Congenital myotonic dystrophy: assisted ventilation duration and outcome

Parental diagnostic delay and developmental outcomes in congenital and childhood-onset myotonic dystrophy type 1

AIM

To investigate the timing of type 1 myotonic dystrophy (DM1) diagnosis in parents of affected children and describe children's perinatal characteristics and developmental outcomes.

METHOD

This was a descriptive case series of children with congenital myotonic dystrophy (CDM) and childhood-onset myotonic dystrophy (ChDM). Parental timing of DM1 diagnosis and the perinatal, motor, and cognitive outcomes of paediatric patients were recorded.

RESULTS

A total of 139 children followed by 12 highly specialized tertiary care neuromuscular centres in Italy and one tertiary neuromuscular centre in the USA were included: 105 children with CDM and 34 children with ChDM (mean age 8 years 8 months and 12 years 2 months respectively; 49 males and 17 males respectively). Seventy (50%) parents were diagnosed with adult-onset DM1 after the affected child was diagnosed. Only 12 (17%) of the 69 parents known to be affected had prenatal testing. Of the 105 children with CDM, 98% had maternally inherited CDM, 36% were born preterm, 83% required a stay in the neonatal intensive care unit for more than 48 hours, 84% and 79% had ambulation and speech delay, and 84% had an IQ lower than 70. Of the 34 children with ChDM, 59% had paternally inherited ChDM, 91% were born at term, and 36% had an IQ lower than 70.

INTERPRETATION

Delay in diagnosing DM1 affects family planning. The prenatal and perinatal outcomes of the affected offspring emphasize the need for proactive counselling as parents may be reluctant to conduct prenatal testing.

[S3 Guideline: Treating Chronic Respiratory Failure with Non-invasive Ventilation]

The S3 guideline on non-invasive ventilation as a treatment for chronic respiratory failure was published on the website of the Association of the Scientific Medical Societies in Germany (AWMF) in July 2024. It offers comprehensive recommendations for the treatment of chronic respiratory failure in various underlying conditions, such as COPD, thoraco-restrictive diseases, obesity-hypoventilation syndrome, and neuromuscular diseases. An important innovation is the separation of the previous S2k guideline dating back to 2017, which included both invasive and non-invasive ventilation therapy. Due to increased scientific evidence and a significant rise in the number of affected patients, these distinct forms of therapy are now addressed separately in two different guidelines.The aim of the guideline is to improve the treatment of patients with chronic respiratory insufficiency using non-invasive ventilation and to make the indications and therapy recommendations accessible to all involved in the treatment process. It is based on the latest scientific evidence and replaces the previous guideline. This revised guideline provides detailed recommendations on the application of non-invasive ventilation, ventilation settings, and the subsequent follow-up of treatment.In addition to the updated evidence, important new features of this S3 guideline include new recommendations on patient care and numerous detailed treatment pathways that make the guideline more user-friendly. Furthermore, a completely revised section is dedicated to ethical issues and offers recommendations for end-of-life care. This guideline is an important tool for physicians and other healthcare professionals to optimize the care of patients with chronic respiratory failure. This version of the guideline is valid for three years, until July 2027.

Fetal Brain MRI Findings in Myotonic Dystrophy and Considerations for Prenatal Genetic Testing

Background

Congenital myotonic dystrophy type 1 (DM1) is a rare congenital neuromuscular disorder associated with high morbidity and potential early mortality requiring lifelong symptomatic management. Prenatal presentations of DM1 have been associated with nonspecific ultrasound findings such as clubbed foot, polyhydramnios, ventriculomegaly, and decreased fetal movement, but many cases of DM1 have no ultrasound anomalies.

Methods

We sought to compare the clinical course and prenatal imaging findings in two cases of DM1 using retrospective chart review.

Results

This report demonstrates potential expansion of the prenatal phenotype of DM1 including fetal SVT and frontal bossing. Both cases shared unique prenatal imaging features of lateral ventricle dilation involving the anterior bodies and frontal horns on fetal MRI.

Discussion

Because congenital DM1 is most often maternally inherited, attention to maternal symptoms, physical examination, and family history can be helpful in recognizing cases. Molecular diagnosis of DM1 requires specialized testing of the 3' untranslated region of the DMPK gene, and DM1 will not be detected by current standard prenatal genetic testing with microarray, karyotype, or exome sequencing.

Main features and disease outcome of congenital myotonic dystrophy - experience from a single tertiary center

Congenital myotonic dystrophy type 1 (CDM1) is a rare neuromuscular disease. The aim of our study was to evaluate clinical variability of CDM1 and factors that may influence survival in CDM1. Research included 24 pediatric patients with CDM1. Most of our patients had some form of hypoxic ischemic encephalopathy (HIE) (74 %), from mild to severe. Prolonged and complicated deliveries (75 %), high percentage of children resuscitated at birth (57 %) and respiratory insufficiency (46 %) with consequent hypoxia were the main reasons that could explain high percentage of HIE. Therapeutic hypothermia was applied in three children with poor outcome. Median survival of all CDM1 was 14.2 ± 1.5 years. Six patients had a fatal outcome (25 %). Their mean age of death was 3.0 ± 2.8 years. Poor prognostic factors for the survival of our CDM1 patients were: preterm delivery, resuscitation at birth, severe HIE, hypothermia treatment and permanent mechanical ventilation. Respiratory insufficiency was the main life-threatening factor. Our data clearly indicates the need to develop natural history studies in CDM1 in order to enhance the standards of care and to develop clinical trials investigating causative therapies in pediatric patients with CDM1.

Antisense oligonucleotides as a potential treatment for brain deficits observed in myotonic dystrophy type 1

Myotonic dystrophy, or dystrophia myotonica type 1 (DM1), is a multi-systemic disorder and is the most common adult form of muscular dystrophy. It affects not only muscles but also many organs, including the brain. Cerebral impairments include cognitive deficits, daytime sleepiness, and loss of visuospatial and memory functions. The expression of mutated transcripts with CUG repeats results in a gain of toxic mRNA function. The antisense oligonucleotide (ASO) strategy to treat DM1 brain deficits is limited by the fact that ASOs do not cross the blood-brain barrier after systemic administration, indicating that other methods of delivery should be considered. ASO technology has emerged as a powerful tool for developing potential new therapies for a wide variety of human diseases, and its potential has been proven in a recent clinical trial. Targeting DMPK mRNA in neural cells derived from human induced pluripotent stem cells obtained from a DM1 patient with the IONIS 486178 ASO abolished CUG-expanded foci, enabled nuclear redistribution of MBNL1/2, and corrected aberrant splicing. Intracerebroventricular injection of the IONIS 486178 ASO in DMSXL mice decreased the levels of mutant DMPK mRNAs by up to 70% throughout different brain regions. It also reversed behavioral abnormalities following neonatal administration. The present study indicated that the IONIS 486178 ASO targets mutant DMPK mRNAs in the brain and strongly supports the feasibility of a therapy for DM1 patients based on the intrathecal injection of an ASO.

Accelerating the genetic diagnosis of neurological disorders presenting with episodic apnoea in infancy

Unexplained episodic apnoea in infants (aged ≤1 year), including recurrent brief (<1 min) resolved unexplained events (known as BRUE), can be a diagnostic challenge. Recurrent unexplained apnoea might suggest a persistent, debilitating, and potentially fatal disorder. Genetic diseases are prevalent among this group, particularly in those who present with paroxysmal or episodic neurological symptoms. These disorders are individually rare and challenging for a general paediatrician to recognise, and there is often a delayed or even posthumous diagnosis (sometimes only made in retrospect when a second sibling becomes unwell). The disorders can be debilitating if untreated but pharmacotherapies are available for the vast majority. That any child should suffer from unnecessary morbidity or die from one of these disorders without a diagnosis or treatment having been offered is a tragedy; therefore, there is an urgent need to simplify and expedite the diagnostic journey. We propose an apnoea gene panel for hospital specialists caring for any infant who has recurrent apnoea without an obvious cause. This approach could remove the need to identify individual rare conditions, speed up diagnosis, and improve access to therapy, with the ultimate aim of reducing morbidity and mortality.

An Integrative Analysis of DNA Methylation Pattern in Myotonic Dystrophy Type 1 Samples Reveals a Distinct DNA Methylation Profile between Tissues and a Novel Muscle-Associated Epigenetic Dysregulation

Myotonic dystrophy type 1 (DM1) is a progressive, non-treatable, multi-systemic disorder. To investigate the contribution of epigenetics to the complexity of DM1, we compared DNA methylation profiles of four annotated CpG islands (CpGis) in the DMPK locus and neighbouring genes, in distinct DM1 tissues and derived cells, representing six DM1 subtypes, by bisulphite sequencing. In blood, we found no differences in CpGi 74, 43 and 36 in DNA methylation profile. In contrast, a CTCF1 DNA methylation gradient was found with 100% methylation in congenital cases, 50% in childhood cases and 13% in juvenile cases. CTCF1 methylation correlated to disease severity and CTG expansion size. Notably, 50% of CTCF1 methylated cases showed methylation in the CTCF2 regions. Additionally, methylation was associated with maternal transmission. Interestingly, the evaluation of seven families showed that unmethylated mothers passed on an expansion of the CTG repeat, whereas the methylated mothers transmitted a contraction. The analysis of patient-derived cells showed that DNA methylation profiles were highly preserved, validating their use as faithful DM1 cellular models. Importantly, the comparison of DNA methylation levels of distinct DM1 tissues revealed a novel muscle-specific epigenetic signature with methylation of the CTCF1 region accompanied by demethylation of CpGi 43, a region containing an alternative DMPK promoter, which may decrease the canonical promoter activity. Altogether, our results showed a distinct DNA methylation profile across DM1 tissues and uncovered a novel and dual epigenetic signature in DM1 muscle samples, providing novel insights into the epigenetic changes associated with DM1.

Respiratory outcomes in children with congenital myotonic dystrophy

PURPOSE

Congenital myotonic dystrophy (CDM) results in hypotonia and acute respiratory distress at birth. Previous studies show that prolonged periods of intubation (>4 weeks) correlate with increased mortality rates. The objective is to describe the use and duration of respiratory support in newborns with CDM and how these relate to mortality.

METHODS

A retrospective chart review was performed at a tertiary pediatric hospital among children with confirmed diagnosis of CDM. The main outcome measures were: mortality, duration of invasive mechanical ventilation (IMV) and non-invasive partial pressure ventilation (NIPPV), along with long-term use of respiratory support and equipment.

RESULTS

A total of 18 subjects met inclusion criteria, 83%.f which had documented respiratory distress at birth, 39%.equired NIPPV, and 50%.equired intubation in the neonatal period. The earliest NIPPV was initiated at day one of life, and the latest extubation to NIPPV was at 17 days of life.

CONCLUSION

This cohort required IMV for shorter periods with earlier transitions to NIPPV which suggests a possible change in practice and earlier transition to NIPPV recently. Further data are needed to determine if there is a possible correlation between the need for NIPPV/IMV and mortality rates.

Deciphering the mechanisms underlying brain alterations and cognitive impairment in congenital myotonic dystrophy

Myotonic dystrophy type 1 (DM1) is a multisystemic and heterogeneous disorder caused by the expansion of CTG repeats in the 3' UTR of the myotonic dystrophy protein kinase (DMPK) gene. There is a congenital form (CDM1) of the disease characterized by severe hypotonia, respiratory insufficiency as well as developmental delays and intellectual disabilities. CDM1 infants manifest important brain structure abnormalities present from birth while, in contrast, older patients with adult-onset DM1 often present neurodegenerative features and milder progressive cognitive deficits. Promising therapies targeting central molecular mechanisms contributing to the symptoms of adult-onset DM1 are currently in development, but their relevance for treating cognitive impairment in CDM1, which seems to be a partially distinct neurodevelopmental disorder, remain to be elucidated. Here, we provide an update on the clinical presentation of CDM1 and review recent in vitro and in vivo models that have provided meaningful insights on its consequences in development, with a particular focus on the brain. We discuss how enhanced toxic gain-of-function of the mutated DMPK transcripts with larger CUG repeats and the resulting dysregulation of RNA-binding proteins may affect the developing cortex in utero. Because the methylation of CpG islets flanking the trinucleotide repeats has emerged as a strong biomarker of CDM1, we highlight the need to investigate the tissue-specific impacts of these chromatin modifications in the brain. Finally, we outline promising potential therapeutic treatments for CDM1 and propose future in vitro and in vivo models with great potential to shed light on this disease.

Chylothorax as a complication of congenital myotonic dystrophy: A retrospective cohort study

BACKGROUND

The association between congenital myotonic dystrophy (CMD) and chylothorax is poorly recognized.

AIMS

To evaluate the proportion of chylothorax in infants with CMD compared to its prevalence in infants without CMD.

STUDY DESIGN

Single-center, retrospective, cohort study.

SUBJECTS

Infants managed at a neonatal intensive care unit from 2003 to 2019.

OUTCOME MEASURES

CMD was diagnosed using Southern blot for the quantification of CTG repeats in the dystrophia myotonica protein kinase (DMPK) gene. Prenatal and postnatal data of eligible infants with CMD were collected from the patients' medical records. The primary outcome was the proportion of chylothorax.

RESULTS

While the proportion of chylothorax in eligible infants without CMD was 0.25% (27/10714), that in infants with CMD was 50% (5/10; odds ratio (OR), 386.3; 95% confidence interval (CI), 84.4-1850.8; P < 0.001). The variables that were significantly different between infants with CMD with chylothorax and those without chylothorax were as follows: maternal age (33.0 vs. 24.8; P = 0.005), polyhydramnios (5/5 vs 1/5; P = 0.034), number of CTG repeats (1980 vs. 1500; P = 0.038), duration of invasive mechanical ventilation (220 vs. 2, P = 0.009), and duration of hospitalization (217.2 vs 68.0; P = 0.014). The mortality rate of all eligible infants with CMD was 5/10 (50%). No variables were significantly associated with mortality.

CONCLUSIONS

The proportion of chylothorax in infants with CMD was significantly higher than that in infants without CMD. Furthermore, the proportion was higher than that reported in previous studies on congenital chylothorax. This suggests that chylothorax may be frequently experienced in the clinical course of CMD.

Management of respiratory complications and rehabilitation in individuals with muscular dystrophies: 1st Consensus Conference report from UILDM - Italian Muscular Dystrophy Association (Milan, January 25-26, 2019)

Respiratory complications are common in the patient with muscular dystrophy. The periodic clinical and instrumental respiratory evaluation is extremely important. Despite the presence in the literature of updated guidelines, patient associations often report lack of knowledge of these pathologies, particularly in peripheral hospitals. The purpose of this work, inspired by the Italian Muscular Dystrophy Association (UILDM) is to improve management of respiratory problems necessary for the management of these patients complex. To this end, the main items that the specialist can meet in the follow-up of these pathologies have been analyzed and discussed, among which the respiratory basal evaluation, the criteria of adaptation to non-invasive ventilation, management of bronchial secretions, situations of respiratory emergency, indications for tracheostomy and the subject of advance directives of treatment (DAT).

The Biomarker Potential of miRNAs in Myotonic Dystrophy Type I

MicroRNAs (miRNAs) are mostly known for their gene regulation properties, but they also play an important role in intercellular signaling. This means that they can be found in bodily fluids, giving them excellent biomarker potential. Myotonic Dystrophy type I (DM1) is the most frequent autosomal dominant muscle dystrophy in adults, with an estimated prevalence of 1:8000. DM1 symptoms include muscle weakness, myotonia, respiratory failure, cardiac conduction defects, cataracts, and endocrine disturbances. Patients display heterogeneity in both age of onset and disease manifestation. No treatment or cure currently exists for DM1, which shows the necessity for a biomarker that can predict disease progression, providing the opportunity to implement preventative measures before symptoms arise. In the past two decades, extensive research has been conducted in the miRNA expression profiles of DM1 patients and their biomarker potential. Here we review the current state of the field with a tissue-specific focus, given the multi-systemic nature of DM1 and the intracellular signaling role of miRNAs.

Ethical decision-making for children with neuromuscular disorders in the COVID-19 crisis

The sudden appearance and proliferation of coronavirus disease 2019 has forced societies and governmental authorities across the world to confront the possibility of resource constraints when critical care facilities are overwhelmed by the sheer numbers of grievously ill patients. As governments and health care systems develop and update policies and guidelines regarding the allocation of resources, patients and families affected by chronic disabilities, including many neuromuscular disorders that affect children and young adults, have become alarmed at the possibility that they may be determined to have less favorable prognoses due to their underlying diagnoses and thus be assigned to lower priority groups. It is important for health care workers, policymakers, and government officials to be aware that the long-term prognoses for children and young adults with neuromuscular disorders are often more promising than previously believed due to a better understanding of the natural history of these diseases, benefits of multidisciplinary supportive care, and novel molecular therapies that can dramatically improve the disease course. Although the realities of a global pandemic have the potential to require a shift from our usual, highly individualistic standards of care to crisis standards of care, shifting priorities should nonetheless be informed by good facts. Resource allocation guidelines with the potential to affect children and young adults with neuromuscular disorders should take into account the known trajectory of acute respiratory illness in this population and rely primarily on contemporary long-term outcome data.

Myotonic Muscular Dystrophies

PURPOSE OF REVIEW

This article describes the clinical features, pathogenesis, prevalence, diagnosis, and management of myotonic dystrophy type 1 and myotonic dystrophy type 2.

RECENT FINDINGS

The prevalence of myotonic dystrophy type 1 is better understood than the prevalence of myotonic dystrophy type 2, and new evidence indicates that the risk of cancer is increased in patients with the myotonic dystrophies. In addition, descriptions of the clinical symptoms and relative risks of comorbidities such as cardiac arrhythmias associated with myotonic dystrophy type 1 have been improved.

SUMMARY

Myotonic dystrophy type 1 and myotonic dystrophy type 2 are both characterized by progressive muscle weakness, early-onset cataracts, and myotonia. However, both disorders have multisystem manifestations that require a comprehensive management plan. While no disease-modifying therapies have yet been identified, advances in therapeutic development have a promising future.

Patient-reported study of the impact of pediatric-onset myotonic dystrophy

INTRODUCTION

The prevalence and impact of symptoms affecting individuals with pediatric forms of myotonic dystrophy type-1 (DM1) are not well understood.

METHODS

Patients from the United States, Canada, and Sweden completed a survey that investigated 20 themes associated with pediatric-onset DM1. Participants reported the prevalence and importance of each theme affecting their lives. Surveys from participants were matched with surveys from their caregivers for additional analysis.

RESULTS

The most prevalent symptomatic themes included problems with hands or fingers (79%) and gastrointestinal issues (75%). Problems with urinary/bowel control and gastrointestinal issues were reported to have the greatest impact on patients' lives. Responses from participants and their caregivers had varying levels of agreement among symptomatic themes.

DISCUSSION

Many symptoms have meaningful impact on disease burden. The highest levels of agreement between caregivers and individuals with pediatric forms of myotonic dystrophy were found for physical activity themes.

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.

Orofacial strength, dysarthria, and dysphagia in congenital myotonic dystrophy

INTRODUCTION

Herein we present an exploratory study of orofacial function in children with congenital myotonic dystrophy (CDM) vs. healthy controls.

METHODS

We evaluated 41 children with CDM and 29 healthy controls for speech and swallow function and for lingual and labial strength.

RESULTS

The Iowa Oral Performance Instrument (IOPI), measuring tongue strength, and a lip force meter (LFM), measuring lip strength, had excellent interrater reliability with intraclass correlation coefficients (ICCs) of 0.75 (n = 19, P < 0.001) and 0.96 (n = 20, P < 0.001), respectively. Mean overall lingual strength was 3.5-fold less and labial strength was about 7-fold less in CDM patients than in healthy controls. Eighteen of 24 children with CDM demonstrated dysarthria and an additional 11 participants were nonverbal. Dysarthria correlated moderately with lingual strength, age, and dysphagia. Strength measures correlated moderately with dysphagia.

DISCUSSION

Children with CDM have impaired orofacial functioning that affects communication and swallowing. Reliability of strength measures may be useful for future therapeutic trials. Muscle Nerve 58: 413-417, 2018.

Consensus-based care recommendations for congenital and childhood-onset myotonic dystrophy type 1

Purpose of review

Myotonic dystrophy type 1 is a multisystemic disorder caused by a noncoding triplet repeat. The age of onset is variable across the lifespan, but in its most severe form, the symptoms appear at birth (congenital myotonic dystrophy) or in the pediatric age range (childhood-onset myotonic dystrophy). These children have a range of disabilities that reduce the lifespan and cause significant morbidity. Currently, there are no agreed upon recommendations for caring for these children.

Recent findings

The Myotonic Dystrophy Foundation recruited 11 international clinicians who are experienced with congenital and childhood-onset myotonic dystrophy to create consensus-based care recommendations. The experts used a 2-step methodology using elements of the single text procedure and nominal group technique. Completion of this process has led to the development of clinical care recommendations for this population.

Summary

Children with myotonic dystrophy often require monitoring and interventions to improve the lifespan and quality of life. The resulting recommendations are intended to standardize and improve the care of children with myotonic dystrophy.

Myotonic Dystrophy and Developmental Regulation of RNA Processing

Myotonic dystrophy (DM) is a multisystemic disorder caused by microsatellite expansion mutations in two unrelated genes leading to similar, yet distinct, diseases. DM disease presentation is highly variable and distinguished by differences in age-of-onset and symptom severity. In the most severe form, DM presents with congenital onset and profound developmental defects. At the molecular level, DM pathogenesis is characterized by a toxic RNA gain-of-function mechanism that involves the transcription of noncoding microsatellite expansions. These mutant RNAs disrupt key cellular pathways, including RNA processing, localization, and translation. In DM, these toxic RNA effects are predominantly mediated through the modulation of the muscleblind-like and CUGBP and ETR-3-like factor families of RNA binding proteins (RBPs). Dysfunction of these RBPs results in widespread RNA processing defects culminating in the expression of developmentally inappropriate protein isoforms in adult tissues. The tissue that is the focus of this review, skeletal muscle, is particularly sensitive to mutant RNA-responsive perturbations, as patients display a variety of developmental, structural, and functional defects in muscle. Here, we provide a comprehensive overview of DM1 and DM2 clinical presentation and pathology as well as the underlying cellular and molecular defects associated with DM disease onset and progression. Additionally, fundamental aspects of skeletal muscle development altered in DM are highlighted together with ongoing and potential therapeutic avenues to treat this muscular dystrophy. © 2018 American Physiological Society. Compr Physiol 8:509-553, 2018.

Physical function and mobility in children with congenital myotonic dystrophy

INTRODUCTION

Congenital myotonic dystrophy (CDM) occurs when symptoms of myotonic dystrophy present at birth. In this study we evaluated the relationship between physical function, muscle mass, and age to provide an assessment of the disease and help prepare for therapeutic trials.

METHODS

CDM participants performed timed functional tests (TFTs), the first 2 minutes of 6-minute walk tests (2/6MWTs), and myometry tests, and also performed dual-energy X-ray absorption (DEXA) scans. Healthy controls (HCs) performed TFTs, 6MWTs, and myometry.

RESULTS

Thirty-seven children with CDM and 27 HCs (age range 3-13 years) participated in the study. There were significant differences in the 10-meter walk (11.3 seconds in CDM vs. 6.8 seconds in HC) and 2MWT (91 meters in CDM vs. 193 meters in HCs). DEXA lean mass of the right arm correlated with grip strength (r = 0.91), and lean mass of the right leg correlated with 6MWT (r = 0.62).

CONCLUSION

Children with CDM have significant limitations in strength and mobility. The tests performed were reliable, and lean muscle mass may serve as a useful biomarker. Muscle Nerve 56: 224-229, 2017.

Parent-reported multi-national study of the impact of congenital and childhood onset myotonic dystrophy

AIM

The frequency and impact of symptoms experienced by patients with congenital, childhood, and juvenile-onset myotonic dystrophy (CDM/ChDM/JDM) is not documented. This report identifies symptomatic areas with the greatest disease burden in an international population of patients with early-onset myotonic dystrophy type-1 (DM1).

METHOD

We distributed surveys to parents of patients with CDM/ChDM/JDM. Patients with CDM/ChDM/JDM were members of the US National Registry of DM1 Patients and Family Members, the Canadian Neuromuscular Disease Registry, or the Swedish Health System. Surveys inquired about 325 symptoms and 20 themes associated with CDM/ChDM/JDM. Parents identified the importance of each symptom and theme to their affected child. The prevalence of each symptom and theme were compared across subgroups of patients. The statistical analysis was performed using Fisher's exact and Kruskal-Wallis tests.

RESULTS

One hundred and fifty parents returned surveys. The most frequently reported symptomatic themes in children were issues involving communication (81.7%) and problems with hands or fingers (79.6%). Problems with communication and fatigue were the issues that were reported to have the greatest impact on childrens' lives, while 24.1% of children reported cardiac disorders and 15.8% had problems with anesthesia.

INTERPRETATION

A range of symptoms contribute to the burden of disease faced by children with DM1. Many of these symptoms are under-recognized.

Disease burden and functional outcomes in congenital myotonic dystrophy: A cross-sectional study

OBJECTIVE

Herein, we describe the disease burden and age-related changes of congenital-onset myotonic dystrophy (CDM) in childhood.

METHODS

Children with CDM and age-matched controls aged 0 to 13 years were enrolled. Participants were divided into cohorts based on the following age groups: 0-2, 3-6, and 7-13 years. Each cohort received age-appropriate evaluations including functional testing, oral facial strength testing, neuropsychological testing, quality-of-life measurements, and ECG. Independent-samples t test or Wilcoxon 2-sample test was used to compare the differences between children with CDM and controls. Probability values less than 0.05 are reported as significant.

RESULTS

Forty-one participants with CDM and 29 healthy controls were enrolled. The 6-minute walk was significantly different between CDM (258.3 m [SD 176.0]) and control participants (568.2 m [SD 73.2]). The mean lip force strength was significantly different in CDM (2.1 N [SD 2.8)] compared to control participants (17.8 N [SD 7.6]). In participants with CDM, the mean IQ (65.8; SD 18.4) was 3 SDs below the mean compared to standardized norms. Measurements of grip strength, sleep quality, and quality of life were also significantly different. Strength measures (oral facial strength, grip strength, and 6-minute walk) correlated with each other but not with participant IQ.

CONCLUSIONS

This work identifies important phenotypes associated with CDM during childhood. Several measures of strength and function were significantly different between participants with CDM and controls and may be useful during future therapeutic trials.

Congenital myotonic dystrophy: ventriculomegaly and shunt considerations for the pediatric neurosurgeon

PURPOSE

Ventriculomegaly in infants with congenital myotonic dystrophy (CDM) is common, and the neurosurgical determination of shunting is complex. The natural history of CDM-associated ventriculomegaly from prenatal to natal to postnatal stages is poorly known. The relationship between macrocephaly and ventriculomegaly, incidence of shunt necessity, and early mortality outcomes lack pooled data analysis. This study aims to review clinical features and pathophysiology of CDM, with emphasis on ventriculomegaly progression, ventriculomegaly association with macrocephaly, and incidence of shunting.

METHODS

This is a literature review with pooled data analysis and case report.

RESULTS

One hundred four CDM patients were reviewed in 13 articles that mentioned CDM with ventriculomegaly and/or head circumference. Data was very limited: only 7 patients had data on the presence or absence of prenatal ventriculomegaly, 97 on ventriculomegaly at birth, and 32 on whether or not the ventricles enlarged post-natally. Three patients of 7 (43 %) had pre-natally diagnosed ventriculomegaly, 43 of 97 (44 %) had ventriculomegaly at birth, and only 5 of 32 (16 %) had progressive enlargement of ventricles post-natally. Only 5 of 104 patients had a documented shunt placement: 1 for obstructive, 1 for a post-hemorrhagic communicating, 2 for a communicating hydrocephalus without hemorrhage, and 1 with unknown indication. Of 13 macrocephalic patients with data about ventricular size, 12 had ventriculomegaly.

CONCLUSIONS

Ventriculomegaly occurs regularly with CDM but most often does not require CSF diversion. Decisions regarding neurosurgical intervention will necessarily be based on limited information, but shunting should only occur once dynamic data confirms hydrocephalus.

A Systematic Review and Meta-analysis on the Epidemiology of the Muscular Dystrophies

Background: The muscular dystrophies are a heterogeneous group of genetic muscle diseases with variable distribution of weakness and mode of inheritance.Methods: We previously performed a systematic review of worldwide population-based studies on Duchenne and Becker muscular dystrophies; the current study focused on the epidemiology of other muscular dystrophies using Medline and EMBASE databases. Two reviewers independently reviewed all abstracts, full-text articles, and abstracted data from 1985 to 2011. Pooling of prevalence estimates was performed using random-effect models.Results: A total of 1104 abstracts and 167 full-text articles were reviewed. Thirty-one studies met all eligibility criteria and were included in the final analysis. The overall pooled prevalence of combined muscular dystrophies was 16.14 (confidence interval [CI], 11.21-23.23) per 100,000. The prevalence estimates per 100,000 were 8.26 (CI, 4.99-13.68) for myotonic dystrophy, 3.95 (CI, 2.89-5.40) for facioscapulohumeral dystrophy, 1.63 (CI, 0.94-2.81) for limb girdle muscular dystrophy, and 0.99 (CI, 0.62-1.57) for congenital muscular dystrophies.Conclusions: The studies differed widely in their approaches to case ascertainment, and substantial gaps remain in the global estimates of many other types of muscular dystrophies. Additional epidemiological studies using standardized diagnostic criteria as well as multiple sources of case ascertainment will help address the economic impact and health care burden of muscular dystrophies worldwide.

[Congenital myotonic dystrophy type I in a very premature neonate: ethical concerns]

The congenital form of myotonic dystrophy type I (CDM1) corresponds to a>1500 expansion of an unstable trinucleotide (CTG) repeat. Two prognostic factors predict the risk of death in early infancy: maturity of less than 35 weeks of gestation and neonatal invasive ventilation for more than 30 days.

OBSERVATION

The case of a 29-week-old premature female infant, conceived by in vitro fertilization, is reported. Generalized hypotonia led to the diagnosis of the disease. Ethical concertation about withdrawal or maintenance of intensive care was engaged, taking into account the prolonged ventilation, the degree of prematurity, and the parental wishes for maximum care. The infant was extubated after 2 months. At 17 months, motor development and precursors of language were delayed, and difficulties in feeding had required a gastrostomy.

DISCUSSION

Technical advances in neonatal intensive care now allow CDM1 children to survive prolonged ventilation. The signification of such ventilatory needs on patient outcome, particularly for motor handicaps, speech and language delay, and mental deficiency, remains uncertain. The potential impact of in vitro fertilization on disease expression may also be considered.

CONCLUSION

CDM1 is a severe condition, but variability in clinical manifestations and absence of genotype-phenotype correlation result in problems predicting prognosis at the individual level. Ethical issues about the level of care, notably for tracheostomy and gastrostomy, should be adapted to each case, in partnership with parents.

Transient complete atrioventricular block in a preterm neonate with congenital myotonic dystrophy: case report

Congenital myotonic dystrophy (CMD) is an inherited neuromuscular disorder with cardiac rhythm abnormalities that may occur as a child grows. No report has described complete atrioventricular (AV) block detected in a neonate with CMD. We report a floppy infant of 31(+4) weeks gestation with complete AV block at birth, who was diagnosed with CMD by Southern analysis. She recovered from complete AV block 32 hr after temporary transcutaneous pacing was applied. To the best our knowledge, this is the first recorded case of a complete AV block accompanied by CMD during the neonatal period. When a newborn has a complete AV block, the physician should consider the possibility of the CMD and conduct a careful physical examination.

Congenital and infantile myotonic dystrophy

Myotonic dystrophy (DM) encompasses two gene defects, DM1 (myotonic dystrophy type 1) being currently the sole disorder leading to a childhood form of the disease. As consequence of the non coding unstable CTG repeat expansion mutation, DM1 presents as an extremely wide and diverse clinical continuum ranging from antenatal to late adult forms, the complexity of the disease being reinforced by multisystemic involvement. The congenital form appears as the most severe end of the phenotypic spectrum and may include marked neonatal hypotonia, respiratory failure, facial diplegia, contractures, and mental retardation. Brain involvement is the hallmark of childhood-onset DM1, distinguished by a normal neonatal period, with learning difficulties as the main presenting symptom, resulting from various degrees of mental delay, psychopathological manifestations, speech defects, hypersomnolence, and fatigue. In contrast, muscle weakness remains usually moderate in childhood, limited to facial weakness, ptosis, and dysarthria, until a decline from the second decade. Orthopedic manifestations including kyphoscoliosis and equinovarus may require surgery. Other organs involvement includes frequent abdominal symptoms, whereas endocrine disturbance is rare. Symptomatic cardiac arrhythmia, mainly exercise-induced, can be observed. While current treatment is mainly symptomatic, future clinical trials are expected following significant progress in pathophysiology and the recent development of molecular therapy approaches.

Neonatal neuroimaging findings in congenital myotonic dystrophy

We report on a preterm neonate of 30 weeks gestational age who presented with marked muscular hypotonia and severe respiratory failure at birth and was diagnosed with congenital myotonic dystrophy. Neuroimaging at 36 gestational weeks demonstrated diffuse T2-hyperintense signal of the supratentorial white matter and a simplified gyration and sulcation pattern. Follow-up imaging showed progressive myelination, brain maturation and decrease in T2-signal of the white matter. We discuss possible pathomechanisms for white matter signal abnormalities in this neonate.

Congenital myotonic dystrophy: Canadian population-based surveillance study

OBJECTIVES

To determine the incidence and neonatal morbidity and mortality of congenital myotonic dystrophy (CDM) in Canada.

STUDY DESIGN

The study has 2 phases. A 5-year prospective monthly surveillance of incident cases of CDM conducted via the Canadian Pediatric Surveillance Program, from March 1, 2005-February 28, 2010, and a 5-year cohort study of eligible incident cases, which is ongoing and not the subject of this report.

RESULTS

A total of 121 cases were reported, with 38 confirmed as CDM. The incidence of CDM in Canada is 2.1/100,000 (1/47,619) live births. The cases were reported from 8 provinces and 1 territory. The highest reported incidence was Ontario with 15, followed by British Columbia with 7, and Quebec with 6. External validation of cases was performed. The trinucleotide repeat level varied from 550-3100. Twenty-two (58%) of the children were the index cases for their families. Seventeen children are currently enrolled in the ongoing cohort study.

CONCLUSION

Surveillance and prospective examination of CDM at a population level is important, as the impact of this rare disease is systemic, chronic, and associated with significant morbidity and mortality throughout childhood.

Successful use of BiPAP in infants with congenital myotonic dystrophy

Reported herein are two cases of severe phenotype of congenital myotonic dystrophy (CDM) with presentation of respiratory insufficiency at birth. The infants were successfully managed with bi-level positive airway pressure (BiPAP) via nasal mask. The use of BiPAP in infants with CDM has not been reported before. The rationale for using BiPAP is discussed. BiPAP may be more effective than continuous positive airway pressure in managing respiratory insufficiency, especially in infants with the more severe phenotype of CDM.

A case report on 30-week premature twin babies with congenital myotonic dystrophy conceived by in vitro fertilization

Congenital myotonic dystrophy type 1 (DM1) presents severe generalized weakness, hypotonia, and respiratory compromise after delivery with high mortality and poor prognosis. We presented a congenital DM1 of premature twins in the 30th week of gestation. These twins were conceived by in vitro fertilization (IVF). Both babies presented apnea and hypotonia and had characteristic facial appearance. They were diagnosed DM1 by genetic method. They were complicated by chylothorax and expired at 100 and 215 days of age, respectively. Mother was diagnosed DM1 during the evaluation of babies. This is the first report on congenital DM1 which accompanied the chylothorax. More investigation on the association with chylothorax and congenital DM1 is recommended. With a case of severe neonatal hypotonia, congenital DM1 should be differentiated in any gestational age. Finally, since DM1 is a cause of infertility, we should consider DM1 in infertility clinic with detailed history and physical examination.

Congenital myotonic dystrophy in a national registry

AIM

To describe the neonatal symptoms, developmental problems and chronic multisystem medical morbidities of congenital myotonic dystrophy (CDM) patients registered in the United States National Registry of Myotonic Dystrophy - a disease-specific, self-report program maintained since 2002. Comparisons with the Canadian Paediatric Surveillance Program for CDM are highlighted.

METHODS

Genetically confirmed cases of CDM demonstrating symptoms in the first four weeks of life are described. Patients (or their caregivers) and physicians completed survey information at baseline and annually thereafter.

RESULTS

Twenty-one patients were included (13 male and eight female), ranging from three to 24 years of age. The CTG trinucleotide repeat number ranged from 940 to 2100. Gastrointestinal, pneumonia and cardiac morbidities were most common. No deaths were noted.

CONCLUSIONS

The United States Registry is a valuable resource for clinical research on patients with CDM; however, in contrast with the Canadian Paediatric Surveillance Program, some limitations are identified.

Therapeutics development in myotonic dystrophy type 1

Myotonic dystrophy (DM1), the most common adult muscular dystrophy, is a multisystem, autosomal dominant genetic disorder caused by an expanded CTG repeat that leads to nuclear retention of a mutant RNA and subsequent RNA toxicity. Significant insights into the molecular mechanisms of RNA toxicity have led to the previously unforeseen possibility that treating DM1 is a viable prospect. In this review, we briefly present the clinical picture in DM1, and describe how the research in understanding the pathogenesis of RNA toxicity in DM1 has led to targeted approaches to therapeutic development at various steps in the pathogenesis of the disease. We discuss the promise and current limitations of each with an emphasis on RNA-based therapeutics and small molecules. We conclude with a discussion of the unmet need for clinical tools and outcome measures that are essential prerequisites to proceed in evaluating these potential therapies in clinical trials.

Myotonic dystrophy types 1 and 2

Myotonic dystrophies (dystrophia myotonica, or DM) are inherited disorders characterized by myotonia and progressive muscle degeneration, which are variably associated with a multisystemic phenotype. To date, two types of myotonic dystrophy, type 1 (DM1) and type 2 (DM2), are known to exist; both are autosomal dominant disorders caused by expansion of an untranslated short tandem repeat DNA sequence (CTG)(n) and (CCTG)(n), respectively. These expanded repeats in DM1 and DM2 show different patterns of repeat-size instability. Phenotypes of DM1 and DM2 are similar but there are some important differences, most conspicuously in the severity of the disease (including the presence or absence of the congenital form), muscles primarily affected (distal versus proximal), involved muscle fiber types (type 1 versus type 2 fibers), and some associated multisystemic phenotypes. The pathogenic mechanism of DM1 and DM2 is thought to be mediated by the mutant RNA transcripts containing expanded CUG and CCUG repeats. Strong evidence supports the hypothesis that sequestration of muscle-blind like (MBNL) proteins by these expanded repeats leads to misregulated splicing of many gene transcripts in corroboration with the raised level of CUG-binding protein 1. However, additional mechanisms, such as changes in the chromatin structure involving CTCN-binding site and gene expression dysregulations, are emerging. Although treatment of DM1 and DM2 is currently limited to supportive therapies, new therapeutic approaches based on pathogenic mechanisms may become feasible in the near future.

Orthopaedic manifestations of congenital myotonic dystrophy during childhood and adolescence

BACKGROUND

Congenital myotonic dystrophy (CMD) is a dominantly inherited disorder manifested in childhood by muscle weakness which can be profound at birth, but which progressively improves over the first few years. Congenital myotonic dystrophy represents the severe end of the spectrum of myotonic dystrophy, which in milder cases may not be diagnosed until adulthood. The goal of the study was to identify and quantitate the musculoskeletal deformities which may significantly affect the function of children with CMD.

METHODS

A retrospective chart and radiograph review was performed after Institutional Review Board approval for all cases of myotonic dystrophy from 1987 to 2004 followed at a children's specialty orthopaedic hospital. Inclusion criteria were either a conclusive testing for CMD by gene testing, electromyography, and/or muscle biopsy in the child or parent and the presence of a typical clinical picture. Skeletal manifestations were classified by body segment (upper extremity, hand, spine, hip, lower extremity, foot) and by the type of deformity. Surgical procedures and outcomes were also documented.

RESULTS

Thirty children and adolescents met the inclusion criteria. The male/female ratio was 1 (15 boys and 15 girls). In 27 cases, the mother transmitted the disease, and in 2 cases, the father transmitted the disease; in one case, it was impossible to reconstitute the family history of the child who was adopted. The mean age at onset of gait was 29 months. Twenty-two (73%) out of 30 children underwent surgery for lower extremity-, foot-, or spinal-related deformities. The mean follow-up was 11.4 years (range, 3-20 years).No contractures or deformities were observed in the upper extremities. Spinal deformities affected 9 patients (30%), and 3 of these required surgery. These spinal deformities when present usually had an early onset and included thoracolumbar scoliosis as well as kyphoscoliosis. Problems at the level of the hips and knee were infrequent and included only 2 patients who had unilateral hip abduction contracture and 1 patient who had significant fixed knee flexion contracture. Congenital clubfoot occurred in 5 patients (17%) and generally responded well after posteromedial release and recurrence occurred in only one case. Developmental equinus and equinovarus exclusive of clubfoot affected 7 patients (23%), 70% of whom required surgery. Outcome after Achilles tendon lengthening was positive, and many of the children began walking soon after the Achilles lengthening, and recurrence did not occur.

CONCLUSIONS

Child with CMD are at high risk for musculoskeletal deformities of the spine and lower extremities. In our experience, correction and improved function were likely after surgery.

LEVEL OF EVIDENCE

Retrospective study; level IV.

Myotonic dystrophy type I in childhood Long-term evolution in patients surviving the neonatal period

In a retrospective study, 32 patients with myotonic dystrophy, including congenital (n=17) and infantile/juvenile forms (n=15) were studied during a long follow-up lasting 7-28 years (median: 17 years). The clinical presentation was extremely variable; however, a continuum did exist between severe and less severe congenital forms, and later-onset forms, without genotype-phenotype correlation. We observed some unusual presentations, such as 3 cases of isolated club-feet during the neonatal period, and 7 patients (23%) with a completely isolated mental deficiency, language delay and school failure, who only completed the clinical picture several years later. Wechsler scale testing was performed in all cases, and repeated with 8 patients. It demonstrated a decrease in intellectual abilities in 5 patients, suggesting the possibility of a degenerative cerebral process occurring in these children. This decrease has also been reported in some adult cases. This study illustrates the extremely heterogeneous clinical presentation of myotonic dystrophy in childhood.