Respiratory failure and sleep-disordered breathing in late-onset Pompe disease: a narrative review

Diaphragm weakness in late-onset Pompe disease: A complex interplay between lower motor neuron and muscle fibre degeneration

BACKGROUND

Late-onset Pompe disease (LOPD) patients may still need ventilation support at some point of their disease course, despite regular recombinant human alglucosidase alfa treatment. This suggest that other pathophysiological mechanisms than muscle fibre lesion can contribute to the respiratory failure process. We investigate through neurophysiology whether spinal phrenic motor neuron dysfunction could contribute to diaphragm weakness in LOPD patients.

MATERIAL AND METHODS

A group of symptomatic LOPD patients were prospectively studied in our centre from January 2022 to April 2023. We collected both demographic and clinical data, as well as neurophysiological parameters. Phrenic nerve conduction studies and needle EMG sampling of the diaphragm were perfomed.

RESULTS

Eight treated LOPD patients (3 males, 37.5%) were investigated. Three patients (37.5%) with no respiratory involvement had normal phrenic nerve motor responses [median phrenic compound muscle action potential (CMAP) amplitude of 0.49 mV; 1st-3rd interquartile range (IQR), 0.48-0.65]. Those with respiratory failure (under nocturnal non-invasive ventilation) had abnormal phrenic nerve motor responses (median phrenic CMAP amplitude of 0 mV; 1st-3rd IQR, 0-0.15), and were then investigated with EMG. Diaphragm needle EMG revealed both myopathic and neurogenic changes in 3 (60%) and myopathic potentials in 1 patient. In the last one, no motor unit potentials could be recruited.

CONCLUSIONS

Our study provide new insights regarding respiratory mechanisms in LOPD, suggesting a contribution of spinal phrenic motor neuron dysfunction for diaphragm weakness. If confirmed in further studies, our results recommend the need of new drugs crossing the blood-brain barrier.

Glycogen storage diseases

Glycogen storage diseases (GSDs) are a group of rare, monogenic disorders that share a defect in the synthesis or breakdown of glycogen. This Primer describes the multi-organ clinical features of hepatic GSDs and muscle GSDs, in addition to their epidemiology, biochemistry and mechanisms of disease, diagnosis, management, quality of life and future research directions. Some GSDs have available guidelines for diagnosis and management. Diagnostic considerations include phenotypic characterization, biomarkers, imaging, genetic testing, enzyme activity analysis and histology. Management includes surveillance for development of characteristic disease sequelae, avoidance of fasting in several hepatic GSDs, medically prescribed diets, appropriate exercise regimens and emergency letters. Specific therapeutic interventions are available for some diseases, such as enzyme replacement therapy to correct enzyme deficiency in Pompe disease and SGLT2 inhibitors for neutropenia and neutrophil dysfunction in GSD Ib. Progress in diagnosis, management and definitive therapies affects the natural course and hence morbidity and mortality. The natural history of GSDs is still being described. The quality of life of patients with these conditions varies, and standard sets of patient-centred outcomes have not yet been developed. The landscape of novel therapeutics and GSD clinical trials is vast, and emerging research is discussed herein.

Monitoring and Management of Respiratory Function in Pompe Disease: Current Perspectives

Pompe disease (PD) is a neuromuscular disorder caused by a deficiency of acid alpha-glucosidase (GAA) - a lysosomal enzyme responsible for hydrolyzing glycogen. GAA deficiency leads to accumulation of glycogen in lysosomes, causing cellular disruption. The severity of PD is directly related to the extent of GAA deficiency - if no or minimal GAA is produced, symptoms are severe and manifest in infancy, known as infantile onset PD (IOPD). If left untreated, infants with IOPD experience muscle hypotonia and cardio-respiratory failure leading to significant morbidity and mortality in the first year of life. In contrast, late-onset PD (LOPD) patients have more GAA activity and present later in life, but also have significant respiratory function decline. Despite FDA-approved enzyme replacement therapy, respiratory insufficiency remains a major cause of morbidity and mortality, emphasizing the importance of early detection and management of respiratory complications. These complications include impaired cough and airway clearance, respiratory muscle weakness, sleep-related breathing issues, and pulmonary infections. This review aims to provide an overview of the respiratory pathology, monitoring, and management of PD patients. In addition, we discuss the impact of novel approaches and therapies on respiratory function in PD.

Expert opinion on the diagnostic odyssey and management of late-onset Pompe disease: a neurologist's perspective

This consensus statement by a panel of neurology experts aimed to provide a practical and implementable guidance document to assist clinicians with the best clinical practice in terms of diagnosis, treatment, and monitoring of late-onset Pompe disease (LOPD). The participating experts consider the clinical suspicion of LOPD by the physician to be of utmost importance in the prevention of diagnostic and therapeutic delay in LOPD patients. A diagnostic algorithm is proposed to facilitate the diagnosis of LOPD in patients presenting with unexplained proximal/axial weakness (with or without respiratory symptoms) or restrictive respiratory insufficiency with hyperCKemia and/or exercise intolerance as the red flag symptoms/signs that raise the index of suspicion for LOPD diagnosis. The diagnosis is based on the subsequent use of dried blood spot (DBS) assay, and the DBS assay can be confirmed by acid alpha-glucosidase (GAA) tissue analysis in leukocytes, fibroblasts, or muscle fibers and/or genetic mutation analysis. Accordingly, experts consider increased awareness among physicians about potential presenting characteristics with a high index of suspicion for LOPD to be crucial to suspect and consider LOPD in the differential diagnosis, while strongly suggesting the use of a diagnostic algorithm combined with DBS assay and confirmatory tests in the timely diagnosis of LOPD and implementation of best practice patterns.

Home-based enzyme replacement therapy in children and adults with Pompe disease; a prospective study

BACKGROUND

Pompe disease is a lysosomal storage disease treated with life-long enzyme replacement therapy (ERT). Home-based ERT has been provided in the Netherlands since 2008 because it diminishes the burden of treatment, increases patient flexibility and autonomy, and is thus a more patient-centred approach to ERT.

METHODS

All Dutch Pompe patients receiving alglucosidase alfa infusions at home were approached to participate in a questionnaire to validate the safety of home-based ERT. Prospective data on symptoms occurring during or within 48 h after infusion and retrospective data on infusion associated reactions (IARs) in the last three months were collected four times during one year.

RESULTS

In total, 116 out of 120 eligible patients (17 classic infantile, 2 atypical infantile, 15 childhood onset and 82 adult) filled out 423 questionnaires (response rate: 88.1%). Symptoms during or after infusion were reported 27 times in 17 patients. Fatigue was the most commonly reported health complaint (in 9.5% of patients). Four health complaints were judged to be IARs and reported to the Erasmus MC University Medical Center. None of the IARs reported in this study warranted emergency clinical care.

CONCLUSIONS

Our data demonstrate that home-based ERT in Pompe disease can be safely implemented as few, mostly mild, symptoms were reported during or after infusion. Insights from this study can be used as a base for implementing home-based ERT in other countries and to further optimize patient care, as unreported mild symptoms do not pose a health risk but may still be relevant to the patient.

Airway abnormalities and pulmonary complications in long-term treated late-onset Pompe disease: Diagnostic and interventional by flexible bronchoscopy

This study evaluates the whole airway abnormalities of long-term treated late-onset Pompe disease (LOPD) patients, with interventions using the flexible bronchoscope (FB). As a retrospective study, we follow up with our five LOPD patients treated with Myozyme from 2012 to 2021 regularly, but with a focus on the whole airway abnormalities of these patients visualized through FB. The long-term clinical outcomes and relevant airway symptoms were assessed. Pulmonary function test and polysomnography were performed to evaluate the degree of respiratory compromise. All patients in the study had varying degrees of airway collapsibility, pulmonary complications, sleep apnea syndrome, and facial anomalies. Pulmonary function could preserve after Myozyme treatment, but potential deterioration thereafter. This is the first study that focuses on airway abnormalities and pulmonary complications in long-term treated LOPD patients using FB. Despite years of Myozyme treatment, we still observed airway abnormalities in these patients. In our series, the pulmonary complications seem more obvious than those observed in patients with infantile-onset Pompe disease, which might be related to the late diagnosis and treatment. We might recommend that FB could provide dynamic evaluation and interventions of airway abnormalities simultaneously. Early diagnosis of respiratory dysfunction is a critical prognostic factor of the long-term outcome of treated LOPD patients.

Motor and respiratory decline in patients with Late-onset Pompe disease after cessation of enzyme replacement therapy during COVID-19 pandemic

BACKGROUND

Data on interruption of enzyme replacement therapy are scarce in late-onset Pompe disease. Due to the COVID-19 crisis, 8 neuromuscular reference centers in France were obligated to stop the treatment for 31 patients.

METHOD

We collected the motor and respiratory data from our French registry, before COVID-19 and at treatment restart.

RESULTS

In 2.2 months (mean), patients showed a significant deterioration of 37 meters (mean) in the 6-minute walk test and a loss of 210 mL (mean) of forced vital capacity, without ad integrum restoration after 3 months of ERT restart.

CONCLUSION

This national study based on data from the French Pompe registry shows that the interruption of enzyme replacement therapy, even as short as only few months, worsens Pompe patients' motor and respiratory function.