine (CTG) repeat expansion in the DMPK gene. This disease is characterized by high clinical and genetic variability, leading to some difficulties in the diagnosis and prognosis of DM1. Better understanding the origin of this variability is important for developing new challenging therapies and, in particular, for progressing on the path of personalized treatments. Here, we reviewed CTG triplet repeat instability and its modifiers as an important source of phenotypic variability in patients with DM1.

Fragility fractures and bone mineral density in male patients affected by type 1 and type 2 myotonic dystrophy

Myotonic dystrophy is a multisystemic disorder affecting skeletal muscle. Male patients have an increased risk of fractures and develop a number of endocrine/metabolic impairments known to adversely affect bone health. The aim of this study was primarily to determine the occurrence of fragility fractures and the bone mineralization status (lumbar spine, hip and total body by dual X-ray absorptiometry) in 36 male patients affected with type 1 myotonic dystrophy and 13 male patients affected with type 2 myotonic dystrophy. Fragility fractures occurred in 15 type 1 and 7 type 2 myotonic dystrophy in non-classical osteoporotic sites, such as metatarses. Hip osteopenia was the most frequent finding, particularly in type 2 (n = 6) than type 1 myotonic dystrophy patients (n = 1), while osteoporosis was rare. Patients with type 1 myotonic dystrophy presented higher total body bone mass density than patients with type 2 myotonic dystrophy and healthy controls and lumbar spine was associated positively with the severity of the disease. Gonadic failure, with low testosterone and reduced INSL3 levels, visceral adiposity and insulin resistance correlated with reduced body mass index in both type 1 and type 2 myotonic dystrophic patients. The independent determinant of fragility fractures were low total body mass index, low blood testosterone and low global muscle mass.

High incidence of falls in patients with myotonic dystrophy type 1 and 2: A prospective study

We aimed to examine the incidence as well as the circumstances and the consequences of falling in adult patients with myotonic dystrophy type 1 and 2 (DM1/DM2). We performed a prospective cohort study in 209 subjects, of which 102 had DM1, 42 had DM2 and 65 healthy controls. An assessment of their falls was carried out during 100 consecutive days. In addition, falls during the previous year were reported. The primary outcome measure was the number of self-reported falls per participant during these 100 days. The secondary outcome measures included self-reported causes, circumstances and consequences of the falls. Mean (SD) falls per participant in 100 days was seven- to eightfold higher in patients with DM1 (0.74 (0.14)) and DM2 (0.62 (0.20)) compared to the controls (0.09 (0.04); p < 0.001)). Sixteen percent of DM1 and 17% of DM2 patients fell at least twice. Two-thirds of the falls occurred inside. Fifty percent of falls resulted in an injury, including a head trauma in four patients. Compared to non-fallers, those patients who fell were older (DM1/DM2), had a lower DM1-Activ score (DM1), had more muscle weakness (DM1), and reported less confidence in balance (DM1). This study demonstrates a high incidence and clinical relevance of falling in patients with DM1 and DM2. Fall prevention strategies in both DM1 and DM2 should focus on adaptations of the home environment and the patient's interaction in this environment.

Repeat-associated RNA structure and aberrant splicing

Over 30 hereditary disorders attributed to the expansion of microsatellite repeats have been identified. Despite variant nucleotide content, number of consecutive repeats, and different locations in the genome, many of these diseases have pathogenic RNA gain-of-function mechanisms. The repeat-containing RNAs can form structures in vitro predicted to contribute to the disease through assembly of intracellular RNA aggregates termed foci. The expanded repeat RNAs within these foci sequester RNA binding proteins (RBPs) with important roles in the regulation of RNA metabolism, most notably alternative splicing (AS). These deleterious interactions lead to downstream alterations in transcriptome-wide AS directly linked with disease symptoms. This review summarizes existing knowledge about the association between the repeat RNA structures and RBPs as well as the resulting aberrant AS patterns, specifically in the context of myotonic dystrophy. The connection between toxic, structured RNAs and dysregulation of AS in other repeat expansion diseases is also discussed. This article is part of a Special Issue entitled: RNA structure and splicing regulation edited by Francisco Baralle, Ravindra Singh and Stefan Stamm.

Eight years after an international workshop on myotonic dystrophy patient registries: case study of a global collaboration for a rare disease

BACKGROUND

Myotonic Dystrophy is the most common form of muscular dystrophy in adults, affecting an estimated 10 per 100,000 people. It is a multisystemic disorder affecting multiple generations with increasing severity. There are currently no licenced therapies to reverse, slow down or cure its symptoms. In 2009 TREAT-NMD (a global alliance with the mission of improving trial readiness for neuromuscular diseases) and the Marigold Foundation held a workshop of key opinion leaders to agree a minimal dataset for patient registries in myotonic dystrophy. Eight years after this workshop, we surveyed 22 registries collecting information on myotonic dystrophy patients to assess the proliferation and utility the dataset agreed in 2009. These registries represent over 10,000 myotonic dystrophy patients worldwide (Europe, North America, Asia and Oceania).

RESULTS

The registries use a variety of data collection methods (e.g. online patient surveys or clinician led) and have a variety of budgets (from being run by volunteers to annual budgets over €200,000). All registries collect at least some of the originally agreed data items, and a number of additional items have been suggested in particular items on cognitive impact.

CONCLUSIONS

The community should consider how to maximise this collective resource in future therapeutic programmes.

Core Clinical Phenotypes in Myotonic Dystrophies

Myotonic dystrophy type 1 (DM1) and type 2 (DM2) represent the most frequent multisystemic muscular dystrophies in adulthood. They are progressive, autosomal dominant diseases caused by an abnormal expansion of an unstable nucleotide repeat located in the non-coding region of their respective genes DMPK for DM1 and CNBP in DM2. Clinically, these multisystemic disorders are characterized by a high variability of muscular and extramuscular symptoms, often causing a delay in diagnosis. For both subtypes, many symptoms overlap, but some differences allow their clinical distinction. This article highlights the clinical core features of myotonic dystrophies, thus facilitating their early recognition and diagnosis. Particular attention will be given to signs and symptoms of muscular involvement, to issues related to respiratory impairment, and to the multiorgan involvement. This article is part of a Special Issue entitled “Beyond Borders: Myotonic Dystrophies—A European Perception.”