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Remote respiratory resistance exercise training improves respiratory function in individuals with VCP multisystem proteinopathy

Valosin-containing protein (VCP) disease is an autosomal dominant multisystem proteinopathy associated with hereditary inclusion body myopathy, Paget disease of bone, and frontotemporal dementia. Myopathy frequently results in respiratory muscle weakness, leading to early mortality due to respiratory failure. We investigated the effects of a remotely administered inspiratory muscle training program in individuals with VCP disease. Nine adults with VCP mutation-positive familial myopathy without evidence of dementia were recruited for a 40-week remotely administered study. Baseline performance was established during the first 8 weeks, followed by 32 weeks of inspiratory muscle training. The primary outcome was maximum inspiratory pressure (MIP). The secondary and exploratory endpoints included spirometry, grip strength, Inclusion Body Myopathy Functional Rating Scale (IBMFRS), Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS), timed up and go, and six-minute walk test (6MWT). During the treatment phase, MIP increased significantly by a weekly mean of 0.392cm. H2O (p=0.023). In contrast, grip strength and ALSFRS significantly decreased by 0.088 lbs. (p=0.031) and 0.043 points (p=0.004) per week, respectively, as expected from the natural progression of this disease. A remotely administered inspiratory muscle training program is therefore feasible, safe, and well-tolerated in individuals with VCP disease and results in improved inspiratory muscle strength.

Quality of Life with Late-Onset Pompe Disease: Qualitative Interviews and General Public Utility Estimation in the United Kingdom

Background: Late-onset Pompe disease (LOPD) is a rare, progressive neuromuscular condition typically characterized by weakness of skeletal muscles, including those involved in respiration and diaphragmatic dysfunction. Individuals with LOPD typically eventually require mobility and/or ventilatory support. Objectives: This study aimed to develop health state vignettes and estimate health state utility values for LOPD in the United Kingdom. Methods: Vignettes were developed for 7 health states of LOPD with states defined in terms of mobility and/or ventilatory support. Vignettes were drafted based on patient-reported outcome data from the Phase 3 PROPEL trial (NCT03729362) and supplemented by a literature review. Qualitative interviews with individuals living with LOPD and clinical experts were conducted to explore the health-related quality-of-life (HRQoL) impact of LOPD and to review the draft vignettes. Vignettes were finalized following a second round of interviews with individuals living with LOPD and used in health state valuation exercises with people of the UK population. Participants rated the health states using the EQ-5D-5L, visual analogue scale, and time trade-off interviews. Results: Twelve individuals living with LOPD and 2 clinical experts were interviewed. Following the interviews, 4 new statements were added regarding dependence on others, bladder control problems, balance issues/fear of falling, and frustration. One hundred interviews with a representative UK population sample were completed. Mean time trade-off utilities ranged from 0.754 (SD = 0.31) (no support) to 0.132 (SD = 0.50) (invasive ventilatory and mobility support-dependent). Similarly, EQ-5D-5L utilities ranged from 0.608 (SD = 0.12) to -0.078 (SD = 0.22). Discussion: The utilities obtained in the study are consistent with utilities reported in the literature (0.670-0.853 for nonsupport state). The vignette content was based on robust quantitative and qualitative evidence and captured the main HRQoL impacts of LOPD. The general public rated the health states consistently lower with increasing disease progression. There was greater uncertainty around utility estimates for the severe states, suggesting that participants found it harder to rate them. Conclusion: This study provides utility estimates for LOPD that can be used in economic modeling of treatments for LOPD. Our findings highlight the high disease burden of LOPD and reinforce the societal value of slowing disease progression.

Qualitative interviews to improve patient-reported outcome measures in late-onset Pompe disease: the patient perspective

Background

Late-onset Pompe Disease (LOPD) is a rare, heterogeneous disease manifested by a range of symptoms varying in severity. Research establishing the frequency of these symptoms and their impact on patients’ daily lives is limited. The objective of this study was to develop a conceptual model that captures the most relevant symptoms and functional limitations experienced by patients with LOPD, to inform the development of new patient-reported outcome (PRO) tools.

Methods

A preliminary conceptual model was constructed following a literature review and revised through interviews with expert clinicians to identify important and relevant concepts regarding symptoms and impacts of LOPD. This preliminary model informed the development of a qualitative patient interview guide, which was used to gather the patient perspective on symptoms and impacts relating to LOPD or its treatment (including symptom/impact frequency and levels of disturbance). Patient interviews aided further refinement of the conceptual model. The findings from the patient interviews were triangulated with the literature review and clinician interviews to identify the most relevant and significant effects of LOPD from the patient perspective.

Results

Muscle weakness, fatigue, pain, and breathing difficulties (especially while lying down) were the most common and highly disturbing symptoms experienced by patients. Limitations associated with mobility (e.g., difficulty rising from a sitting position, getting up after bending) and activities of daily living, (e.g., reduced ability to participate in social/family activities or work/study) were the most frequently reported impacts with the highest levels of disturbance on the patient’s daily life. These identified symptoms and impacts were included in the new conceptual model of disease.

Conclusions

This qualitative patient interview study, also informed by a literature review and clinician interviews, identified the most frequent and relevant symptoms and the functional impact of LOPD on patients. The study interviews also captured the patient-preferred language to describe symptoms and impacts of LOPD. The results from this study can be used to develop future PRO instruments that are tailored to the specific symptoms and impacts experienced by patients with LOPD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02067-x.

Respiratory muscle training in late-onset Pompe disease: Results of a sham-controlled clinical trial

To address progressive respiratory muscle weakness in late-onset Pompe disease (LOPD), we developed a 12-week respiratory muscle training (RMT) program. In this exploratory, double-blind, randomized control trial, 22 adults with LOPD were randomized to RMT or sham-RMT. The primary outcome was maximum inspiratory pressure (MIP). Secondary and exploratory outcomes included maximum expiratory pressure (MEP), peak cough flow, diaphragm ultrasound, polysomnography, patient-reported outcomes, and measures of gross motor function. MIP increased 7.6 cmH₂O (15.9) in the treatment group and 2.7 cmH₂O (7.6) in the control group (P = 0.4670). MEP increased 14.0 cmH₂O (25.9) in the treatment group and 0.0 cmH₂O (12.0) in the control group (P = 0.1854). The only statistically significant differences in secondary/exploratory outcomes were improvements in time to climb 4 steps (P = 0.0346) and daytime sleepiness (P = 0.0160). The magnitude of changes in MIP and MEP in the treatment group were consistent with our pilot findings but did not achieve statistical significance in comparison to controls. Explanations for this include inadequate power and baseline differences in subject characteristics between groups. Additionally, control group subjects appeared to exhibit an active response to sham-RMT and therefore sham-RMT may not be an optimal control condition for RMT in LOPD.

The Respiratory Phenotype of Pompe Disease Mouse Models

Pompe disease is a glycogen storage disease caused by a deficiency in acid α-glucosidase (GAA), a hydrolase necessary for the degradation of lysosomal glycogen. This deficiency in GAA results in muscle and neuronal glycogen accumulation, which causes respiratory insufficiency. Pompe disease mouse models provide a means of assessing respiratory pathology and are important for pre-clinical studies of novel therapies that aim to treat respiratory dysfunction and improve quality of life. This review aims to compile and summarize existing manuscripts that characterize the respiratory phenotype of Pompe mouse models. Manuscripts included in this review were selected utilizing specific search terms and exclusion criteria. Analysis of these findings demonstrate that Pompe disease mouse models have respiratory physiological defects as well as pathologies in the diaphragm, tongue, higher-order respiratory control centers, phrenic and hypoglossal motor nuclei, phrenic and hypoglossal nerves, neuromuscular junctions, and airway smooth muscle. Overall, the culmination of these pathologies contributes to severe respiratory dysfunction, underscoring the importance of characterizing the respiratory phenotype while developing effective therapies for patients.