Attention deficit hyperactivity disorder and cognitive function in Duchenne muscular dystrophy: phenotype-genotype correlation

The care of patients with Duchenne, Becker, and other muscular dystrophies in the COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) pandemic has resulted in the reorganization of health-care settings affecting clinical care delivery to patients with Duchenne and Becker muscular dystrophy (DBMD) as well as other inherited muscular dystrophies. The magnitude of the impact of this public health emergency on the care of patients with DBMD is unclear as they are suspected of having an increased risk for severe manifestations of COVID-19. In this article, the authors discuss their consensus recommendations pertaining to care of these patients during the pandemic. We address issues surrounding corticosteroid and exon-skipping treatments, cardiac medications, hydroxychloroquine use, emergency/respiratory care, rehabilitation management, and the conduct of clinical trials. We highlight the importance of collaborative treatment decisions between the patient, family, and health-care provider, considering any geographic or institution-specific policies and precautions for COVID-19. We advocate for continuing multidisciplinary care for these patients using telehealth.

Cognitive Deficits in Myopathies

Myopathies represent a wide spectrum of heterogeneous diseases mainly characterized by the abnormal structure or functioning of skeletal muscle. The current paper provides a comprehensive overview of cognitive deficits observed in various myopathies by consulting the main libraries (Pubmed, Scopus and Google Scholar). This review focuses on the causal classification of myopathies and concomitant cognitive deficits. In most studies, cognitive deficits have been found after clinical observations while lesions were also present in brain imaging. Most studies refer to hereditary myopathies, mainly Duchenne muscular dystrophy (DMD), and myotonic dystrophies (MDs); therefore, most of the overview will focus on these subtypes of myopathies. Most recent bibliographical sources have been preferred.

Mental health and coping strategies in families of children and young adults with muscular dystrophies

BACKGROUND

Living with a progressive disease as muscular dystrophy (MD) can be challenging for the patient and the entire family from both emotional and practical point of view. We aimed to extend our previously published data about mental health in patients with MDs, also investigating coping profiles of both themselves and their parents. Furthermore, we wanted to verify whether psychological adaptation of patients can be predicted by coping strategies, taking also into account physical impairment, cognitive level and socioeconomic status.

METHODS

112 patients with MDs, aged 2-32 were included. Their emotional and behavioural features were assessed through parent- and self-report Achenbach System for Empirically Based Assessment questionnaires and Strength and Difficulties Questionnaires. Development and Well-Being Assessment or Autism Diagnostic Observation Schedule were administered to confirm suspected diagnoses. Coping profile of both parents and patients was assessed through the self-administered New Italian Version of the Coping Orientation to the Problems Experienced questionnaire and its relationship with emotional/behavioural outcome was examined in linear regression analyses.

RESULTS

High prevalence of intellectual disability and autism spectrum disorders was confirmed in Duchenne MD. Despite the high rate of internalizing symptomatology, we did not report higher rate of psychopathological disorders compared to general population. Parents tend to rely more on positive reinterpretation and less on disengagement coping. Avoidance coping, whether used by parents or patients, and ID, predicted increased emotional/behavioural problems.

CONCLUSIONS

Psychosocial interventions should address problems of anxiety and depression that people with MDs frequently experience, even through fostering parents' and childrens' engagement coping over disengagement coping.

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.

Neurodevelopmental, behavioral, and emotional symptoms common in Duchenne muscular dystrophy

INTRODUCTION

We studied neurodevelopmental and behavioral/emotional symptoms in patients with Duchenne muscular dystrophy (DMD).

METHODS

Retrospective case series of neurodevelopmental and behavioral/emotional symptoms obtained through review of systems of 700 DMD patients in relation to dystrophin gene mutations.

RESULTS

The most common symptoms encountered were emotional/behavioral dysregulation (38.7%), inattention/hyperactive features (31.4%), obsessive and compulsive features (25.0%), and language/speech delays (24.4%). Most patients (72.7%) had at least one symptom. Patients with mutations near the 3' end of the dystrophin gene were at higher risk for developing inattention/hyperactive features, language/speech delays, and global intellectual delays. Those with mutations between exon 31 and 79 had higher risk of clustering of symptoms when compared with those upstream of exon 30.

DISCUSSION

Neurodevelopmental, emotional, and behavioral symptoms are common comorbidities in DMD. There is higher prevalence of inattention/hyperactive features, language/speech delays, and global intellectual delays in genotypes affecting the 3' end of the dystrophin gene.

The Neurocognitive and Behavioral Profiles of 3 Brothers With Becker Muscular Dystrophy

Becker muscular dystrophy patients generally carry in-frame mutations in the dystrophin gene, allowing the production of partially functional dystrophin protein. The presence of cognitive and behavioral comorbidities and the relation with the location of mutations has been scarcely investigated in Becker. This case report describes the neurocognitive and behavioral profiles of 3 brothers with Becker carrying an in-frame deletion of exons 45-48. The 3 cases underwent 2 consecutive neuropsychological assessments of which one assessment took place when they completed their primary education (age range of the cases: 11.2 -12.1 years). Intellectual abilities were normal to high and all cases had difficulties with processing speed and math. The brothers differed in intellectual abilities, executive functions, working memory, attention and reading abilities. Variability in cognitive development was noted as well. This report suggests that cognitive and behavioral functions in Becker vary regardless of gene mutation and exposer to similar environmental factors.

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.

Dystrophin deficiency leads to dysfunctional glutamate clearance in iPSC derived astrocytes

Duchenne muscular dystrophy (DMD) results, beside muscle degeneration in cognitive defects. As neuronal function is supported by astrocytes, which express dystrophin, we hypothesized that loss of dystrophin from DMD astrocytes might contribute to these cognitive defects. We generated cortical neuronal and astrocytic progeny from induced pluripotent stem cells (PSC) from six DMD subjects carrying different mutations and several unaffected PSC lines. DMD astrocytes displayed cytoskeletal abnormalities, defects in Ca⁺² homeostasis and nitric oxide signaling. In addition, defects in glutamate clearance were identified in DMD PSC-derived astrocytes; these deficits were related to a decreased neurite outgrowth and hyperexcitability of neurons derived from healthy PSC. Read-through molecule restored dystrophin expression in DMD PSC-derived astrocytes harboring a premature stop codon mutation, corrected the defective astrocyte glutamate clearance and prevented associated neurotoxicity. We propose a role for dystrophin deficiency in defective astroglial glutamate homeostasis which initiates defects in neuronal development.

Instruments for the Assessment of Behavioral and Psychosocial Functioning in Duchenne and Becker Muscular Dystrophy; a Systematic Review of the Literature

Objective

This systematic review aims to provide an overview of instruments used to assess behavioral and psychosocial functioning of patients with Duchenne and Becker muscular dystrophy, as well as to review the psychometric properties and applicability of these instruments.

Methods

Five databases (Embase, Psyc.info, ERIC, Pubmed/Medline, and Cochrane) were searched from inception to June, 2018. Potential articles were rated by two independent reviewers. A predefined PROSPERO form (CRD42017074518) was used to extract data from included articles.

Results

Sixty-one instruments were used in 54 studies. The Child Behavior Checklist is commonly used, but it lacks disease specific psychometric information. Sixteen instruments that contained disease specific psychometric information were included for final evaluation. The results displayed three instruments that are potentially valid for screening of psychosocial problems: The Psychosocial Adjustment and Role Skills Scale 3rd edition, the Pediatric Quality of Life Inventory Generic module, and the Life Satisfaction Index for Adolescents with Duchenne muscular dystrophy. Appropriate instruments for screening of behavioral problems may be: the Strengths and Difficulties Questionnaire, the Generalized Anxiety Disorder-7 item questionnaire, and the Patient Health Questionnaire-9 item questionnaire.

Conclusions

Further research on psychometric properties of screening instruments is crucial to ascertain a gold standard for clinical and research purposes. Meanwhile, for definite diagnostics purposes we recommend a multimethod, multisource, multisetting assessment in this high-risk population.

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.

Neurodevelopmental Needs in Young Boys with Duchenne Muscular Dystrophy (DMD): Observations from the Cooperative International Neuromuscular Research Group (CINRG) DMD Natural History Study (DNHS)

INTRODUCTION

Duchenne muscular dystrophy (DMD) is the most common X-linked neuromuscular condition manifested by progressive skeletal muscle weakness, cardiopulmonary involvement and cognitive deficits. Neurodevelopmental symptoms and signs are under-appreciated in this population despite the recognition that cognition has a major impact on quality-of-life. We describe the neurodevelopmental needs in a large cohort of young boys with DMD from the DMD Natural History Study (DNHS). We explore the association between neurodevelopmental needs and DMD mutation location, and with glucocorticoid use.   Methods: We prospectively evaluated 204 participants between ages 4 to less than 9 years of age with DMD as part of a large, longitudinal, international DNHS. We obtained parent- or primary care-giver report of neurodevelopmental needs as part of their study visit. We assessed the relationship between parent/care-giver neurodevelopmental needs and DMD mutation location, and glucocorticoid use.

RESULTS

The neurodevelopmental needs that were most commonly reported included speech delay (33%), mild developmental delay (24%), significant behavioral problems (16.5%), language impairment (14.5%), learning disability (14.5%), attention-deficit hyperactivity disorder (5%) and autism spectrum disorder (3%). Neurodevelopmental needs were more commonly reported by care-givers in those with DMD mutations downstream of exon 51. There was no relationship between care-giver reported neurodevelopmental needs and glucocorticoid use.

CONCLUSION

Neurodevelopmental needs are highly prevalent in young boys with DMD. Care-givers report higher neurodevelopmental needs when subjects have DMD mutations downstream of exon 51. Early interventions aimed at cognitive health are critical to improve the quality-of-life of individuals with DMD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00468832.

Psychosocial Management of the Patient With Duchenne Muscular Dystrophy

In this article, we outline a comprehensive plan for the psychosocial management of patients with Duchenne muscular dystrophy (DMD) across the life span. In 2010, the Centers for Disease Control and Prevention sponsored the development of multidisciplinary management guidance for DMD, and in 2018, that guidance was updated. In the intervening years, a new emphasis was placed on studying and addressing the psychosocial issues that affect patients with DMD, driven in part by improved patient survival. Once viewed as ancillary to managing the significant medical needs of patients with DMD, it is now standard practice to integrate psychosocial management into the multidisciplinary management of the disease. It is also increasingly recognized that neurodevelopmental disorders in DMD occur at a higher rate than what was previously understood and that these disorders warrant early and intensive intervention. In this article, we expand on the content found in the 2018 DMD Care Considerations.

Current and Emerging Therapies for Duchenne Muscular Dystrophy

PURPOSE OF REVIEW

The purpose of this review is to summarize the current and emerging therapies for Duchenne muscular dystrophy (DMD).

RECENT FINDINGS

Coinciding with new standardized care guidelines, there are a growing number of therapeutic options to treat males with DMD. Treatment of the underlying pathobiology, such as micro-dystrophin gene replacement, exon skipping, stop codon read-through agents, and utrophin modulators showed variable success in animal and human studies. Symptomatic therapies to target muscle ischemia, enhance muscle regeneration, prevent muscle fibrosis, inhibit myostatin, and reduce inflammation are also under investigation. DMD is a complex, heterogeneous degenerative disease. The pharmacological and technological achievements made in recent years, plus timely supportive interventions will likely lead to an improved quality of life for many individuals with DMD.

Diagnosis and management of Duchenne muscular dystrophy, part 3: primary care, emergency management, psychosocial care, and transitions of care across the lifespan

Improvements in the function, quality of life, and longevity of patients with Duchenne muscular dystrophy (DMD) have been achieved through a multidisciplinary approach to management across a range of health-care specialties. In part 3 of this update of the DMD care considerations, we focus on primary care, emergency management, psychosocial care, and transitions of care across the lifespan. Many primary care and emergency medicine clinicians are inexperienced at managing the complications of DMD. We provide a guide to the acute and chronic medical conditions that these first-line providers are likely to encounter. With prolonged survival, individuals with DMD face a unique set of challenges related to psychosocial issues and transitions of care. We discuss assessments and interventions that are designed to improve mental health and independence, functionality, and quality of life in critical domains of living, including health care, education, employment, interpersonal relationships, and intimacy.

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

AIM

Duchenne Muscular Dystrophy (DMD) is more than a muscle disease since there is a higher prevalence of neuropsychological comorbidities. Similarly, the prevalence of epilepsy is increased. Given the nowadays-increasing interest in brain-related comorbidities in DMD, this study aimed to evaluate the relationship between DMD, epilepsy, and associated neurodevelopmental disorders in an international sample of DMD patients.

METHOD

Using a questionnaire-based study we investigated the occurrence of self/by-proxy reported brain-related comorbidities in a group of 228 DMD patients. We evaluated the presence of epilepsy and other brain-related comorbidities, but also the specific mutation in the dystrophin gene. With respect to epilepsy, all individually reported epilepsy cases as based on the questionnaire results including information provided on epilepsy treatment, EEG abnormalities, and a description of how a typical seizure would look like, were independently and blindly re-assessed by two external paediatric neurologists (Cohen's kappa of 0.85).

RESULTS

Based on the latter, 18 (7.9%) DMD patients were considered to have epilepsy. In patients with both DMD and epilepsy, certain other brain-related comorbidities (i.e. attention deficit hyperactivity disorder, obsessive compulsive disorder, anxiety disorders and sleep disorders) were significantly more prevalent.

CONCLUSION

This study is supportive of a high occurrence of epilepsy and other brain-related comorbidities in DMD. Furthermore this study shows for the first time that the frequency of some of these disorders appear to be further increased when epilepsy is present next to DMD. As this study is limited by the self/by proxy setup and the lack of response rates, future studies should elucidate the true incidence of the (triangular) cooccurrence between epilepsy, neurodevelopmental deficits, and DMD.

Influence of full-length dystrophin on brain volumes in mouse models of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) affects besides muscle also the brain, resulting in memory and behavioral problems. The consequences of dystrophinopathy on gross macroscopic alterations are unclear. To elucidate the effect of full-length dystrophin expression on brain morphology, we used high-resolution post-mortem MRI in mouse models that either express 0% (mdx), 100% (BL10) or a low amount of full-length dystrophin (mdx-XistΔhs). While absence or low amounts of full-length dystrophin did not significantly affect whole brain volume and skull morphology, we found differences in volume of individual brain structures. The results are in line with observations in humans, where whole brain volume was found to be reduced only in patients lacking both full-length dystrophin and the shorter isoform Dp140.

Autism spectrum disorders are prevalent among patients with dystrophinopathies

Recent studies have reported a higher prevalence of autism spectrum disorders among patients with dystrophinopathies. The aim of this study was to investigate the prevalence of autism spectrum disorder (ASD) among those with dystrophinopathies. The possible role of dystrophin isoforms in patients was also explored. Fifty-six patients recruited from Toneyama National Hospital were included in this study (mean age = 12.9 years, SD = 5.2 years). Autistic symptoms were evaluated using the Pervasive Developmental Disorders/Autism Spectrum Disorders Rating Scale (PARS), a clinician rating scale. Eleven patients (19.6%; 95% confidence interval 10.2-32.4) met the criteria for ASD based on their PARS scores. Patients were separated into two groups based on the cumulative loss of dystrophin isoforms predicted from the mutation location. The prevalence of ASD was examined between these groups. Infantile and current autistic symptoms did not differ between the groups, except on one subscale of the PARS. This study revealed that there was a high prevalence of ASD in patients with dystrophinopathies.

Consensus on the diagnosis, treatment and follow-up of patients with Duchenne muscular dystrophy

INTRODUCTION

Duchenne muscular dystrophy (DMD) is the most common myopathy in children, with a worldwide prevalence of approximately 0.5 cases per 10,000 male births. It is characterised by a progressive muscular weakness manifesting in early childhood, with the subsequent appearance of musculoskeletal, respiratory, and cardiac complications, causing disability, dependence, and premature death. Currently, DMD is mainly managed with multidisciplinary symptomatic treatment, with favourable results in terms of the progression of the disease. It is therefore crucial to establish clear, up-to-date guidelines enabling early detection, appropriate treatment, and monitoring of possible complications.

DEVELOPMENT

We performed a literature search of the main biomedical databases for articles published in the last 10years in order to obtain an overview of the issues addressed by current guidelines and to identify relevant issues for which no consensus has yet been established. The degree of evidence and level of recommendation of the information obtained were classified and ordered according to the criteria of the American Academy of Neurology.

CONCLUSIONS

DMD management should be multidisciplinary and adapted to the patient's profile and the stage of clinical progression. In addition to corticotherapy, treatment targeting gastrointestinal, respiratory, cardiac, and orthopaedic problems, as well as physiotherapy, should be provided with a view to improving patients' quality of life. Genetic studies play a key role in the management of the disease, both in detecting cases and potential carriers and in characterising the mutation involved and developing new therapies.

Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and neuromuscular, rehabilitation, endocrine, and gastrointestinal and nutritional management

Since the publication of the Duchenne muscular dystrophy (DMD) care considerations in 2010, multidisciplinary care of this severe, progressive neuromuscular disease has evolved. In conjunction with improved patient survival, a shift to more anticipatory diagnostic and therapeutic strategies has occurred, with a renewed focus on patient quality of life. In 2014, a steering committee of experts from a wide range of disciplines was established to update the 2010 DMD care considerations, with the goal of improving patient care. The new care considerations aim to address the needs of patients with prolonged survival, to provide guidance on advances in assessments and interventions, and to consider the implications of emerging genetic and molecular therapies for DMD. The committee identified 11 topics to be included in the update, eight of which were addressed in the original care considerations. The three new topics are primary care and emergency management, endocrine management, and transitions of care across the lifespan. In part 1 of this three-part update, we present care considerations for diagnosis of DMD and neuromuscular, rehabilitation, endocrine (growth, puberty, and adrenal insufficiency), and gastrointestinal (including nutrition and dysphagia) management.

[Pathogenesis of cognitive disorders in patients with Duchenne muscular dystrophy]

AIM

Clarification of the pathogenesis of cognitive disorders in patients with Duchenne muscular dystrophy in the clinical laboratory and molecular genetic study.

MATERIAL AND METHODS

Thirty-six male patients with Duchenne muscular dystrophy (DMD), aged from 5 to 22 years (mean age 13.7 years), were examined. The control group consisted of 30 healthy people (7-22 years old, mean age 13.8). The clinical, molecular-genetic and laboratory study was conducted. The search for mutations in the dystrophin gene was carried out using multiplex PCR and multiplex ligation-dependent probe amplification. The laboratory study included determination of neurotrophins: brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) and ciliary neurotrophic factor (CNTF) using immunoenzyme method in serum.

RESULTS AND CONCLUSION

Severe cognitive impairment was found in 33% of patients with DMD. The distribution of mutations in the DMD gene was not uniform, most often the mutations were found in the region from exon 43 to exon 50. Serum concentration of NGF in patients with DMD was higher than in the control group (2391 pg/ml [1587; 4136] and 553 pg / ml [314; 864], respectively (p<0.001)). In the group of patients with cognitive disorders, there was a decreased concentration of BGF (23 670 [21 700; 30 720] pg/ml (p<0.001)). In patients with BGF concentration less than 31 000 pg/ml, the chances of cognitive disorders were more than 10 times higher (p<0.001, odds ratio OR=12.0, 95% CI [1.9-76.4]). Thus, biochemical mechanisms, such as NGF overexpression and BGF deficiency, are involved in the development of cognitive disorders in patients with DMD.

Implicit learning deficit in children with Duchenne muscular dystrophy: Evidence for a cerebellar cognitive impairment?

This study aimed at comparing implicit sequence learning in individuals affected by Duchenne Muscular Dystrophy without intellectual disability and age-matched typically developing children. A modified version of the Serial Reaction Time task was administered to 32 Duchenne children and 37 controls of comparable chronological age. The Duchenne group showed a reduced rate of implicit learning even if in the absence of global intellectual disability. This finding provides further evidence of the involvement of specific aspects of cognitive function in Duchenne muscular dystrophy and on its possible neurobiological substrate.

Genetic modifiers of Duchenne and facioscapulohumeral muscular dystrophies

Muscular dystrophy is defined as the progressive wasting of skeletal muscles that is caused by inherited or spontaneous genetic mutations. Next-generation sequencing has greatly improved the accuracy and speed of diagnosis for different types of muscular dystrophy. Advancements in depth of coverage, convenience, and overall reduced cost have led to the identification of genetic modifiers that are responsible for phenotypic variability in affected patients. These genetic modifiers have been postulated to explain key differences in disease phenotypes, including age of loss of ambulation, steroid responsiveness, and the presence or absence of cardiac defects in patients with the same form of muscular dystrophy. This review highlights recent findings on genetic modifiers of Duchenne and facioscapulohumeral muscular dystrophies based on animal and clinical studies. These genetic modifiers hold great promise to be developed into novel therapeutic targets for the treatment of muscular dystrophies. Muscle Nerve 57: 6-15, 2018.

Proteomic Profiling of the Dystrophin-Deficient Brain

Duchenne muscular dystrophy is a highly progressive neuromuscular disorder caused by primary abnormalities in the Dmd gene encoding the membrane cytoskeletal protein dystrophin. Dystrophinopathies are multi-systems disorders that are characterized by severe skeletal muscle wasting, with loss of independent ambulation in the early teenage years, followed by cardio-respiratory complications and premature death. Nonprogressive cognitive impairments are estimated to affect approximately one-third of dystrophic children. To identify the molecular mechanisms behind the impaired brain function in dystrophinopathy, liquid chromatography-based mass spectrometry offers an unbiased and technology-driven approach. In this chapter, we give a detailed description of a label-free mass spectrometric method to investigate proteome-wide changes in the dystrophin-deficient brain from a genetic mouse model of Duchenne muscular dystrophy.

Cognitive profile in Duchenne muscular dystrophy boys without intellectual disability: The role of executive functions

The aim of our prospective observational study was to assess profiles of cognitive function and a possible impairment of executive functions in a cohort of boys with Duchenne muscular dystrophy without intellectual and behavior disability. Forty Duchenne boys (range of age: 6 years to 11 years and 6 months) were assessed by Wechsler Intelligence scale and battery of tests including tasks assessing working memory and executive functions (inhibition and switching, problem solving and planning). In our cohort some aspects of cognitive function were often impaired. These included multitasking, problem solving, inhibition and working memory necessary to plan and direct goal oriented behavior. Our results support the suggestion that aspects of cognitive function could be impaired even in boys without intellectual disability and support the hypothesis that executive functions may play an important role in specific aspects of cognitive impairment in Duchenne muscular dystrophy.

Evaluation of cardiac functions in children with Duchenne Muscular Dystrophy: A prospective case-control study

Background

Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. The incidence of cardiomyopathy in DMD increases with age, so its early detection is important because institution of cardioprotective medical therapies may slow adverse remodeling and attenuate heart failure symptoms in these patients.

Objective

To assess the cardiac functions in children clinically suspected to have DMD.

Methods

Over a one-year period, 28 male children aged from 3 to 18 years old, who met the criteria for diagnosis of DMD compared to 47 healthy controls children, were approached to participate in the study. The included children were subjected to full clinical examination, and blood samples were collected to determine creatinine phosphokinase (CPK), troponin I enzyme, myoglobin and lactate dehydrogenase (LDH) enzyme level. Echocardiography and 12-leads electrocardiogram (ECG) were also done for children in both groups. Data were analyzed using Independent-samples t-test, Mann-Whitney U, Chi square, and Fisher’s exact test.

Results

The mean age of the cases group was 7.29±3.24 years versus 8.06±2.86 years for controls. In DMD group, 25% had positive family history of DMD while 35.7% of them had positive consanguinity. All cases had elevated CPK level while CPK level in controls was normal (p<0.0001). LDH level was elevated in 19 cases (67.86%) of DMD while all controls children had normal LDH level (p<0.0001). Furthermore, the mean serum myoglobin level of DMD patients was higher relative to that of healthy controls (39.39±7.25 versus 33.68 ±12.38 ng/ml respectively) (p=0.01). Echocardiography of our patients revealed that seven cases (25%) had low ejection fraction (EF) and fraction shortening (FS). In addition, all controls children had normal EF (p<0.0001) and normal FS (p<0.0001). Interestingly, ECG showed that 28.57% of cases had sinus tachycardia vs. 6.88% for controls (p=0.0001). Prolonged QTc interval was present in 39.29% of cases (mean 431.39±43.60) while all controls had normal QTc duration for age (mean of 415.17±25.2) (p<0.0001).

Conclusion

ECG manifestations in children with DMD in the form of sinus tachycardia and prolonged QTc interval are an early alarm for developing cardiomyopathy before overt echocardiographic findings appear.

Assessing mental health in boys with Duchenne muscular dystrophy: Emotional, behavioural and neurodevelopmental profile in an Italian clinical sample

OBJECTIVE

To evaluate through a comprehensive protocol, the psychopathological profile of DMD boys. The primary aim of this observational study was to describe the emotional and behavioural profile and the neurodevelopmental problems of Italian boys with Duchenne Muscular Dystrophy (DMD); the secondary aim was to explore the relation between psychopathological profile and DMD genotype.

METHOD

47 DMD boys, aged 2-18, were included in the study and assessed through structured and validated tools including Wechsler scales or Griffiths for cognitive ability, Child Behavior Check List (CBCL), Youth Self Report (YSR) and Strengths and Difficulties Questionnaire (SDQ) for emotional and behavioural features. Patients "at risk" based on questionnaires scores were evaluated by a clinical structured interview using Development and Well Being Assessment (DAWBA) or Autism Diagnostic Observation Schedule (ADOS), as required.

RESULTS

The 47 enrolled patients, defined with a Full Scale Intelligence Quotient (FSIQ) of 80.38 (one SD below average), and presenting a large and significant difference in FSIQ in relation to the site of mutation along the dystrophin gene (distal mutations associated with a more severe cognitive deficit), were showing Internalizing Problems (23.4%) and Autism Spectrum Disorders (14.8%). Interestingly, an association of internalizing problems with distal deletion of the DMD gene is documented.

CONCLUSION

Even though preliminary, these data show that the use of validated clinical instruments, that focus on the impact of emotional/behaviour problems on everyday life, allows to carefully identify clinically significant psychopathology.

Secondary Conditions Among Males With Duchenne or Becker Muscular Dystrophy

Duchenne and Becker muscular dystrophy are X-linked neuromuscular disorders characterized by progressive muscle degeneration. Despite the involvement of multiple systems, secondary conditions among affected males have not been comprehensively described. Two hundred nine caregivers of affected males (aged 3-31 years) identified by the Muscular Dystrophy Surveillance, Tracking, and Research Network completed a mailed survey that included questions about secondary conditions impacting multiple body functions. The 5 most commonly reported conditions in males with Duchenne were cognitive deficits (38.4%), constipation (31.7%), anxiety (29.3%), depression (27.4%), and obesity (19.5%). Higher frequencies of anxiety, depression, and kidney stones were found among nonambulatory males compared to ambulatory males. Attention-deficit hyperactivity disorder (ADHD) was more common in ambulatory than nonambulatory males. These data support clinical care recommendations for monitoring of patients with Duchenne or Becker muscular dystrophy by a multidisciplinary team to prevent and treat conditions that may be secondary to the diagnosis.

State-Of-The-Art Advances in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a severe and fatal muscle condition affecting young children. Without interventions, affected boys lose the ability to walk independently by the age of 10 and develop progressive cardiac and respiratory failure. The last 20 years have seen a change in the natural history of DMD following improvements in clinical care and proactive interventions to manage complications of the disease. An international collaboration of DMD experts has created care imperatives for best practice in DMD; these are now available in 30 different languages and are disseminated worldwide. An update of these care recommendations is currently under review. More recently, the field has seen encouraging scientific progress in regard to new therapeutic approaches of which a large number are currently being evaluated in clinical trials. With time, improvements in clinical care and access to new treatments and innovations are changing the natural course of DMD, from a relentless progressive illness with death in teenage years to a more chronic illness with a good quality of life and increased life expectancy. This is a particularly encouraging time for DMD, and experiences built in the muscular dystrophy field are likely to be of benefit to the development of new approaches and therapies in other rare diseases.

Mismatch Negativity Recording in Children With Duchenne Muscular Dystrophy: A Preliminary Study Integrating Neurophysiological and Neuropsychological Results

Many studies on Duchenne muscular dystrophy children support the hypothesis of a specific neuropsychological phenotype affecting mostly phonological skills. This prospective study aimed to shed light on the role of phonological abilities. Fourteen Duchenne muscular dystrophy children and 7 healthy children underwent mismatch negativity. Moreover, verbal intelligence, visuospatial attention, immediate verbal memory, working memory, grammar, vocabulary, visuomotor skills, reading, text comprehension, writing, and arithmetic were tested in Duchenne muscular dystrophy children. No significant difference between control and Duchenne muscular dystrophy children was found neither for mismatch negativity amplitude (P = .191 and .116, respectively) nor for latency (P = .135). Eight (57.14%) patients showed an impairment of immediate verbal memory and of visuomotor skills, 7 (63.64%) patients had a deficit in writing and arithmetic skills, even with a mean normal intelligence quotient. Taken together, the results put in evidence a heterogeneous neuropsychological profile not explainable on the basis of a phonological deficit.

[Central manifestations of dystrophinopathies]

The dystrophin gene involved in Duchenne and Becker muscular dystrophy is expressed in three main tissues resulting in clinical manifestations: skeletal muscle, heart and central nervous system. The 6 different existing dystrophins in the brain may play a role in the maturation and plasticity of neuronal synapses in particular by their functions in clustering and stabilization of different receptors at the post synaptic membrane. The possibility of an intellectual deficiency in Duchenne muscular dystrophy is known from the original description by Duchenne himself. Current data are in line with a constant cognitive impairment with a Gaussian curve shifted intellectual quotient (IQ) at -1 standard deviation from the standard population with an average IQ around 80. Clinical manifestations suggestive of a central nervous system involvement can affect all dystrophinopathies, including isolated central presentations without myopathic sign. The phenotypic spectrum appears broader and more subtle than non specific intellectual deficiency. The isolated or shared involvement of specific cognitive functions is possible (memory functions, executive functions, attention) with or without intellectual deficiency. Autism spectrum disorders are also among the encountered events. In clinical practice, it seems worth to ask for a measurement of serum creatine kinase (CK) in these different situations, keeping in mind that pure forms of central dystrophinopathies with a normal CK level have been recently reported.

Reversal of neurobehavioral social deficits in dystrophic mice using inhibitors of phosphodiesterases PDE5A and PDE9A

Duchenne muscular dystrophy is caused by mutations in the DYSTROPHIN gene. Although primarily associated with muscle wasting, a significant portion of patients (approximately 25%) are also diagnosed with autism spectrum disorder. We describe social behavioral deficits in dystrophin-deficient mice and present evidence of cerebellar deficits in cGMP production. We demonstrate therapeutic potential for selective inhibitors of the cGMP-specific PDE5A and PDE9A enzymes to restore social behaviors in dystrophin-deficient mice.

Diagnosis and treatment of obsessive compulsive behavior in a boy with Duchenne muscular dystrophy and autism spectrum disorder: A case report

We describe a case study of comorbid obsessive-compulsive disorder (OCD) in a nine-year-old boy with Duchenne muscular dystrophy (DMD). Patient history included persistent deficits in social communication and restrictive and repetitive patterns of behavior: a diagnosis of autism spectrum was formalized. Due to serious disruption on social functioning and negative development of the obsessive behavior we decided to start pharmacotherapy. Fluoxetine 5 mg/day was started and gradually increased to 20 mg/day. A significant positive effect was observed by both parents and teacher in daily functioning. Although parents reported a positive change in mood, formal behavior rating by them did not reveal a significant effect, reflecting the insensitivity of general behavior rating scales. However, neuropsychological testing revealed a significant effect. This case report highlights the diagnostic and therapeutic challenges of complex neuropsychiatric comorbidities in DMD. It is the first scientific report on fluoxetine effectiveness in this patient group. Further research is needed.

Current and emerging treatment strategies for Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy in childhood. It is caused by mutations of the DMD gene, leading to progressive muscle weakness, loss of independent ambulation by early teens, and premature death due to cardiorespiratory complications. The diagnosis can usually be made after careful review of the history and examination of affected boys presenting with developmental delay, proximal weakness, and elevated serum creatine kinase, plus confirmation by muscle biopsy or genetic testing. Precise characterization of the DMD mutation is important for genetic counseling and individualized treatment. Current standard of care includes the use of corticosteroids to prolong ambulation and to delay the onset of secondary complications. Early use of cardioprotective agents, noninvasive positive pressure ventilation, and other supportive strategies has improved the life expectancy and health-related quality of life for many young adults with DMD. New emerging treatment includes viral-mediated microdystrophin gene replacement, exon skipping to restore the reading frame, and nonsense suppression therapy to allow translation and production of a modified dystrophin protein. Other potential therapeutic targets involve upregulation of compensatory proteins, reduction of the inflammatory cascade, and enhancement of muscle regeneration. So far, data from DMD clinical trials have shown limited success in delaying disease progression; unforeseen obstacles included immune response against the generated mini-dystrophin, inconsistent evidence of dystrophin production in muscle biopsies, and failure to demonstrate a significant improvement in the primary outcome measure, as defined by the 6-minute walk test in some studies. The long-term safety and efficacy of emerging treatments will depend on the selection of appropriate clinical end points and sensitive biomarkers to detect meaningful changes in disease progression. Correction of the underlying mutations using new gene-editing technologies and corticosteroid analogs with better safety profiles offers renewed hope for many individuals with DMD and their families.

Dystrophin Distribution and Expression in Human and Experimental Temporal Lobe Epilepsy

OBJECTIVE

Dystrophin is part of a protein complex that connects the cytoskeleton to the extracellular matrix. In addition to its role in muscle tissue, it functions as an anchoring protein within the central nervous system such as in hippocampus and cerebellum. Its presence in the latter regions is illustrated by the cognitive problems seen in Duchenne Muscular Dystrophy (DMD). Since epilepsy is also supposed to constitute a comorbidity of DMD, it is hypothesized that dystrophin plays a role in neuronal excitability. Here, we aimed to study brain dystrophin distribution and expression in both, human and experimental temporal lobe epilepsy (TLE).

METHOD

Regional and cellular dystrophin distribution was evaluated in both human and rat hippocampi and in rat cerebellar tissue by immunofluorescent colocalization with neuronal (NeuN and calbindin) and glial (GFAP) markers. In addition, hippocampal dystrophin levels were estimated by Western blot analysis in biopsies from TLE patients, post-mortem controls, amygdala kindled (AK)-, and control rats.

RESULTS

Dystrophin was expressed in all hippocampal pyramidal subfields and in the molecular-, Purkinje-, and granular cell layer of the cerebellum. In these regions it colocalized with GFAP, suggesting expression in astrocytes such as Bergmann glia (BG) and velate protoplasmic astrocytes. In rat hippocampus and cerebellum there were neither differences in dystrophin positive cell types, nor in the regional dystrophin distribution between AK and control animals. Quantitatively, hippocampal full-length dystrophin (Dp427) levels were about 60% higher in human TLE patients than in post-mortem controls (p < 0.05), whereas the level of the shorter Dp71 isoform did not differ. In contrast, AK animals showed similar dystrophin levels as controls.

CONCLUSION

Dystrophin is ubiquitously expressed by astrocytes in the human and rat hippocampus and in the rat cerebellum. Hippocampal full-length dystrophin (Dp427) levels are upregulated in human TLE, but not in AK rats, possibly indicating a compensatory mechanism in the chronic epileptic human brain.

Genetic and Early Clinical Manifestations of Females Heterozygous for Duchenne/Becker Muscular Dystrophy

BACKGROUND

Female carriers of Duchenne muscular dystrophy (DMD), although usually asymptomatic, develop muscle weakness up to 17% of the time, and a third present cardiac abnormalities or cognitive impairment. Clinical features of DMD carriers during childhood are poorly known.

PATIENTS

We describe a cohort of pediatric DMD carriers, providing clinical, genetic, and histopathologic features, with a mean follow-up of 7 years.

RESULTS

Fifteen females with a DMD mutation (age range 5 to 18 years) were included. Seven patients (46%) presented with clinically evident symptoms and signs such as limb girdle weakness, abnormal gait, and exercise intolerance. The other eight patients (53%) were evaluated because of an incidental finding of elevated level of creatine kinase. Creatine kinase level was elevated in all, ranging from 392 to 13,000 U/L. Calf hypertrophy was observed in eight patients (53%). No patient developed respiratory or cardiac involvement. The most frequent complication was scoliosis (46%). Four patients (29%) also presented minor learning disabilities or behavioral problems. We performed electromyography in half of patients, showing myopathic pattern in four (53%). Muscle biopsy revealed a mosaic reduction of dystrophin in nine available cases. DMD gene mutations were mostly deletions (71%), resulting in loss of reading frame in five patients (36%). The three patients who experienced the most severe disease course were affected either by a nonsense or frameshift mutation.

CONCLUSIONS

Our analysis suggests that DMD gene mutations may be suspected in a female child with persistently elevated levels of creatine kinase. Evidence of scoliosis, calf hypertrophy, or myopathic pattern at electromyography may also be helpful, and muscle biopsy is always indicative. DMD carriers should be followed for subtle orthopedic and psychiatric complications during childhood.

Neurodevelopmental, emotional, and behavioural problems in Duchenne muscular dystrophy in relation to underlying dystrophin gene mutations

AIM

Duchenne muscular dystrophy (DMD) is associated with neuropsychiatric disorders. The aim of the study was to characterize the DMD neuropsychiatric profile fully and to explore underlying genotype/phenotype associations.

METHOD

One hundred and thirty males with DMD (mean age 9y 10mo, range 5-17y) in four European centres were included and completed IQ assessment and a neurodevelopmental-screening questionnaire. Of these, 87 underwent comprehensive neuropsychiatric assessment using structured diagnostic interview and parent-reported questionnaires.

RESULTS

The overall mean score on the neurodevelopmental questionnaire was significantly abnormal compared with the general population of children (p<0.001). On average, intelligence was below the population mean, with intellectual disability observed in 34 males (26%). Autistic spectrum disorder was identified in 18 (21%), hyperactivity in 21 (24%), and inattention in 38 (44%). Clinical levels of internalizing and externalizing problems were observed in 21 (24%) and 13 (15%) respectively. Over a third of males scored more than two measures of emotional, behavioural, or neurodevelopmental problems. Males with mutations at the 3' end of the DMD gene affecting all protein isoforms had higher rates of intellectual disability and clusters of symptoms.

INTERPRETATION

Males with DMD are at very high risk of neuropsychiatric disturbance, and this risk appears to increase with mutations at the 3' end of the gene. Patterns of symptom clusters suggest a DMD neuropsychiatric syndrome, which may require prompt evaluation and early intervention.

Animal models of Duchenne muscular dystrophy: from basic mechanisms to gene therapy

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disorder. It is caused by loss-of-function mutations in the dystrophin gene. Currently, there is no cure. A highly promising therapeutic strategy is to replace or repair the defective dystrophin gene by gene therapy. Numerous animal models of DMD have been developed over the last 30 years, ranging from invertebrate to large mammalian models. mdx mice are the most commonly employed models in DMD research and have been used to lay the groundwork for DMD gene therapy. After ~30 years of development, the field has reached the stage at which the results in mdx mice can be validated and scaled-up in symptomatic large animals. The canine DMD (cDMD) model will be excellent for these studies. In this article, we review the animal models for DMD, the pros and cons of each model system, and the history and progress of preclinical DMD gene therapy research in the animal models. We also discuss the current and emerging challenges in this field and ways to address these challenges using animal models, in particular cDMD dogs.

Cognitive and Neurobehavioral Profile in Boys With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy is a progressive neuromuscular condition that has a high rate of cognitive and learning disabilities as well as neurobehavioral disorders, some of which have been associated with disruption of dystrophin isoforms. Retrospective cohort of 59 boys investigated the cognitive and neurobehavioral profile of boys with Duchenne muscular dystrophy. Full-scale IQ of < 70 was seen in 27%; learning disability in 44%, intellectual disability in 19%; attention-deficit/hyperactivity disorder in 32%; autism spectrum disorders in 15%; and anxiety in 27%. Mutations affecting Dp260 isoform and 5'untranslated region of Dp140 were observed in 60% with learning disability, 50% intellectual disability, 77% with autism spectrum disorders, and 94% with anxiety. No statistically significant correlation was noted between comorbidities and dystrophin isoforms; however, there is a trend of cumulative loss of dystrophin isoforms with declining full-scale IQ. Enhanced psychology testing to include both cognitive and neurobehavioral disorders is recommended for all individuals with Duchenne muscular dystrophy.

Reading impairment in Duchenne muscular dystrophy: A pilot study to investigate similarities and differences with developmental dyslexia

Below-average reading performances have been reported in individuals with Duchenne muscular dystrophy (DMD), but literacy problems in these subjects have yet to be characterized. In this study, the presence and characteristics of literacy deficits in boys with DMD were investigated through a comparison with typically developing children and with children affected by developmental dyslexia, with the aim of clarifying whether DMD and developmental dyslexia have overlapping profiles of literacy deficits and whether these deficits are associated, as in children with dyslexia, with impairments in phonological processing and rapid lexical access. The results confirmed the high incidence of literacy problems in boys with DMD and revealed a profile less severe than, but qualitatively similar to, that of Italian children with developmental dyslexia. Both groups showed specific difficulties in reading and writing words and a reduced rapid automatized naming (RAN) speed. This is the first time that a RAN speed deficit has been documented in DMD. Moreover, the boys with DMD and the subgroup of dyslexic children with a previous language delay showed additional deficits in phonological processing. The impairments highlighted in this study could explain the reading difficulties observed in boys with DMD and suggest that there is a need for targeted preschool interventions.

Diagnostic overshadowing in a population of children with neurological disabilities: A cross sectional descriptive study on acquired ADHD

AIM

Diagnostic overshadowing refers to the underdiagnosis of comorbid conditions in children with known neurological diagnoses. To demonstrate diagnostic overshadowing we determined the prevalence of attention deficit-hyperactivity disorders (ADHD) in a cohort of children with a wide range of neurological disabilities.

METHOD

The study cohort consisted of 685 children (mean age 10.3 years, SD: 3.1; 425 boys and 260 girls) who visited a tertiary outpatient multidisciplinary clinic for neurological learning disabilities. Patients with ADHD were identified by retrospective chart review using DSM-IV criteria.

RESULTS

The prevalence of ADHD in this cohort was 38.8% (266 children); of these children only 28.2% (75 children) were diagnosed with ADHD before referral.

INTERPRETATION

ADHD is a common problem in children with neurological disabilities and may be underdiagnosed due to overshadowing of somatic, physical or syndromal features of the disability. In our heterogeneous population ADHD was overshadowed in 71.8% of the cases. This finding may have important implications for diagnosis and treatment of mental health needs in children with neurological disabilities.

Early Neurodevelopmental Findings Predict School Age Cognitive Abilities in Duchenne Muscular Dystrophy: A Longitudinal Study

Objective

Neurodevelopmental and cognitive difficulties are known to occur frequently in boys with Duchenne muscular dystrophy but so far none of the published studies have reported both early neurodevelopmental assessments and cognitive tests in the same cohort. The aim of the present longitudinal study was to establish the correlation between early neurodevelopmental assessments performed in preschool boys and the cognitive scales performed at school age or later.

Methods

We performed cognitive tests at school age (mean age 5.7 year ±1.7 SD) (69 months+19 SD) in a cohort of Duchenne boys, previously assessed using the Griffiths scales before the age of 4 years (mean age when the Griffiths scales were performed 30 months ±8.9 SD).

Results

The range of total Developmental quotients on the Griffiths ranged between 56 and 116 (mean 89 ± 15.6 SD). The total Intelligence Quotients on the Wechsler scales ranged between 35 and 119 (mean 87 ± 17.2 SD). There was a significant correlation between the findings on the two scales. P = <0.0001. When we subdivided the cohort according to site of mutations, there was a difference between boys with mutations upstream exon 44 and those with mutations in exon 44–45 affecting Dp140 on both Developmental and Intelligence Quotient (p 0.01 and p 0,003 respectively).

Conclusions

Our results confirm that Duchenne boys tend to slightly underperform on both neurodevelopmental and cognitive assessments. Early neurodevelopmental findings correlated with the cognitive results obtained at school age with a clear concordance between subscales exploring similar domains on the two scales.

Dystrophin induced cognitive impairment: mechanisms, models and therapeutic strategies

Existence of conserved domains in dystrophin and its associated complexes provide an opportunity to understand the role of dystrophin associated signalling and its association with neuronal metabolism in a variety of model organisms. We critically reviewed the studies till 2013 through established search engines and databases. Thus, we review the role of dystrophin and its isoforms in different animal models at developmental stages in the neuronal metabolism to enhance the therapeutic strategies. Dystrophin interacts with other proteins in such a way that, when affected, it results in co-morbidities including autism and other neuropsychiatric disorders. It is speculated that various signalling molecules may converge to disrupt neuronal metabolism not adequately studied. TGF-β, RhoGAP and CAM mediated signalling molecules are the chief cause of mortalities due to respiratory and cardiac involvement but remain underevaluated targets for cognitive impairment in DMD/BMD. Manipulation of these signalling pathways could be potent intervention in dystrophin induced cognitive impairment while complementary therapeutic approaches may also be helpful in the treatment of cognitive impairment associated with DMD/BMD.

Duchenne muscular dystrophy: current cell therapies

Duchenne muscular dystrophy is a genetically determined X-linked disease and the most common, progressive pediatric muscle disorder. For decades, research has been conducted to find an effective therapy. This review presents current therapeutic methods for Duchenne muscular dystrophy, based on scientific articles in English published mainly in the period 2000 to 2014. We used the PubMed database to identify and review the most important studies. An analysis of contemporary studies of stem cell therapy and the use of granulocyte colony-stimulating factor (G-CSF) in muscular dystrophy was performed.

Ocular and neurodevelopmental features of Duchenne muscular dystrophy: a signature of dystrophin function in the central nervous system

Multiple isoforms of dystrophin (Dp427, Dp260, Dp140, Dp71) are expressed differentially in the central nervous system (CNS) including the retinal layers. Disruption of these protein products is responsible for cognitive dysfunction, electroretinogram (ERG) abnormalities and behavioural disorders in Duchenne muscular dystrophy (DMD). We studied the ocular characteristics and neuropsychiatric profile of 16 DMD boys. The ISCEV standard, full-field flash ERGs were assessed. Intellectual ability and behavioural disturbances were measured. All genotypes were associated with mildly abnormal photopic ERG a:b-wave amplitude ratios. In addition, we identified the following genotype/phenotype correlations: boys with mutations upstream of exon 30 (ie, isolated Dp427 altered expression) showed normal scotopic a:b ratios, abnormal photopic oscillatory potential OP2 and normal scotopic OP2. Conversely, all boys with DMD mutations downstream of exon 30 showed profoundly 'negative' scotopic ERGs (a:b ratios >1). In these patients, the involvement of Dp260 isoform resulted in the absence of slow rod pathway signalling in15 Hz scotopic flicker ERGs. These boys had abnormal scotopic OP2 and normal photopic OP2. Finally, children with mutations also affecting Dp71 were associated with more pronounced electronegative ERGs. When correlating ERGs to neurodevelopmental outcome, we found a positive correlation between negative scotopic ERGs and neurodevelopmental disturbances, and the most severe findings were in boys with Dp71 disruption. These findings suggest a strong association between DMD mutations affecting different DMD isoforms with characteristically abnormal scotopic ERGs and severe neurodevelopmental problems. The role of the ERG as a potential biomarker for dystrophin function in the CNS and response to novel genetic therapies warrants further exploration.