Life Expectancy and Causes of Death in Patients with Myotonic Dystrophy Type 2.

Background: Myotonic Dystrophy type 2 (DM2) is a dominantly inherited multisystem disease caused by a CCTG repeat expansion in intron 1 of the CNBP gene. Although in the last two decades over 1500 patients with DM2 have been diagnosed worldwide, our clinical impression of a reduced life expectancy in DM2 has not been investigated previously. Objective: The aim of this observational study was to determine the life expectancy and the causes of death in patients with genetically confirmed DM2. Methods: We identified the data of all deceased patients with DM2 in the Dutch neuromuscular database between 2000 and 2023. Ages and causes of death and the patients' clinical features during lifetime were determined. Age of death in DM2 was compared to the general population by using life tables with prognostic cohort life expectancy (CLE) and period life expectancy (PLE) data of the Dutch electronic database of statistics (CBS StatLine). Results: Twenty-six deceased patients were identified in the Dutch DM2 cohort (n = 125). Median age of death in DM2 (70.9 years) was significantly lower compared to sex- and age-matched CLE (78.1 years) and PLE (82.1 years) in the Netherlands. Main causes of death were cardiac diseases (31%) and pneumonia (27%). Seven patients (27%) had a malignancy at the time of death. Conclusion: These results provide new insights into the phenotype of DM2. Life expectancy in patients with DM2 is reduced, possibly attributable to multiple causes including increased risk of cardiac disease, pneumonia, and malignancies. The occurrence of a significantly reduced life expectancy has implications for clinical practice and may form a basis for advanced care planning, including end-of-life care, to optimize quality of life for patients with DM2 and their family. Research in larger cohorts should be done to confirm these findings and to ascertain more about the natural course in DM2.

A Likely Pathogenic variant in the KBTBD13 Gene: A Case Series of Three Patients with Nemaline Myopathy Type 6.

Background: Nemaline myopathy type 6 (NEM6) or KBTBD13-related congenital myopathy is the most prevalent type of nemaline myopathy in the Netherlands and is characterised by mild childhood-onset axial, proximal and distal muscle weakness with prominent neck flexor weakness combined with slowness of movements. The most prevalent variant in the Netherlands is the c.1222C > T p.(Arg408Cys) variant in the KBTBD13 gene, also called the Dutch founder variant. Objective: To provide a comprehensive clinical and functional characterisation of three patients to assess the pathogenicity of a newly identified variant in the KBTBD13 gene. Results: We present three cases (Patient 1: female, 76 years old; Patient 2: male, 63 years old; and his brother Patient 3: male, 61 years old) with a c.1222C > A p.(Arg408Ser) variant in the KBTBD13 gene. Patient 1 was also included previously in a histopathological study on NEM6. Symptoms of muscle weakness started in childhood and progressed to impaired functional abilities in adulthood. All three patients reported slowness of movements. On examination, they have mild axial, proximal and distal muscle weakness. None of the patients exhibited cardiac abnormalities. Spirometry in two patients showed a restrictive lung pattern. Muscle ultrasound showed symmetrically increased echogenicity indicating fatty replacement and fibrosis in a subset of muscles and histopathological analyses revealed nemaline rods and cores. Slower muscle relaxation kinetics with in vivo functional tests was observed. This was confirmed by in vitro functional tests showing impaired relaxation kinetics in isolated muscle fibres. We found a genealogic link between patient 1, and patient 2 and 3 nine generations earlier. Conclusions: The c.1222C > A p.(Arg408Ser) variant in the KBTBD13 gene is a likely pathogenic variant causing NEM6.

Ameliorated cellular hallmarks of myotonic dystrophy in hybrid myotubes from patient and unaffected donor cells.

BACKGROUND: Cell-based strategies are being explored as a therapeutic option for muscular dystrophies, using a variety of cell types from different origin and with different characteristics. Primary pericytes are multifunctional cells found in the capillary bed that exhibit stem cell-like and myogenic regenerative properties. This unique combination allows them to be applied systemically, presenting a promising opportunity for body-wide muscle regeneration. We previously reported the successful isolation of ALP+ pericytes from skeletal muscle of patients with myotonic dystrophy type 1 (DM1). These pericytes maintained normal growth parameters and myogenic characteristics in vitro despite the presence of nuclear (CUG)n RNA foci, the cellular hallmark of DM1. Here, we examined the behaviour of DM1 pericytes during myogenic differentiation. METHODS: DMPK (CTG)n repeat lengths in patient pericytes were assessed using small pool PCR, to be able to relate variation in myogenic properties and disease hallmarks to repeat expansion. Pericytes from unaffected controls and DM1 patients were cultured under differentiating conditions in vitro. In addition, the pericytes were grown in co-cultures with myoblasts to examine their regenerative capacity by forming hybrid myotubes. Finally, the effect of pericyte fusion on DM1 disease hallmarks was investigated. RESULTS: Small pool PCR analysis revealed the presence of somatic mosaicism in pericyte cell pools. Upon differentiation to myotubes, DMPK expression was upregulated, leading to an increase in nuclear foci sequestering MBNL1 protein. Remarkably, despite the manifestation of these disease biomarkers, patient-derived pericytes demonstrated myogenic potential in co-culture experiments comparable to unaffected pericytes and myoblasts. However, only the unaffected pericytes improved the disease hallmarks in hybrid myotubes. From 20% onwards, the fraction of unaffected nuclei in myotubes positively correlated with a reduction of the number of RNA foci and an increase in the amount of free MBNL1. CONCLUSIONS: Fusion of only a limited number of unaffected myogenic precursors to DM1 myotubes already ameliorates cellular disease hallmarks, offering promise for the development of cell transplantation strategies to lower disease burden.

Population-based incidence rates of 15 neuromuscular disorders: a nationwide capture-recapture study in the Netherlands.

Most neuromuscular disorders are rare, but as a group they are not. Nevertheless, epidemiological data of specific neuromuscular disorders are scarce, especially on the incidence. We applied a capture-recapture approach to a nationwide hospital-based dataset and a patients association-based dataset to estimate the annual incidence rates for fifteen neuromuscular disorders in the Netherlands. The annual incidence rates per 100,000 population varied from 0.03/100,000 (95% CI 0.00 ‒ 0.06) for glycogenosis type 5 to 0.9/100,000 (95% confidence interval 0.7 ‒ 1.0) for myotonic dystrophy type 1. The summed annual incidence rate of these disorders was 4.1 per 100,000 per population. Nine of the provided incidence rates were previously unavailable, three rates were similar to the rates in the literature, and three rates were generally higher compared to previous findings but with overlapping confidence intervals. This study provides nationwide incidence rates for fifteen neuromuscular disorders predominantly diagnosed in adult life, nine which were previously unavailable. The capture-recapture approach provided estimates of the total number of individuals with neuromuscular disorders. To complete the gaps in the knowledge of disease frequencies, there is a need for estimates from an automated, obligatory data collection system of diagnosed and newly diagnosed patients with neuromuscular disorders.

Cardiac Involvement in LAMA2-Related Muscular Dystrophy and SELENON-Related Congenital Myopathy: A Case Series.

Background: LAMA2-related muscular dystrophy (LAMA2-MD) and SELENON-related myopathy (SELENON-RM) are two rare neuromuscular diseases characterized by proximal and axial muscle weakness, scoliosis, spinal rigidity, low bone quality and respiratory impairment. Cardiac involvement has previously been described in retrospective studies and case reports, but large case series and prospective studies in unselected cohorts are lacking. Objective: The objective of this study is to conduct prevalence estimations, perform cardiac phenotyping, and provide recommendations for clinical care. Methods: In this case series including two time points, we conducted comprehensive assessments with electrocardiography (ECG) and transthoracic echocardiography (TTE). ECGs were systematically assessed for a large subset of variables. TTE included left and right ventricular ejection fraction (LVEF/RVEF) and left ventricular global longitudinal strain (GLS), the latter being a more early and sensitive marker of left ventricular dysfunction. Results: 21 LAMA2-MD (M = 5; 20±14 years) and 10 SELENON-RM patients (M = 7; 18±12 years) were included. In most patients, QRS fragmentation and Q waves, markers of heterogeneous ventricular activation, were present both at baseline and at follow-up. GLS was abnormal (age specific in children, > -18% in adults) in 33% of LAMA2-MD and 43% of SELENON-RM patients at baseline. Reduced LVEF (<52% in males, <54% in females and <55% in pediatric population) was observed in three LAMA2-MD patients at baseline and in none of the SELENON-RM patients. GLS and LVEF did not change between baseline and follow-up. RVEF was normal in all patients. Conclusion: ECG abnormalities and abnormal GLS are prevalent in LAMA2-MD and SELENON-RM, yet abnormal LVEF was only seen in LAMA2-MD patients. One LAMA2-MD patient had a clinically relevant deterioration in LVEF during 1.5-year follow-up. We advise routine screening of all patients with LAMA2-MD or SELENON-RM with ECG and echocardiography at diagnosis, minimally every two years from second decade of life and if new cardiac signs arise.

A cross-sectional study in 18 patients with typical and mild forms of nemaline myopathy in the Netherlands.

Nemaline myopathy (NM) is a congenital myopathy with generalised muscle weakness, most pronounced in neck flexor, bulbar and respiratory muscles. The aim of this cross-sectional study was to assess the Dutch NM patient cohort. We assessed medical history, physical examination, quality of life (QoL), fatigue severity, motor function (MFM), and respiratory muscle function. We included 18 of the 28 identified patients (13 females (11-67 years old); five males (31-74 years old)) with typical or mild NM and eight different genotypes. Nine patients (50 %) used a wheelchair, eight patients (44 %) used mechanical ventilation, and four patients (22 %) were on tube feeding. Spinal deformities were found in 14 patients (78 %). The median Medical Research Council (MRC) sum score was 38/60 [interquartile range 32-51] in typical and 48/60 [44-50] in mild NM. The experienced QoL was lower and fatigue severity was higher than reference values of the healthy population. The total MFM score was 55 % [49-94] in typical and 88 % [72-93] in mild NM. Most of the patients who performed spirometry had a restrictive lung function pattern (11/15). This identification and characterisation of the Dutch NM patient cohort is important for international collaboration and can guide the design of future clinical trials.

An open-label pilot study of losmapimod to evaluate the safety, tolerability, and changes in biomarker and clinical outcome assessments in participants with facioscapulohumeral muscular dystrophy type 1.

INTRODUCTION: Facioscapulohumeral muscular dystrophy (FSHD) is a genetic disease caused by aberrant DUX4 expression, leading to progressive muscle weakness. No effective pharmaceutical treatment is available. Losmapimod, a small molecule selective inhibitor of p38 α/ß MAPK, showed promising results in a phase 1 trial for the treatment of FSHD, prompting additional studies. We report the findings of an open-label phase 2 trial (NCT04004000) investigating the safety, tolerability, pharmacokinetics, pharmacodynamics, and exploratory efficacy of losmapimod in participants with FSHD1. METHODS: This study was conducted at a single site in the Netherlands from August 2019 to March 2021, with an optional, ongoing open-label extension. Participants aged 18 to 65 years with FSHD1 took 15 mg of losmapimod twice daily for 52 weeks. Primary endpoints were measures of losmapimod safety and tolerability. Secondary endpoints were assessments of losmapimod pharmacokinetics and pharmacodynamics. RESULTS: Fourteen participants were enrolled. No deaths, serious treatment-emergent adverse events (TEAEs), or discontinuations due to TEAEs were reported. Losmapimod achieved blood concentrations and target engagements that were previously associated with decreased DUX4 expression in vitro. Clinical outcome measures showed a trend toward stabilization or improvement. CONCLUSIONS: Losmapimod was well tolerated and may be a promising new treatment for FSHD; a larger phase 3 study is ongoing.

Nerve enlargement in patients with Noonan syndrome: A retrospective cohort study.

Noonan syndrome (NS) is an autosomal dominant condition characterized by facial dysmorphism, congenital heart disease, development delay, growth retardation and lymphatic disease. It is caused by germline pathogenic variants in genes encoding proteins in the Ras/mitogen-activated protein kinase signaling pathway. Nerve enlargement is not generally considered as a feature of NS, although some cases have been reported. High-resolution nerve ultrasound enables detailed anatomical assessment of peripheral nerves and can show enlarged nerves. This retrospective cohort study aims to describe the sonographic findings of patients with NS performed during a 1-year time period. Data on the degree of enlargement, the relation to increasing age, pain in extremities, genotype on the gene level and clinical features were collected. Twenty-nine of 93 patients visiting the NS Center of Expertise of the Radboud University Medical Center Nijmegen underwent high-resolution ultrasound. In 24 patients (83%) nerve enlargement was found. Most of them experienced pain. We observed a weak correlation with increasing age and the degree of nerve enlargement but no association with pain, genotype at the gene level or clinical features. This study shows that patients with NS have a high predisposition for sonographic nerve enlargement and that the majority experience pain.

Transcriptomic gene signatures measure satellite cell activity in muscular dystrophies.

The routine need for myonuclear turnover in skeletal muscle, together with more sporadic demands for hypertrophy and repair, are performed by resident muscle stem cells called satellite cells. Muscular dystrophies are characterized by muscle wasting, stimulating chronic repair/regeneration by satellite cells. Here, we derived and validated transcriptomic signatures for satellite cells, myoblasts/myocytes, and myonuclei using publicly available murine single cell RNA-Sequencing data. Our signatures distinguished disease from control in transcriptomic data from several muscular dystrophies including facioscapulohumeral muscular dystrophy (FSHD), Duchenne muscular dystrophy, and myotonic dystrophy type I. For FSHD, the expression of our gene signatures correlated with direct counts of satellite cells on muscle sections, as well as with increasing clinical and pathological severity. Thus, our gene signatures enable the investigation of myogenesis in bulk transcriptomic data from muscle biopsies. They also facilitate study of muscle regeneration in transcriptomic data from human muscle across health and disease.

Quality of life and support needs in children, adolescents, and young adults with facioscapulohumeral dystrophy, a mixed-method study.

BACKGROUND AND OBJECTIVES: Quality of life (QoL) in children with facioscapulohumeral dystrophy (FSHD) seems plausible decreased. Little is known about factors influencing QoL in children with FSHD. Our objective is to explore factors contributing to the QoL of children, adolescents, and young adults with FSHD, to describe how they experience life with FSHD, and to report their support needs. METHODS: We performed a mixed-method study with individual age-appropriate semi-structured interviews assessing QoL in children, adolescents, and young adults with FSHD and their parents. To characterize the sample, quantitative data on QoL, pain, fatigue, and participation were collected. Interview data was analyzed using a thematic analysis. RESULTS: Fourteen patients participated (age between 9 and 26 years old, eight males and six females). The degree of FSHD severity, as indicated by the FSHD-score, did not correlate with QoL. Older children had a lower QoL than younger children. Children and adolescents strived for normality regardless of physical discomfort. Phenotypical features of FSHD led to insecurity aggravated by hurtful comments of others. The unpredictability of disease progression and its implications for career and parenthood choices led to a generalized feeling of uncertainty about the future. Support was found within family and friends. Participants expressed a need for peer support and psychological support as well as recommending it to others. DISCUSSION: Quality of life in childhood FSHD is diminished caused by their physical limitations, altered appearance, fear of social rejection, and uncertainty of the disease progression in the future. A fear of social rejection most likely contributes to striving for normality regardless of physical discomfort. Support should be focused on acceptance and coping with hurtful comments. It should preferably be individualized, easily accessible and not offered as therapy but rather as tutoring for children.

The capability approach in rehabilitation: developing capability care.

PURPOSE: To develop a multidisciplinary outpatient rehabilitation intervention for people with neuromuscular diseases (NMD) based on the capability approach: capability care for persons with NMD. MATERIALS AND METHODS: The development process is described using a framework of actions for intervention development. It has been an iterative process consisting of a design phase based on theoretical insights and project group discussions, and a refine phase involving input from relevant stakeholders. RESULTS: Multidisciplinary efforts have resulted in the development of capability care for rehabilitation of persons with NMD. It can focus both on facilitating and achieving functionings (beings and doings), as well as looking for alternative functionings that fulfil the same underlying value, thereby contributing to the persons' well-being. To facilitate a conversation on broader aspects that impact on well-being, persons with NMD receive a preparation letter and healthcare professionals are provided with guiding questions and practical tools to use. CONCLUSIONS: We have shown that it is possible to develop a healthcare intervention based on the capability approach. We hope that rehabilitation professionals will be encouraged to use capability care and that other medical professionals will be inspired to develop capability care in their respective fields. REGISTRATION: Registered at trialregister.nl NL8946.

The capability approach can be used for development of healthcare interventions.Capability care in rehabilitation focuses on realising what is of real value to the person.The capability approach and the ICF are complementary and can both be used in rehabilitation.

The complementary use of muscle ultrasound and MRI in FSHD: Early versus later disease stage follow-up.

OBJECTIVES: Muscle MRI and ultrasound provide complementary techniques for characterizing muscle changes and tracking disease progression in facioscapulohumeral muscular dystrophy (FSHD). In this cohort study, we provide longitudinal data that compares both imaging modalities head-to-head. METHODS: FSHD patients were assessed at baseline and after five years. Standardized muscle MRI and ultrasound images of five leg muscles were assessed bilaterally. Fat replacement was quantified using MRI fat-fraction (FF) and ultrasound Heckmatt and echogenicity z-scores (EZ-score). Muscle edema was evaluated using T2-weighted turbo inversion recovery magnitude (TIRM) MRI. RESULTS: Twenty FSHD patients were included. Muscles with normal baseline imaging showed increases in ultrasound EZ-scores (≥1; in 17%) more often than MRI FF increases (≥10%; in 7%) over time. Muscles with only baseline ultrasound abnormalities often showed considerable FF increases (in 22%), and TIRM positivity at follow-up (44%). Muscles with increased FF at baseline showed stable (80%) or increasing FF (20%) over time. EZ-scores of those muscles either increased (23%), decreased (33%) or remained stable (44%). CONCLUSIONS: Muscle ultrasound may capture accelerated pathological muscle changes in FSHD in early disease, while muscle MRI appears better-suited to detecting and monitoring pathology in later stages. SIGNIFICANCE: Our results help establish each techniques' optimal use as imaging biomarker.

Treatment Approaches for Altered Facial Expression: A Systematic Review in Facioscapulohumeral Muscular Dystrophy and Other Neurological Diseases.

Background: Facial weakness is a key feature of facioscapulohumeral muscular dystrophy (FSHD) and may lead to altered facial expression and subsequent psychosocial impairment. There is no cure and supportive treatments focus on optimizing physical fitness and compensation of functional disabilities. Objective: We hypothesize that symptomatic treatment options and psychosocial interventions for other neurological diseases with altered facial expression could be applicable to FSHD. Therefore, the aim of this review is to collect symptomatic treatment approaches that target facial muscle function and psychosocial interventions in various neurological diseases with altered facial expression in order to discuss the applicability to FSHD. Methods: A systematic search was performed. Selected studies had to include FSHD, Bell's palsy, Moebius syndrome, myotonic dystrophy type 1, or Parkinson's disease and treatment options which target altered facial expression. Data was extracted for study and patients' characteristics, outcome assessment tools, treatment, outcome of facial expression and or psychosocial functioning. Results: Forty studies met the inclusion criteria, of which only three studies included FSHD patients exclusively. Most, twenty-one, studies were performed in patients with Bell's palsy. Studies included twelve different therapy categories and results were assessed with different outcomes measures. Conclusions: Five therapy categories were considered applicable to FSHD: training of (non-verbal) communication compensation strategies, speech training, physical therapy, conference attendance, and smile restoration surgery. Further research is needed to establish the effect of these therapies in FSHD. We recommend to include outcome measures in these studies that cover at least cosmetic, functional, communication, and quality of life domains.

Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children.

Brody disease is a rare autosomal recessive myopathy, caused by pathogenic variants in the ATP2A1 gene. It is characterized by an exercise-induced delay in muscle relaxation, often reported as muscle stiffness. Children may manifest with an abnormal gait and difficulty running. Delayed relaxation is commonly undetected, resulting in a long diagnostic delay. Almost all published cases so far were adults with childhood onset and adult diagnosis. With diagnostic next-generation sequencing, an increasing number of patients are diagnosed in childhood. We describe the clinical and genetic features of 9 children from 6 families with Brody disease. All presented with exercise-induced delayed relaxation, reported as difficulty running and performing sports. Muscle strength and mass was normal, and several children even had an athletic appearance. However, the walking and running patterns were abnormal. The diagnostic delay ranged between 2 and 7 years. Uniformly, a wide range of other disorders were considered before genetic testing was performed, revealing pathogenic genetic variants in ATP2A1. To conclude, this case series is expected to improve clinical recognition and timely diagnosis of Brody disease in children. We propose that ATP2A1 should be added to gene panels for congenital myopathies, developmental and movement disorders, and muscle channelopathies.

IL-6 and TNF are Potential Inflammatory Biomarkers in Facioscapulohumeral Muscular Dystrophy.

Background: FSHD is a highly prevalent inherited myopathy with a still poorly understood pathology. Objective: To investigate whether proinflammatory cytokines are associated with FSHD and which specific innate immune cells are involved in its pathology. Methods: First, we measured circulating cytokines in serum samples: IL-6 (FSHD, n = 150; HC, n = 98); TNF (FSHD, n = 150; HC, n = 59); IL-1α (FSHD, n = 150; HC, n = 66); IL-1ß (FSHD, n = 150; HC, n = 98); MCP-1 (FSHD, n = 14; HC, n = 14); VEGF-A (FSHD, n = 14; HC, n = 14). Second, we tested trained immunity in monocytes (FSHD, n = 15; HC, n = 15) and NK cells (FSHD, n = 11; HC, n = 11). Next, we explored the cytokine production capacity of NK cells in response to different stimuli (FSHD, n = 39; HC, n = 22). Lastly, we evaluated the cytokine production of ex vivo stimulated MRI guided inflamed (TIRM+) and paired MRI guided non inflamed (TIRM-) muscle biopsies of 21 patients and of 8 HC muscle biopsies. Results: We included a total of 190 FSHD patients (N = 190, 48±14 years, 49% men) and of 135 HC (N = 135, 44±15 years, 47% men). We found that FSHD patients had higher concentrations of IL-6 and TNF measured (a) in the circulation, (b) after ex-vivo stimulation of NK cells, and (c) in muscle specimens. Besides, IL-6 circulating concentrations, as well as its production by NK cells and IL-6 content of FSHD muscle specimens, showed a mild correlation with disease duration, disease severity, and muscle weakness. Conclusion: These results show that IL-6 and TNF may contribute to FSHD pathology and suggest novel therapeutic targets. Additionally, the activation of NK cells in FSHD may be a novel pathway contributing to FSHD pathology.

Living with facioscapulohumeral muscular dystrophy during the first two COVID-19 outbreaks: a repeated patient survey in the Netherlands.

BACKGROUND: Patients with facioscapulohumeral dystrophy (FSHD) suffer from slowly progressive muscle weakness. Approximately 20% of FSHD patients end up wheelchair-dependent. FSHD patients benefit from physical activity to maintain their muscle strength as much as possible. The impact of the COVID-19 pandemic on the health of FSHD patients was unknown. OBJECTIVE: This study assessed changes in daily care received, perceived psychosocial stress, and worsening of FSHD complaints in 2020. Furthermore, we compared COVID-19 infection incidence and severity of symptoms between FSHD patients and non-FSHD housemates. METHODS: Three online survey rounds were sent out to all adult participants of the Dutch FSHD registry regarding daily care received, perceived psychosocial stress, COVID-19 infection rate, and COVID-19 symptoms severity. They also included COVID-19-related questions regarding the participants' housemates, which served as control group. RESULTS: Participation rate was 210 (61%), 186 (54%), and 205 (59%) for survey 1, 2, and 3, respectively. Care reduction was reported by 42.7%, 40%, and 28.8% of the participants in the respective surveys. Perceived psychosocial stress increased in 44%, 30%, and 40% of the participants. Compared to the 197 non-FSHD housemates, the 213 FSHD patients reported more possibly COVID-19-related symptoms (27% vs. 39%, p = 0.017) of mostly minimal severity (63%). No difference in (possible) COVID-19 infection incidence rates was found (2.0% vs. 2.8%, p = 0.527). CONCLUSIONS: The COVID-19 pandemic negatively impacted care received and increased perceived psychosocial stress in FSHD patients. However, COVID-19 infection incidence in FSHD patients was similar to their non-FSHD housemates.

Muscle MRI in Patients With Oculopharyngeal Muscular Dystrophy: A Longitudinal Study

BACKGROUND AND OBJECTIVES: Oculopharyngeal muscular dystrophy (OPMD) is a rare progressive neuromuscular disease. MRI is one of the techniques that is used in neuromuscular disorders to evaluate muscle alterations. The aim of this study was to describe the pattern of fatty infiltration of orofacial and leg muscles using quantitative muscle MRI in a large national cohort and to determine whether MRI can be used as an imaging biomarker of disease progression in OPMD. METHODS: Patients with OPMD (18 years or older) were invited from the national neuromuscular database or by their treating physicians and were examined twice with an interval of 20 months, with quantitative MRI of orofacial and leg muscles to assess fatty infiltration which were compared with clinical measures. RESULTS: In 43 patients with genetically confirmed OPMD, the muscles that were affected most severely were the tongue (mean fat fraction: 37.0%, SD 16.6), adductor magnus (31.9%; 27.1), and soleus (27.9%; 21.5) muscles. The rectus femoris and tibialis anterior muscles were least severely affected (mean fat fractions: 6.8%; SD 4.7, 7.5%; 5.9). Eleven of 14 significant correlations were found between fat fraction and a clinical task in the corresponding muscles (r = -0.312 to -0.769, CI = -0.874 to -0.005). At follow-up, fat fractions had increased significantly in 17 of the 26 muscles: mean 1.7% in the upper leg muscles (CI = 0.8-2.4), 1.7% (1.0-2.3) in the lower leg muscles, and 1.9% (0.6-3.3) in the orofacial muscles (p < 0.05). The largest increase was seen for the soleus (3.8%, CI = 2.5-5.1). Correlations were found between disease duration and repeat length vs increased fat fraction in 7 leg muscles (r = 0.323 to -0.412, p < 0.05). DISCUSSION: According to quantitative muscle MRI, the tongue, adductor magnus and soleus show the largest fat infiltration levels in patients with OPMD. Fat fractions increased in several orofacial and leg muscles over 20 months, with the largest fat fraction increase seen in the soleus. This study supports that this technique is sensitive enough to show worsening in fat fractions of orofacial and leg muscles and therefore a responsive biomarker for future clinical trials.

FSHD muscle shows perturbation in fibroadipogenic progenitor cells, mitochondrial function and alternative splicing independently of inflammation.

Facioscapulohumeral muscular dystrophy (FSHD) is a prevalent, incurable myopathy. FSHD is highly heterogeneous, with patients following a variety of clinical trajectories, complicating clinical trials. Skeletal muscle in FSHD undergoes fibrosis and fatty replacement that can be accelerated by inflammation, adding to heterogeneity. Well controlled molecular studies are thus essential to both categorize FSHD patients into distinct subtypes and understand pathomechanisms. Here, we further analyzed RNA-sequencing data from 24 FSHD patients, each of whom donated a biopsy from both a non-inflamed (TIRM-) and inflamed (TIRM+) muscle, and 15 FSHD patients who donated peripheral blood mononucleated cells (PBMCs), alongside non-affected control individuals. Differential gene expression analysis identified suppression of mitochondrial biogenesis and up-regulation of fibroadipogenic progenitor (FAP) gene expression in FSHD muscle, which was particularly marked on inflamed samples. PBMCs demonstrated suppression of antigen presentation in FSHD. Gene expression deconvolution revealed FAP expansion as a consistent feature of FSHD muscle, via meta-analysis of 7 independent transcriptomic datasets. Clustering of muscle biopsies separated patients in an unbiased manner into clinically mild and severe subtypes, independently of known disease modifiers (age, sex, D4Z4 repeat length). Lastly, the first genome-wide analysis of alternative splicing in FSHD muscle revealed perturbation of autophagy, BMP2 and HMGB1 signalling. Overall, our findings reveal molecular subtypes of FSHD with clinical relevance and identify novel pathomechanisms for this highly heterogeneous condition.

Respiratory function in LAMA2-related muscular dystrophy and SELENON-related congenital myopathy, a 1.5-year natural history study.

INTRODUCTION: LAMA2-related muscular dystrophy (LAMA2-MD) and SELENON(SEPN1)-related congenital myopathy (SELENON-RM) are rare neuromuscular diseases with respiratory impairment from a young age. Prospective natural history studies are needed for prevalence estimations, respiratory characterization, optimizing clinical care and selecting outcome measures for trial readiness. METHODS: Our prospective 1.5-year natural history study included spirometry (forced vital capacity (FVC); difference between upright and supine vital capacity (dVC)), respiratory muscle strength tests (sniff nasal inspiratory pressure (SNIP)) (age≥5 years), and diaphragm ultrasound (thickness; thickening; echogenicity; all ages). RESULTS: Twenty-six LAMA2-MD patients (M = 8, median 21 [9; 31] years) and 11 SELENON-RM patients (M = 8, 20 [10; 33] years) were included. At baseline, 17 (85 %) LAMA2-MD (FVC%: 59 % [33; 68]) and all SELENON-RM patients (FVC%: 34 % [31; 46]) had an impaired respiratory function (FVC%<80 %). Nine (35 %) LAMA2-MD and eight (73 %) SELENON-RM patients received mechanical ventilation at baseline, and two additional SELENON-RM patients started during follow-up. Contrarily to LAMA2-MD, SELENON-RM patients had severe diaphragm atrophy (diaphragm thickness z-score: 2.5 [-3.1; -2.1]) and dysfunction (diaphragm thickness ratio: 1.2 [1.0; 1.7]; dVC: 30 % [7.7; 41]). SNIP was low in both neuromuscular diseases and correlated with motor function. In SELENON-RM, respiratory function decreased during follow-up. CONCLUSION: The majority of LAMA2-MD and all SELENON-RM patients had respiratory impairment. SELENON-RM patients showed lower respiratory function which was progressive, more prevalent mechanical ventilation, and more severe diaphragm atrophy and dysfunction than LAMA2-MD patients. Spirometry (FVC%, dVC) and respiratory muscle strength tests (SNIP) are useful in clinical care and as outcome measure in clinical trials. CLINICAL TRIAL NUMBER: NCT04478981.