Dual-energy X-ray absorptiometry measures of lean body mass as a biomarker for progression in boys with Duchenne muscular dystrophy.

We evaluated whether whole-body dual-energy X-ray absorptiometry (DXA) measures of lean body mass can be used as biomarkers for disease progression and treatment effects in patients with Duchenne muscular dystrophy. This post hoc analysis utilized data from a randomized, 2-period study of domagrozumab versus placebo in 120 ambulatory boys with DMD. DXA measures of lean body mass were obtained from the whole body (excluding head), arms, legs and appendicular skeleton at baseline and every 16 weeks. Treatment effects on DXA measures for domagrozumab versus placebo were assessed at Week 49. At Week 49, domagrozumab statistically significantly increased lean body mass versus placebo in the appendicular skeleton (p = 0.050) and arms (p < 0.001). The relationship between lean body mass at Week 49 and functional endpoints at Week 97 was evaluated. Changes in lean body mass at Week 49 in all regions except arms were significantly correlated with percent change from baseline in 4-stair climb (4SC) at Week 97. DXA-derived percent lean mass at Week 49 also correlated with 4SC and North Star Ambulatory Assessment at Week 97. These data indicate that whole-body DXA measures can be used as biomarkers for treatment effects and disease progression in patients with DMD, and warrant further investigation.Trial registration: ClinicalTrials.gov, NCT02310763; registered 8 December 2014.

Quantitative magnetic resonance imaging measures as biomarkers of disease progression in boys with Duchenne muscular dystrophy: a phase 2 trial of domagrozumab.

Duchenne muscular dystrophy (DMD) is a progressive, neuromuscular disorder caused by mutations in the DMD gene that results in a lack of functional dystrophin protein. Herein, we report the use of quantitative magnetic resonance imaging (MRI) measures as biomarkers in the context of a multicenter phase 2, randomized, placebo-controlled clinical trial evaluating the myostatin inhibitor domagrozumab in ambulatory boys with DMD (n = 120 aged 6 to < 16 years). MRI scans of the thigh to measure muscle volume, muscle volume index (MVI), fat fraction, and T2 relaxation time were obtained at baseline and at weeks 17, 33, 49, and 97 as per protocol. These quantitative MRI measurements appeared to be sensitive and objective biomarkers for evaluating disease progression, with significant changes observed in muscle volume, MVI, and T2 mapping measures over time. To further explore the utility of quantitative MRI measures as biomarkers to inform longer term functional changes in this cohort, a regression analysis was performed and demonstrated that muscle volume, MVI, T2 mapping measures, and fat fraction assessment were significantly correlated with longer term changes in four-stair climb times and North Star Ambulatory Assessment functional scores. Finally, less favorable baseline measures of MVI, fat fraction of the muscle bundle, and fat fraction of lean muscle were significant risk factors for loss of ambulation over a 2-year monitoring period. These analyses suggest that MRI can be a valuable tool for use in clinical trials and may help inform future functional changes in DMD.Trial registration: ClinicalTrials.gov identifier, NCT02310763; registered December 2014.

A Combined Prospective and Retrospective Comparison of Long-Term Functional Outcomes Suggests Delayed Loss of Ambulation and Pulmonary Decline with Long-Term Eteplirsen Treatment.

BACKGROUND: Studies 4658-201/202 (201/202) evaluated treatment effects of eteplirsen over 4 years in patients with Duchenne muscular dystrophy and confirmed exon-51 amenable genetic mutations. Chart review Study 4658-405 (405) further followed these patients while receiving eteplirsen during usual clinical care. OBJECTIVE: To compare long-term clinical outcomes of eteplirsen-treated patients from Studies 201/202/405 with those of external controls. METHODS: Median total follow-up time was approximately 6 years of eteplirsen treatment. Outcomes included loss of ambulation (LOA) and percent-predicted forced vital capacity (FVC%p). Time to LOA was compared between eteplirsen-treated patients and standard of care (SOC) external controls and was measured from eteplirsen initiation in 201/202 or, in the SOC group, from the first study visit. Comparisons were conducted using univariate Kaplan-Meier analyses and log-rank tests, and multivariate Cox proportional hazards models with regression adjustment for baseline characteristics. Annual change in FVC%p was compared between eteplirsen-treated patients and natural history study patients using linear mixed models with repeated measures. RESULTS: Data were included from all 12 patients in Studies 201/202 and the 10 patients with available data from 405. Median age at LOA was 15.16 years. Eteplirsen-treated patients experienced a statistically significant longer median time to LOA by 2.09 years (5.09 vs. 3.00 years, p < 0.01) and significantly attenuated rates of pulmonary decline vs. natural history patients (FVC%p change: -3.3 vs. -6.0 percentage points annually, p < 0.0001). CONCLUSIONS: Study 405 highlights the functional benefits of eteplirsen on ambulatory and pulmonary function outcomes up to 7 years of follow-up in comparison to external controls.

A homozygous CAP2 pathogenic variant in a neonate presenting with rapidly progressive cardiomyopathy and nemaline rods.

Nemaline Myopathy (NM) is a disorder of skeletal muscles caused by mutations in sarcomere proteins and characterized by accumulation of microscopic rod or thread-like structures (nemaline bodies) in skeletal muscles. Patients diagnosed with both NM and infantile cardiomyopathy are very rare. A male infant presented, within the first few hours of life, with severe dilated cardiomyopathy, biventricular dysfunction and left ventricular noncompaction. A muscle biopsy on the 8th day of life from the right sternocleidomastoid muscle identified nemaline rods. Whole exome sequencing identified a c.1288 delT (homozygous pathogenic variant) in the CAP2 gene (NM_006366), yielding a CAP2 protein (NP_006357.1) with a p.C430fs. Both parents were heterozygous for the same variant but have no history of heart or muscle disease. Analysis of patient derived fibroblasts and cardiomyocytes derived from induced pluripotent stem cells confirmed the p.C430fs mutation (pathogenic variant), which appears to cause loss of both CAP2 protein and mRNA. The CAP2 gene encodes cyclase associated protein 2, an actin monomer binding and filament depolymerizing protein and CAP2 knockout mice develop severe dilated cardiomyopathy and muscle weakness. The patient underwent a heart transplant at 1 year of age. Heart tissue explanted at that time also showed nemaline rods and additionally disintegration of the myofibrillar structure. Other extra cardiac concerns include mild hypotonia, atrophic and widened scarring. This is the first description of a patient presenting with nemaline myopathy associated with a pathogenic variant of CAP2.

Open-Label Evaluation of Eteplirsen in Patients with Duchenne Muscular Dystrophy Amenable to Exon 51 Skipping: PROMOVI Trial.

BackgroundEteplirsen received accelerated FDA approval for treatment of Duchenne muscular dystrophy (DMD) with mutations amenable to exon 51 skipping, based on demonstrated dystrophin production.ObjectiveTo report results from PROMOVI, a phase 3, multicenter, open-label study evaluating efficacy and safety of eteplirsen in a larger cohort.MethodsAmbulatory patients aged 7-16 years, with confirmed mutations amenable to exon 51 skipping, received eteplirsen 30 mg/kg/week intravenously for 96 weeks. An untreated cohort with DMD not amenable to exon 51 skipping was also enrolled.Results78/79 eteplirsen-treated patients completed 96 weeks of treatment. 15/30 untreated patients completed the study; this cohort was considered an inappropriate control group because of genotype-driven differences in clinical trajectory. At Week 96, eteplirsen-treated patients showed increased exon skipping (18.7-fold) and dystrophin protein (7-fold) versus baseline. Post-hoc comparisons with patients from eteplirsen phase 2 studies (4658-201/202) and mutation-matched external natural history controls confirmed previous results, suggesting clinically notable attenuation of decline on the 6-minute walk test over 96 weeks (PROMOVI: -68.9 m; phase 2 studies: -67.3 m; external controls: -133.8 m) and significant attenuation of percent predicted forced vital capacity annual decline (PROMOVI: -3.3%, phase 2 studies: -2.2%, external controls: -6.0%; p < 0.001). Adverse events were generally mild to moderate and unrelated to eteplirsen. Most frequent treatment-related adverse events were headache and vomiting; none led to treatment discontinuation.ConclusionsThis large, multicenter study contributes to the growing body of evidence for eteplirsen, confirming a positive treatment effect, favorable safety profile, and slowing of disease progression versus natural history.

Medical management of muscle weakness in Duchenne muscular dystrophy.

INTRODUCTION: Duchenne muscular dystrophy (DMD) is a childhood onset muscular dystrophy leading to shortened life expectancy. There are gaps in published DMD care guidelines regarding recently approved DMD medications and alternative steroid dosing regimens. METHODS: A list of statements about use of currently available therapies for DMD in the United States was developed based on a systematic literature review and expert panel feedback. Panelists' responses were collected using a modified Delphi approach. RESULTS: Among corticosteroid regimens, either deflazacort or prednisone weekend dosing was preferred when payer requirements do not dictate choice. Most patients with exon 51 skip-amenable mutations should be offered eteplirsen, before or with a corticosteroid. DISCUSSION: The options available for medical management of the motor symptoms of DMD are expanding rapidly. The choice of medical therapies should balance expected benefit with side effects.

Randomized phase 2 trial and open-label extension of domagrozumab in Duchenne muscular dystrophy.

We report results from a phase 2, randomized, double-blind, 2-period trial (48 weeks each) of domagrozumab and its open-label extension in patients with Duchenne muscular dystrophy (DMD). Of 120 ambulatory boys (aged 6 to <16 years) with DMD, 80 were treated with multiple ascending doses (5, 20, and 40 mg/kg) of domagrozumab and 40 treated with placebo. The primary endpoints were safety and mean change in 4-stair climb (4SC) time at week 49. Secondary endpoints included other functional tests, pharmacokinetics, and pharmacodynamics. Mean (SD) age was 8.4 (1.7) and 9.3 (2.3) years in domagrozumab- and placebo-treated patients, respectively. Difference in mean (95% CI) change from baseline in 4SC at week 49 for domagrozumab vs placebo was 0.27 (-7.4 to 7.9) seconds (p = 0.94). There were no significant between-group differences in any secondary clinical endpoints. Most patients had ≥1 adverse event in the first 48 weeks; most were mild and not treatment-related. Median serum concentrations of domagrozumab increased with administered dose within each dose level. Non-significant increases in muscle volume were observed in domagrozumab- vs placebo-treated patients. Domagrozumab was generally safe and well tolerated in patients with DMD. Efficacy measures did not support a significant treatment effect. Clinicaltrials.gov identifiers: NCT02310763 and NCT02907619.

MYL2-associated congenital fiber-type disproportion and cardiomyopathy with variants in additional neuromuscular disease genes; the dilemma of panel testing.

Next-generation sequencing has led to transformative advances in our ability to diagnose rare diseases by simultaneously sequencing dozens, hundreds, or even entire genomes worth of genes to efficiently identify pathogenic mutations. These studies amount to multiple hypothesis testing on a massive scale and not infrequently lead to discovery of multiple genetic variants whose relative contributions to a patient's disease are unclear. Panel testing, in particular, can be problematic because each of the many genes being sequenced might represent a plausible explanation for a given case. We performed targeted gene panel analysis of 43 established neuromuscular disease genes in a patient with congenital fiber-type disproportion (CFTD) and fatal infantile cardiomyopathy. Initial review of variants identified changes in four genes that could be considered relevant candidates to cause this child's disease. Further analysis revealed that two of these are likely benign, but a homozygous frameshift variant in the myosin light chain 2 gene, MYL2, and a heterozygous nonsense mutation in the nebulin gene, NEB, met criteria to be classified as likely pathogenic or pathogenic. Recessive MYL2 mutations are a rare cause of CFTD associated with both skeletal and cardiomyopathy, whereas recessive NEB mutations cause nemaline myopathy. Although the proband's phenotype is likely largely explained by the MYL2 variant, the heterozygous pathogenic NEB variant cannot be ruled out as a contributing factor. This case illustrates the complexity when analyzing large numbers of variants from targeted gene panels in which each of the genes might plausibly contribute to the patient's clinical presentation.

What Is in the Myopathy Literature?

We review the development of exon 51 skipping therapy with eteplirsen for Duchenne muscular dystrophy, including the recent report of long-term, sustained dystrophin production. Studies of the late-life health profile of patients with Duchenne muscular dystrophy, early detection of left ventricular systolic dysfunction, and caregiver burden are also covered. A study of skeletal muscle magnetic resonance imaging in dysferlinopathies provides an extensive, detailed map of the involved muscles and consistency across phenotypes. Regarding the category of autoimmune myopathies, we discuss an article on the clinical and laboratory features associated with PM/Scl antibodies in comparison with other autoimmune myopathy subgroups. Finally, the overall increase in mortality in inflammatory myopathies is highlighted in a recent report from Sweden.

Clinical Follow-Up for Duchenne Muscular Dystrophy Newborn Screening: A Proposal.

New developments in the rapid diagnosis and treatment of boys with Duchenne muscular dystrophy (DMD) have led to growing enthusiasm for instituting DMD newborn screening (NBS) in the United States. Our group has been interested in developing clinical guidance to be implemented consistently in specialty care clinics charged with the care of presymptomatically identified newborns referred after DMD-NBS. We reviewed the existing literature covering patient-centered clinical follow-up after NBS, educational material from public health and advocacy sites, and federal recommendations on effective NBS follow-up. We discussed the review as a group and added our own experience to develop materials suitable for initial parent and primary care provider education. These materials and a series of templates for subspecialist encounters could be used to provide consistent care across centers and serve as the basis for ongoing quality improvement. Muscle Nerve 54: 186-191, 2016.

Twenty-year follow-up of newborn screening for patients with muscular dystrophy.

INTRODUCTION: An opt-out newborn screening (NBS) program for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) was implemented at 2 hospitals in Pittsburgh, Pennsylvania, between 1987 and 1995. METHODS: For patients and their parents in families who received a diagnosis of DMD or BMD, either by NBS or by traditional diagnostics after symptom onset, attitudes toward NBS for DMD and BMD were assessed. RESULTS: All patients and most parents supported NBS for DMD and BMD. In contrast to the NBS parent cohort, the non-NBS cohort felt that diagnosis by NBS would cause anxiety. CONCLUSIONS: There was strong support of NBS for DMD and BMD in both patients and their parents in families who received a diagnosis through NBS or through traditional diagnostics. No negative psychosocial impacts of NBS were identified among those families who received a diagnosis through NBS.

Parental attitudes toward newborn screening for Duchenne/Becker muscular dystrophy and spinal muscular atrophy.

INTRODUCTION: Disease inclusion in the newborn screening (NBS) panel should consider the opinions of those most affected by the outcome of screening. We assessed the level and factors that affect parent attitudes regarding NBS panel inclusion of Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and spinal muscular atrophy (SMA). METHODS: The attitudes toward NBS for DMD, BMD, and SMA were surveyed and compared for 2 categories of parents, those with children affected with DMD, BMD, or SMA and expectant parents unselected for known family medical history. RESULTS: The level of support for NBS for DMD, BMD, and SMA was 95.9% among parents of children with DMD, BMD, or SMA and 92.6% among expectant parents. CONCLUSIONS: There was strong support for NBS for DMD, BMD, and SMA in both groups of parents. Given advances in diagnostics and promising therapeutic approaches, discussion of inclusion in NBS should continue.

Spinal Deformity in Bethlem Myopathy.

STUDY DESIGN: Retrospective review. OBJECTIVES: To report the characteristics of spinal deformity in a series of 3 patients with Bethlem myopathy. SUMMARY OF BACKGROUND DATA: Bethlem myopathy presents with mild muscular weakness and typically has a benign course. Severe scoliosis in patients affected with Bethlem myopathy has not been previously reported. METHODS: Clinical records of 3 brothers with Bethlem myopathy were reviewed. Clinical and radiographic features of the spinal deformity are presented. RESULTS: All 3 patients had progressive scoliosis with coronal and sagittal imbalance. At a minimum of 26 months of follow-up after posterior instrumented fusion, there were no complications and deformity correction was maintained. Posterior instrumentation and fusion did not negatively affect the pulmonary function in this group of patients with Bethlem myopathy. CONCLUSIONS: Bethlem myopathy may present with severe scoliosis along with proximal muscle weakness. This condition should be included in the differential diagnosis of adolescent patients with progressive spinal deformity.

Brachium pontis stroke revealing neurofibromatosis type-2.

NF2 is an autosomal dominant disorder with neuroectodermal dysplasia. Most patients present with characteristic clinical tumors during or beyond the adolescent age group. The diagnosis is mainly clinical. Vasculopathy is rarely associated with NF2. Vascular complication as the presenting symptom in NF-2 is unknown. We report a case of a 2-year-old child with no prior family history of neurofibromatosis presenting with ataxia and brain-stem stroke.

Genotype-phenotype analysis of 4q deletion syndrome: proposal of a critical region.

Chromosome 4q deletion syndrome (4q- syndrome) is a rare condition, with an estimated incidence of 1 in 100,000. Although variable, the clinical spectrum commonly includes craniofacial, developmental, digital, skeletal, and cardiac involvement. Data on the genotype-phenotype correlation within the 4q arm are limited. We present detailed clinical and genetic information by array CGH on 20 patients with 4q deletions. We identified a patient who has a ∼465 kb deletion (186,770,069-187,234,800, hg18 coordinates) in 4q35.1 with all clinical features for 4q deletion syndrome except for developmental delay, suggesting that this is a critical region for this condition and a specific gene responsible for orofacial clefts and congenital heart defects resides in this region. Since the patients with terminal deletions all had cleft palate, our results provide further evidence that a gene associated with clefts is located on the terminal segment of 4q. By comparing and contrasting our patients' genetic information and clinical features, we found significant genotype-phenotype correlations at a single gene level linking specific phenotypes to individual genes. Based on these data, we constructed a hypothetical partial phenotype-genotype map for chromosome 4q which includes BMP3, SEC31A, MAPK10, SPARCL1, DMP1, IBSP, PKD2, GRID2, PITX2, NEUROG2, ANK2, FGF2, HAND2, and DUX4 genes.