Characterization of patients with Becker muscular dystrophy by histology, magnetic resonance imaging, function, and strength assessments

Lessons for future clinical trials in adults with Becker muscular dystrophy: Disease progression detected by muscle magnetic resonance imaging, clinical and patient-reported outcome measures

BACKGROUND AND PURPOSE

Because Becker muscular dystrophy (BMD) is a heterogeneous disease and only few studies have evaluated adult patients, it is currently still unclear which outcome measures should be used in future clinical trials.

METHODS

Muscle magnetic resonance imaging, patient-reported outcome measures and a wide range of clinical outcome measures, including motor function, muscle strength and timed-function tests, were evaluated in 21 adults with BMD at baseline and at 9 and 18 months of follow-up.

RESULTS

Proton density fat fraction increased significantly in 10/17 thigh muscles after 9 months, and in all thigh and lower leg muscles after 18 months. The 32-item Motor Function Measurement (MFM-32) scale (-1.3%, p = 0.017), North Star Ambulatory Assessment (-1.3 points, p = 0.010) and patient-reported activity limitations scale (-0.3 logits, p = 0.018) deteriorated significantly after 9 months. The 6-min walk distance (-28.7 m, p = 0.042), 10-m walking test (-0.1 m/s, p = 0.032), time to climb four stairs test (-0.03 m/s, p = 0.028) and Biodex peak torque measurements of quadriceps (-4.6 N m, p = 0.014) and hamstrings (-5.0 N m, p = 0.019) additionally deteriorated significantly after 18 months. At this timepoint, domain 1 of the MFM-32 was the only clinical outcome measure with a large sensitivity to change (standardized response mean 1.15).

DISCUSSION

It is concluded that proton density fat fraction imaging of entire thigh muscles is a sensitive outcome measure to track progressive muscle fat replacement in patients with BMD, already after 9 months of follow-up. Finally, significant changes are reported in a wide range of clinical and patient-reported outcome measures, of which the MFM-32 appeared to be the most sensitive to change in adults with BMD.

Brothers with Becker muscular dystrophy show discordance in skeletal muscle computed tomography findings: A case report

Becker muscular dystrophy is caused by DMD mutations and is characterized by progressive muscle atrophy. The wide variations observed in muscle atrophy progression in Becker muscular dystrophy are considered multifactorial, including differences in mutations and environmental factors. In this case, two brothers, aged 2 and 3 years, had the identical DMD mutation, confirming their Becker muscular dystrophy diagnosis. They began using handrails when ascending and descending stairs at the age of 16 due to progressive muscular weakness. Over an 18-year follow-up, the older brother consistently had high serum creatine kinase levels, significantly over median levels. Muscle computed tomography finings revealed that the older brother's gluteus maximus and vastus femoris cross-sectional areas were only half and one-third of the younger brother's, respectively. The mean computed tomography values of gluteus maximus and vastus femoris were significantly lower in the older brother. Our report suggests that muscle atrophy in Becker muscular dystrophy cannot be solely explained by dystrophin mutation or environmental factors.

Social cognition in DMD and BMD dystrophinopathies: A cross-sectional preliminary study

Objective: The dystrophinopathies called Duchenne and Becker muscular dystrophies (DMD/BMD) are rare, progressive, incurable, and life-limiting paediatric-onset neuromuscular diseases. These diseases have long been associated with specific neuropsychological deficits. However, the performance of these patients in the social cognition domain has not been properly investigated. Thus, the main objective of this study was to compare the performance on social cognition between DMD/BMD patients and healthy age-matched boys. Method: This cross-sectional study included 20 DMD/BMD children and adolescents and 20 healthy controls. The protocol included the Social Perception Domain of the NEPSY-II, the Reading the Mind in the Eyes Test - Child and Happé's Strange Stories test. General intelligence was controlled to eliminate the possible influence of covariables. All the assessments were performed remotely. Results: Most social cognition tasks were worse in patients with DMD/BMD than in matched healthy controls. These differences remained even after controlling for the general intelligence variable, with the exception of Total Disgust Errors (F = 1.462, p = .234, η2p= .038) and Verbal task (F = 1.820, p = .185, η2p= .047) scores from the NEPSY-II. Conclusions: This is the first study to demonstrate that the neuropsychological domain of social cognition is impaired in DMD/BMD patients, independent of the level of general intelligence. Screening assessments in DMD/BMD patients should be promoted to allow social cognition difficulties to be detected at an early stage to enhance patients' quality of life and social development.

Diffusion-tensor magnetic resonance imaging captures increased skeletal muscle fibre diameters in Becker muscular dystrophy

BACKGROUND

Becker muscular dystrophy (BMD) is an X-linked disorder characterized by slow, progressive muscle damage and muscle weakness. Hallmarks include fibre-size variation and replacement of skeletal muscle with fibrous and adipose tissues, after repeated cycles of regeneration. Muscle histology can detect these features, but the required biopsies are invasive, are difficult to repeat and capture only small muscle volumes. Diffusion-tensor magnetic resonance imaging (DT-MRI) is a potential non-invasive alternative that can calculate muscle fibre diameters when applied with the novel random permeable barrier model (RPBM). In this study, we assessed muscle fibre diameters using DT-MRI in BMD patients and healthy controls and compared these with histology.

METHODS

We included 13 BMD patients and 9 age-matched controls, who underwent water-fat MRI and DT-MRI at multiple diffusion times, allowing RPBM parameter estimation in the lower leg muscles. Tibialis anterior muscle biopsies were taken from the contralateral leg in 6 BMD patients who underwent DT-MRI and from an additional 32 BMD patients and 15 healthy controls. Laminin and Sirius-red stainings were performed to evaluate muscle fibre morphology and fibrosis. Twelve ambulant patients from the MRI cohort underwent the North Star ambulatory assessment, and 6-min walk, rise-from-floor and 10-m run/walk functional tests.

RESULTS

RPBM fibre diameter was significantly larger in BMD patients (P = 0.015): mean (SD) = 68.0 (25.3) μm versus 59.4 (19.2) μm in controls. Inter-muscle differences were also observed (P ≤ 0.002). Both inter- and intra-individual RPBM fibre diameter variability were similar between groups. Laminin staining agreed with the RPBM, showing larger median fibre diameters in patients than in controls: 72.5 (7.9) versus 63.2 (6.9) μm, P = 0.006. However, despite showing similar inter-individual variation, patients showed more intra-individual fibre diameter variability than controls-mean variance (SD) = 34.2 (7.9) versus 21.4 (6.9) μm, P < 0.001-and larger fibrosis areas: median (interquartile range) = 21.7 (5.6)% versus 14.9 (3.4)%, P < 0.001. Despite good overall agreement of RPBM and laminin fibre diameters, they were not associated in patients who underwent DT-MRI and muscle biopsy, perhaps due to lack of colocalization of DT-MRI with biopsy samples.

CONCLUSIONS

DT-MRI RPBM metrics agree with histology and can quantify changes in muscle fibre size that are associated with regeneration without the need for biopsies. They therefore show promise as imaging biomarkers for muscular dystrophies.

Givinostat for Becker muscular dystrophy: A randomized, placebo-controlled, double-blind study

Objective

No treatments are approved for Becker muscular dystrophy (BMD). This study investigated the efficacy and safety of givinostat, a histone deacetylase pan-inhibitor, in adults with BMD.

Methods

Males aged 18-65 years with a diagnosis of BMD confirmed by genetic testing were randomized 2:1 to 12 months treatment with givinostat or placebo. The primary objective was to demonstrate statistical superiority of givinostat over placebo for mean change from baseline in total fibrosis after 12 months. Secondary efficacy endpoints included other histological parameters, magnetic resonance imaging and spectroscopy (MRI and MRS) measures, and functional evaluations.

Results

Of 51 patients enrolled, 44 completed treatment. At baseline, there was greater disease involvement in the placebo group than givinostat, based on total fibrosis (mean 30.8 vs. 22.8%) and functional endpoints. Mean total fibrosis did not change from baseline in either group, and the two groups did not differ at Month 12 (least squares mean [LSM] difference 1.04%; p = 0.8282). Secondary histology parameters, MRS, and functional evaluations were consistent with the primary. MRI fat fraction in whole thigh and quadriceps did not change from baseline in the givinostat group, but values increased with placebo, with LSM givinostat-placebo differences at Month 12 of -1.35% (p = 0.0149) and -1.96% (p = 0.0022), respectively. Adverse events, most mild or moderate, were reported by 88.2% and 52.9% patients receiving givinostat and placebo.

Conclusion

The study failed to achieve the primary endpoint. However, there was a potential signal from the MRI assessments suggesting givinostat could prevent (or slow down) BMD disease progression.

MicroRNAs as serum biomarkers in Becker muscular dystrophy

Becker muscular dystrophy (BMD) is an X‐linked neuromuscular disorder due to mutation in the DMD gene, encoding dystrophin. Despite a wide clinical variability, BMD is characterized by progressive muscle degeneration and proximal muscle weakness. Interestingly, a dysregulated expression of muscle‐specific microRNAs (miRNAs), called myomirs, has been found in patients affected with muscular dystrophies, although few studies have been conducted in BMD. We analysed the serum expression levels of a subset of myomirs in a cohort of 29 ambulant individuals affected by BMD and further classified according to the degree of alterations at muscle biopsy and in 11 age‐matched healthy controls. We found a significant upregulation of serum miR‐1, miR‐133a, miR‐133b and miR‐206 in our cohort of BMD patients, supporting the role of these miRNAs in the pathophysiology of the disease, and we identified serum cut‐off levels discriminating patients from healthy controls, confiming the potential of circulating miRNAs as promising noninvasive biomarkers. Moreover, serum levels of miR‐133b were found to be associated with fibrosis at muscle biopsy and with patients' motor performances, suggesting that miR‐133b might be a useful prognostic marker for BMD patients. Taken together, our data showed that these serum myomirs may represent an effective tool that may support stratification of BMD patients, providing the opportunity of both monitoring disease progression and assessing the treatment efficacy in the context of clinical trials.

Muscle histological changes in a large cohort of patients affected with Becker muscular dystrophy

Becker muscular dystrophy (BMD) is a severe X-linked muscle disease. Age of onset, clinical variability, speed of progression and affected tissues display wide variability, making a clinical trial design for drug development very complex. The histopathological changes in skeletal muscle tissue are central to the pathogenesis, but they have not been thoroughly elucidated yet. Here we analysed muscle biopsies from a large cohort of BMD patients, focusing our attention on the histopathological muscle parameters, as fibrosis, fatty replacement, fibre cross sectional area, necrosis, regenerating fibres, splitting fibres, internalized nuclei and dystrophy evaluation. We correlated histological parameters with both demographic features and clinical functional evaluations. The most interesting results of our study are the accurate quantification of fibroadipose tissue replacement and the identification of some histopathological aspects that well correlate with clinical performances. Through correlation analysis, we divided our patients into three clusters with well-defined histological and clinical features. In conclusion, this is the first study that analyses in detail the histological characteristics of muscle biopsies in a large cohort of BMD patients, correlating them to a functional impairment. The collection of these data help to better understand the histopathological progression of the disease and can be useful to validate any pharmacological trial in which the modification of muscle biopsy is utilized as outcome measure.