Low bone mineral density and reduced bone-specific alkaline phosphatase in 5q spinal muscular atrophy type 2 and type 3: A 2-year prospective study of bone health.

AIM: Individuals with spinal muscular atrophy (SMA) are at risk of developing skeletal problems. This study investigated bone mineral density (BMD), bone turnover markers and motor function in children and adolescents with SMA type 2 and type 3 over a two-year period. The effect of nusinersen was studied in a subgroup. METHODS: Single-centre study, including 20 patients, 2-18 years, of whom ten patients received nusinersen treatment. BMD was measured by dual-energy X-ray absorptiometry. RESULTS: All patients had low BMD levels at baseline; mean Z-score -2.3 for total body less head (TBLH) and -2.9 for total hip left (THL). Significant correlations were found both at baseline and for the follow-up change for motor function and Z-scores (TBLH and THL). For the whole study group, reduced bone formation and unchanged bone resorption, assessed by bone-specific alkaline phosphatase (BALP) (p = 0.0006, ES = -0.83) and C-terminal cross-linking telopeptide of type I collagen (CTX), respectively, were found over the study period. However, BALP decreased less in the nusinersen treatment group, which suggests a positive development on bone mass in these patients. CONCLUSION: Bone health evaluation is important in follow-up programmes for SMA patients. Further investigations are warranted for individuals on survival motor neuron-targeted treatments.

One in five patients with Duchenne muscular dystrophy dies from other causes than cardiac or respiratory failure.

Duchenne muscular dystrophy (DMD) is a severe neuromuscular disorder with increasing life expectancy from late teens to over 30 years of age. The aim of this nationwide study was to explore the prevalence, life expectancy and leading causes of death in patients with DMD in Sweden. Patients with DMD were identified through the National Quality Registry for Neuromuscular Diseases in Sweden, the Swedish Registry of Respiratory Failure, pathology laboratories, neurology and respiratory clinics, and the national network for neuromuscular diseases. Age and cause of death were retrieved from the Cause of Death Registry and cross-checked with medical records. 373 DMD patients born 1970-2019 were identified, of whom 129 patients deceased during the study period. Point prevalence of adult patients with DMD on December 31st 2019 was 3.2 per 100,000 adult males. Birth prevalence was 19.2 per 100,000 male births. Median survival was 29.9 years, the leading cause of death being cardiopulmonary in 79.9% of patients. Non-cardiopulmonary causes of death (20.1% of patients) mainly pertained to injury-related pulmonary embolism (1.3 per 1000 person-years), gastrointestinal complications (1.0 per 1000 person-years), stroke (0.6 per 1000 person-years) and unnatural deaths (1.6 per 1000 person-years). Death from non-cardiopulmonary causes occurred at younger ages (mean 21.0 years, SD 8.2; p = 0.004). Age at loss of independent ambulation did not have significant impact on overall survival (p = 0.26). We found that non-cardiopulmonary causes contribute to higher mortality among younger patients with DMD. We present novel epidemiological data on the increasing population of adult patients with DMD.

Long term treatment with ataluren-the Swedish experience.

INTRODUCTION: Ataluren is a relatively new treatment for male patients with Duchenne muscular dystrophy (DMD) due to a premature stop codon. Long-term longitudinal data as well as efficacy data on non-ambulant patients are still lacking. Here we present the results from a long-term follow-up study of all DMD patients treated with ataluren and followed at the Queen Silvia Children's Hospital in Gothenburg, Sweden, with focus on the evolution of patients' upper motor and respiratory function over time. METHODS: This is a retrospective longitudinal case-series study of all male DMD patients treated with ataluren and followed at the Queen Silvia Children's Hospital in Gothenburg, Sweden, since 2008. RESULTS: Our eleven patients had a median exposure to ataluren of 2312 days which is almost a fourfold higher than previous studies. Loss of ambulation occurred at a median age of 13.2 years. Patients who lost ambulation prior to 13.2 years of age had received ataluren for 5 years, whereas patients who continued to be ambulatory after 13.2 years of age had received ataluren for 6.5 years until loss of ambulation or last follow-up if still ambulatory. Four of six non ambulatory patients had Performance of the Upper Limb scores above the expected mean values over time. All but one patient maintained a pulmonary decline above the expected over time. All ambulatory patients increased in their predicted forced vital capacity (FVC) with 2.8 to 8.2% annually. Following loss of ambulation, 5 of 6 patients declined in predicted FVC (%), with annual rate of decline varying from 1.8 to 21.1%. The treatment was safe and well tolerated throughout the follow-up period. CONCLUSIONS: This is the first study to present long-term cumulative treatment outcomes over a median period of 6.3 years on ataluren treatment. Our results indicate a delay in loss of ambulation, as well as a slower decline in FVC and upper limb motor function even after loss of ambulation. We suggest that treatment with ataluren should be initiated as soon as the diagnosis is confirmed, closely monitored and, in case of sustainable benefit, continued even after loss of ambulation.

Cognitive and adaptive functioning in congenital and childhood forms of myotonic dystrophy type 1: a longitudinal study.

AIM: To conduct a longitudinal follow-up of the development of global cognitive abilities and adaptive skills in individuals with congenital and childhood forms of myotonic dystrophy type 1 (DM1). METHOD: Fifty-one participants (29 males, 22 females, mean age 19y 5mo, SD 4y 11mo, range 10y 10mo-28y 11mo) were divided into severe congenital (n=16), mild congenital (n=17), and childhood DM1 (n=18) subgroups. The average time between the first and second assessments was 7 years 8 months. Adaptive skills were evaluated using the Vineland Adaptive Behavior Scales and global cognitive functioning using Wechsler scales. RESULTS: There was no statistically significant decline in cognitive abilities and adaptive behaviour. A tendency of decline regarding the level of intellectual disability was found in the congenital DM1 groups but not in the childhood group. In the congenital DM1 groups, the gap in relation to typically developing peers in cognitive and adaptive functioning increased. Predictors of change over time in adaptive skills were age and current level of intellectual disability: individuals with severe intellectual disability and younger individuals deteriorated the most. However, when raw scores were compared, no actual regression in adaptive functioning was found. INTERPRETATION: The participants had not lost any important adaptive skills. Greater cognitive and adaptive development was found in the childhood group than in the congenital groups. WHAT THIS PAPER ADDS: There is no absolute decline in cognitive and adaptive abilities in individuals with congenital and childhood myotonic dystrophy type 1. Pace of development is slow in comparison with normative data. The childhood group tended to show greater cognitive and adaptive development than the congenital groups.

FUNCIONAMIENTO COGNITIVO Y ADAPTATIVO EN LA INFANCIA Y FORMAS CONGÉNITAS DE DISTROFIA MIOTÓNICA TIPO 1: UN ESTUDIO LONGITUDINAL: OBJETIVO: Realizar un seguimiento longitudinal del desarrollo de las capacidades cognitivas globales y las habilidades de adaptación en individuos con formas congénitas e infantiles de distrofia miotónica tipo 1 (DM1). MÉTODO: Cincuenta y un participantes (29 varones, 22 mujeres, edad media 19 y 5 meses, SD 4 años y 11 meses, rango 10 años y 10 meses y 28 años y 11 meses) se dividieron en congénitos graves (n = 16), congénitos leves (n = 17) y DM infantil 1 (n = 18). El tiempo promedio entre la primera y la segunda evaluación fue de 7 años y 8 meses. Las habilidades adaptativas se evaluaron utilizando las escalas de comportamiento adaptativo de Vineland y el funcionamiento cognitivo global utilizando escalas de Wechsler. RESULTADOS: No hubo una disminución estadísticamente significativa en las capacidades cognitivas y el comportamiento adaptativo. Se encontró una tendencia de disminución con respecto al nivel de discapacidad intelectual en los grupos de DM1 congénitos, pero no en el grupo de la infancia. En los grupos de DM1 congénitos, la brecha en relación con los compañeros de desarrollo típico en el funcionamiento cognitivo y adaptativo aumentó. Los factores predictivos del cambio a lo largo del tiempo en las habilidades de adaptación fueron la edad y el nivel actual de discapacidad intelectual: las personas con discapacidad intelectual grave y las personas más jóvenes se deterioraron más. Sin embargo, cuando se compararon las puntuaciones brutas, no se encontró una regresión real en el funcionamiento adaptativo. INTERPRETACIÓN: Los participantes no habían perdido ninguna habilidad adaptativa importante. Se encontró mayor desarrollo cognitivo y adaptativo en el grupo infantil que en los grupos congénitos.

FUNCIONAMENTO COGNITIVO E ADAPTATIVO EM FORMAS CONGÊNITAS INFANTIS DA DISTROFIA MIOTÔNICA TIPO 1: UM ESTUDO LONGITUDINAL: OBJETIVO: Conduzimos um acompanhamento longitudinal do desenvolviemtno de capacidades cognitivas globais e capacidades adaptativas em indivíduos com formas congênitas e da infantis da distrofia miotônica tipo 1 (DM1). MÉTODO: Cinquenta e um participantes (29 do sexo masculino, 22 do sexo feminino, média de idade 19a 5m, DP 4a 11m, variação 10a 10m-28a 11m) foram divididos em DM1 congênita severa (n=16), congênita leve (n=17), e da infância (n=18). O tempo médio entre a primeira e a segunda avaliação foi 7 anos e 8 meses. Capacidades adaptativas foram avaliadas usando as Escalas Vineland de Comportamento Adaptativo, e as escalas Wechsler de funcionamento cognitivo global. RESULTADOS: Não houve declínio estatisticamente significativo nas capacidades cognitivas e comportamento adaptativo. Uma tendência de declínio no nível de incapacidade intelectual foi encontrado nos grupos de DM1congênita, mas não no grupo da infância. Nos grupos com DM1 congênita, a distância em relação aos pares com desenvolvimento típico no funcionamento cognitivo e adaptativo aumentou. Preditores de mudança com o passar do tempo nas habilidades adaptativas foram a idade e o nível atual de incapacidade intelectual: indivíduos com incapacidade intelectual severa e indivíduos mais jovens deterioraram mais. No entanto, quando as pontuações brutas foram comparadas, nenhuma regressão real no funcionamento adaptativo foi encontrada. INTERPRETAÇÃO: Os participantes não perderam nenhuma habilidade adaptativa importante. Maior desenvolvimento cognitivo e adaptativo foi encontrado no grupo da infância comparado aos grupos congênitos.

Respiratory comorbidities and treatments in Duchenne muscular dystrophy: impact on life expectancy and causes of death.

BACKGROUND: Duchenne muscular dystrophy (DMD) is a neuromuscular disorder with progressive decline of pulmonary function increasing the risk of early mortality. The aim of this study was to explore the respiratory-related comorbidities, and the effect of these comorbidities and treatments on life expectancy and causes of death. METHODS: All male patients living in Sweden with DMD, born and deceased 1970-2019, were included. Data regarding causes of death were collected from the Cause of Death Registry and cross-checked with the medical records along with diagnostics and relevant clinical features. RESULTS: Hundred and twenty nine patients were included with a median lifespan of 24.3 years. Acute respiratory failure accounted for 63.3% of respiratory-related causes of death. 70.1% suffered at least one pneumonia, with first episode at a median age of 17.8 years. Hypoventilation was found in 73.0% with onset at 18.1 years. 60.5% had their first pneumonia before established hypoventilation. Age at onset of hypoventilation showed a strong correlation with age at first pneumonia. First pneumonia and scoliosis non-treated with scoliosis surgery increased the risk of dying of respiratory-related causes. In 10% of the patients, first pneumonia resulted in acute tracheostomy or early death. Patients treated with assisted ventilation had higher life expectancy compared to untreated patients. CONCLUSIONS: Our results highlight the importance of identifying subclinical hypoventilation in a timely manner and the importance of an active treatment regime upon clinical signs of pneumonia.

Healthcare resource utilisation and direct medical cost for individuals with 5q spinal muscular atrophy in Sweden.

BACKGROUND: Spinal muscular atrophy (SMA) is a rare, progressive, neuromuscular disorder. Recent advances in treatment require an updated assessment of burden to inform reimbursement decisions. OBJECTIVES: To quantify healthcare resource utilisation (HCRU) and cost of care for patients with SMA. METHODS: Cohort study of patients with SMA identified in the Swedish National Patient Registry (2007-2018), matched to a reference cohort grouped into four SMA types (1, 2, 3, unspecified adult onset [UAO]). HCRU included inpatient admissions, outpatient visits, procedures, and dispensed medications. Direct medical costs were estimated by multiplying HCRU by respective unit costs. Average annual HCRU and medical costs were modelled for SMA versus reference cohorts to estimate differences attributable to the disease (i.e., average treatment effect estimand). The trajectory of direct costs over time were assessed using synthetic cohorts. RESULTS: We identified 290 SMA patients. Annualised HCRU was higher in SMA patients compared with reference cohorts. Highest risk ratios were observed for inpatient overnight stays for type 1 (risk ratio [RR]: 29.2; 95% confidence interval [CI]: 16.0, 53.5) and type 2 (RR: 23.3; 95% CI: 16.4,33.1). Mean annual direct medical costs per patient for each year since first diagnosis were greatest for type 1 (€114,185 and SMA-attributable: €113,380), type 2 (€61,876 and SMA-attributable: €61,237), type 3 (€45,518 and SMA-attributable: €44,556), and UAO (€4046 and SMA-attributable: €2098). Costs were greatest in the 2-3 years after the first diagnosis for all types. DISCUSSION AND CONCLUSION: The economic burden attributable to SMA is significant. Further research is needed to understand the burden in other European countries and the impact of new treatments.

Behavioural strengths and difficulties in relation to intellectual functions and age in Swedish boys with Duchenne muscular dystrophy.

The aim of this study was to describe behavioral strengths and difficulties in relation to intellectual function and age in boys with DMD. In a cross-sectional design, 70 boys with DMD were tested at 5, 8, 11, and 14 years of age (mean age 10y 5 m). Parental ratings of behavioral strengths and difficulties were studied in relation to age, intellectual function, motor function, and family socioeconomic status (SES). Results show a significant relation between behavioral strengths and difficulties and age with parents rating increasingly more difficulties (slightly higher, higher and very high) from 5 years (11.1%) to 9 years (30.8%) and 11 years (78.9%) of age and then fewer difficulties at 14 years (50%) of age. Working Memory Index (WMI) explained significant variance in SDQ-Total-Score (17.5%) and SDQ-Impact-Score (11.2%). WMI together with upper motor function explained 19.5% variance in SDQ-Hyperactivity and 19.7% in SDQ-Peer-Problems. Age and SES explained an 18.9% variance in SDQ-Emotional-Problems. Age is an important factor when analyzing behavioral strengths and difficulties for boys with DMD. The development of boys with DMD needs to be understood in the context of expected developmental trajectory as well as in the decline of psychical functioning. Our study supports that age, cognition, motor function, and family SES all contribute to how behavioral strengths and difficulties evolves in boys with DMD.

Distal arthrogryposis: clinical and genetic findings.

AIM: Distal arthrogryposis is characterized by congenital contractures predominantly in hands and feet. Mutations in sarcomeric protein genes are involved in several types of distal arthrogryposis. Our aim is to describe clinical and molecular genetic findings in individuals with distal arthrogryposis and evaluate the genotype-phenotype correlation. METHOD: We investigated 39 patients from 21 families. Clinical history, including neonatal findings, joint involvement and motor function, was documented. Clinical examination was performed including evaluation of muscle strength. Molecular genetic investigations were carried out in 19 index cases. Muscle biopsies from 17 patients were analysed. RESULTS: A pathogenic mutation was found in six families with 19 affected family members with autosomal dominant inheritance and in one child with sporadic occurrence. In three families and in one child with sporadic form, the identified mutation was de novo. Muscle weakness was found in 17 patients. Ambulation was affected in four patients and hand function in 28. Fourteen patients reported pain related to muscle and joint affection. CONCLUSION: The clinical findings were highly variable between families and also within families. Mutations in the same gene were found in different syndromes suggesting varying clinical penetrance and expression, and different gene mutations were found in the same clinical syndrome demonstrating genetic heterogeneity.

Bone mass development in patients with Duchenne and Becker muscular dystrophies: a 4-year clinical follow-up.

AIM: To investigate the longitudinal development of bone mass in patients with Duchenne and Becker muscular dystrophies and to study the impact of muscle strength and motor function on bone mass in these patients. METHODS: Eighteen patients with Duchenne muscular dystrophy (2.3-19.7 years at baseline) and six patients with the milder Becker muscular dystrophy (10.8-18.9 years at baseline) were followed during a 4-year period with respect to areal bone mineral density (BMD), motor function and muscle strength. RESULTS: Greater bone mineral accretion was observed in the Becker patient group compared with the age-related Duchenne group above 10 years of age, and the older patients with Duchenne experienced decreased femoral neck BMD during the study period. In the study group, significant correlations were found between BMD in the lower extremities and muscle function parameters. CONCLUSIONS: The differences in BMD between patients with Duchenne and Becker as well as between different bone measurement sites demonstrated in the present study point out the importance of preserving muscle strength and motor function in patients with muscular dystrophy. Moreover; it highlights the value of performing region-specific analysis of the bone quality in these patients.

A population-based study of genotypic and phenotypic variability in children with spinal muscular atrophy.

AIMS: To describe the occurrence of spinal muscular atrophy (SMA) in childhood; to evaluate if any of the genes in the SMA region on chromosome 5q13 correlates with disease severity; to make genotype-phenotype correlations; to evaluate the variability of different disease alleles in carriers and the sensitivity of multiplex ligation-dependent probe amplification (MLPA) for detecting carriers. METHODS: In a population-based study from Western Sweden MLPA was used to determine the copy-numbers of several genes in the SMA region (SMN1, SMN2, BIRC1, GTF2H2 and SERF1A) in SMA-patients and their parents. RESULTS: We estimated the incidence of SMN1-related SMA in childhood at 1 in 11 800 live births and confirmed the relationship between the number of SMN2 copies and the severity of disease. No other direct relationships were found. All but one of the analysed parents were confirmed as carriers by MLPA analysis. A total of at least 30 different disease alleles were identified and no specific disease allele represented more than 15% of the total. CONCLUSION: The childhood incidence of SMA in the Swedish population is around 1 in 12,000 live births and it is unlikely that there is any founder effect involved in SMA in western Sweden.

NFL is a marker of treatment response in children with SMA treated with nusinersen.

BACKGROUND: Recently, the anti-sense oligonucleotide drug nusinersen was approved for spinal muscular atrophy (SMA) and our aim was to find a response marker for this treatment. METHODS: Twelve children with SMA type 1 and two copies of the SMN2 gene were included in a consecutive single-center study. The children were sampled for CSF at baseline and every time nusinersen was given intrathecally. The neuronal biomarkers NFL and tau and the glial biomarker GFAP were measured. Motor function was assessed using CHOP INTEND. Eleven similarly aged children, who were investigated to rule out neurological or infectious disease, were used as controls. RESULTS: Baseline levels of NFL (4598 ± 981 vs 148 ± 39, P = 0.001), tau (939 ± 159 vs 404 ± 86, P = 0.02), and GFAP (236 ± 44 vs 108 ± 26, P = 0.02) were significantly higher in SMA children than controls. Motor function improved by nusinersen treatment in median 13 points corresponding to 5.4 points per month of treatment (P = 0.001). NFL levels typically normalized ( < 380 pg/ml) between the fourth and fifth doses [- 879.5 pg/mL/dose, 95% CI (- 1243.4, - 415.6), P = 0.0001], tau levels decreased [- 112.6 pg/mL/dose, 95% CI (- 206-7, - 18.6), P = 0.01], and minor decreases in GFAP were observed [- 16.9 pg/mL/dose, 95% CI (- 22.8, - 11.2), P = 0.02] by nusinersen treatment. Improvement in motor function correlated with reduced concentrations of NFL (rho = - 0.64, P = 0.03) and tau (rho = - 0.85, P = 0.0008) but not GFAP. CONCLUSIONS: Nusinersen normalized the axonal damage marker NFL and correlated with motor improvement in children with SMA. NFL may, therefore, be a novel biomarker to monitor treatment response early in the disease course.

Evaluation of hand orthoses in Duchenne muscular dystrophy.

PURPOSE: The purpose of this study was to evaluate whether treatment of boys with Duchenne muscular dystrophy using hand orthoses could benefit joint mobility, grip strength, or fine motor function. METHOD: Eight boys with Duchenne muscular dystrophy were provided with individually customised rest orthoses. The results were analysed using single-subject design. The study included a baseline and an intervention phase. A follow-up examination was also performed. RESULTS: Boys with less than 50° passive wrist extension mobility were included. Wrist extension of the dominant hand increased in four and was maintained in four. Wrist extension in the non-dominant hand increased in five, was maintained in two and decreased in one. Thumb abduction in the dominant hand increased in six and two remained stable. In the non-dominant hand five increased and three remained stable. Grip strength and fine motor function showed also positive results. CONCLUSIONS: This study indicates that the use of hand orthoses in Duchenne muscular dystrophy can delay development of contractures and improve passive wrist extension and thumb abduction. Hand orthoses can therefore be recommended for boys who start to develop contractures in the long finger flexors. Due to small sample size further studies are needed to confirm this result. Implications for rehabilitation Evaluation of hand orthoses in Duchenne muscular dystrophy. Preserved hand function is of uttermost importance for performance of activities in the late stages of Duchenne muscular dystrophy. Contractures of long finger flexors affect hand function and limit performance of daily activities. Hand orthoses can delay development of contractures and preserve hand function and give prerequisites for independence. The occupational therapists should measure wrist joint mobility regularly to be able to find the right time for intervention with hand orthoses in this progressive disorder.

Health-related quality of life and orthosis use in a Swedish population with arthrogryposis.

BACKGROUND: Joint contractures are the main characteristics for children with arthrogryposis multiplex congenita. Orthoses are often used to enable or facilitate walking. OBJECTIVES: To describe health-related quality of life in children with arthrogryposis multiplex congenita and satisfaction with orthoses in those using orthoses. STUDY DESIGN: Cross-sectional study. METHODS: A total of 33 children with arthrogryposis multiplex congenita participated in the study. Questionnaires were used which measured health-related quality of life (Child Health Questionnaire-Parent Form and EQ-5D youth), mobility and self-care (Paediatric Evaluation of Disability Inventory) and satisfaction with orthoses (Quebec User Evaluation of Satisfaction with Assistive Technology 2.0). Children were divided into groups based on the use of orthoses: Ort-D were dependent on orthoses for walking, Ort-ND used orthoses but were not dependent on them for walking and Non-Ort did not use orthoses. RESULTS: Children with arthrogryposis multiplex congenita had significantly lower Child Health Questionnaire scores in 9 of 12 subscales compared to healthy controls. The children's reported perceived health with EQ-5D youth did not show any difference between children using orthoses or children using only shoes. Paediatric Evaluation of Disability Inventory showed less mobility in Ort-D than in Non-Ort. In total, both orthosis groups were 'quite satisfied' with their orthoses. CONCLUSION: Child Health Questionnaire-physical functioning was lowest in children who were dependent on orthoses (Ort-D) for walking. Both Ort-D and Ort-ND were similar satisfied with their orthoses. Clinical relevance This study contributes to knowledge about health-related quality of life in a group of ambulatory children with arthrogryposis multiplex congenita. For children using orthoses, it is relevant to capture their opinion about their orthoses but a questionnaire specifically for children should be developed.

Low bone mineral density and decreased bone turnover in Duchenne muscular dystrophy.

This cross-sectional study examined bone mineral density, bone turnover, body composition and calciotropic hormones in 24 boys with Duchenne muscular dystrophy (DMD) (2.3-19.7 years), most of whom were being treated with prednisolone, and 24 age-matched healthy boys. Our study demonstrated lower bone mineral density in the DMD group for total body, spine, hip, heel and forearm measurements. These differences between DMD patients and controls increased with increasing age. Biochemical markers of both bone formation and resorption revealed reduced bone turnover in DMD patients. The fracture rate was not higher in DMD patients. The DMD group had low vitamin D levels but high leptin levels in comparison with the control group. Muscle strength correlated with bone mineral density assessed at the hip and heel in the DMD group. Interventions that increase bone formation should be considered, as DMD patients have reduced bone turnover in addition to their low bone mineral density.

Long-term follow-up of motor function and muscle strength in the congenital and childhood forms of myotonic dystrophy type 1.

The aims of this study were to explore how motor function and muscle strength change over time in the congenital and childhood forms of myotonic dystrophy type 1, further to investigate whether sex, age, disease severity or size of the mutation could explain these changes. Motor function and isometric muscle strength were evaluated at three occasions during 1999-2013 in 57 patients aged 0.7-28.9 years. Median time between first and last assessment was 11.5 years ranging from 9.6 to 13.3 years. The study shows that motor function improves during the first decade, is most pronounced during the first six years, reaches a plateau during adolescence and starts to deteriorate in the beginning of the second decade. The most predictive variables for change are age (p < 0.0001) and number of CTG-repeat expansions (p = 0.0018). Sex or disease severity grade do not predict changes in motor function. Deterioration of muscle strength is most pronounced in ankle dorsiflexors. Knowledge of development and deterioration of motor function is important for clinical decision making and for planning of interventions. This knowledge can also be of interest for patient recruitment in drug trials, since treatment effect might be easier to evaluate in the stable phases of this progressive disorder.

Comparison of ambulatory capacity and disease progression of Duchenne muscular dystrophy subjects enrolled in the drisapersen DMD114673 study with a matched natural history cohort of subjects on daily corticosteroids.

Duchenne muscular dystrophy is a rare genetic disorder with life-limiting pathology. Drisapersen induces exon 51 skipping, thereby producing a shorter but functional dystrophin protein. The longest available data are from an open-label extension study (PRO051-02) treating 12 boys with drisapersen (6 mg/kg/week subcutaneously). The median change (range) from baseline to week 177 in six-minute walking distance (6MWD) was 8 (-263, 163) metres. The current analysis aimed to put the results from PRO051-02 in the context of natural progression by comparing the functional trajectory of drisapersen-treated subjects to a matched natural history (NH) cohort, treated by standard of care. Subjects were matched individually by age and 6MWD, as the primary analysis, and by age and rise from floor (RFF), as sensitivity analysis. A total of 75 NH subjects were available for 6MWD analysis, of which matching was possible for 9 ambulant drisapersen-treated subjects. None of the 6 "stable" (baseline 6MWD ≥330 metres) drisapersen-treated subjects lost ambulation vs 4 out of 10 matched NH subjects over a comparable timeframe (~3.4 years), compared with 2 out of 3 ambulant "in decline" drisapersen-treated subjects vs all 6 matched NH subjects. A total of 79 NH subjects were available for RFF analysis. For continuous ambulatory subjects (N = 4), the RFF decline was more pronounced in the NH cohort than in the drisapersen-treated subjects. In conclusion, a comparison of ambulant drisapersen-treated subjects with matched NH subjects showed a difference in functional trajectories over a timeframe of up to 3.4 years in favour of drisapersen.

Long-Term Efficacy, Safety, and Pharmacokinetics of Drisapersen in Duchenne Muscular Dystrophy: Results from an Open-Label Extension Study.

BACKGROUND: Drisapersen induces exon 51 skipping during dystrophin pre-mRNA splicing and allows synthesis of partially functional dystrophin in Duchenne muscular dystrophy (DMD) patients with amenable mutations. METHODS: This 188-week open-label extension of the dose-escalation study assessed the long-term efficacy, safety, and pharmacokinetics of drisapersen (PRO051/GSK2402968), 6 mg/kg subcutaneously, in 12 DMD subjects. Dosing was once weekly for 72 weeks. All subjects had a planned treatment interruption (weeks 73-80), followed by intermittent dosing (weeks 81-188). RESULTS: Subjects received a median (range) total dose of 5.93 (5.10 to 6.02) mg/kg drisapersen. After 177 weeks (last efficacy assessment), median (mean [SD]) six-minute walk distance (6MWD) improved by 8 (-24.5 [161]) meters for the 10 subjects able to complete the 6MWD at baseline (mean age [SD]: 9.5 [1.9] years). These statistics include 2 subjects unable to complete the test at later visits and who scored "zero". When only the 8 ambulant subjects at week 177 were taken into account, a median (mean [SD]) increase of 64 (33 [121]) meters in 6MWD was observed. Of 7 subjects walking ≥330 m at extension baseline, 5 walked farther at week 177. Of 3 subjects walking <330 m, 2 lost ambulation, while 1 declined overall but walked farther at some visits. Over the 188 weeks, the most common adverse events were injection-site reactions, raised urinary α1-microglobulin and proteinuria. Dystrophin expression was detected in all muscle biopsies obtained at week 68 or 72. CONCLUSION: Drisapersen was generally well tolerated over 188 weeks. Possible renal effects, thrombocytopenia and injection-site reactions warrant continued monitoring. Improvements in the 6MWD at 12 weeks were sustained after 3.4 years of dosing for most patients. For a small, uncontrolled study, the outcomes are encouraging, as natural history studies would anticipate a decline of over 100 meters over a 3-year period in a comparable cohort. TRIAL REGISTRATION: ClinicalTrials.gov NCT01910649.

Pain in adolescents with spinal muscular atrophy and Duchenne and Becker muscular dystrophy.

BACKGROUND/PURPOSE: The purpose of this study was to explore the prevalence, nature and scope of pain in adolescents with spinal muscular atrophy and Duchenne and Becker muscular dystrophy and whether the pain differs between diagnostic groups or between adolescents with different ambulation status. Furthermore to study the consequences of pain and to identify pain-exacerbating and pain-relieving factors. METHODS: In a national survey, fifty-five adolescents with spinal muscular atrophy and dystrophinopathy completed a questionnaire assessing pain frequency, duration, location using a body map, intensity and discomfort using visual analogue scales, pain interference using a modified version of Brief Pain Inventory and factors exacerbating and relieving pain. RESULTS: Sixty-nine per cent of the adolescents reported pain during the past three months and 50% reported chronic pain. The pain prevalence did not differ significantly between diagnostic groups or between ambulators and non-ambulators. The average pain intensity was graded as mild and the worst pain as moderate. The pain typically occurred weekly, most frequently in the neck/back or legs. General activity and mood were the areas that were most affected by pain. Common pain-exacerbating factors were sitting, too much movement/activity and being lifted or transferred. CONCLUSION: Pain is a frequent problem in adolescents with spinal muscular atrophy and dystrophinopathy. The assessments used enable an understanding both of the nature and scope of pain and of the impact of pain in everyday life. The study highlights the importance of assessing pain in a systematic manner and offering an individual approach to interventions designed to reduce pain in this population.

Embryonic myosin heavy-chain mutations cause distal arthrogryposis and developmental myosin myopathy that persists postnatally.

BACKGROUND: Myosin is a molecular motor and the essential part of the thick filament of striated muscle. The expression of myosin heavy-chain (MyHC) isoforms is developmentally regulated. The embryonic isoform encoded from MYH3 (OMIM *160720) is expressed during fetal life. Recently, mutations in MYH3 were demonstrated to be associated with congenital joint contractures, that is, Freeman-Sheldon and Sheldon-Hall syndromes, which are both distal arthrogryposis syndromes. Mutations in other MyHC isoforms cause myopathy. It is unknown whether MYH3 mutations cause myopathy because muscle tissue has not been studied. OBJECTIVES: To determine whether novel MYH3 mutations are associated with distal arthrogryposis and to demonstrate myopathic changes in muscle biopsy specimens from 4 patients with distal arthrogryposis and MYH3 mutations. DESIGN: In a cohort of patients with distal arthrogryposis, we analyzed the entire coding sequence of MYH3. Muscle biopsy specimens were obtained, and in addition to morphologic analysis, the expression of MyHC isoforms was investigated at the protein and transcript levels. RESULTS: We identified patients from 3 families with novel MYH3 mutations. These mutations affect developmentally conserved residues that are located in different regions of the adenosine triphosphate-binding pocket of the MyHC head. The embryonic (MYH3) isoform was not detected in any of the muscle biopsy samples, indicating a normal developmental downregulation of MYH3 in these patients. However, morphologic analysis of muscle biopsy specimens from the 4 patients revealed mild and variable myopathic features and a pathologic upregulation of the fetal MyHC isoform (MYH8) in 1 patient. CONCLUSIONS: Distal arthrogryposis associated with MYH3 mutations is secondary to myosin myopathy, and postnatal muscle manifestations are variable.