Congenital myopathies and muscular dystrophies

Anaesthesia management of a patient with Bethlem Myopathy for elective tonsillectomy: a case report

BACKGROUND

Bethlem Myopathy is a collagen VI-related myopathy presenting as a rare hereditary muscular disorder with progressive muscular weakness and joint contractures. Despite its milder clinical course relative to other myopathies, anaesthetic management can be challenging. High arched palates and fixed flexion deformities may contribute to a difficult airway. A progressive decline in pulmonary function can present later into adulthood. This respiratory decline can carry secondary cardiovascular consequences due to the progressive nature of restrictive lung disease, including right sided heart disease and pulmonary hypertension. We describe a case of a male patient with Bethlem Myopathy undergoing anaesthesia, to contribute to the limited body of literature on this condition and enhance awareness and guidance amongst anaesthesiologists on approaching patients with this condition. This is the first case report within the literature of its kind.

CASE PRESENTATION

This case details a 33-year-old male with Bethlem Myopathy undergoing tonsillectomy. Diagnosed in childhood following developmental delays, the patient had no prior anaesthetic exposure and no family history of anaesthetic complications. Anaesthetic induction was achieved without complications, avoiding depolarizing muscle relaxants and careful airway management. Extreme care was taken in patient positioning to prevent complications. The surgery proceeded without incident and muscle paralysis was reversed with Suggammadex, resulting in no adverse post-operative respiratory complications. The patient was discharged on the first post-operative day without any respiratory or cardiovascular compromise.

CONCLUSIONS

Bethlem Myopathy, while often exhibiting a mild clinical course, can present anaesthetic challenges. Awareness of potential complications including a difficult airway, cardiovascular and respiratory implications as well as the need for specialised monitoring and positioning is crucial to ensure a safe peri-operative course.

Unusual cause of muscle weakness, type II respiratory failure and pulmonary hypertension: a case report of ryanodine receptor type 1(RYR1)-related myopathy

BACKGROUND

Patients with congenital myopathies may experience respiratory involvement, resulting in restrictive ventilatory dysfunction and respiratory failure. Pulmonary hypertension (PH) associated with this condition has never been reported in congenital ryanodine receptor type 1(RYR1)-related myopathy.

CASE PRESENTATION

A 47-year-old woman was admitted with progressively exacerbated chest tightness and difficulty in neck flexion. She was born prematurely at week 28. Her bilateral lower extremities were edematous and muscle strength was grade IV-. Arterial blood gas analysis revealed hypoventilation syndrome and type II respiratory failure, while lung function test showed restrictive ventilation dysfunction, which were both worse in the supine position. PH was confirmed by right heart catheterization (RHC), without evidence of left heart disease, congenital heart disease, or pulmonary artery obstruction. Polysomnography indicated nocturnal hypoventilation. The ultrasound revealed reduced mobility of bilateral diaphragm. The level of creatine kinase was mildly elevated. Magnetic resonance imaging showed myositis of bilateral thigh muscle. Muscle biopsy of the left biceps brachii suggested muscle malnutrition and congenital muscle disease. Gene testing revealed a missense mutation in the RYR1 gene (exon33 c.C4816T). Finally, she was diagnosed with RYR1-related myopathy and received long-term non-invasive ventilation (NIV) treatment. Her symptoms and cardiopulmonary function have been greatly improved after 10 months.

CONCLUSIONS

We report a case of RYR1-related myopathy exhibiting hypoventilation syndrome, type II respiratory failure and PH associated with restrictive ventilator dysfunction. Pulmonologists should keep congenital myopathies in mind in the differential diagnosis of type II respiratory failure, especially in patients with short stature and muscle weakness.

An early onset benign myopathy with glycogen storage caused by a de novo 1.4 Mb-deletion of chromosome 14

Early onset myopathies are a clinically and histologically heterogeneous monogenic diseases linked to approximately 90 genes. Molecular diagnosis is challenging, especially in patients with a mild phenotype. We describe a 26-year-old man with neonatal hypotonia, motor delay and seizures during infancy, and non-progressive, mild muscular weakness in adulthood. Serum Creatine kinase level was normal. Whole-body muscle MRI showed thin muscles, and brain MRI was unremarkable. A deltoid muscle biopsy showed glycogen storage. WGS revealed a de novo 1.4 Mb-deletion of chromosome 14, confirmed by Array-CGH. This microdeletion causes the loss of ten genes including RALGAPA1, encoding for RalA, a regulator of glucose transporter 4 (GLUT4) expression at the membrane of myofibers. GLUT4 was overexpressed in patient's muscle. Here we highlight the importance to search for chromosomal alterations in the diagnostic workup of early onset myopathies.

Transcriptome Analysis of Leg Muscles and the Effects of ALOX5 on Proliferation and Differentiation of Myoblasts in Haiyang Yellow Chickens

Skeletal muscle growth and development from embryo to adult consists of a series of carefully regulated changes in gene expression. This study aimed to identify candidate genes involved in Haiyang Yellow Chickens' growth and to understand the regulatory role of the key gene ALOX5 (arachidonate 5-lipoxygenase) in myoblast proliferation and differentiation. In order to search the key candidate genes in the process of muscle growth and development, RNA sequencing was used to compare the transcriptomes of chicken muscle tissues at four developmental stages and to analyze the effects of ALOX5 gene interference and overexpression on myoblast proliferation and differentiation at the cellular level. The results showed that 5743 differentially expressed genes (DEGs) (|fold change| ≥ 2; FDR ≤ 0.05) were detected by pairwise comparison in male chickens. Functional analysis showed that the DEGs were mainly involved in the processes of cell proliferation, growth, and developmental process. Many of the DEGs, such as MYOCD (Myocardin), MUSTN1 (Musculoskeletal Embryonic Nuclear Protein 1), MYOG (MYOGenin), MYOD1 (MYOGenic differentiation 1), FGF8 (fibroblast growth factor 8), FGF9 (fibroblast growth factor 9), and IGF-1 (insulin-like growth factor-1), were related to chicken growth and development. KEGG pathway (Kyoto Encyclopedia of Genes and Genomes pathway) analysis showed that the DEGs were significantly enriched in two pathways related to growth and development: ECM-receptor interaction (Extracellular Matrix) and MAPK signaling pathway (Mitogen-Activated Protein Kinase). With the extension of differentiation time, the expression of the ALOX5 gene showed an increasing trend, and it was found that interference with the ALOX5 gene could inhibit the proliferation and differentiation of myoblasts and that overexpression of the ALOX5 gene could promote the proliferation and differentiation of myoblasts. This study identified a range of genes and several pathways that may be involved in regulating early growth, and it can provide theoretical research for understanding the regulation mechanism of muscle growth and development of Haiyang Yellow Chickens.

The Presentation of Two Unrelated Clinical Cases from the Republic of North Ossetia-Alania with the Same Previously Undescribed Variant in the COL6A2 Gene

Here, we described three affected boys from two unrelated families of Ossetian-Digor origin from the Republic of North Ossetia-Alania who were admitted to the Research Centre for Medical Genetics with unspecified muscular dystrophy. High-throughput sequencing was performed and revealed two novel frameshift variants in the COL6A2 gene (NM_001849.3) in a heterozygous state each in both cases: c.508_535delinsCTGTGG and c.1659_1660del (case 1) and c.1689del and c.1659_1660del (case 2). In two cases, the same nucleotide variant in the COL6A2 gene (c.1659_1660del) was observed. We have suggested that the variant c.1659_1660del may be common in the Ossetian-Digor population because two analyzed families have the same ancestry from the same subethnic group of Ossetians). The screening for an asymptomatic carriage of the nucleotide variant c.1659_1660del in 54 healthy donors from Ossetian-Digor population revealed that the estimated carrier frequency is 0.0093 (CI: 0.0002–0.0505), which is high for healthy carriers of the pathogenic variant. Molecular genetic, anamnestic data and clinical examination results allowed us to diagnose Ullrich muscular dystrophy in those affected boys. Genetic heterogeneity and phenotypic diversity of muscular dystrophies complicate diagnosis. It is important to make a differential diagnosis of such conditions and use HTS methods to determine the most accurate diagnosis.

Clinico-pathological features and mutational spectrum of 16 nemaline myopathy patients from a Chinese neuromuscular center

Nemaline myopathy (NM) is a congenital myopathy of great heterogeneity, characterized by the presence of rods in the cytoplasm of muscle fibers. The samples of 16 nemaline myopathy patients diagnosed by characteristically pathological features went through whole exon sequencing. Clinico-pathological and genetic features of the cases were systematically analyzed. According to the classification of nemaline myopathy by ENMC, 8 cases are typical congenital subtype, 6 cases are childhood/juvenile onset subtype and 2 case are adult onset subtype. In histological findings, characteristic purple-colored rods are discovered under modified gömöri trichrome staining (MGT). Electron microscopy revealed the presence of high electron-dense nemaline bodies around the submucosa and the nucleus nine patients (9/16 56.3%) were detected pathogenic causative mutations, among whom mutations in the NEB gene were the most frequent (6 patients, 66.7%). KBTBD13 gene mutation was discovered in two patients and ACTA1 gene mutation was discovered in 1 patient. Nemaline myopathy is a congenital myopathy with highly clinico-pathological and genetic heterogeneity. NEB gene mutation is the most common mutation, in which splicing change c.21522 +3A > G is hotspot mutation in Chinese NM patients.

A Systematic Review and Meta-Analysis of the Prevalence of Congenital Myopathy

Background: Congenital myopathy constitutes a heterogeneous group of orphan diseases that are mainly classified on the basis of muscle biopsy findings. This study aims to estimate the prevalence of congenital myopathy through a systematic review and meta-analysis of the literature.

Methods: The PubMed, MEDLINE, Web of Science, and Cochrane Library databases were searched for original research articles published in English prior to July 30, 2021. The quality of the included studies was assessed by a checklist adapted from STrengthening the Reporting of OBservational studies in Epidemiology (STROBE). To derive the pooled epidemiological prevalence estimates, a meta-analysis was performed using the random effects model. Heterogeneity was assessed using the Cochrane Q statistic as well as the I² statistic.

Results: A total of 11 studies were included in the systematic review and meta-analysis. Of the 11 studies included, 10 (90.9%) were considered medium-quality, one (9.1%) was considered low-quality, and no study was assessed as having a high overall quality. The pooled prevalence of congenital myopathy in the all-age population was 1.62 (95% CI, 1.13–2.11) per 100,000, while the prevalence in the child population was 2.76 (95% CI, 1.34–4.18) per 100,000. In the pediatric population, the prevalence among males was 2.92 (95% CI, −1.70 to 7.55) per 100,000, while the prevalence among females was 2.47 (95% CI, −1.67 to 6.61) per 100,000. The prevalence estimates of the all-age population per 100,000 were 0.20 (95% CI 0.10–0.35) for nemaline myopathy, 0.37 (95% CI 0.21–0.53) for core myopathy, 0.08 (95% CI −0.01 to 0.18) for centronuclear myopathy, 0.23 (95% CI 0.04–0.42) for congenital fiber-type disproportion myopathy, and 0.34 (95% CI, 0.24–0.44) for unspecified congenital myopathies. In addition, the prevalence estimates of the pediatric population per 100,000 were 0.22 (95% CI 0.03–0.40) for nemaline myopathy, 0.46 (95% CI 0.03–0.90) for core myopathy, 0.44 (95% CI 0.03–0.84) for centronuclear myopathy, 0.25 (95% CI −0.05 to 0.54) for congenital fiber-type disproportion myopathy, and 2.63 (95% CI 1.64–3.62) for unspecified congenital myopathies.

Conclusions: Accurate estimates of the prevalence of congenital myopathy are fundamental to supporting public health decision-making. The high heterogeneity and the lack of high-quality studies highlight the need to conduct higher-quality studies on orphan diseases.

An Overview of Mitochondrial Protein Defects in Neuromuscular Diseases

Neuromuscular diseases (NMDs) are dysfunctions that involve skeletal muscle and cause incorrect communication between the nerves and muscles. The specific causes of NMDs are not well known, but most of them are caused by genetic mutations. NMDs are generally progressive and entail muscle weakness and fatigue. Muscular impairments can differ in onset, severity, prognosis, and phenotype. A multitude of possible injury sites can make diagnosis of NMDs difficult. Mitochondria are crucial for cellular homeostasis and are involved in various metabolic pathways; for this reason, their dysfunction can lead to the development of different pathologies, including NMDs. Most NMDs due to mitochondrial dysfunction have been associated with mutations of genes involved in mitochondrial biogenesis and metabolism. This review is focused on some mitochondrial routes such as the TCA cycle, OXPHOS, and β-oxidation, recently found to be altered in NMDs. Particular attention is given to the alterations found in some genes encoding mitochondrial carriers, proteins of the inner mitochondrial membrane able to exchange metabolites between mitochondria and the cytosol. Briefly, we discuss possible strategies used to diagnose NMDs and therapies able to promote patient outcome.

Challenges and Advances in Molecular Diagnosis of Myopathies and Dystrophies in Perspective of Their Use in Developing Countries: Past, Present, and Future

Background

Proper diagnosis is the first and most critical step for effective identification and treatment of myopathy and dystrophy disorders. Although various histochemical and biochemical studies have paved the way for efficient testing of these disorders, they are insufficient for accurate diagnosis. To overcome this, the diagnostic procedure has now shifted more toward the "genetic first approach," with the remarkable role played by various genetic and molecular techniques.

Objective

In developing countries, successful diagnosis of such disorders is affected by the shortage of hospitals, poor lab setup, limited diagnostic methods, and unavailability of technical expertise. As a major population living in developing countries faces such inadequate healthcare facilities, there has always been a need for identifying effective diagnostic techniques that could identify genetic alterations more prone in such regions.

Materials and Methods

This article reviews studies done in the last few years that primarily use nonsequencing-based molecular diagnosis methods to identify myopathy- and dystrophy-specific gene alterations and thus could equally hold potential for screening key genetic alterations reported in certain regions in developing countries. Further, this review deals with new emerging sequencing and next-generation sequencing (NGS)-based approach and their potential in providing an adequate diagnosis.

Conclusions

This study promotes nonsequencing-based molecular methods to be an effective method for early-stage diagnosis and management of myopathies and dystrophies in developing countries and suggests the high importance of emerging NGS methods in proper diagnosis and identifying new players in neuromuscular disorders.

Redox Homeostasis in Muscular Dystrophies

In recent years, growing evidence has suggested a prominent role of oxidative stress in the pathophysiology of several early- and adult-onset muscle disorders, although effective antioxidant treatments are still lacking. Oxidative stress causes cell damage by affecting protein function, membrane structure, lipid metabolism, and DNA integrity, thus interfering with skeletal muscle homeostasis and functionality. Some features related to oxidative stress, such as chronic inflammation, defective regeneration, and mitochondrial damage are shared among most muscular dystrophies, and Nrf2 has been shown to be a central player in antagonizing redox imbalance in several of these disorders. However, the exact mechanisms leading to overproduction of reactive oxygen species and deregulation in the cellular antioxidants system seem to be, to a large extent, disease-specific, and the clarification of these mechanisms in vivo in humans is the cornerstone for the development of targeted antioxidant therapies, which will require testing in appropriately designed clinical trials.

CircRILPL1 promotes muscle proliferation and differentiation via binding miR-145 to activate IGF1R/PI3K/AKT pathway

Many novel non-coding RNAs, such as microRNAs (miRNAs) and circular RNAs (circRNAs), are involved in various physiological and pathological processes. The PI3K/AKT signaling pathway is important for its role in regulating skeletal muscle development. In this study, molecular and biochemical assays were used to confirm the role of miRNA-145 (miR-145) in myoblast proliferation and apoptosis. Based on sequencing data and bioinformatics analysis, we identified a new circRILPL1, which acts as a sponge for miR-145. The interactions between circRILPL1 and miR-145 were examined by bioinformatics, a luciferase assay, and RNA immunoprecipitation. Mechanistically, knockdown or exogenous expression of circRILPL1 in the primary myoblasts was performed to prove the functional significance of circRILPL1. We investigated the inhibitory effect of miR-145 on myoblast proliferation by targeting IGF1R to regulate the PI3K/AKT signaling pathway. A novel circRILPL1 was identified that could sponge miR-145 and is related to AKT activation. In addition, circRILPL1 was positively correlated with muscle proliferation and differentiation in vitro and could inhibit cell apoptosis. The newly identified circRILPL1 functions as a miR-145 sponge to regulate the IGF1R gene and rescue the inhibitory effect of miR-145 on the PI3K/AKT signaling pathway, thereby promoting myoblast growth.

Associations between magnetic resonance imaging and EMG findings in myopathies

OBJECTIVES

Magnetic resonance imaging (MRI) is a cornerstone in diagnosis of myopathies. The present study sought to elucidate possible associations between electromyography (EMG) findings and histogram parameters derived from clinical MRI in myositis and other myopathies.

MATERIALS AND METHODS

Twenty six patients with myopathies were included in this retrospective study. Clinical MRI was performed with a 1.5T MRI scanner including T2- and T1-weighted images. EMG analysis was performed during clinical diagnostic workup. The histogram parameters of the MRI sequences were obtained of the same muscle, which was investigated with EMG.

RESULTS

Several correlations were identified between mean duration of the motor unit potentials (MUP) and histogram parameters derived from T1- and T2-weighted images. The highest for T1-weighted images was mode (r = -.73, P < .0001) and for T2-weighted images was p25 (r = -.57, P = .022). There were significant differences for several histogram parameters between muscles with pathological spontaneous activity and without. So, for T1-weighted images, the best discrimination was achieved with mean (P = .096), and for T2-weighted images for p10 (P = .05). Mean SI values derived from T1-weighted images achieved an AUC of 0.84 with a sensitivity of 0.81 and a specificity of 0.86 to discriminate patients with and without pathological spontaneous activity (PSA).

CONCLUSIONS

The present study identified strong associations between histogram analysis derived from morphological MRI sequences and the duration of the MUP derived from EMG in myopathies strengthening the fact that both diagnostic modalities can reflect disease state in a similar fashion. Histogram parameters can predict muscles with PSA.

The Impact of Mitochondrial Deficiencies in Neuromuscular Diseases

Neuromuscular diseases (NMDs) are a heterogeneous group of acquired or inherited rare disorders caused by injury or dysfunction of the anterior horn cells of the spinal cord (lower motor neurons), peripheral nerves, neuromuscular junctions, or skeletal muscles leading to muscle weakness and waste. Unfortunately, most of them entail serious or even fatal consequences. The prevalence rates among NMDs range between 1 and 10 per 100,000 population, but their rarity and diversity pose difficulties for healthcare and research. Some molecular hallmarks are being explored to elucidate the mechanisms triggering disease, to set the path for further advances. In fact, in the present review we outline the metabolic alterations of NMDs, mainly focusing on the role of mitochondria. The aim of the review is to discuss the mechanisms underlying energy production, oxidative stress generation, cell signaling, autophagy, and inflammation triggered or conditioned by the mitochondria. Briefly, increased levels of inflammation have been linked to reactive oxygen species (ROS) accumulation, which is key in mitochondrial genomic instability and mitochondrial respiratory chain (MRC) dysfunction. ROS burst, impaired autophagy, and increased inflammation are observed in many NMDs. Increasing knowledge of the etiology of NMDs will help to develop better diagnosis and treatments, eventually reducing the health and economic burden of NMDs for patients and healthcare systems.

Congenital Muscular Dystrophy and Congenital Myopathy

PURPOSE OF REVIEW

Congenital muscular dystrophies and congenital myopathies are a heterogeneous group of disorders resulting in hypotonia, muscle weakness, and dystrophic or myopathic features on muscle biopsy. This article summarizes the clinical and genetic aspects of these disorders.

RECENT FINDINGS

Historically, diagnoses of congenital muscular dystrophy and congenital myopathy have been made by clinical features and histopathology; however, recent advances in genetics have changed diagnostic practice by relying more heavily on genetic findings. This article reviews the clinical and genetic features of the most common congenital muscular dystrophies including laminin subunit alpha 2 (LAMA2)-related (merosin deficient), collagen VI-related, and α-dystroglycan-related congenital muscular dystrophies and reviews the most common congenital myopathies including nemaline rod, core, and centronuclear myopathies. With the increasing accessibility of genetic testing, the number of genes found to be associated with these disorders has increased dramatically. A wide spectrum of severity and onset (from birth to adulthood) exist across all subtypes. Progression and other features are variable depending on the subtype and severity of the specific genetic mutation.

SUMMARY

Congenital muscular dystrophy and congenital myopathy are increasingly recognized disorders. A growing appreciation for the breadth of phenotypic variability and overlap between established subtypes has challenged long-standing phenotypic and histopathologic classifications of these disorders but has driven a greater understanding of pathogenesis and opened the door to the development of novel treatments.

Myopathic Blepharoptoses: A New Classification System

PURPOSE

Myopathic blepharoptoses (ptoses) is a complex group of disorders. To date, no formal categorization scheme has been developed based on associated ocular and systemic findings, genetic fingerprint, treatment, and prognosis for each ptosis in this group. We report a new classification scheme for myopathic ptoses.

METHODS

Literature review and classification development.

RESULTS

A new classification scheme of myopathic ptoses includes isolated static myopathic ptosis (congenital ptosis), static myopathic ptosis associated with aberrant innervation and those associated with periocular abnormalities, and progressive myopathic ptoses that affect the levator muscle and other muscle groups in childhood and adulthood.

CONCLUSIONS

Making the distinction of myopathic ptosis type early will maximize patient outcomes by optimizing surgical and systemic management and facilitating the recruitment of subspecialists to care for patients with these challenging conditions.The authors present a comprehensive and effective myopathic ptosis classification scheme to optimize surgical management and facilitate subspecialty care.

Early-Onset Myopathies: Clinical Findings, Prevalence of Subgroups and Diagnostic Approach in a Single Neuromuscular Referral Center in Germany

BACKGROUND

Early-onset myopathies are a heterogeneous group of neuromuscular diseases with broad clinical, genetic and histopathological overlap. The diagnostic approach has considerably changed since high throughput genetic methods (next generation sequencing, NGS) became available.

OBJECTIVE

We present diagnostic subgroups in a single neuromuscular referral center and describe an algorithm for the diagnostic work-up.

METHODS

The diagnostic approach of 98 index patients was retrospectively analysed. In 56 cases targeted sequencing of a known gene was performed, in 44 patients NGS was performed using large muscle specific panels, and in 12 individuals whole exome sequencing (WES) was undertaken. One patient was diagnosed via array CGH. Clinical features of all patients are provided.

RESULTS

The final diagnosis could be found in 63 out of 98 patients (64%) with molecular genetic analysis. In 55% targeted gene sequencing could establish the genetic diagnosis. However, this rate largely depended on the presence of distinct histological or clinical features. NGS (large myopathy-related panels and WES) revealed genetic diagnosis in 58.5% (52% and 67%, respectively). The genes detected by WES in our cohort of patients were all covered by the panels. Based on our findings we propose an algorithm for a practical diagnostic approach.Prevalences:MTM1- and LAMA2-patients are the two biggest subgroups, followed by SEPN1-, RYR1- and Collagen VI-related diseases. 31% of genetically confirmed cases represents a group with overlap between "congenital myopathies (CM)" and "congenital muscular dystrophies (CMD)". In 36% of the patients a specific genetic diagnosis could not be assigned.

CONCLUSIONS

A final diagnosis can be confirmed by high throughput genetic analysis in 58.5% of the cases, which is a higher rate than reported in the literature for muscle biopsy and should in many cases be considered as a first diagnostic tool. NGS cannot replace neuromuscular expertise and a close discussion with the geneticists on NGS is mandatory. Targeted candidate gene sequencing still plays a role in selected cases with highly suspicious clinical or histological features. There is a relevant clinical and genetic overlap between the entities CM and CMD.

Compound heterozygous POMGNT1 mutations leading to muscular dystrophy-dystroglycanopathy type A3: a case report

Background

Dystroglycanopathies, which are caused by reduced glycosylation of alpha-dystroglycan, are a heterogeneous group of neurodegenerative disorders characterized by variable brain and skeletal muscle involvement. Muscle-eye-brain disease (or muscular dystrophy-dystroglycanopathy type 3 A) is an autosomal recessive disorder characterized by congenital muscular dystrophy, ocular abnormalities, and lissencephaly.

Case presentation

We report clinical and genetic characteristics of a 6-year-old boy affected by muscular dystrophy-dystroglycanopathy. He has severe a delay in psychomotor and speech development, muscle hypotony, congenital myopia, partial atrophy of the optic nerve disc, increased level of creatine kinase, primary-muscle lesion, polymicrogyria, ventriculomegaly, hypoplasia of the corpus callosum, cysts of the cerebellum. Exome sequencing revealed compound heterozygous mutations in POMGNT1 gene (transcript NM_001243766.1): c.1539 + 1G > A and c.385C > T.

Conclusions

The present case report shows diagnostic algorithm step by step and helps better understand the clinical and genetic features of congenital muscular dystrophy.

VEPTR: Are We Reducing Respiratory Assistance Requirements?

BACKGROUND

The assisted ventilation rating (AVR) indicates the degree of external respiratory support required in children with thoracic insufficiency syndrome (TIS) and early onset scoliosis. For skeletally immature patients with TIS, the vertical expandable prosthetic titanium rib (VEPTR) device can be used to improve lung volume and growth. We hypothesized that patients who underwent early thoracic reconstruction by VEPTR treatment had an improved respiratory status.

METHODS

Preoperative and postoperative AVR ratings were prospectively collected in a multicenter study group and compared to determine change after VEPTR treatment. Patients under 10 years of age at initial implant with minimum of 2-year follow-up data were included. Patients were excluded if there were incomplete data or if initial AVR was normal (breathing on room air). Statistical analysis was performed on groups which had stable, declined, and improved AVR at final follow-up.

RESULTS

Database search yielded 77 patients with initial abnormal AVR. Average follow-up was 5.6 years. The most frequent primary diagnoses were congenital scoliosis (n=14) and spinal muscular atrophy (n=14). In total, 19 (24%) demonstrated improvement, 9 (12%) patients deteriorated, and 49 (64%) remained at the same level. The average preoperative major curve in those with improvement (58.4 degrees) and those with no change (63.5 degrees) was less than in those with deterioration (85.5 degrees) (P=0.014). The average age in years at implant of those with improvement (4) was less than those declined (6.7) and those with no change (5.5). In total, 16 (84.2%) of those that improved had a normal AVR and did not require respiratory support at last follow-up.

CONCLUSIONS

There is evidence that a subset of patients with early onset scoliosis and TIS who received early thoracic reconstruction with VEPTR treatment show complete resolution of pulmonary support at final follow-up. In total, 89% of 79 patients did not experience respiratory deterioration. A total of 24% (n=19) had a positive change with over 84% (n=16) of this group no longer requiring support.

LEVEL OF EVIDENCE

Level III-prognostic.

Obstetrical, maternal and neonatal outcomes in pregnancies affected by muscular dystrophy

Objective:

Pregnancies in women affected by a muscular dystrophy are at an increased risk of adverse maternal and neonatal outcomes due to the effect of the disease on the muscular, cardiac and respiratory systems. We sought to evaluate the risk of adverse outcomes within a large population-based cohort study.

Methods:

We used the data extracted from the Nationwide Inpatient Sample (NIS) to conduct a retrospective population-based cohort study consisting of over 12 million births that occurred in the United States between 1999 and 2013. Births to mothers with muscular dystrophy were identified using the International Classification of Diseases, Ninth Revision (ICD-9) codes and were compared with births to mothers with no maternal muscular dystrophy. Unconditional logistic regression analysis was used to evaluate the adjusted effect of muscular dystrophy on maternal and neonatal outcomes.

Results:

During the 14-year study period, there was an increasing trend in the incidence of muscular dystrophy, with a cumulative incidence of 7.26 in 100,000 births. Women with muscular dystrophy and their neonates were at a significantly increased risk of adverse pregnancy outcomes: specifically, an increased risk of preeclampsia, preterm premature rupture of membranes, preterm labor, venous thromboembolism, cardiac dysrhythmia, requiring a blood transfusion and giving birth by cesarean section. Neonates born to affected mothers were at a significantly higher risk of being born preterm, with a congenital malformation and suffering intrauterine growth restriction.

Conclusion:

The risk of several adverse maternal and neonatal outcomes is increased in pregnant women with muscular dystrophy. As such, additional surveillance in order to mitigate the risk of adverse outcomes is warranted in these pregnancies.

Treating pediatric neuromuscular disorders: The future is now

Pediatric neuromuscular diseases encompass all disorders with onset in childhood and where the primary area of pathology is in the peripheral nervous system. These conditions are largely genetic in etiology, and only those with a genetic underpinning will be presented in this review. This includes disorders of the anterior horn cell (e.g., spinal muscular atrophy), peripheral nerve (e.g., Charcot-Marie-Tooth disease), the neuromuscular junction (e.g., congenital myasthenic syndrome), and the muscle (myopathies and muscular dystrophies). Historically, pediatric neuromuscular disorders have uniformly been considered to be without treatment possibilities and to have dire prognoses. This perception has gradually changed, starting in part with the discovery and widespread application of corticosteroids for Duchenne muscular dystrophy. At present, several exciting therapeutic avenues are under investigation for a range of conditions, offering the potential for significant improvements in patient morbidities and mortality and, in some cases, curative intervention. In this review, we will present the current state of treatment for the most common pediatric neuromuscular conditions, and detail the treatment strategies with the greatest potential for helping with these devastating diseases.

Synergizing Engineering and Biology to Treat and Model Skeletal Muscle Injury and Disease

Although skeletal muscle is one of the most regenerative organs in our body, various genetic defects, alterations in extrinsic signaling, or substantial tissue damage can impair muscle function and the capacity for self-repair. The diversity and complexity of muscle disorders have attracted much interest from both cell biologists and, more recently, bioengineers, leading to concentrated efforts to better understand muscle pathology and develop more efficient therapies. This review describes the biological underpinnings of muscle development, repair, and disease, and discusses recent bioengineering efforts to design and control myomimetic environments, both to study muscle biology and function and to aid in the development of new drug, cell, and gene therapies for muscle disorders. The synergy between engineering-aided biological discovery and biology-inspired engineering solutions will be the path forward for translating laboratory results into clinical practice.

Congenital muscular dystrophy: from muscle to brain

Congenital muscular dystrophies (CMDs) are a wide group of muscular disorders that manifest with very early onset of muscular weakness, sometime associated to severe brain involvement.The histologic pattern of muscle anomalies is typical of dystrophic lesions but quite variable depending on the different stages and on the severity of the disorder.Recent classification of CMDs have been reported most of which based on the combination of clinical, biochemical, molecular and genetic findings, but genotype/phenotype correlation are in constant progression due to more diffuse utilization of the molecular analysis.In this article, the Authors report on CMDs belonging to the group of dystroglycanopathies and in particular on the most severe forms represented by the Fukuyama CMD, Muscle-Eye-Brain disease and Walker Walburg syndrome.Clinical diagnosis of infantile hypotonia is particularly difficult considering the different etiologic factors causing the lesions, the difficulty in localizing the involved CNS area (central vs. peripheral) and the limited role of the diagnostic procedures at this early age.The diagnostic evaluation is not easy mainly in differentiating the various types of CMDs, and represents a challenge for the neonatologists and pediatricians. Suggestions are reported on the way to reach a correct diagnosis with the appropriate use of the diagnostic means.

Muscle redox disturbances and oxidative stress as pathomechanisms and therapeutic targets in early-onset myopathies

Because of their contractile activity and their high oxygen consumption and metabolic rate, skeletal muscles continually produce moderate levels of reactive oxygen and nitrogen species (ROS/RNS), which increase during exercise and are buffered by multiple antioxidant systems to maintain redox homeostasis. Imbalance between ROS/RNS production and elimination results in oxidative stress (OxS), which has been implicated in ageing and in numerous human diseases, including cancer, diabetes or age-related muscle loss (sarcopenia). The study of redox homeostasis in muscle was hindered by its lability, by the many factors influencing technical OxS measures and by ROS/RNS important roles in signaling pathways and adaptative responses to muscle contraction and effort, which make it difficult to define a threshold between physiological signaling and pathological conditions. In the last years, new tools have been developed that facilitate the study of these key mechanisms, and deregulation of redox homeostasis has emerged as a key pathogenic mechanism and potential therapeutic target in muscle conditions. This is in particular the case for early-onset myopathies, genetic muscle diseases which present from birth or early childhood with muscle weakness interfering with ambulation and often with cardiac or respiratory failure leading to premature death. Inherited defects of the reductase selenoprotein N in SEPN1-related myopathy leads to chronic OxS of monogenic origin as a primary disease pathomechanism. In myopathies associated with mutations of the genes encoding the calcium channel RyR1, the extracellular matrix protein collagen VI or the sarcolemmal protein dystrophin (Duchenne Muscular Dystrophy), OxS has been identified as a relevant secondary pathophysiological mechanism. OxS being drug-targetable, it represents an interesting therapeutic target for these incurable conditions, and following preclinical correction of the cell or animal model phenotype, the first clinical trials with the antioxidants N-acetylcysteine (SEPN1- and RYR1-related myopathies) or epigallocatechin-gallate (DMD) have been launched recently. In this review, we provide an overview of the mechanisms involved in redox regulation in skeletal muscle, the technical tools available to measure redox homeostasis in muscle cells, the bases of OxS as a primary or secondary pathomechanism in early-onset myopathies and the innovative clinical trials with antioxidants which are currently in progress for these so-far untreatable infantile muscle diseases. Progress in our knowledge of redox homeostasis defects in these rare muscle conditions may be useful as a model paradigm to understand and treat other conditions in which OxS is involved, including prevalent conditions with major socioeconomic impact such as insulin resistance, cachexia, obesity, sarcopenia or ageing.

New era in genetics of early-onset muscle disease: Breakthroughs and challenges

Early-onset muscle disease includes three major entities that present generally at or before birth: congenital myopathies, congenital muscular dystrophies and congenital myasthenic syndromes. Almost exclusively there is weakness and hypotonia, although cases manifesting hypertonia are increasingly being recognised. These diseases display a wide phenotypic and genetic heterogeneity, with the uptake of next generation sequencing resulting in an unparalleled extension of the phenotype-genotype correlations and "diagnosis by sequencing" due to unbiased sequencing. Perhaps now more than ever, detailed clinical evaluations are necessary to guide the genetic diagnosis; with arrival at a molecular diagnosis frequently occurring following dialogue between the molecular geneticist, the referring clinician and the pathologist. There is an ever-increasing blurring of the boundaries between the congenital myopathies, dystrophies and myasthenic syndromes. In addition, many novel disease genes have been described and new insights have been gained into skeletal muscle development and function. Despite the advances made, a significant percentage of patients remain without a molecular diagnosis, suggesting that there are many more human disease genes and mechanisms to identify. It is now technically- and clinically-feasible to perform next generation sequencing for severe diseases on a population-wide scale, such that preconception-carrier screening can occur. Newborn screening for selected early-onset muscle diseases is also technically and ethically-achievable, with benefits to the patient and family from early management of these diseases and should also be implemented. The need for world-wide Reference Centres to meticulously curate polymorphisms and mutations within a particular gene is becoming increasingly apparent, particularly for interpretation of variants in the large genes which cause early-onset myopathies: NEB, RYR1 and TTN. Functional validation of candidate disease variants is crucial for accurate interpretation of next generation sequencing and appropriate genetic counseling. Many published "pathogenic" variants are too frequent in control populations and are thus likely rare polymorphisms. Mechanisms need to be put in place to systematically update the classification of variants such that accurate interpretation of variants occurs. In this review, we highlight the recent advances made and the challenges ahead for the molecular diagnosis of early-onset muscle diseases.

The transcription coactivator ASC-1 is a regulator of skeletal myogenesis, and its deficiency causes a novel form of congenital muscle disease

Despite recent progress in the genetic characterization of congenital muscle diseases, the genes responsible for a significant proportion of cases remain unknown. We analysed two branches of a large consanguineous family in which four patients presented with a severe new phenotype, clinically marked by neonatal-onset muscle weakness predominantly involving axial muscles, life-threatening respiratory failure, skin abnormalities and joint hyperlaxity without contractures. Muscle biopsies showed the unreported association of multi-minicores, caps and dystrophic lesions. Genome-wide linkage analysis followed by gene and exome sequencing in patients identified a homozygous nonsense mutation in TRIP4 encoding Activating Signal Cointegrator-1 (ASC-1), a poorly characterized transcription coactivator never associated with muscle or with human inherited disease. This mutation resulted in TRIP4 mRNA decay to around 10% of control levels and absence of detectable protein in patient cells. ASC-1 levels were higher in axial than in limb muscles in mouse, and increased during differentiation in C2C12 myogenic cells. Depletion of ASC-1 in cultured muscle cells from a patient and in Trip4 knocked-down C2C12 led to a significant reduction in myotube diameter ex vivo and in vitro, without changes in fusion index or markers of initial myogenic differentiation. This work reports the first TRIP4 mutation and defines a novel form of congenital muscle disease, expanding their histological, clinical and molecular spectrum. We establish the importance of ASC-1 in human skeletal muscle, identify transcriptional co-regulation as novel pathophysiological pathway, define ASC-1 as a regulator of late myogenic differentiation and suggest defects in myotube growth as a novel myopathic mechanism.