Duchenne muscular dystrophy (DMD) is the commonest inherited neuromuscular disorder of childhood and mainly affects males. Over the course of the last century, the average life expectancy of these ...patients has doubled and now stands at ∼25 years. This progress has been made possible through advances in the diagnosis, treatment and long-term care of patients with DMD. Basic and clinical research, national and international scientific networks, and parent and patient support groups have all contributed to achieving this goal. The advent of molecular genetic therapies and personalised medicine has opened up new avenues and raised hopes that one day a cure for this debilitating orphan disease will be found. The main purpose of this short review is to enable paediatricians to have informed discussions with parents of boys with DMD about recent scientific advances affecting their child's clinical care.
Mutations in the cytoplasmic dynein 1 heavy chain gene (DYNC1H1) have been identified in rare neuromuscular (NMD) and neurodevelopmental (NDD) disorders such as spinal muscular atrophy with lower ...extremity dominance (SMALED) and autosomal dominant mental retardation syndrome 13 (MRD13). Phenotypes and genotypes of ten pediatric patients with pathogenic DYNC1H1 variants were analyzed in a multi-center study. Data mining of large-scale genomic variant databases was used to investigate domain-specific vulnerability and conservation of DYNC1H1. We identified ten patients with nine novel mutations in the DYNC1H1 gene. These patients exhibit a broad spectrum of clinical findings, suggesting an overlapping disease manifestation with intermixed phenotypes ranging from neuropathy (peripheral nervous system, PNS) to severe intellectual disability (central nervous system, CNS). Genomic profiling of healthy and patient variant datasets underlines the domain-specific effects of genetic variation in DYNC1H1, specifically on toleration towards missense variants in the linker domain. A retrospective analysis of all published mutations revealed domain-specific genotype–phenotype correlations, i.e., mutations in the dimerization domain with reductions in lower limb strength in DYNC1H1–NMD and motor domain with cerebral malformations in DYNC1H1–NDD. We highlight that the current classification into distinct disease entities does not sufficiently reflect the clinical disease manifestation that clinicians face in the diagnostic work-up of DYNC1H1-related disorders. We propose a novel clinical classification for DYNC1H1-related disorders encompassing a spectrum from DYNC1H1–NMD with an exclusive PNS phenotype to DYNC1H1–NDD with concomitant CNS involvement.
•A consensus was reached on an updated definition of LGMD, and current sub-types were evaluated by application of the updated definition.•Consensus was reached on the most useful LGMD classification ...system that also allowed space for further discoveries of new sub-types.•Potential ramifications of the new definition and classification of LGMD for patients were discussed and several action points around how to disseminate this proposal were identified.
Cardiac failure is a major cause of mortality in patients with Duchenne muscular dystrophy (DMD). Antisense-mediated exon skipping has the ability to correct out-of-frame mutations in DMD to produce ...truncated but functional dystrophin. Traditional antisense approaches have however been limited by their poor uptake into cardiac muscle. The addition of cell-penetrating peptides to antisense molecules has increased their potency and improved their uptake into all muscles, including the heart. We have investigated the efficacy of the Peptide-conjugated phosphodiamidate morpholino oligomer (P-PMO) Pip6a-PMO, for restoration of cardiac dystrophin and functional rescue in DMD mice- the mdx mouse and the less well characterised Cmah-/-mdx mouse (which carry a human-like mutation in the mouse Cmah gene as well as a mutation in DMD). In our first study male mdx mice were administered Pip6a-PMO, i.v, fortnightly from 12 to 30 weeks of age alongside mock-injected age-matched mdx and C57BL10 controls. Mice received 4 doses of 18 mg/kg followed by 8 doses of 12.5 mg/kg. The cardiac function of the mice was analysed 2 weeks after their final injection by MRI followed by conductance catheter and their muscles were harvested for dystrophin quantification. In the second study, male Cmah-/-mdx mice, received 12.5 mg/kg Pip6a-PMO, i.v fortnightly from 8 to 26 weeks and assessed by MRI at 3 time points (12, 18 and 28 weeks) alongside mock-injected age-matched mdx, C57BL10 and Cmah-/-mdx controls. The mice also underwent MEMRI and conductance catheter at 28 weeks. This allowed us to characterise the cardiac phenotype of Cmah-/-mdx mice as well as assess the effects of P-PMO on cardiac function. Pip6a-PMO treatment resulted in significant restoration of dystrophin in mdx and Cmah-/-mdx mice (37.5% and 51.6%, respectively), which was sufficient to significantly improve cardiac function, ameliorating both right and left ventricular dysfunction. Cmah-/-mdx mice showed an abnormal response to dobutamine stress test and this was completely ameliorated by PIP6a-PMO treatment. These encouraging data suggest that total restoration of dystrophin may not be required to significantly improve cardiac outcome in DMD patients and that it may be realistic to expect functional improvements with modest levels of dystrophin restoration which may be very achievable in future clinical trials.
Summary Background We report clinical safety and biochemical efficacy from a dose-ranging study of intravenously administered AVI-4658 phosphorodiamidate morpholino oligomer (PMO) in patients with ...Duchenne muscular dystrophy. Method We undertook an open-label, phase 2, dose-escalation study (0·5, 1·0, 2·0, 4·0, 10·0, and 20·0 mg/kg bodyweight) in ambulant patients with Duchenne muscular dystrophy aged 5–15 years with amenable deletions in DMD. Participants had a muscle biopsy before starting treatment and after 12 weekly intravenous infusions of AVI-4658. The primary study objective was to assess safety and tolerability of AVI-4658. The secondary objectives were pharmacokinetic properties and the ability of AVI-4658 to induce exon 51 skipping and dystrophin restoration by RT-PCR, immunohistochemistry, and immunoblotting. The study is registered, number NCT00844597. Findings 19 patients took part in the study. AVI-4658 was well tolerated with no drug-related serious adverse events. AVI-4658 induced exon 51 skipping in all cohorts and new dystrophin protein expression in a significant dose-dependent (p=0·0203), but variable, manner in boys from cohort 3 (dose 2 mg/kg) onwards. Seven patients responded to treatment, in whom mean dystrophin fluorescence intensity increased from 8·9% (95% CI 7·1–10·6) to 16·4% (10·8–22·0) of normal control after treatment (p=0·0287). The three patients with the greatest responses to treatment had 21%, 15%, and 55% dystrophin-positive fibres after treatment and these findings were confirmed with western blot, which showed an increase after treatment of protein levels from 2% to 18%, from 0·9% to 17%, and from 0% to 7·7% of normal muscle, respectively. The dystrophin-associated proteins α-sarcoglycan and neuronal nitric oxide synthase were also restored at the sarcolemma. Analysis of the inflammatory infiltrate indicated a reduction of cytotoxic T cells in the post-treatment muscle biopsies in the two high-dose cohorts. Interpretation The safety and biochemical efficacy that we present show the potential of AVI-4658 to become a disease-modifying drug for Duchenne muscular dystrophy. Funding UK Medical Research Council; AVI BioPharma.
Summary Background Duchenne muscular dystrophy is caused by dystrophin deficiency and muscle deterioration and preferentially affects boys. Antisense-oligonucleotide-induced exon skipping allows ...synthesis of partially functional dystrophin. We investigated the efficacy and safety of drisapersen, a 2′-O-methyl-phosphorothioate antisense oligonucleotide, given for 48 weeks. Methods In this exploratory, double-blind, placebo-controlled study we recruited male patients (≥5 years of age; time to rise from floor ≤7 s) with Duchenne muscular dystrophy from 13 specialist centres in nine countries between Sept 1, 2010, and Sept 12, 2012. By use of a computer-generated randomisation sequence, we randomly allocated patients (2:2:1:1; block size of six; no stratification) to drisapersen 6 mg/kg or placebo, each given subcutaneously and either continuously (once weekly) or intermittently (nine doses over 10 weeks). The primary endpoint was change in 6-min walk distance (6MWD) at week 25 in patients in the intention-to-treat population for whom data were available. Safety assessments included renal, hepatic, and haematological monitoring and recording of adverse events. This trial is registered with ClinicalTrials.gov , number NCT01153932. Findings We recruited 53 patients: 18 were given continuous drisapersen, 17 were given intermittent drisapersen, and 18 were given placebo (continuous and intermittent groups combined). At week 25, mean 6MWD had increased by 31·5 m (SE 9·8) from baseline for continuous drisapersen, with a mean difference in change from baseline of 35·09 m (95% CI 7·59 to 62·60; p=0·014) versus placebo. We recorded no difference in 6MWD changes from baseline between intermittent drisapersen (mean change −0·1 SE 10·3) and placebo (mean difference 3·51 m −24·34 to 31·35) at week 25. The most common adverse events in drisapersen-treated patients were injection-site reactions (14 patients given continuous drisapersen, 15 patients given intermittent drisapersen, and six given placebo) and renal events (13 for continuous drisapersen, 12 for intermittent drisapersen, and seven for placebo), most of which were subclinical proteinuria. None of the serious adverse events reported (one for continuous, two for intermittent, and two for placebo) resulted in withdrawal from the study. Interpretation Continuous drisapersen resulted in some benefit in 6MWD versus placebo at week 25. The safety findings are similar to those from previous studies. Ambulation improvements in this young population with early-stage Duchenne muscular dystrophy are encouraging but need to be confirmed in larger studies. Funding GlaxoSmithKline, Prosensa Therapeutics BV (a subsidiary of Prosensa Holding NV).
OBJECTIVEGenetic diagnosis of muscular dystrophies (MDs) has classically been guided by clinical presentation, muscle biopsy, and muscle MRI data. Muscle MRI suggests diagnosis based on the pattern ...of muscle fatty replacement. However, patterns overlap between different disorders and knowledge about disease-specific patterns is limited. Our aim was to develop a software-based tool that can recognize muscle MRI patterns and thus aid diagnosis of MDs.
METHODSWe collected 976 pelvic and lower limbs T1-weighted muscle MRIs from 10 different MDs. Fatty replacement was quantified using Mercuri score and files containing the numeric data were generated. Random forest supervised machine learning was applied to develop a model useful to identify the correct diagnosis. Two thousand different models were generated and the one with highest accuracy was selected. A new set of 20 MRIs was used to test the accuracy of the model, and the results were compared with diagnoses proposed by 4 specialists in the field.
RESULTSA total of 976 lower limbs MRIs from 10 different MDs were used. The best model obtained had 95.7% accuracy, with 92.1% sensitivity and 99.4% specificity. When compared with experts on the field, the diagnostic accuracy of the model generated was significantly higher in a new set of 20 MRIs.
CONCLUSIONMachine learning can help doctors in the diagnosis of muscle dystrophies by analyzing patterns of muscle fatty replacement in muscle MRI. This tool can be helpful in daily clinics and in the interpretation of the results of next-generation sequencing tests.
CLASSIFICATION OF EVIDENCEThis study provides Class II evidence that a muscle MRI-based artificial intelligence tool accurately diagnoses muscular dystrophies.
Duchenne muscular dystrophy (DMD) is a rare pediatric neuromuscular disease associated with progressive muscle degeneration and extensive care needs. Our objective was to estimate the caregiver ...burden associated with DMD. We made cross-sectional assessments of caregiver health-related quality of life (HRQL) and burden using the EuroQol EQ-5D, a Visual Analogue Scale (VAS), the SF-12 Health Survey, and the Zarit Caregiver Burden Interview (ZBI) administered online. Results were stratified by disease stage (early/late ambulatory/non-ambulatory) and caregivers’ rating of patients’ health and mental status. In total, caregivers to 770 patients participated. Mean EQ-5D utility ranged between 0.85 (95 % CI 0.82–0.88) and 0.77 (0.74–0.80) across ambulatory classes and 0.88 (0.85–0.90) and 0.57 (0.39–0.74) across caregivers’ rating of patients’ health and mental status. Mean VAS score was 0.74 (0.73–0.75), mean SF-12 Mental Health Component Summary score 44 (43–45), and mean ZBI score 29 (28–30). Anxiety and depression, recorded in up to 70 % of caregivers depending on patients’ health and mental status, was significantly associated with annual household cost burden (>$5000 vs. <$1000, odds ratio 1.76, 95 % CI 1.18–2.63) and hours of leisure time devoted to informal care per week (25–50 vs. <25 h 2.01, 1.37–2.94; >50 vs. <25 h 3.35, 2.32–4.83) (
p
< 0.007). We show that caring for a person with DMD can be associated with a substantial burden and impaired HRQL. Our findings suggest that caregivers to patients with DMD should be screened for depression and emphasize the need for a holistic approach to family mental health in the context of chronic childhood disease.
Children with Duchenne muscular dystrophy (DMD) are shorter than their healthy peers. The introduction of corticosteroid (CS) has beneficial effects on muscle function but slows growth further and is ...associated with pubertal delay. In contrast to CS usage in most children and adolescents, weaning glucocorticoid is not a key objective of management in DMD. As the outlook for these young people improves, one of the main challenges is to reduce or offset the detrimental effects of CS on growth and development. This is a review of the aetiology and prevalence of short stature and delayed puberty in DMD, a summary of the treatments available and suggestions for areas of further research.