Brain-related comorbidities in boys and men with Duchenne Muscular Dystrophy: A descriptive study

Probing diffusion of water and metabolites to assess white matter microstructure in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive X-linked neuromuscular disorder caused by the absence of functional dystrophin protein. In addition to muscle, dystrophin is expressed in the brain in both neurons and glial cells. Previous studies have shown altered white matter microstructure in patients with DMD using diffusion tensor imaging (DTI). However, DTI measures the diffusion properties of water, a ubiquitous molecule, making it difficult to unravel the underlying pathology. Diffusion-weighted spectroscopy (DWS) is a complementary technique which measures diffusion properties of cell-specific intracellular metabolites. Here we performed both DWS and DTI measurements to disentangle intra- and extracellular contributions to white matter changes in patients with DMD. Scans were conducted in patients with DMD (15.5 ± 4.6 y/o) and age- and sex-matched healthy controls (16.3 ± 3.3 y/o). DWS measurements were obtained in a volume of interest (VOI) positioned in the left parietal white matter. Apparent diffusion coefficients (ADCs) were calculated for total N-acetylaspartate (tNAA), choline compounds (tCho), and total creatine (tCr). The tNAA/tCr and tCho/tCr ratios were calculated from the non-diffusion-weighted spectrum. Mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), and fractional anisotropy of water within the VOI were extracted from DTI measurements. DWS and DTI data from patients with DMD (respectively n = 20 and n = 18) and n = 10 healthy controls were included. No differences in metabolite ADC or in concentration ratios were found between patients with DMD and controls. In contrast, water diffusion (MD, t = -2.727, p = 0.011; RD, t = -2.720, p = 0.011; AD, t = -2.715, p = 0.012) within the VOI was significantly higher in patients compared with healthy controls. Taken together, our study illustrates the potential of combining DTI and DWS to gain a better understanding of microstructural changes and their association with disease mechanisms in a clinical setting.

Use of the experience sampling method in adolescents with Duchenne muscular dystrophy: a feasibility study

Experience sampling methods (ESM) using mobile health (mHealth) technology with a smartphone application are increasingly used in clinical practice and research. Still, recommendations are limited in young people, and adaptations may be necessary. Patients with Duchenne muscular dystrophy (DMD) are chronically treated with steroids from a young age. However, the impact of intermittent treatment schedules on fluctuations in somatic, cognitive and behavioural symptoms is poorly investigated. Existing studies are often cross-sectional and occur in controlled clinical settings, which do not provide sufficiently detailed insights into possible correlations. ESM might alleviate these problems. ESM innovates data collection with a smartphone application, which repeatedly assesses specific symptoms and contextual factors at random moments in daily life. We aimed to evaluate its feasibility in adolescents with DMD. In three (without/with/without steroids) 4-day periods of ESM, that were nested in 10/10 or 11/9 day on/off-medication periods, we evaluated its user-friendliness and compliance, and explored its ability to objectify fluctuations in somatic, cognitive and behavioural symptom severity and their relationship with contextual factors in seven DMD patients (age range 12-18 years) using intermittent corticosteroid treatment (dosage range 0.3-0.6 mg/kg/day). Patients reported that ESM was convenient and user-friendly. We were able to capture extensive intra-individual symptom fluctuations during intermittent corticosteroid treatment that were not revealed by routine clinical assessment. Implementing ESM to evaluate symptom fluctuation patterns in relation to treatment effects shows promise in adolescents with DMD. Optimization in further research is needed.

Epilepsy in Duchenne and Becker muscular dystrophies

OBJECTIVE

Duchenne and Becker muscular dystrophies (DMD and BMD) are dystrophinopathies caused by variants in DMD gene, resulting in reduced or absent dystrophin. These conditions, characterized by muscle weakness, also manifest central nervous system (CNS) comorbidities due to dystrophin expression in the CNS. Prior studies have indicated a higher prevalence of epilepsy in individuals with dystrophinopathy compared to the general population. Our research aimed to investigate epilepsy prevalence in dystrophinopathies and characterize associated electroencephalograms (EEGs) and seizures.

METHODS

We reviewed 416 individuals with dystrophinopathy, followed up at three centers between 2010 and 2023, to investigate the lifetime epilepsy prevalence and characterize EEGs and seizures in those individuals diagnosed with epilepsy. Associations between epilepsy and type of dystrophinopathy, genotype, and cognitive involvement were studied.

RESULTS

Our study revealed a higher epilepsy prevalence than the general population (1.4%; 95% confidence interval: 0.7-3.2%), but notably lower than previously reported in smaller dystrophinopathy cohorts. No significant differences were found in epilepsy prevalence between DMD and BMD or based on underlying genotypes. Cognitive impairment was not found to be linked to higher epilepsy rates. The most prevalent epilepsy types in dystrophinopathies resembled those observed in the broader pediatric population, with most individuals effectively controlled through monotherapy.

INTERPRETATION

The actual epilepsy prevalence in dystrophinopathies may be markedly lower than previously estimated, possibly half or even less. Our study provides valuable insights into the epilepsy landscape in individuals with dystrophinopathy, impacting medical care, especially for those with concurrent epilepsy.

Observing the Clinical Course of Duchenne Muscular Dystrophy in Medicaid Real-World Healthcare Data

INTRODUCTION

Duchenne muscular dystrophy (DMD) is a rare, severe progressive neuromuscular disease. Health insurance claims allow characterization of population-level real-world outcomes, based on observed healthcare resource use. An analysis of data specific to those with Medicaid insurance is presently unavailable. The objective was to describe the real-world clinical course of DMD based on claims data from Medicaid-insured individuals in the USA.

METHODS

Individuals with DMD were identified from the MarketScan Multi-State Medicaid datasets (2013-2018). Diagnosis and procedure codes from healthcare claims were used to characterize the occurrence of DMD-relevant clinical observations; categories were scoliosis, cardiovascular-related, respiratory and severe respiratory-related, and neurologic/neuropsychiatric. Age-restricted analyses were conducted to focus on the ages at which DMD-relevant clinical observations were more likely to be captured, and to better understand the impact of both age and follow-up time.

RESULTS

Of 2007 patients with DMD identified, median (interquartile range) age at index was 14 (9-20) years, and median follow-up was 3.1 (1.6-4.7) years. Neurologic and neuropsychiatric observations were most frequently identified, among 49.3% of the cohort; followed by cardiovascular (48.5%), respiratory (38.1%), scoliosis (36.3%), and severe respiratory (25.0%). Prevalence estimates for each category were higher when analyzed within age-restricted subgroups; and increased as follow-up time increased.

CONCLUSIONS

This study is the first to use diagnosis and procedure codes from real-world Medicaid claims to document the clinical course in DMD. Findings were consistent with previously published estimates from commercially insured populations and clinical registries; and contribute to the expanding body of real-world evidence around clinical progression of patients with DMD.

Prevalence of Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in Individuals With Dystrophinopathy at a Tertiary Care Center in Chicago

OBJECTIVE

To study the prevalence of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in individuals with dystrophinopathy compared with the general population.

METHODS

Retrospective chart review to examine the prevalence of ADHD and ASD, diagnosed both formally and informally, in individuals with dystrophinopathy receiving care in the multidisciplinary neuromuscular clinic at the Ann and Robert H. Lurie Children's Hospital of Chicago.

RESULTS

Our results demonstrate an ADHD prevalence of 18.40% and ASD prevalence of 12.73%, both significantly higher than those reported for the general population. Our results revealed a significant association between ADHD diagnosis and a positive family history but did not show a statistically significant association between prevalence of ADHD and the use of steroids.

CONCLUSION

Based on our current study results, we plan to further evaluate the prevalence, in a prospective cross-sectional manner, using validated screens for both ADHD and ASD.

Neurodiversity, treatment compliance and survival in adults with Duchenne muscular dystrophy: a single-centre retrospective cohort review

Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy worldwide. With increasing survival, there is now a greater awareness of associated neurodevelopmental co-morbidities. Despite this, there is currently a limited understanding of how these co-morbidities might potentially impact on health outcomes. This study reviewed the characteristics of 37 adults with DMD who died between 2011 and 2022. The median age of death was 22.25 years, and those with neurodevelopmental co-morbidities had statistically poorer survival than those without a neurodevelopmental disorder. Notably, the proportion of patients within this cohort with a diagnosis of a neurodevelopmental disorder was higher than previously reported studies in living cohorts. This study suggests that patients with a co-morbid neurodevelopmental disorder may have worse health outcomes than those who do not.

Epilepsy in dystrophinopathies: A retrospective cohort and review of the literature

OBJECTIVE

This study aimed to assess the prevalence and characteristics of epilepsy in dystrophinopathies within a cohort of 142 patients at a tertiary neuromuscular center in Istanbul, Turkey.

METHODS

We recorded the age at seizure onset, seizure type, family history, history of febrile seizures, treatment, and EEG results. Epilepsy was classified according to the latest International League Against Epilepsy (ILAE) classification.

RESULTS

Of the 142 DMD patients, 8 experienced epileptic seizures (5.6 %). The median age of the patients was 11 years (8.0-15.2). The median age for the first DMD symptoms was 24 months (16.5-37.5). All seizures were consistent with generalized tonic-clonic seizures. Three patients are currently on anti-seizure medication.

SIGNIFICANCE

The prevalence of epilepsy in our study (5.6 %) exceeds that of the general pediatric population (0.5-1 %). However, the frequency of febrile seizures in children with dystrophinopathy is similar to that of the general population.

Astrocytes in human central nervous system diseases: a frontier for new therapies

Astroglia are a broad class of neural parenchymal cells primarily dedicated to homoeostasis and defence of the central nervous system (CNS). Astroglia contribute to the pathophysiology of all neurological and neuropsychiatric disorders in ways that can be either beneficial or detrimental to disorder outcome. Pathophysiological changes in astroglia can be primary or secondary and can result in gain or loss of functions. Astroglia respond to external, non-cell autonomous signals associated with any form of CNS pathology by undergoing complex and variable changes in their structure, molecular expression, and function. In addition, internally driven, cell autonomous changes of astroglial innate properties can lead to CNS pathologies. Astroglial pathophysiology is complex, with different pathophysiological cell states and cell phenotypes that are context-specific and vary with disorder, disorder-stage, comorbidities, age, and sex. Here, we classify astroglial pathophysiology into (i) reactive astrogliosis, (ii) astroglial atrophy with loss of function, (iii) astroglial degeneration and death, and (iv) astrocytopathies characterised by aberrant forms that drive disease. We review astroglial pathophysiology across the spectrum of human CNS diseases and disorders, including neurotrauma, stroke, neuroinfection, autoimmune attack and epilepsy, as well as neurodevelopmental, neurodegenerative, metabolic and neuropsychiatric disorders. Characterising cellular and molecular mechanisms of astroglial pathophysiology represents a new frontier to identify novel therapeutic strategies.

Psychological test usage in duchenne muscular dystrophy: An EU multi-centre study

AIM

During the last two decades brain related comorbidities of Duchenne have received growing scientific and clinical interest and therefore systematic assessment of cognition, behaviour and learning is important. This study aims to describe the instruments currently being used in five neuromuscular clinics in Europe as well as the diagnoses being made in these clinics.

METHOD

A Delphi based procedure was developed by which a questionnaire was sent to the psychologist in five of the seven participating clinics of the Brain Involvement In Dystrophinopathy (BIND) study. Instruments and diagnoses being used were inventoried for three domains of functioning (cognition, behaviour and academics) and three age groups (3-5 years, 6-18 years and adulthood 18+ years).

RESULTS

Data show wide diversity of tests being used in the five centres at different age groups and different domains. For the intelligence testing there is consensus in using the Wechsler scales, but all other domains such as memory, attention, behavioural problems and reading are tested in very different ways by different instruments in the participating centres.

CONCLUSION

The heterogeneity of tests and diagnoses being used in current clinical practice underlines the importance for developing a Standard Operating Procedure (SOP) to improve both clinical practice and scientific research over different countries and improve comparative work.

Long-term outcomes for females with early-onset dystrophinopathy

AIM

To study long-term disease course for females with early-onset dystrophinopathy, including common (female) symptoms, challenges in social participation, the need for care, and current healthcare management to support guideline development.

METHOD

Twelve females with early-onset dystrophinopathy were followed for a median period of more than 17 years (range 1-36).

RESULTS

One patient died owing to end-stage cardiac failure. Cardiac abnormalities were observed in three of the remaining 11 participants. Respiratory function was reduced in seven of 10 participants. Fatigue, myalgia, lower back pain, and arthralgia were reported in more than six of the participants. Functional status varied from exercise intolerance to wheelchair dependency. Most or all of the 10 participants reported restrictions in participation in work (n = 10), household duties (n = 10), sports (n = 9), and education (n = 8). Only a few participants received followed-up pulmonary (n = 2) or rehabilitation (n = 3) care.

INTERPRETATION

Females with early-onset dystrophinopathy experience a wide range of impairments, comorbidities, limitations in activities, and restrictions in social participation. The whole spectrum should be acknowledged in the healthcare setting. Neuromuscular and cardiac follow-up are indispensable. Additional respiratory assessment and rehabilitation care are expected to improve health status and support daily activities and participation.

WHAT THIS PAPER ADDS

No standard diagnostic procedures seem to exist for female patients suspected for dystrophinopathy. Female participants with early-onset dystrophinopathy experienced a broad scope of burdening symptoms, such as fatigue, myalgia, lower back pain, and arthralgia. None of participants worked full time, all felt restricted in paid work, and most felt restricted in education. Most participants showed decreased lung function, while only one was symptomatic. Availability of rehabilitation care may improve support for daily activities and participation for females with early-onset dystrophinopathy.

DMD Gene and Dystrophinopathy Phenotypes Associated With Mutations: A Systematic Review for Clinicians

ABSTRACT

The diagnosis of Duchenne and Becker muscular dystrophy (DBMD) is made by genetic testing in approximately 95% of cases. Although specific mutations can be associated with skeletal muscle phenotype, pulmonary and cardiac comorbidities (leading causes of death in Duchenne) have not been associated with Duchenne muscular dystrophy mutation type or location and vary within families. Therefore, identifying predictors for phenotype severity beyond frameshift prediction is important clinically. We performed a systematic review assessing research related to genotype-phenotype correlations in DBMD. While there are severity differences across the spectrum and within mild and severe forms of DBMD, few protective or exacerbating mutations within the dystrophin gene were reported. Except for intellectual disability, clinical test results reporting genotypic information are insufficient for clinical prediction of severity and comorbidities and the predictive validity is too low to be useful when advising families. Including expanded information coupled with proposed severity predictions in clinical genetic reports for DBMD is critical for improving anticipatory guidance.

Investigating the Impact of Delivery Routes for Exon Skipping Therapies in the CNS of DMD Mouse Models

Nucleic acid-based therapies have demonstrated great potential for the treatment of monogenetic diseases, including neurologic disorders. To date, regulatory approval has been received for a dozen antisense oligonucleotides (ASOs); however, these chemistries cannot readily cross the blood–brain barrier when administered systemically. Therefore, an investigation of their potential effects within the central nervous system (CNS) requires local delivery. Here, we studied the brain distribution and exon-skipping efficacy of two ASO chemistries, PMO and tcDNA, when delivered to the cerebrospinal fluid (CSF) of mice carrying a deletion in exon 52 of the dystrophin gene, a model of Duchenne muscular dystrophy (DMD). Following intracerebroventricular (ICV) delivery (unilateral, bilateral, bolus vs. slow rate, repeated via cannula or very slow via osmotic pumps), ASO levels were quantified across brain regions and exon 51 skipping was evaluated, revealing that tcDNA treatment invariably generates comparable or more skipping relative to that with PMO, even when the PMO was administered at higher doses. We also performed intra-cisterna magna (ICM) delivery as an alternative route for CSF delivery and found a biased distribution of the ASOs towards posterior brain regions, including the cerebellum, hindbrain, and the cervical part of the spinal cord. Finally, we combined both ICV and ICM injection methods to assess the potential of an additive effect of this methodology in inducing efficient exon skipping across different brain regions. Our results provide useful insights into the local delivery and associated efficacy of ASOs in the CNS in mouse models of DMD. These findings pave the way for further ASO-based therapy application to the CNS for neurological disease.

Epilepsy Characteristics in Duchenne and Becker Muscular Dystrophies

Dystrophinopathies cover a spectrum of X-linked muscle disorders including Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and cardiomyopathy due to pathogenic variants in the DMD gene. Neuropsychiatric manifestations occur approximately in one-third of patients with dystrophinopathy. Epilepsy has been described. Here we report seizure and electroencephalographic features of boys with dystrophinopathy and epilepsy. This is a retrospective chart review of eight patients with dystrophinopathy and epilepsy seen at Arkansas Children's Hospital and University of Rochester Medical center. Six patients had DMD and two had BMD. Five patients had generalized epilepsy. Three patients had focal epilepsy and the seizures were intractable in two of them. Brain imaging was available for five patients and were within normal limits. EEG abnormalities were noted in six patients. Seizures were well controlled on the current antiepileptic medication regimen in all patients. Further research is needed to better elucidate the underlying mechanisms and genotype-phenotype correlations.

Unique genotype-phenotype correlations within LAMA2-related limb girdle muscular dystrophy in Chinese patients

Background

LAMA2-related limb girdle muscular dystrophy (LGMD R23) is rare. The detailed clinical phenotypes and genetic information associated with LGMD R23 are unknown.

Methods

We conducted a retrospective cross-sectional and longitudinal study on 19 LGMD R23 patients.

Results

Normal early motor development was observed in 84.2% patients. Mild orthopedic complications were observed in 42.1% patients. 36.8% patients had seizures, which is unusually frequent in LGMD. Epilepsy was eventually diagnosed in 26.3% patients. 46.7% patients presented with motor neuropathy. Genetic analysis identified 29 pathogenic variants, with missense and frameshift variants being the most common. The mutant sites were mainly distributed in the N-terminal and G-like domains of laminin. The missense variants are distributed near the N-terminus (exons 3-11), whereas frameshift variants are distributed in exons 12-65. Five patients were diagnosed with epilepsy and all of them harbor at least one missense variants in exon 4. 71.4% variants of patients with motor neuropathy located in the LN domain.

Conclusions

Missense variants in exon 4 maybe correlated with epilepsy and variants in the LN domain maybe correlated with motor neuropathy in Chinese patients. Our study expands the clinical and genetic spectrum caused by LAMA2 variations and provides novel genotype-phenotype correlations of LGMD R23.

Prevalence of Neuropsychiatric Disorders in Duchenne and Becker Muscular Dystrophies: A Systematic Review and Meta-analysis

OBJECTIVE

To estimate the prevalence of neuropsychiatric disorders, including autism spectrum disorders (ASDs), attention-deficit hyperactivity disorder (ADHD), depression, anxiety disorders, and obsessive-compulsive disorder (OCD), in populations with Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD).

DATA SOURCES

MEDLINE (via PubMed), Scopus, Web of Science, and Cochrane Library from inception to November 2021.

STUDY SELECTION

Observational studies of individuals with DMD or BMD that estimated the prevalence of ASDs, ADHD, depression, anxiety disorders, and OCD in each population.

DATA EXTRACTION

A random-effects meta-analysis was performed on each outcome and each population (ie, DMD, BMD).

DATA SYNTHESIS

Twenty-three studies were included in the meta-analysis. In DMD, there was a prevalence of 7.0% of ASDs, 18.0% of ADHD, 11.0% of depression, 24.0% of anxiety disorders, and 12.0% of OCD. Furthermore, in BMD, there was a prevalence of 6.0% of ASDs, 28.0% of ADHD, 7.0% of depression, 25.0% of anxiety disorders, and 7.0% of OCD.

CONCLUSIONS

The prevalence of these neuropsychiatric disorders is higher among patients with DMD or BMD than among the general population, and the presence of these disorders may negatively influence optimal medical management.

Global prevalence of intellectual developmental disorder in dystrophinopathies: A systematic review and meta-analysis

AIM

To estimate the global prevalence of intellectual developmental disorder (IDD) and the IDD prevalence-genotype association in Becker muscular dystrophy (BMD) or Duchenne muscular dystrophy (DMD) according to the affected isoforms of the DMD gene: Dp427, Dp140, Dp71.

METHOD

Systematic searches in MEDLINE, Scopus, Web of Science, and the Cochrane Library were conducted from inception of each database to March 2022. Observational studies that determined the prevalence of IDD in the population with BMD or DMD were included. Meta-analyses of IDD prevalence and prevalence ratios of the IDD-genotype association were conducted.

RESULTS

Forty-nine studies were included. The prevalence of IDD in BMD was 8.0% (95% confidence interval 5.0-11.0), and in DMD it was 22.0% (18.0-27.0). Meta-analyses of IDD-genotype association showed a deleterious association between IDD and the number of isoforms affected in DMD, with a prevalence ratio = 0.43 (0.28-0.64) and 0.17 (0.09-0.34) for Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71⁺ and Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71^- comparisons respectively. However, in BMD, there was no association for Dp140⁺ /Dp71⁺ versus Dp140^- /Dp71⁺ .

INTERPRETATION

There is a high prevalence of IDD in BMD and DMD. Moreover, the number of isoforms affected is strongly and negatively associated with the prevalence of IDD in DMD.

Characterizing the Occurrence of Key Clinical Milestones in Duchenne Muscular Dystrophy in the United States Using Real-World Data

Background: Data on the clinical course of Duchenne muscular dystrophy (DMD) exist from well-characterized clinical cohorts but estimates from real-world populations are fewer. Objective: The objective was to estimate the prevalence of key clinical milestones by age, among real-world commercially-insured DMD patients in the United States. Methods: MarketScan claims (2013–2018) were used to identify males with DMD. The percentages with wheelchair use or experiencing scoliosis, neurologic/neuropsychiatric involvement, cardiomyopathy, and respiratory involvement were tabulated; as were the median (interquartile range [IQR]) ages at first observed occurrence within the claims data. Results: Among DMD patients (n = 1,964), the median (IQR) baseline age was 15 (9–21) years, and median follow-up was 1.7 years. Wheelchair use was observed in 55% of those aged 8 to 13 years at cohort entry; scoliosis, among 38% of those 8 to 10 and 52% of those 11 to 13 years; neurologic/neuropsychiatric involvement, among 41–43% of those 8 to 13 years; respiratory involvement, among 45% of those 14 to 19 years; and cardiomyopathy, among 68% of those 14 to 16 and 58% of those 17 to 19 years. Conclusions: The prevalence of key clinical milestones across ages was broadly consistent with published findings. Variability in estimates reflect clinical heterogeneity; these contemporary estimates from real-world data help characterize clinical outcomes in DMD.

Synaptic alterations as a neurodevelopmental trait of Duchenne muscular dystrophy

Dystrophinopaties, e.g., Duchenne muscular dystrophy (DMD), Becker muscular dystrophy and X-linked dilated cardiomyopathy are inherited neuromuscular diseases, characterized by progressive muscular degeneration, which however associate with a significant impact on general system physiology. The more severe is the pathology and its diversified manifestations, the heavier are its effects on organs, systems, and tissues other than muscles (skeletal, cardiac and smooth muscles). All dystrophinopaties are characterized by mutations in a single gene located on the X chromosome encoding dystrophin (Dp427) and its shorter isoforms, but DMD is the most devasting: muscular degenerations manifests within the first 4 years of life, progressively affecting motility and other muscular functions, and leads to a fatal outcome between the 20s and 40s. To date, after years of studies on both DMD patients and animal models of the disease, it has been clearly demonstrated that a significant percentage of DMD patients are also afflicted by cognitive, neurological, and autonomic disorders, of varying degree of severity. The anatomical correlates underlying neural functional damages are established during embryonic development and the early stages of postnatal life, when brain circuits, sensory and motor connections are still maturing. The impact of the absence of Dp427 on the development, differentiation, and consolidation of specific cerebral circuits (hippocampus, cerebellum, prefrontal cortex, amygdala) is significant, and amplified by the frequent lack of one or more of its lower molecular mass isoforms. The most relevant aspect, which characterizes DMD-associated neurological disorders, is based on morpho-functional alterations of selective synaptic connections within the affected brain areas. This pathological feature correlates neurological conditions of DMD to other severe neurological disorders, such as schizophrenia, epilepsy and autistic spectrum disorders, among others. This review discusses the organization and the role of the dystrophin-dystroglycan complex in muscles and neurons, focusing on the neurological aspect of DMD and on the most relevant morphological and functional synaptic alterations, in both central and autonomic nervous systems, described in the pathology and its animal models.

Epileptic disorders in Becker and Duchenne muscular dystrophies: a systematic review and meta-analysis

Dystrophin alterations in the brain have been associated with an increased risk of epilepsy in Becker and Duchenne muscular dystrophies (BMD and DMD). Moreover, an association between the mutation site and the risk of epilepsy is not ruled out. The aim of this systematic review and meta-analysis was to estimate the prevalence of epilepsy in BMD and DMD populations and to establish a possible association between the site of mutation in the dystrophin gene and the risk of epilepsy. Systematic searches of Medline, Scopus, Web of Science, and Cochrane Library were conducted to identify relevant studies published from inception to January 2022. Observational studies of participants with BMD/DMD estimating the prevalence of epilepsy were included. The main outcome was the prevalence of epilepsy, and the secondary outcome was the prevalence ratio considering genotype. A random effects meta-analysis was performed for the prevalence of epilepsy. Eight studies were included in the systematic review and meta-analysis. The prevalence of epilepsy was 7% (95% CI 3-11%) in BMD, 5% (95% CI 2-8%) in DMD, and 5% (95% CI 3-7%) in the overall estimate. No association was observed between mutation site and the prevalence of epilepsy. BMD/DMD is strongly associated with the prevalence of epilepsy, with a higher prevalence in BMD/DMD populations than in the general population, probably owing to alterations in Dp427. The current evidence does not support the hypothesis that Dp140 or Dp71 affect epilepsy risk.

Dystrophin deficiency affects human astrocyte properties and response to damage

In addition to progressive muscular degeneration due to dystrophin mutations, 1/3 of Duchenne muscular dystrophy (DMD) patients present cognitive deficits. However, there is currently an incomplete understanding about the function of the multiple dystrophin isoforms in human brains. Here, we tested the hypothesis that dystrophin deficiency affects glial function in DMD and could therefore contribute to neural impairment. We investigated human dystrophin isoform expression with development and differentiation and response to damage in human astrocytes from control and induced pluripotent stem cells from DMD patients. In control cells, short dystrophin isoforms were up-regulated with development and their expression levels changed differently upon neuronal and astrocytic differentiation, as well as in 2-dimensional versus 3-dimensional astrocyte cultures. All DMD-astrocytes tested displayed altered morphology, proliferative activity and AQP4 expression. Furthermore, they did not show any morphological change in response to inflammatory stimuli and their number was significantly lower as compared to stimulated healthy astrocytes. Finally, DMD-astrocytes appeared to be more sensitive than controls to oxidative damage as shown by their increased cell death. Behavioral and metabolic defects in DMD-astrocytes were consistent with gene pathway dysregulation shared by lines with different mutations as demonstrated by bulk RNA-seq analysis. Together, our DMD model provides evidence for altered astrocyte function in DMD suggesting that defective astrocyte responses may contribute to neural impairment and might provide additional potential therapeutic targets.

Generation of dystrophin short product-specific tag-insertion mouse: distinct Dp71 glycoprotein complexes at inhibitory postsynapse and glia limitans

Duchenne muscular dystrophy (DMD), the most severe form of dystrophinopathies, is a fatal X-linked recessive neuromuscular disorder characterized by progressive muscle degeneration and various extents of intellectual disabilities. Physiological and pathological roles of the responsible gene, dystrophin, in the brain remain elusive due to the presence of multiple dystrophin products, mainly full-length dystrophin, Dp427, and the short product, Dp71. In this study, we generated a Dp71-specific hemagglutinin (HA) peptide tag-insertion mice to enable specific detection of intrinsic Dp71 expression by anti-HA-tag antibodies. Immunohistochemical detections in the transgenic mice demonstrated Dp71 expression not only at the blood-brain barrier, where astrocytic endfeet surround the microvessels, but also at the inhibitory postsynapse of hippocampal dentate granule neurons. Interestingly, hippocampal cornu ammonis (CA)1 pyramidal neurons were negative for Dp71, although Dp427 detected by anti-dystrophin antibody was clearly present at the inhibitory postsynapse, suggesting cell-type dependent dystrophin expressions. Precise examination using the primary hippocampal culture validated exclusive localization of Dp71 at the inhibitory postsynaptic compartment but not at the excitatory synapse in neurons. We further performed interactome analysis and found that Dp71 formed distinct molecular complexes, i.e. synapse-associated Dp71 interacted with dystroglycan (Dg) and dystrobrevinβ (Dtnb), whereas glia-associated Dp71 did with Dg and dystrobrevinα (Dtna). Thus, our data indicate that Dp71 and its binding partners are relevant to the inhibitory postsynaptic function of hippocampal granule neurons and the novel Dp71-transgenic mouse provides a valuable tool to understand precise physiological expressions and functions of Dp71 and its interaction proteins in vivo and in vitro.

Principles of Astrogliopathology

The role of astrocytes in the nervous system pathology was early on embraced by neuroscientists at end of the nineteenth and the beginning of the twentieth century, only to be pushed aside by neurone-centric dogmas during most of the twentieth century. However, the last decade of the twentieth century and the twenty-first century have brought the astroglial "renaissance", which has put astroglial cells as key players in pathophysiology of most if not all disorders of the nervous system and has regarded astroglia as a fertile ground for therapeutic intervention.Astrocytic contribution to neuropathology can be primary, whereby cell-autonomous changes, such as mutations in gene encoding for glial fibrillary acidic protein, can drive the pathologic progression, in this example, Alexander disease. They can also be secondary, when astrocytes respond to a variety of insults to the nervous tissue. Regardless of their origin, being cell-autonomous or not, changes in astroglia that occur in pathology, that is, astrogliopathology, can be contemporary and arbitrary classified into four forms: (i) reactive astrogliosis, (ii) astrocytic atrophy with loss of function, (iii) pathological remodelling of astrocytes and (iv) astrodegeneration morphologically manifested as clasmatodendrosis. Inevitably, as with any other classification, this classification of astrogliopathology awaits its revision that shall be rooted in new discoveries and concepts.

Characterizing demographics, comorbidities, and costs of care among populations with Duchenne muscular dystrophy with Medicaid and commercial coverage

BACKGROUND: Duchenne muscular dystrophy (DMD) is a severe X-linked progressive neurodegenerative disease characterized by loss of ambulation, cardiomyopathy, respiratory insufficiency, and early mortality. Few data are available that describe the direct medical costs among patients with DMD in the United States. OBJECTIVE: To characterize the demographics, comorbidity burden, and direct monthly costs of care among patients with DMD with Medicaid and with commercial insurance coverage. METHODS: IBM MarketScan Commercial and Multi-State Medicaid claims (2013-2018) were used to identify males aged 30 years or under with diagnostic codes for muscular dystrophy or DMD; additional exclusion criteria were applied to identify those with probable DMD. Baseline characteristics and comorbidities were tabulated. The frequency of health care resource use and median (interquartile range [IQR]) monthly costs (in 2018 USD) were estimated from those with at least 12 months of continuous follow-up. RESULTS: Median (IQR) baseline ages were similar between the Medicaid (14 [9-20] years; n = 2,007) and commercial (15 [9-21] years; n = 1,964) DMD cohorts. The frequency of comorbidities over the period was slightly higher with those on Medicaid. The median duration of follow-up was 3.1 years among members of the Medicaid DMD cohort and 1.7 years among the commercial DMD cohort. Median monthly resource use was generally higher among the Medicaid DMD cohort; nonetheless, median (IQR) monthly costs were similar at $1,735 ($367-$5,281) for the Medicaid DMD cohort vs $1,883 ($657-$6,796) for the commercial DMD cohort. CONCLUSIONS: The demographic characteristics and median direct medical costs were similar between patients with commercial vs Medicaid coverage, even though patients with Medicaid coverage had higher resource use. Despite challenges in definitively identifying DMD patients using claims data, these findings help characterize contemporary DMD populations in the United States and the related direct economic burden to the payer. DISCLOSURES: This study was funded by Sarepta Therapeutics, Inc. Klimchak and Gooch are employees of Sarepta Therapeutics Inc. Szabo, Qian, and Popoff are employees of Broadstreet HEOR, which received funds from Sarepta Therapeutics, Inc., for work on this study. Iannaccone has received research funding or consulting fees from Avexis, Biogen, Fibrogen, Mallinkrodt, Regeneron, Sarepta Therapeutics, Inc., Scholar Rock, PTC Therapeutics, Pfizer, MDA, CureSMA, NIH, Genentech-Roche, and BCBS. Publication of the study results was not contingent on the sponsor's approval or censorship of the manuscript. Information from this study was presented, in part, at the AMCP Virtual Annual Meeting, April 21-24, 2020.

Autism Spectrum Disorder and Duchenne Muscular Dystrophy: A Clinical Case on the Potential Role of the Dystrophin in Autism Neurobiology

A diagnosis of autism spectrum disorder is reported in up to 19% of dystrophinopathies. However, over the last ten years, only a few papers have been published on this topic. Therefore, further studies are required to analyze this association in depth and ultimately to understand the role of the brain dystrophin isoform in the pathogenesis of ASD and other neurodevelopmental disorders. In this paper, we report a clinical case of a patient affected by ASD and Duchenne muscular dystrophy, who carries a large deletion of the dystrophin gene. Then we present a brief overview of the literature about similar cases and about the potential role of the dystrophin protein in the neurobiology of autism spectrum disorder.

The expanding spectrum of dystrophinopathies: HyperCKemia to manifest female carriers

Background:

X-linked dystrophinopathies have a wide spectrum of manifestation. The most common forms are severe Duchenne muscular dystrophy (DMD) and Becker’s muscular dystrophy (BMD). However, less common manifestations are isolated cardiomyopathy, myalgia, cramps, rhabdomyolysis, hyperCKemia, and manifest female carriers.

Materials and Methods:

This case series is a part of an ongoing long-term prospective cohort of children with DMD and BMD from the year 2013. The clinical details are maintained in the clinic files and standard management protocols are followed. For this case series, clinical details were collected from the clinic files and recorded on a case record proforma. Details of cardiology, radiology, and genetic investigations were collected.

Results:

We report cases of classical DMD, BMD, manifest female carrier with proximal pelvic girdle weakness, a female carrier with isolated dilated cardiomyopathy, and infantile-onset asymptomatic hyperCKemia. We also report less common but notable clinical presentations of DMD, autism, intellectual disability, epilepsy, and asymptomatic transaminitis.

Conclusions:

It is important for clinicians to be aware of these less common clinical presentations for prompt diagnosis, and to avoid unnecessary investigations. Here, we report the clinical spectrum of dystrophinopathies seen in pediatric neuromuscular clinic and emphasize the variability and expanding knowledge about different manifestations of dystrophinopathies.

Assessing Physical Activity Using Accelerometers in Youth with Duchenne Muscular Dystrophy

BACKGROUND

Physical activity, assessed by accelerometers, has been proposed as a quantitative outcome measure for patients with DMD, but research is limitedObjective:To assess the total amount and patterns of physical activity in patients with DMD using accelerometers.

METHODS

Physical activity was assessed in patients with DMD (n = 49, 13.6±4.0-year-old) and age- and sex-matched healthy controls (n = 15, 14.0±2.3-year-old) using wrist- and ankle-worn accelerometers. To assess the amount of activity, accelerometer recordings were converted into acceleration estimates (counts/min). Patterns of activity were assessed as the time that participants spent in sedentary, low-intensity, and moderate-to-vigorous physical activity categories. The sedentary category was divided into three (sedentary -1, -2, and -3) and the low-intensity into two (low-intensity-1, and -2) subcategories.

RESULTS

Physical activity across intensity categories differed between study groups (p < 0.001). Patients with DMD spent on average 98.8% of their daytime in the sedentary and low-intensity categories. Compared to non-ambulatory, ambulatory patients spent more time in sedentary-3 and low-intensity-2 subcategories (p < 0.001). Amount of activity was lower in all patients than controls (p < 0.05) and in non-ambulatory than ambulatory patients and controls (p < 0.001), but similar between ambulatory patients and controls. Activity measures in patients were significantly affected by age and ambulation status (p < 0.05) but not corticosteroid use.

CONCLUSION

Patients with DMD spent most of their daytime in sedentary and low-intensity activities. Dividing these intensities into three and two subcategories, respectively, allows better characterization of activity patterns in DMD. Ambulation status and age but not corticosteroid use affected activity measures in patients with DMD.

Dystrophin Dp71 and the Neuropathophysiology of Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is caused by frameshift mutations in the DMD gene that prevent the body-wide translation of its protein product, dystrophin. Besides a severe muscle phenotype, cognitive impairment and neuropsychiatric symptoms are prevalent. Dystrophin protein 71 (Dp71) is the major DMD gene product expressed in the brain and mutations affecting its expression are associated with the DMD neuropsychiatric syndrome. As with dystrophin in muscle, Dp71 localises to dystrophin-associated protein complexes in the brain. However, unlike in skeletal muscle; in the brain, Dp71 is alternatively spliced to produce many isoforms with differential subcellular localisations and diverse cellular functions. These include neuronal differentiation, adhesion, cell division and excitatory synapse organisation as well as nuclear functions such as nuclear scaffolding and DNA repair. In this review, we first describe brain involvement in DMD and the abnormalities observed in the DMD brain. We then review the gene expression, RNA processing and functions of Dp71. We review genotype-phenotype correlations and discuss emerging cellular/tissue evidence for the involvement of Dp71 in the neuropathophysiology of DMD. The literature suggests changes observed in the DMD brain are neurodevelopmental in origin and that their risk and severity is associated with a cumulative loss of distal DMD gene products such as Dp71. The high risk of neuropsychiatric syndromes in Duchenne patients warrants early intervention to achieve the best possible quality of life. Unravelling the function and pathophysiological significance of dystrophin in the brain has become a high research priority to inform the development of brain-targeting treatments for Duchenne.

Relationships between DMD mutations and neurodevelopment in dystrophinopathy

OBJECTIVE

We performed a prospective, cross-sectional analysis of neurodevelopmental concerns and psychosocial adjustment in relation to DMD mutations in young steroid-naive boys with dystrophinopathy.

METHODS

We evaluated 196 steroid-naive boys with dystrophinopathy who were enrolled in the Finding the Optimal Regimen for Duchenne Muscular Dystrophy trial. The neurodevelopmental concerns and psychosocial adjustment challenges were analyzed in relation to DMD mutation. A parent or legal guardian reported neurodevelopmental concerns in 4 domains (speech, learning and attentional difficulties, and autism spectrum disorder [ASD]) and completed the Personal Adjustment and Role Skills Scale to assess psychosocial adjustment. We also assessed whether boys of DMD carrier mothers were more vulnerable to speech delay and learning difficulties.

RESULTS

We found that 39% of boys were reported to have speech delay with a mean age of speaking at 28 months (range 7-66 months). Learning difficulties were reported in 28% of participants. Inattentive-overactive and oppositional-defiant behavior was reported in 8% and 5% of participants, respectively. Psychosocial adjustment challenges were reported in 4% of participants. An ASD diagnosis was reported in 3 participants. Speech delay and learning difficulties were more common in boys with mutations downstream of DMD exon 45. Neurodevelopmental concerns were not associated with DMD deletion, duplication, or point mutation subtype. Boys of DMD carrier mothers did not have longer speech delay or more learning difficulties.

CONCLUSION

Our data support evidence for a relationship between neurodevelopmental concerns and DMD mutation. A longitudinal assessment of developmental trajectory is necessary to evaluate how specific DMD mutations affect brain function.

Another Rush to Judgment: The Imaginary Worlds of ICER and Recommendations in Duchenne Muscular Dystrophy

Previous commentaries in the Formulary Evaluation section of INNOVATIONS in Pharmacy have pointed to the lack of credibility in modeled claims for cost-effectiveness and associated recommendations for pricing by the Institute for Clinical and Economic Review (ICER). The principal objection to ICER reports has been that their modeled claims fail the standards of normal science: they are best seen as pseudoscience. The purpose of this latest commentary is to consider the recently released ICER report for Duchennemuscular dystrophy (DMD). As ICER has continued in the case of DMD to apply its modeled cost utility framework with consequent recommendations for pricing adjustments, these recommendations also lack credibility. This commentary emphasizes again not only why the ICER methodology fails to meet the standards of normal science but to point to the importance in rare diseases for accelerated approval, while recognizing that evidence generation will continue.While this assessment of the ICER DMD model does not imply any support for this methodology, a key point is the application of quality of life measures which fail to capture the experience of patients with DMD and, importantly, the interests of both patients and caregivers. While ICER would argue that even with a limited evidence base it is important to address issues of pricing and access for new products, their reports are used as justification for coverage and reimbursement by insurers and health system decision makers without recognition of their lack of scientific merit. This rush to judgement by ICER must raise concerns about potentially adverse formulary decisions that result in access restrictions on new products. If ICER is to make a contribution to the entry of new products in the health market place then it should consider an alternative methodology that generates claims that are empirically evaluable in a timeframe relevant to health decision makers. As it stands, ICER's recommendation should be rejected. This is not a research program that meets accepted scientific standards but one that relies on the willingness of an audience to accept the proposition that evidence is constructed not discovered.

Methylphenidate use in males with Duchenne muscular dystrophy and a comorbid attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a common comorbidity in Duchenne muscular dystrophy (DMD). Until now, treatment with methylphenidate (MPH) has never been systematically assessed and described in this population. Our aim was to evaluate the effectiveness and safety of short acting MPH for learning problems in males with DMD and ADHD. Neuropsychological (cognition and behavior) and medical data of a sample of ten males (mean age = 8.1 years, range 6.3-9.8) with DMD and an ADHD diagnosis was retrospectively analyzed at baseline (T0; without MPH), short-term follow-up (T1; with MPH; mean interval T0-T1 = 8.3 months, range 4.3-15.6), and long-term follow-up (T2; mean interval T1-T2 = 23.1 months, range 2.6-77.7). An initial MPH dose of 5 mg/day was given on school mornings, with an increase of 2.5-5 mg/week depending on individual tolerance and treatment response, until a sufficiently effective dose was reached (range 0.2-0.6 mg/kg/day). At T1, results demonstrated an improvement in attention (i.e. concentration, impulsivity, and distractibility) in four patients. Suboptimal effects were reported in four patients, and no effects in two patients. At T2, seven patients showed considerable improvement in attention. No major side effects were reported. Overall, our data show that short acting MPH can be clinically effective for learning problems in males with DMD and ADHD, with regular cardiac follow-up, and close monitoring of side effects and neuropsychological effects. Furthermore, this underscores the importance of the use of validated cognitive and behavioral measurement tools with adequate sensitivity to objectively evaluate the effect of MPH.

The expression of the distal dystrophin isoforms Dp140 and Dp71 in the human epileptic hippocampus in relation to cognitive functioning

Dystrophin is an important protein within the central nervous system. The absence of dystrophin, characterizing Duchenne muscular dystrophy (DMD), is associated with brain related comorbidities such as neurodevelopmental (e.g., cognitive and behavioural) deficits and epilepsy. Especially mutations in the downstream part of the DMD gene affecting the dystrophin isoforms Dp140 and Dp71 are found to be associated with cognitive deficits. However, the function of Dp140 is currently not well understood and its expression pattern has previously been implicated to be developmentally regulated. Therefore, we evaluated Dp140 and Dp71 expression in human hippocampi in relation to cognitive functioning in patients with drug-resistant temporal lobe epilepsy (TLE) and post-mortem controls. Hippocampal samples obtained as part of epilepsy surgery were quantitatively analyzed by Western blot and correlations with neuropsychological test results (i.e., memory and intelligence) were examined. First, we demonstrated that the expression of Dp140 does not appear to differ across different ages throughout adulthood. Second, we identified an inverse correlation between memory loss (i.e., verbal and visual memory), but not intelligence (i.e., neither verbal nor performance), and hippocampal Dp140 expression. Finally, patients with TLE appeared to have similar Dp140 expression levels compared to post-mortem controls without neurological disease. Dp140 may thus have a function in normal cognitive (i.e., episodic memory) processes.