Comparison of Pulmonary Function Decline in Steroid-Treated and Steroid-Naïve Patients with Duchenne Muscular Dystrophy

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.

The role of lung volume recruitment therapy in neuromuscular disease: a narrative review

Respiratory muscle weakness results in substantial discomfort, disability, and ultimately death in many neuromuscular diseases. Respiratory system impairment manifests as shallow breathing, poor cough and associated difficulty clearing mucus, respiratory tract infections, hypoventilation, sleep-disordered breathing, and chronic ventilatory failure. Ventilatory support (i.e., non-invasive ventilation) is an established and key treatment for the latter. As survival outcomes improve for people living with many neuromuscular diseases, there is a shift towards more proactive and preventative chronic disease multidisciplinary care models that aim to manage symptoms, improve morbidity, and reduce mortality. Clinical care guidelines typically recommend therapies to improve cough effectiveness and mobilise mucus, with the aim of averting acute respiratory compromise or respiratory tract infections. Moreover, preventing recurrent infective episodes may prevent secondary parenchymal pathology and further lung function decline. Regular use of techniques that augment lung volume has similarly been recommended (volume recruitment). It has been speculated that enhancing lung inflation in people with respiratory muscle weakness when well may improve respiratory system "flexibility", mitigate restrictive chest wall disease, and slow lung volume decline. Unfortunately, clinical care guidelines are based largely on clinical rationale and consensus opinion rather than level A evidence. This narrative review outlines the physiological changes that occur in people with neuromuscular disease and how these changes impact on breathing, cough, and respiratory tract infections. The biological rationale for lung volume recruitment is provided, and the clinical trials that examine the immediate, short-term, and longer-term outcomes of lung volume recruitment in paediatric and adult neuromuscular diseases are presented and the results synthesised.

ATS Core Curriculum 2022. Pediatric Pulmonary Medicine: Updates in pediatric neuromuscular disease

The American Thoracic Society Core Curriculum updates clinicians annually in pediatric pulmonary disease. This is a concise review of the Pediatric Pulmonary Medicine Core Curriculum presented at the 2022 American Thoracic Society International Conference. Neuromuscular diseases (NMD) comprise a variety of conditions that commonly affect the respiratory system and cause significant morbidity including dysphagia, chronic respiratory failure, and sleep disordered breathing. Respiratory failure is the most common cause of mortality in this population. Substantial progress has been made in diagnosis, monitoring and treatment for NMD over the last decade. Pulmonary function testing (PFT) is utilized to objectively measure respiratory pump function and PFT milestones are utilized in NMD-specific pulmonary care guidelines. New disease modifying therapies are approved for the treatment of patients with Duchenne muscular dystrophy and spinal muscular atrophy (SMA), including the first ever approved systemic gene therapy, in the case of SMA. Despite extraordinary progress in the medical management of NMD, little is known regarding the respiratory implications and long-term outcomes for patients in the era of advanced therapeutics and precision medicine. The combination of technological and biomedical advancements has increased the complexity of the medical decision-making process for patients and families, thus emphasizing the importance of balancing respect for autonomy with the other foundational principles of medical ethics. This review features an overview of PFT, noninvasive ventilation strategies, novel and developing therapies, as well as the ethical considerations specific to the management of patients with pediatric NMD.

Initial multicenter experience with ventricular assist devices in children and young adults with muscular dystrophy: An ACTION registry analysis

PURPOSE

Cardiac disease results in significant morbidity and mortality in patients with muscular dystrophy (MD). Single centers have reported their ventricular assist device (VAD) experience in specific MDs and in limited numbers. This study sought to describe the outcomes associated with VAD therapy in an unselected population across multiple centers.

METHODS

We examined outcomes of patients with MD and dilated cardiomyopathy implanted with a VAD at Advanced Cardiac Therapies Improving Outcomes Network (ACTION) centers from 9/2012 to 9/2020.

RESULTS

A total of 19 VADs were implanted in 18 patients across 12 sites. The majority of patients had dystrophinopathy (66%) and the median age at implant was 17.2 years (range 11.7-29.5). Eleven patients were non-ambulatory (61%) and 6 (33%) were on respiratory support pre-VAD. Five (28%) patients were implanted as a bridge to transplant, 4 of whom survived to transplant. Of 13 patients implanted as bridge to decision or destination therapy, 77% were alive at 1 year and 69% at 2 years. The overall frequencies of positive outcome (transplanted or alive on device) at 1 year and 2 years were 84% and 78%, respectively. Two patients suffered a stroke, 2 developed sepsis, 1 required tracheostomy, and 1 experienced severe right heart failure requiring right-sided VAD.

CONCLUSIONS

This study demonstrates the potential utility of VAD therapies in patients with muscular dystrophy. Further research is needed to further improve outcomes and better determine which patients may benefit most from VAD therapy in terms of survival and quality of life.

Obesity and loss of ambulation are associated with lower extremity oedema in Duchenne muscular dystrophy

Patients with Duchenne muscular dystrophy have multiple risk factors for lower extremity oedema. This study sought to define the frequency and predictors of oedema. Patients aged 15 years and older were screened by patient questionnaire, and the presence of oedema was confirmed by subsequent physical exam. Twenty-four of 52 patients (46%) had oedema, 12 of whom had swelling extending above the foot and two with sores/skin breakdown. There was no significant difference in age, frequency, or duration of glucocorticoid use, non-invasive respiratory support use, forced vital capacity, cardiac medication use, or ejection fraction between patients with and without oedema (all p > 0.2). Those with oedema had a greater time since the loss of ambulation (8.4 years versus 3.5 years; p = 0.004), higher body mass index (28.3 versus 24.8; p = 0.014), and lower frequency of deflazacort use (67% versus 89%; p = 0.008). Multivariate analysis revealed a longer duration of loss of ambulation (p = 0.02) and higher body mass index (p = 0.009) as predictors of oedema. Lower extremity oedema is common in Duchenne muscular dystrophy but independent of cardiac function. Interventions focused on minimising body mass index increases over time may be a therapeutic target.

Unmet needs and evolving treatment for limb girdle muscular dystrophies

Limb-girdle muscular dystrophies (LGMDs) represent a major group of muscle disorders. Treatment is sorely needed and currently expanding based on safety and efficacy adopting principles of single-dosing gene therapy for monogenic autosomal recessive disorders. Gene therapy has made in-roads for LGMD and this review describes progress that has been achieved for these conditions. This review first provides a background on the definition and classification of LGMDs. The major effort focuses on progress in LGMD gene therapy, from experimental studies to clinical trials. The disorders discussed include the LGMDs where the most work has been done including calpainopathies (LGMD2A/R1), dysferlinopathies (LGMD2B/R2) and sarcoglycanopathies (LGMD2C/R5, LGMD2D/R3, LGMD2E/R4). Early success in clinical trials provides a template to move the field forward and potentially apply emerging technology like CRISPR/Cas9 that may enhance the scope and efficacy of gene therapy applied to patient care.

Early NIV is associated with accelerated lung function decline in Duchenne muscular dystrophy treated with glucocorticosteroids

Background

Use of non-invasive ventilation (NIV) in adolescents with Duchenne muscular dystrophy (DMD) has increased with concomitant extended survival.

Aim

To describe lung function (LF) changes with NIV in adolescents with DMD and to assess differences between Steroid Users and Steroid Naïve subjects.

Method

A retrospective cohort of adolescents with DMD initiating NIV over 10 years was conducted. Serial LF before and after NIV initiation was collated. Use of systemic glucocorticosteroids, adherence to NIV and presence of cardiac disease were assessed.

Results

Twenty-nine men started NIV, median age 14.66 years (IQR 2.35, 10.47–17.96). Nine were Steroid Users and eight were Steroid Naïve. Indications for NIV were apnoea–hypopnoea index >5 and/or nocturnal hypoventilation. LF is better (forced vital capacity (FVC) z-score −3.26 vs −5.41, p < 0.02) and decline slower (FVC z-score −0.58 per annum (pa) vs −0.68 pa, p<0.001) in Steroid Users compared with Steroid Naïve subjects. Following NIV initiation, FVC z-score decline slowed for the whole (−0.72 pa (95% CI −0.79 to 0.64) to −0.46 pa (95% CI −0.54 to 0.38) p < 0.001) and Steroid Naïve groups (−0.74 (95% CI −0.85 to 0.63) to −0.44 pa (95% CI −0.56 to 0.32) p < 0.001) but accelerated in the Steroid User group (−0.56 (95% CI −0.70 to 0.42) to −0.75 pa (95% CI −0.89 to 0.61) p < 0.001). Adherence to NIV and cardiac disease did not impact decline.

Conclusion

Overall, LF decline is reduced on NIV. Steroid Naïve patients have lower LF and faster decline, which slows following NIV initiation. An accelerated LF decline was seen on NIV in Steroid Users which requires further prospective research.

Recent advances of glucocorticoids in the treatment of Duchenne muscular dystrophy (Review)

Duchenne muscular dystrophy (DMD) is the most common degenerative neuromuscular disease. The incidence of DMD in live births is 1/3,600-1/6,000. Although glucocorticoid-dependent medication is the mainstay treatment option for DMD, a standard treatment regimen has yet to be determined. The present review discusses the literature on the timing, methods and courses of glucocorticoid treatment for DMD. The review highlights the importance of the immediate commencement of glucocorticoid treatment following the diagnosis of DMD, with weekend-only administration being advantageous. Adherence to long-term single-glucocorticoid therapy can delay the loss of ambulation ability, and the side effects of the treatment are controllable. However, the standard medication for patients of different ages and stages of disease development, and the use of combination therapy require further investigation.

Long-term human IgG treatment improves heart and muscle function in a mouse model of Duchenne muscular dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease caused by mutations in the dystrophin gene, which leads to structural instability of the dystrophin-glycoprotein-complex with subsequent muscle degeneration. In addition, muscle inflammation has been implicated in disease progression and therapeutically addressed with glucocorticosteroids. These have numerous adverse effects. Treatment with human immunoglobulin G (IgG) improved clinical and para-clinical parameters in the early disease phase in the well-established mdx mouse model. The aim of the present study was to confirm the efficacy of IgG in a long-term pre-clinical study in mdx mice.

METHODS

IgG (2 g/kg body weight) or NaCl solution as control was administered monthly over 18 months by intraperitoneal injection in mdx mice beginning at 3 weeks of age. Several clinical outcome measures including endurance, muscle strength, and echocardiography were assessed. After 18 months, the animals were sacrificed, blood was collected for analysis, and muscle samples were obtained for ex vivo muscle contraction tests, quantitative PCR, and histology.

RESULTS

IgG significantly improved the daily voluntary running performance (1.9 m more total daily running distance, P < 0.0001) and slowed the decrease in grip strength by 0.1 mN, (P = 0.018). IgG reduced fatigability of the diaphragm (improved ratio to maximum force by 0.09 ± 0.04, P = 0.044), but specific tetanic force remained unchanged in the ex vivo muscle contraction test. Cardiac function was significantly better after IgG, especially fractional area shortening (P = 0.012). These results were accompanied by a reduction in cardiac fibrosis and the infiltration of T cells (P = 0.0002) and macrophages (P = 0.0027). In addition, treatment with IgG resulted in a significant reduction of the infiltration of T cells (P ≤ 0.036) in the diaphragm, gastrocnemius, quadriceps, and a similar trend in tibialis anterior and macrophages (P ≤ 0.045) in gastrocnemius, quadriceps, tibialis anterior, and a similar trend in the diaphragm, as well as a decrease in myopathic changes as reflected by a reduced central nuclear index in the diaphragm, tibialis anterior, and quadriceps (P ≤ 0.002 in all).

CONCLUSIONS

The present study underscores the importance of an inflammatory contribution to the disease progression of DMD. The data demonstrate the long-term efficacy of IgG in the mdx mouse. IgG is well tolerated by humans and could preferentially complement gene therapy in DMD. The data call for a clinical trial with IgG in DMD.

Neurodevelopmental, behavioral, and emotional symptoms in Becker muscular dystrophy

INTRODUCTION

Becker muscular dystrophy (BMD) results in decreased dystrophin with implications for mental health.

METHODS

This is a retrospective case series of neurodevelopmental, behavioral, and emotional symptoms and respective pharmacotherapies of 70 patients with BMD.

RESULTS

Fifty-four (77.1%) patients exhibited at least one symptom, and 19 (27.1%) patients exhibited four or more symptoms. The most prevalent symptoms were specific learning disabilities or special education needs (31.4%), inattention/hyperactivity (35.7%), language/speech delays (35.7%), and emotional or behavioral dysregulation (38.6%). Fisher's exact tests indicated that anxiety was more prevalent with mutations upstream of exon 30 (P = .049), but the prevalence of other symptoms did not differ with respect to mutation sites. Similarly, the number of symptoms individual patients with BMD exhibited did not differ with respect to mutation sites. Seventeen (24.3%) patients required pharmacotherapy to manage symptoms.

DISCUSSION

Neurodevelopmental, behavioral, and emotional symptoms are prevalent in patients with BMD regardless of dystrophin gene mutation site.