American Association of Neuromuscular & Electrodiagnostic Medicine. Diagnostic criteria for late-onset (childhood and adult) Pompe disease

Lung Diseases and Rare Disorders: Is It a Lysosomal Storage Disease? Differential Diagnosis, Pathogenetic Mechanisms and Management

Pulmonologists may be involved in managing pulmonary diseases in children with complex clinical pictures without a diagnosis. Moreover, they are routinely involved in the multidisciplinary care of children with rare diseases, at baseline and during follow-up, for lung function monitoring. Lysosomal storage diseases (LSDs) are a group of genetic diseases characterised by a specific lysosomal enzyme deficiency. Despite varying pathogen and organ involvement, they are linked by the pathological accumulation of exceeding substrates, leading to cellular toxicity and subsequent organ damage. Less severe forms of LSDs can manifest during childhood or later in life, sometimes being underdiagnosed. Respiratory impairment may stem from different pathogenetic mechanisms, depending on substrate storage in bones, with skeletal deformity and restrictive pattern, in bronchi, with obstructive pattern, in lung interstitium, with altered alveolar gas exchange, and in muscles, with hypotonia. This narrative review aims to outline different pulmonary clinical findings and a diagnostic approach based on key elements for differential diagnosis in some treatable LSDs like Gaucher disease, Acid Sphingomyelinase deficiency, Pompe disease and Mucopolysaccharidosis. Alongside their respiratory clinical aspects, which might overlap, we will describe radiological findings, lung functional patterns and associated symptoms to guide pediatric pulmonologists in differential diagnosis. The second part of the paper will address follow-up and management specifics. Recent evidence suggests that new therapeutic strategies play a substantial role in preventing lung involvement in early-treated patients and enhancing lung function and radiological signs in others. Timely diagnosis, driven by clinical suspicion and diagnostic workup, can help in treating LSDs effectively.

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.

Long-term safety and efficacy of cipaglucosidase alfa plus miglustat in individuals living with Pompe disease: an open-label phase I/II study (ATB200-02)

Cipaglucosidase alfa plus miglustat (cipa + mig) is a novel, two-component therapy for Pompe disease. We report data from the Phase I/II ATB200-02 study for up to 48 months of treatment. Four adult cohorts, including one non-ambulatory ERT-experienced (n = 6) and three ambulatory cohorts, (two enzyme replacement therapy [ERT]-experienced cohorts [2-6 years (n = 11) and ≥ 7 years (n = 6)]), one ERT-naïve cohort (n = 6), received 20 mg/kg intravenous-infused cipa plus 260 mg oral mig biweekly. Change from baseline (CFBL) for multiple efficacy endpoints at 12, 24, 36, and 48 months, pharmacodynamics, pharmacokinetics, safety, and immunogenicity data were assessed. Six-minute walking distance (% predicted) improved at 12, 24, 36, and 48 months: pooled ambulatory ERT-experienced cohorts, mean(± standard deviation [SD]) CFBL: 6.1(± 7.84), n = 16; 5.4(± 10.56), n = 13; 3.4(± 14.66), n = 12; 5.9(± 17.36), n = 9, respectively; ERT-naïve cohort: 10.7(± 3.93), n = 6; 11.0(± 5.06), n = 6; 9.0(± 7.98), n = 5; 11.7(± 7.69), n = 4, respectively. Percent predicted forced vital capacity was generally stable in ERT-experienced cohorts, mean(± SD) CFBL - 1.2(± 5.95), n = 16; 1.0(± 7.96), n = 13; - 0.3(± 6.68), n = 10; 1.0(± 6.42), n = 6, respectively, and improved in the ERT-naïve cohort: 3.2(± 8.42), n = 6; 4.7(± 5.09), n = 6; 6.2(± 3.35), n = 5; 8.3(± 4.50), n = 4, respectively. Over 48 months, CK and Hex4 biomarkers improved in ambulatory cohorts. Overall, cipa + mig was well tolerated with a safety profile like alglucosidase alfa. ATB200-02 results show the potential benefits of cipa + mig as a long-term treatment option for Pompe disease. Trial registration number: NCT02675465 January 26, 2016.

Validation of the Patient-Reported Outcomes Measurement Information System (PROMIS®) physical function questionnaire in late-onset Pompe disease using PROPEL phase 3 data

BACKGROUND

The construct validity and interpretation of the Patient-Reported Outcome Measurement Information System (PROMIS®) Physical Function short form 20a (PF20a) questionnaire were evaluated for patients with late-onset Pompe disease (LOPD), a rare, autosomal recessive, progressive neuromuscular disorder treatable by enzyme replacement therapy (ERT).

METHODS

In the phase 3 PROPEL study, adults with LOPD underwent testing of physical functioning and had PRO measurements at baseline and at weeks 12, 26, 38, and 52 while receiving experimental or standard-of-care ERT. All patients were pooled for analyses, without comparisons between treatment groups. Associations and correlations between PROMIS PF20a scores and the 6-minute walk distance (6MWD), % predicted forced vital capacity (FVC), manual muscle test (MMT) of the lower extremities, Gait, Stairs, Gowers' maneuver, Chair (GSGC) score, and Rasch-built Pompe-specific Activity (R-PAct) scale were evaluated by calculating regression coefficients in linear regression models and Pearson correlation coefficients (R); patients' age, sex, race, ERT prior to study, body mass index, and study treatment were included as covariables. The minimal clinically important difference (MCID) of PROMIS PF20a was determined using distribution- and anchor-based methods.

RESULTS

123 patients received at least 1 dose of ERT. In multivariable analyses, PROMIS PF20a scores had strong correlations with R-PAct scores (R = 0.83 at baseline and R = 0.67 when evaluating changes between baseline and 52 weeks) and moderate correlations with the 6MWD (R = 0.57 at baseline and R = 0.48 when evaluating changes between baseline and 52 weeks). Moderate correlations were also observed between PROMIS PF20a and MMT (R = 0.54), GSGC (R=-0.51), and FVC (R = 0.48) at baseline. In multivariable linear regression models, associations were significant between PROMIS PF20a and 6MWD (P = 0.0006), MMT (P = 0.0034), GSGC (P = 0.0278), and R-PAct (P < 0.0001) at baseline, between PROMIS PF20a and 6MWD (P < 0.0001), FVC (P = 0.0490), and R-PAct (P < 0.0001) when combining all measurements, and between PF20a and 6MWD (P = 0.0016) and R-PAct (P = 0.0001) when evaluating changes in scores between baseline and 52 weeks. The anchor-based and distribution-based MCID for a clinically important improvement for PROMIS PF20a were 2.4 and 4.2, respectively.

CONCLUSIONS

PROMIS PF20a has validity as an instrument both to measure and to longitudinally follow physical function in patients with LOPD.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03729362. Registered 2 November 2018, https://www.

CLINICALTRIALS

gov/search?term=NCT03729362 .

Two fluorimetric determinations of acid α-glucosidase activity in dried blood spot: Pompe disease in Iranian population

INTRODUCTION

Pompe disease is a lysosomal storage disorder. This study aimed to validate and compare 2 fluorimetric methods for measuring α-glucosidase acid activity in dried blood spot sample (DBS), with potential applications in neonatal screening, and disease follow-up of Pompe patients among the Iranian population for the first time.

MATERIALS AND METHODS

The evaluation involved 3 enzyme levels and 7 parameters. The analysis included 141 Healthy individuals, 8 Pompe patients, and 10 obligate heterozygotes using reference and modified methods.

RESULTS

Both methods exhibited highly linear calibration curves. The limit of detection (LOD) and limit of quantification (LOQ) were obtained in the micromolar concentration range in 2 methods. Inter-day and intra-day precision, expressed as relative standard deviations (RSD%) were calculated. The normal ranges were determined in healthy individuals. Receiver operating characteristic (ROC) curves were analyzed, and 2 parameters, total neutral α-glucosidase (NAG)/acid α-glucosidase (GAA) and pH ratio, were identified as cut-off values with excellent accuracy, sensitivity, and specificity for evaluating Pompe disease in both methods.

CONCLUSIONS

Establishing and implementing these 2 methods for the Iranian population effectively differentiated between healthy and patient individuals. Method II, with its shorter incubation time, demonstrated practicality in the clinical setting.

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.

Investigating Late-Onset Pompe Prevalence in Neuromuscular Medicine Academic Practices: The IPaNeMA Study

BACKGROUND AND OBJECTIVES

We investigated the prevalence of late-onset Pompe disease (LOPD) in patients presenting to 13 academic, tertiary neuromuscular practices in the United States and Canada.

METHODS

All successive patients presenting with proximal muscle weakness or isolated hyperCKemia and/or neck muscle weakness to these 13 centers were invited to participate in the study. Whole blood was tested for acid alpha-glucosidase (GAA) assay through the fluorometric method, and all cases with enzyme levels of ≤10 pmoL/punch/h were reflexed to molecular testing for mutations in the GAA gene. Clinical and demographic information was abstracted from their clinical visit and, along with study data, entered into a purpose-built REDCap database, and analyzed at the University of California, Irvine.

RESULTS

GAA enzyme assay results were available on 906 of the 921 participants who consented for the study. LOPD was confirmed in 9 participants (1% prevalence). Another 9 (1%) were determined to have pseudodeficiency of GAA, whereas 19 (1.9%) were found to be heterozygous for a pathogenic GAA mutation (carriers). Of the definite LOPD participants, 8 (89%) were Caucasian and were heterozygous for the common leaky (IVS1) splice site mutation in the GAA gene (c -32-13T>G), with a second mutation that was previously confirmed to be pathogenic.

DISCUSSION

The prevalence of LOPD in undiagnosed patients meeting the criteria of proximal muscle weakness, high creatine kinase, and/or neck weakness in academic, tertiary neuromuscular practices in the United States and Canada is estimated to be 1%, with an equal prevalence rate of pseudodeficiency alleles.

TRIAL REGISTRATION INFORMATION

Clinical trial registration number: NCT02838368.

Recommendations for Infantile-Onset and Late-Onset Pompe Disease: An Iranian Consensus

Background: Pompe disease, also denoted as acid maltase or acid α-glucosidase deficiency or glycogen storage disease type II, is a rare, autosomal recessive lysosomal storage disorder. Several reports have previously described Pompe disease in Iran and considering increased awareness of related subspecialties and physicians, the disease's diagnosis is growing.

Objective: This guideline's main objective was to develop a national guideline for Pompe disease based on national and international evidence adapting with national necessities.

Methods: A group of expert clinicians with particular interests and experience in diagnosing and managing Pompe disease participated in developing this guideline. This group included adult neurologists, pediatric neurologists, pulmonologists, endocrinologists, cardiologists, pathologists, and physiatrists. After developing search terms, four authors performed an extensive literature review, including Embase, PubMed, and Google Scholar, from 1932 to current publications before the main meeting. Before the main consensus session, each panel member prepared an initial draft according to pertinent data in diagnosis and management and was presented in the panel discussion. Primary algorithms for the diagnosis and management of patients were prepared in the panel discussion. The prepared consensus was finalized after agreement and concordance between the panel members.

Conclusion: Herein, we attempted to develop a consensus based on Iran's local requirements. The authors hope that disseminating these consensuses will help healthcare professionals in Iran achieve the diagnosis, suitable treatment, and better follow-up of patients with infantile-onset Pompe disease and late-onset Pompe disease.

Late onset Pompe Disease in India - Beyond the Caucasian phenotype

We evaluated the clinical histories, motor and pulmonary functions, cardiac phenotypes and GAA genotypes of an Indian cohort of twenty patients with late onset Pompe disease (LOPD) in this multi-centre study. A mean age at onset of symptoms and diagnosis of 9.9 ± 9.7 years and 15.8 ± 12.1 years respectively was identified. All patients had lower extremity limb-girdle muscle weakness. Seven required ventilatory support and seven used mobility assists. Of the four who used both assists, two received ventilatory support prior to wheelchair use. Cardiac involvement was seen in eight patients with various combinations of left ventricular hypertrophy, tricuspid regurgitation, cardiomyopathy, dilated ventricles with biventricular dysfunction and aortic regurgitation. Amongst 20 biochemically diagnosed patients (low residual GAA enzyme activity) GAA genotypes of 19 patients identified homozygous variants in eight and compound heterozygous in 11: 27 missense, 3 nonsense, 2 initiator codon, 3 splice site and one deletion. Nine variants in 7 patients were novel. The leaky Caucasian, splice site LOPD variant, c.-32-13T>G mutation was absent. This first study from India provides an insight into a more severe LOPD phenotype with earlier disease onset at 9.9 years compared to 33.3 years in Caucasian patients, and cardiac involvement more than previously reported. The need for improvement in awareness and diagnosis of LOPD in India is highlighted.

New Therapeutics Options for Pediatric Neuromuscular Disorders

Neuromuscular disorders (NMDs) of Childhood onset are a genetically heterogeneous group of diseases affecting the anterior horn cell, the peripheral nerve, the neuromuscular junction, or the muscle. For many decades, treatment of NMDs has been exclusively symptomatic. But this has changed fundamentally in recent years due to the development of new drugs attempting either to ameliorate secondary pathophysiologic consequences or to modify the underlying genetic defect itself. While the effects on the course of disease are still modest in some NMDs (e.g., Duchenne muscular dystrophy), new therapies have substantially prolonged life expectancy and improved motor function in others (e.g., spinal muscular atrophy and infantile onset Pompe disease). This review summarizes recently approved medicaments and provides an outlook for new therapies that are on the horizon in this field.

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

Late-onset Pompe disease (LOPD) is a rare autosomal recessive glycogen storage disease that results in accumulation of glycogen in muscle cells causing muscular weakness. It causes a progressive proximal myopathy, accompanied by respiratory muscle weakness, which can lead to ventilatory failure. In untreated LOPD, the most common cause of death is respiratory failure. Patients suffering from respiratory compromise may present with symptoms of sleep-disordered breathing (SDB) before overt signs of respiratory failure. Diaphragm weakness leads to nocturnal hypoventilation, which can result in sleep disruption. Both subjective and objective sleep quality can be impaired with associated excessive daytime sleepiness (EDS). Health-related quality of life worsens as sleep disturbance increases. The mainstay of treatment for SDB and respiratory failure in LOPD is non-invasive ventilation (NIV), which aims to ensure adequate ventilation, particularly during sleep, and prevent acute hypercapnic failure. These patients are at risk of acute deterioration due to lower respiratory tract infections; effective secretion clearance and vaccination against common pathogens is an important facet of care. Whilst disease-modifying enzyme replacement therapy (ERT) delays progression of locomotor dysfunction and prolongs life, its effect on respiratory function and SDB remains unclear. There are no data demonstrating the impact of ERT on sleep quality or SDB.

Cost-effectiveness analysis of enzyme replacement therapy (ERT) for treatment of infantile-onset Pompe disease (IOPD) in the Iranian pharmaceutical market

Infantile-onset Pompe disease (IOPD) or acid maltase deficiency is a rare metabolic disorder. It is caused by a deficiency in functioning of the enzyme acid alpha-glucosidase and leads to the accumulation of glycogen in the liver, heart, muscle, and other tissues. Myozyme is an effective drug, but it imposes a heavy financial burden on societies and healthcare systems. Therefore, this study was conducted to analyze the cost-effectiveness of Myozyme compared to conventional therapy for the treatment of IOPD. PubMed, Scopus, Web of Science, and Cochrane library databases were searched on December 2018 to identify the effectiveness of Myozyme versus conventional therapy. Then, a cost-effectiveness and a cost utility study were conducted in patients suffering from IOPD. In this cost effectiveness and cost utility analysis, Markov and decision tree models were used for modeling. Model parameters were obtained from international data, and the perspective of the payer was considered. Every cycle was one year; the model was run for 22 cycles. TreeAge pro 2011 was used for analysis. Finally, one-way and probabilistic sensitivity analyses were performed. Two papers were included and 39 patients were evaluated as the treatment group in both studies. Results revealed the effectiveness of Myozyme. Results also revealed a wide range of adverse reactions. Enzyme replacement therapy (ERT) resulted in 4.21038 quality-adjusted life years (QALY) per $381,852. The incremental cost per QALY was $96,809 and the incremental cost per life years gained (LYG) was 74,429 over a 22-year time horizon. Sensitivity analysis indicated the robustness of the results. Myozyme is effective for IOPD and could increase the life expectancy of patients significantly. However, since the calculated incremental cost per QALY was 17 times higher than the GDP per capita of Iran, Myozyme is not cost effective in Iran.

Is it Pompe Disease? Australian diagnostic considerations

Pompe Disease is a spectrum disorder with an evolving phenotype in which diagnostic delay is common. Contributing factors include the rarity of the disorder, its wide clinical spectrum, signs and symptoms that overlap with those of other neuromuscular disorders, variable diagnostic approaches, lack of awareness of the clinical manifestations and difficulties in completing the diagnostic inventory. International updates and recommendations have been published providing diagnostic guidelines and management criteria. However, questions remain in the Australian setting. A panel (two neurologists, one clinical geneticist) reviewed the literature, examined clinical questions of relevance to the Australian setting, and developed a framework for the guidance. A wider panel, comprising the initial panel plus eight additional members, critiqued the framework and contributed clinical guidance within the scope of their respective areas of clinical expertise. The resultant expert consensus recommendations build on currently available data to propose an appropriate management framework incorporating the diagnosis, classification, therapeutic approach, multidisciplinary care, and on-going monitoring of patients with Pompe Disease in the Australian setting. It is hoped that diagnostic delay can be reduced with appropriate recourse to evidence-based insights and practical advice on diagnosis and management tailored to the Australian setting.

Mobility assessment using wearable technology in patients with late-onset Pompe disease

Late-onset Pompe disease (LOPD) is a rare genetic disorder due to the absence or deficiency of acid alpha-glucosidase enzyme resulting in slowly progressing reduction of muscle strength, causing difficulties with mobility and respiration. Wearable technologies offer novel options to evaluate mobility in a real-world setting. LOPD patients self-reporting LOPD, ≥18 years, US residents, walking (with or without aid), and not on invasive ventilation were recruited for a 6- to 8-week wearable study via patient organizations. Eligible patients were shipped a wearable tracker (Fitbit One™) and completed self-assessment questionnaires. Mobility outcome measures were median step count and peak 1-min activity. In the analyses cohort (N = 29), engagement in data sharing was high (94% of patients uploaded data for more than half the study days). Mean age was 43 years, 90% were females, and 93% were diagnosed in adulthood. Mean delay in diagnosis was 10 years; most had disease onset for ≥10 years (55%); some required walking aid (17%) and breathing assistance (38%). Mean step count differed by age (20-39 years: 4071 vs. 40-69 years: 2394, p < 0.01), diagnostic delay (<10 years: 3584 vs. ≥10 years: 2232, p < 0.05), disease duration (<10 years: 4219 vs. ≥10 years: 2462, p < 0.05), and ambulatory status (aided: 1883 vs. unaided: 3408, p < 0.05). Patient-reported "fatigue and pain" score was inversely correlated with step count (Pearson's r = -0.42, p < 0.05) and peak 1-min activity (Pearson's r = -0.49, p < 0.01). This study illustrates a new approach to measure mobility in LOPD patients and establishes a framework for future outcomes data collection.

Variable clinical features and genotype-phenotype correlations in 18 patients with late-onset Pompe disease

Background

Pompe disease is a lysosomal storage disorder caused by the deficiency of enzyme acid alpha-glucosidase (GAA) which results in accumulation of glycogen, particularly in the skeletal, cardiac, and smooth muscles. The late-onset form with symptoms presenting in childhood through adulthood, is characterized by proximal muscle weakness, respiratory insufficiency, and unlike the infantile-onset form often with no cardiac involvement.

Methods

We report our experience with 18 adult patients (14 males/4 females) with Pompe disease, several of whom had unique findings and novel pathogenic variants. Patients ranged in ages from 22-74 years (mean 53.7 years) and were diagnosed at an age range of 11-65 years (mean 43.6 years), often after a history of progressive muscle disease of several years' duration. All 18 patients were treated with alglucosidase alfa (Lumizyme) and their response to treatment was monitored by measurements of their pulmonary function and muscle weakness, six-minute walk test (6MWT), and other functional studies.

Results

Genetic sequencing revealed that 16 out of 18 individuals had the common c.-32-13T>G splicing variant, and six patients, including two sibships had four novel pathogenic variants: c.1594G>A, c.2655_2656delCG, c.1951-1952delGGinsT, and c.1134C>G. A male with the c.1594G>A variant developed an intracerebral aneurysm at the age of 43 years treated with surgery. Two siblings with the c.2655_2656delCG developed very high antibody titers, one of whom developed a severe infusion reaction. Other clinical features included BiPAP requirement in twelve, tinnitus in seven, scoliosis in five, cardiomyopathy in three, one individual was diagnosed with a cerebral aneurysm who underwent successful Penumbra coil placement, and another individual was diagnosed with both Graves' disease and testicular cancer.

Conclusions

Our study illustrates significant variability in the range of clinical features, and the variable clinical response to enzyme replacement therapy. It also alerts us to the importance of careful monitoring and early management of complications. Possible genotype-phenotype associations with the novel mutations identified may emerge with larger studies.

Advances in imaging of brain abnormalities in neuromuscular disease

Brain atrophy, white matter abnormalities, and ventricular enlargement have been described in different neuromuscular diseases (NMDs). We aimed to provide a comprehensive overview of the substantial advancement of brain imaging in neuromuscular diseases by consulting the main libraries (Pubmed, Scopus and Google Scholar) including the more common forms of muscular dystrophies such as dystrophinopathies, dystroglycanopathies, myotonic dystrophies, facioscapulohumeral dystrophy, limb-girdle muscular dystrophy, congenital myotonia, and congenital myopathies. A consistent, widespread cortical and subcortical involvement of grey and white matter was found. Abnormalities in the functional connectivity in brain networks and metabolic alterations were observed with positron emission tomography (PET) and single photon emission computed tomography (SPECT). Pathological brain changes with cognitive dysfunction seemed to be frequently associated in NMDs. In particular, in congenital muscular dystrophies (CMDs), skeletal muscular weakness, severe hypotonia, WM abnormalities, ventricular dilatation and abnormalities in cerebral gyration were observed. In dystroglycanopathy 2I subtype (LGMD2I), adult patients showed subcortical atrophy and a WM periventricular involvement, moderate ventriculomegaly, and enlargement of subarachnoid spaces. Correlations with clinical features have been observed with brain imaging characteristics and alterations were prominent in congenital or childhood onset cases. In myotonic dystrophy type 2 (DM2) symptoms seem to be less severe than in type 1 (DM1). In Duchenne and Becker muscular dystrophies (DMD, BMD) cortical atrophy is associated with minimal ventricular dilatation and WM abnormalities. Late-onset glycogenosis type II (GSD II) or Pompe infantile forms are characterized by delayed myelination. Only in a few cases of oculopharyngeal muscular dystrophy (OPMD) central nervous system involvement has been described and associated with executive functions impairment.

Characteristics of Pompe disease in China: a report from the Pompe registry

Background

Pompe disease is a rare, progressive, autosomal recessive lysosomal storage disorder caused by mutations in the acid α-glucosidase gene. This is the first report of Chinese patients from the global Pompe Registry. Chinese patients enrolled in the Registry (ClinicalTrials.gov, NCT00231400) between Jan 2013 and 2 Sep 2016 with late onset Pompe disease (LOPD; presentation after 12 months of age or presentation at ≤12 months without cardiomyopathy) were included. Data analyses were descriptive.

Results

Of the 59 Chinese patients included, 86.4% had never received enzyme replacement therapy (ERT). The age at symptom onset and diagnosis was 14.9 (12.35) and 22.1 (10.08) years, which is younger than previous reports of LOPD patients from the rest of the world (28.4 [18.86] and 34.9 [20.03], respectively). The most common diagnosis methods were enzyme assay (79.7%) and/or DNA analysis (61.0%). Of the 36 patients diagnosed using DNA analysis, 31 had standardized variant data and among these patients the most common mutations were c.2238G > C (n = 18, 58.1%) and c.2662G > T (n = 5, 16.1%). Chinese LOPD patients appeared to have worse lung function versus patients from the rest of the world, indicated by lower forced vital capacity (37.2 [14.00]% vs. 63.5 [26.71]%) and maximal expiratory and inspiratory pressure (27.9 [13.54] vs. 51.0 [38.66] cm H₂O, and 29.4 [12.04] vs. 70.5 [52.78] cm H₂O).

Conclusions

Compared with patients from the rest of the world, Chinese patients with LOPD appeared to have younger age at symptom onset and diagnosis, lower lung function, and the majority had not received ERT. The most common mutations were c.2238G > C and c.2662G > T.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1054-0) contains supplementary material, which is available to authorized users.

Selective screening of late-onset Pompe disease (LOPD) in patients with non-diagnostic muscle biopsies

AIMS

As of 2016, there were five patients with Pompe in Slovenia (two infantile, one childhood and two adult onset) with a prevalence of 1:400 000; however, the prevalence of late-onset Pompe disease (LOPD) in some other countries means this ratio could be an underestimate. Since an LOPD muscle biopsy could be unspecific or even normal, the purpose of this study is to assess the prevalence of LOPD in patients with non-diagnostic muscle biopsies.

METHODS

Six hundred biopsies were recorded at the Neuromuscular Tissue Bank of the University of Ljubljana for the period 2004-2014. All adult patients with non-diagnostic muscle biopsies were invited to the National Slovenian Neuromuscular Centre for dried blood spot testing for LOPD.

RESULTS

A total of 90 patients (56% of those invited) responded. No patient with LOPD was found. A total of 49 patients (54%) had fixed muscle weakness, 31 (34%) had mild symptoms and no weakness and 10 (11%) had asymptomatic hyperCKemia. Ventilatory insufficiency associated with proximal muscle weakness was found in two patients (2%). No patients exhibited vacuolar myopathy, globular accumulations of glycogen or regions of increased acid phosphatase activity within the sarcoplasm.

CONCLUSIONS

The study results do not support the hypothesis that LOPD is underestimated in Slovenian patients with non-diagnostic muscle biopsies; this could be consistent with the fact that LOPD is of low prevalence in Slovenia, as is the case in the populations of Finland, French-speaking Belgium, west Sweden and west Denmark.

Is early detection of late-onset Pompe disease a pneumologist's affair? A lesson from an Italian screening study

Background

Late-onset Pompe disease (LOPD) is a recessive disease caused by α-glucosidase (GAA) deficiency, leading to progressive muscle weakness and/or respiratory failure in children and adults. Respiratory derangement can be the first indication of LOPD, but the diagnosis may be difficult for pneumologists. We hypothesize that assessing the GAA activity in suspected patients by a dried blood spot (DBS) may help the diagnosis of LOPD in the pneumological setting.

Population and methods

We performed a multicenter DBS survey of patients with suspected LOPD according to a predefined clinical algorithm. From February 2015 to December 2017, 140 patients (57 ± 16 yrs., 80 males) were recruited in 19 Italian pneumological units. The DBS test was performed by a drop of blood collected on absorbent paper. Patients with GAA activity < 2.6 μmol/L/h were considered positive. A second DBS test was performed in the patients positive to the first assay. Patients testing positive at the re-test underwent a skeletal muscle biopsy to determine the GAA enzymatic activity.

Results

75 recruited subjects had outpatient access, 65 subjects were admitted for an acute respiratory failure episode. Two patients tested positive in both the first and second DBS test (1.4% prevalence), and the LOPD diagnosis was confirmed through histology, with patients demonstrating a deficient GAA muscle activity (3.6 and 9.1 pmol/min/mg). A further five subjects were positive in the first DBS test but were not confirmed at re-test. The two positive cases were both diagnosed after hospitalization for acute respiratory failure and need of noninvasive ventilation. Most of the recruited patients had reduced maximal respiratory pressures (MIP 50 ± 27% and MEP 55 ± 27% predicted), restrictive pattern (FEV₁/FVC 81.3 ± 13.6) and hypoxaemia (PaO₂ 70.9 ± 14.5 mmHg). Respiratory symptoms were present in all the patients, but only 48.6% of them showed muscle weakness in the pelvic girdle and/or in the scapular girdle (35.7%).

Conclusions

DBS GAA activity test may be a powerful screening tool among pneumologists, particularly in the acute setting. A simple clinical algorithm may aid in the selection of patients on which to administer the DBS test.

Molecular Pathways and Respiratory Involvement in Lysosomal Storage Diseases

Lysosomal storage diseases (LSD) include a wide range of different disorders with variable degrees of respiratory system involvement. The purpose of this narrative review is to treat the different types of respiratory manifestations in LSD, with particular attention being paid to the main molecular pathways known so far to be involved in the pathogenesis of the disease. A literature search was conducted using the Medline/PubMed and EMBASE databases to identify studies, from 1968 through to November 2018, that investigated the respiratory manifestations and molecular pathways affected in LSD. Pulmonary involvement includes interstitial lung disease in Gaucher’s disease and Niemann-Pick disease, obstructive airway disease in Fabry disease and ventilatory disorders with chronic respiratory failure in Pompe disease due to diaphragmatic and abdominal wall muscle weakness. In mucopolysaccharidosis and mucolipidoses, respiratory symptoms usually manifest early in life and are secondary to anatomical malformations, particularly of the trachea and chest wall, and to accumulation of glycosaminoglycans in the upper and lower airways, causing, for example, obstructive sleep apnea syndrome. Although the molecular pathways involved vary, ranging from lipid to glycogen and glycosaminoglycans accumulation, some clinical manifestations and therapeutic approaches are common among diseases, suggesting that lysosomal storage and subsequent cellular toxicity are the common endpoints.

Cough Effectiveness and Pulmonary Hygiene Practices in Patients with Pompe Disease

PURPOSE

While factors leading to hypoventilation have been well studied in Pompe disease, cough effectiveness and airway clearance practices are less understood. We aimed to identify significant factors that influence peak cough flow (PCF) in Pompe, and to detect whether pulmonary hygiene practices were reflective of reduced PCF.

METHODS

This is a prospective observational study of 20 subjects with Pompe disease (infantile-onset: 7, juvenile-onset: 6, adult-onset: 14). Subjects performed spirometry, maximal respiratory pressures, and cough (voluntary: n = 24, spontaneous: n = 3). Subjects or their parents reported airway clearance and secretion management practices. Relationships between disease variables, pulmonary function, and cough parameters as well as group differences in cough parameters were evaluated.

RESULTS

Subjects with infantile-onset disease had significantly lower PCF (p < 0.05) and tended to require more external ventilatory support (p = 0.07). In juvenile- and adult-onset disease, PCF differed according to external ventilatory requirement [daytime: 83.6 L/min (95% CI 41.2-126.0); nighttime: 224.6 L/min (95% CI 139.1-310.2); none: 340.2 L/min (95% CI 193.3-487.6), p < 0.005]. Cough inspiratory volume also differed significantly by ventilatory requirement [daytime: 5.5 mL/kg (95% CI 3.0-8.0); nighttime: 16.0 mL/kg (95% CI 11.8-20.2); none: 26.8 mL/kg (95% CI 11.9-41.7), p < 0.001]. However, routine airway clearance or secretion management practices were only consistently reported among patients with infantile-onset disease (infantile: 86%, juvenile: 0%, adult: 14%, p < 0.005).

CONCLUSIONS

Cough weakness was detected in the majority of patients with Pompe disease and was influenced by both inspiratory and expiratory muscle function. Patients at risk for problems or with ineffective PCF should be urged to complete routine pulmonary hygiene.

Renal artery fibromuscular dysplasia in Pompe disease: A case report

Vascular involvement in Late Onset Pompe Disease, glycogen storage disease type II characterized by limb-girdle muscle and diaphragmatic weakness, is well documented. Abnormalities of posterior cerebral circulation have mostly been reported, whereas there are also cases of associated extracerebral arteriopathy. We report the case of a 42-year-old man diagnosed with LOPD a year after renal infarct due to renal artery fibromuscular dysplasia. We propose that the association of LOPD and arteriopathy should always be considered in clinical practice.

Prevalence of adult Pompe disease in patients with proximal myopathic syndrome and undiagnosed muscle biopsy

We examined patients with limb-girdle muscle weakness and/or hyper-CKaemia and undiagnosed muscle biopsy for late onset Pompe disease (LOPD). Patients with an inconclusive limb-girdle muscle weakness who presented at our neuromuscular centre between 2005 and 2015 with undiagnosed muscle biopsies were examined by dry blood spot testing (DBS) including determination of the enzyme activity of acid alpha-glucosidase (GAA). In the case of depressed enzyme activity, additional gene testing of the GAA gene was carried out. Of the 340 evaluated muscle biopsies, 69 patients fulfilled the inclusion criteria and were examined with DBS. Among those patients, 76% showed a limb-girdle muscle weakness and 14% showed a hyper-CKaemia. A diagnosis of LOPD could be established in the case of two patients (2.9%) with reduced GAA enzyme activity and proof of mutations in the GAA gene. One of the two patients presents in the muscle biopsy suggestive features of Pompe disease including vacuoles with positive acid phosphatase reaction. In summary, our results show that a muscle biopsy can be helpful in identifying LOPD patients, but vacuolation with glycogen storage can also be absent. An inconspicuous muscle biopsy does not rule out Pompe disease. Consequently, all patients with limb-girdle muscle weakness should be examined by DBS before conducting a muscle biopsy.

Respiratory manifestations in late-onset Pompe disease: a case series conducted in Brazil

Objective:

To describe respiratory function in a series of patients with late-onset Pompe disease after the definitive diagnosis and before enzyme replacement therapy.

Methods:

This was a cross-sectional study involving patients with a definitive molecular diagnosis of late-onset Pompe disease. The data analyzed included age at symptom onset; age at definitive diagnosis; type of initial symptoms; time from symptom onset to diagnosis; FVC in the sitting and supine positions; six-minute walk distance; and locomotor ability. Analyses were carried out using frequencies, medians, minimum values, and maximum values.

Results:

Six patients were included in the study. The median age at symptom onset was 15 years (range, 13-50 years), and the median age at diagnosis was 39.5 years (range, 10-64 years). The median time from symptom onset to diagnosis was 8 years (range, 0-45 years). In all cases, the initial manifestation of the disease had been motor weakness. The median FVC in percentage of the predicted value (FVC%) in the sitting and supine positions was 71.0% (range, 22.9-104.6%) and 58.0% (range, 10.9-106.9%), respectively. The median ΔFVC% was 24.5% (range, −4.59 to 52.40%).The median six-minute walk distance was 391.7 m (range, 97-702 m) .

Conclusions:

In this case series, the time from symptom onset to diagnosis was long. Although respiratory signs or symptoms were not the initial manifestations of the disease, 66.7% of the patients showed reduced FVC% in the sitting and supine positions at diagnosis.

The Initial Evaluation of Patients After Positive Newborn Screening: Recommended Algorithms Leading to a Confirmed Diagnosis of Pompe Disease

Newborn screening (NBS) for Pompe disease is done through analysis of acid α-glucosidase (GAA) activity in dried blood spots. When GAA levels are below established cutoff values, then second-tier testing is required to confirm or refute a diagnosis of Pompe disease. This article in the "Newborn Screening, Diagnosis, and Treatment for Pompe Disease" guidance supplement provides recommendations for confirmatory testing after a positive NBS result indicative of Pompe disease is obtained. Two algorithms were developed by the Pompe Disease Newborn Screening Working Group, a group of international experts on both NBS and Pompe disease, based on whether DNA sequencing is performed as part of the screening method. Using the recommendations in either algorithm will lead to 1 of 3 diagnoses: classic infantile-onset Pompe disease, late-onset Pompe disease, or no disease/not affected/carrier. Mutation analysis of the GAA gene is essential for confirming the biochemical diagnosis of Pompe disease. For NBS laboratories that do not have DNA sequencing capabilities, the responsibility of obtaining sequencing of the GAA gene will fall on the referral center. The recommendations for confirmatory testing and the initial evaluation are intended for a broad global audience. However, the Working Group recognizes that clinical practices, standards of care, and resource capabilities vary not only regionally, but also by testing centers. Individual patient needs and health status as well as local/regional insurance reimbursement programs and regulations also must be considered.

Prevalence of late-onset pompe disease in Portuguese patients with diaphragmatic paralysis - DIPPER study

Pompe disease is a rare autosomal recessive neuromuscular disorder caused by acid α-glucosidase enzyme (GAA) deficiency and divided into two distinct variants, infantile- and late-onset. The late-onset variant is characterized by a spectrum of phenotypic variation that may range from asymptomatic, to reduced muscle strength and/or diaphragmatic paralysis. Since muscle strength loss is characteristic of several different conditions, which may also cause diaphragmatic paralysis, a protocol was created to search for the diagnosis of Pompe disease and exclude other possible causes.

METHODS

We collected a sample size of 18 patients (10 females, 8 males) with a median age of 60 years and diagnosis of diaphragmatic paralysis of unknown etiology, followed in the Pulmonology outpatient consultation of 9 centers in Portugal, over a 24-month study period. We evaluated data from patient's clinical and demographic characteristics as well as complementary diagnostic tests including blood tests, imaging, neurophysiologic and respiratory function evaluation. All patients were evaluated for GAA activity with DBS (dried blood test) or serum quantification and positive results confirmed by serum quantification and sequencing.

RESULTS

Three patients were diagnosed with Pompe's disease and recommended for enzyme replacement therapy. The prevalence of Pompe, a rare disease, in our diaphragmatic paralysis patient sample was 16.8%.

CONCLUSION

We conclude that DBS test for GAA activity should be recommended for all patients with diaphragmatic paralysis which, despite looking at all the most common causes, remains of unknown etiology; this would improve both the timing and accuracy of diagnosis for Pompe disease in this patient population. Accurate diagnosis will lead to improved care for this rare, progressively debilitating but treatable neuromuscular disease.

New mutations and genotype-phenotype correlation in late-onset Pompe patients

Pompe disease is a glycogen storage disease caused by acid alfa-glucosidase deficiency. Here, we report clinical properties, genetic features of our late-onset Pompe patients. Seven patients were followed during the last 10 years in our institute. The clinical and laboratory findings were reviewed. Neuropsychological evaluation was performed in four patients. Myotonic discharges of paraspinal muscles and denervation potentials were seen in all patients at the diagnosis and were disappeared during follow-up in two. Only one patient, whose MRI showed cerebral atrophy, had attention and executive dysfunction. Compound heterozygous patients with IVS 1-13T>G have a milder disease. One patient who has homozygous IVS 1-13T>G mutation had more severe disease. Two of our patients who had very severe and fatal disease course carry double mutations on both alleles (c.547-39T>G and c.858+5ins7) that previously scored as "unknown" in Erasmus Pompe Center database. Lastly, we found new mutations (c.1209 C>A, 2737dupG) in two patients carrying IVS 1-13T>G in the other allele. Systemic involvements are very rare in late-onset Pompe patients. Similarly, Pompe disease does not cause cognitive impairment in adult population. Homozygous IVS 1-13T>G mutation and c.547-39T>G mutation which are previously noted as "unknown" pathogenicities cause a more severe disease.

The emerging phenotype of late-onset Pompe disease: A systematic literature review

BACKGROUND

Pompe disease is an autosomal recessive disorder caused by deficiency of the lysosomal glycogen-hydrolyzing enzyme acid α-glucosidase (GAA). The adult-onset form, late-onset Pompe disease (LOPD), has been characterized by glycogen accumulation primarily in skeletal, cardiac, and smooth muscles, causing weakness of the proximal limb girdle and respiratory muscles. However, increased scientific study of LOPD continues to enhance understanding of an evolving phenotype.

PURPOSE

To expand our understanding of the evolving phenotype of LOPD since the approval of enzyme replacement therapy (ERT) with alglucosidase alfa (Myozyme™/Lumizyme™) in 2006.

METHODS

All articles were included in the review that provided data on the charactertistics of LOPD identified via the PubMed database published since the approval of ERT in 2006. All signs and symptoms of the disease that were reported in the literature were identified and included in the review.

RESULTS

We provide a comprehensive review of the evolving phenotype of LOPD. Our findings support and extend the knowledge of the multisystemic nature of the disease.

CONCLUSIONS

With the advent of ERT and the concurrent increase in the scientific study of LOPD, the condition once primarily conceptualized as a limb-girdle muscle disease with prominent respiratory involvement is increasingly recognized to be a condition that results in signs and symptoms across body systems and structures.

Late-onset pompe disease in Iran: A clinical and genetic report

INTRODUCTION

Pompe disease is characterized by absence or deficiency of acid α-glucosidase, and several causative mutations are known. In this study we report clinical and laboratory data in Iranian patients with late-onset Pompe disease (LOPD), focusing on population-specific mutations.

METHODS

Clinical and laboratory data of 14 patients from 10 families with the diagnosis of LOPD were recorded. All had reduced enzyme activity on dried blood spot (DBS) analysis. Genetic investigation was performed to identify the underlying mutations.

RESULTS

The age of onset ranged from <2 to 38 years. The clinical presentations were heterogeneous. Two siblings presented with foot drop. The most common mutation was c.(-32-13T>G). There were 4 novel mutations: c.(2040 + 2dup); c.(1650delG); c.(1837T>G); and c.(2596delG).

CONCLUSION

This is a comprehensive report of LOPD in Iranian patients. Distinct phenotypic and genotypic features in this population are highlighted. Muscle Nerve 55: 835-840, 2017.

Diaphragm Pacing as a Rehabilitative Tool for Patients With Pompe Disease Who Are Ventilator-Dependent: Case Series

BACKGROUND AND PURPOSE

Pompe disease is an inherited disorder notable for severe, progressive ventilatory compromise. Although ventilatory failure has been attributed to myofiber dysfunction secondary to diaphragmatic glycogen accumulation, neural involvement of the phrenic motor system is also a prominent feature. Direct diaphragm pacing supplements respiratory function in other disorders of the phrenic motor system. Accordingly, it is hypothesized that augmented neuromuscular activity via diaphragm pacing would promote weaning from mechanical ventilation in patients with Pompe disease who are unresponsive to conventional, muscle-directed treatments.

CASE DESCRIPTION

Three patients with Pompe disease developed diaphragm paresis that resulted in chronic mechanical ventilation dependence. After preoperative inspiratory muscle strengthening exercises failed to improve function, fine-wire pacing electrodes were laparoscopically implanted into the diaphragm. Diaphragm conditioning was initiated the first postoperative week and consisted of gradual increases in stimulation parameters, lengthening of stimulation sessions, and ventilator weaning. Ventilation and intramuscular electromyographic activity were recorded periodically during conditioning to quantify diaphragm neuromuscular function.

OUTCOMES

During paced breathing without mechanical ventilation, tidal volumes increased, and 2 patients were weaned from daytime ventilator dependence within the first 3 months of pacing, which has been sustained over the long-term. A third patient reduced reliance on daytime ventilation, but weaning was delayed by malacia of the large airways. In all patients, pacing appeared to facilitate spontaneous phrenic motor unit activity during independent breathing without ventilator or pacer support.

DISCUSSION

The findings are consistent with the view that diaphragm pacing has potential rehabilitative value to reduce reliance on mechanical ventilation in people with Pompe disease, but further study is needed. Diaphragm pacing represents a paradigm shift in the management of respiratory insufficiency for Pompe disease that warrants further controlled examination.

Pompe Disease: Diagnosis and Management. Evidence-Based Guidelines from a Canadian Expert Panel

Pompe disease is a lysosomal storage disorder caused by a deficiency of the enzyme acid alpha-glucosidase. Patients have skeletal muscle and respiratory weakness with or without cardiomyopathy. The objective of our review was to systematically evaluate the quality of evidence from the literature to formulate evidence-based guidelines for the diagnosis and management of patients with Pompe disease. The literature review was conducted using published literature, clinical trials, cohort studies and systematic reviews. Cardinal treatment decisions produced seven management guidelines and were assigned a GRADE classification based on the quality of evidence in the published literature. In addition, six recommendations were made based on best clinical practices but with insufficient data to form a guideline. Studying outcomes in rare diseases is challenging due to the small number of patients, but this is in particular the reason why we believe that informed treatment decisions need to consider the quality of the evidence.

Reevaluating Muscle Biopsies in the Diagnosis of Pompe Disease: A Corroborative Report

Background: Previous reports suggest that although a diagnostic muscle biopsy can confirm the presence of Pompe disease, the absence of a definitive biopsy result does not rule out the diagnosis. Methods: In this study, we reviewed patients with a limb-girdle syndrome who demonstrated nonspecific abnormalities of muscle, without evidence of the classical changes of acid maltase deficiency. These patients were rescreened for Pompe disease using dried blood spot (DBS) testing. Results: Twenty-seven patients provided blood samples for the DBS test. Four patients underwent subsequent genetic testing. Genetic analysis demonstrated that one patient tested positive for Pompe disease and one patient had one copy of a pathogenic variant. Conclusions: In conclusion, the ability of a diagnostic muscle biopsy to definitively rule out the presence of Pompe disease is limited. There is a role for a screening DBS in all patients presenting with a limb-girdle syndrome without a clear diagnosis.

Search for Pompe disease among patients with undetermined myopathies

OBJECTIVE

Pompe disease is a rare treatable glycogen storage disease with in adults - a limb-girdle muscle weakness. Muscle biopsy may fail to show the typical vacuolar myopathy. We asked if we had un-diagnosed patients with Pompe disease in western Sweden.

MATERIAL AND METHODS

We searched the muscle biopsy registry during the time period 1986 until 2006 including 3665 biopsies and included patients at our Neuromuscular Center with unspecified myopathy or limb-girdle muscular dystrophy. The dry blood spot test was used to identify patients with Pompe disease.

RESULTS

A total of 82 patients (46 from the biopsy register and 36 from our center) were seen and dry blood spot test was obtained. No patient with Pompe disease was found. The dry blood spot test was low in three cases (11, 16, and 18% of normal) but a second blood sample showed a normal result based on GAA enzyme activity in lymphocytes in all three patients. In one patient with low normal result of the analysis in lymphocytes a genetic test showed no pathogenic mutations. Further investigation gave a definite diagnose of another myopathy in 12 patients.

CONCLUSIONS

The prevalence of Pompe disease in western Sweden (3 in 1.27 million or 0.24 per 100.000 inhabitants) is lower than in the Netherlands and New York. Re-evaluation of patients with myopathies but without definite diagnosis is rewarding since 12 of 82 patients in our study had a definite molecular diagnosis after workup.

A 62-year-old man with dyspnea

We describe the case of a 62-year-old man who presented with shortness of breath that had progressed over several years. He had a history of a paralyzed right hemidiaphragm for at least the previous 10 years. He also reported weakness in his proximal legs and daytime sleepiness. On examination, he was found to have thoracoabdominal paradox when in supine position. Pulmonary function testing revealed severe restriction; arterial blood gas showed chronic respiratory acidosis. Electromyography showed chronic phrenic neuropathy bilaterally, with mild proximal myopathy. Serum aldolase level was mildly elevated, but serologic tests for connective tissue disorders were within reference range. After extensive clinical investigations, the patient was found to have severely reduced acid α-glucosidase. Genetic analysis confirmed the diagnosis of adult-onset Pompe disease. The patient started treatment with bilevel positive airway pressure titrated during polysomnography, and acid α-glucosidase enzyme replacement was recommended.

Guidelines for the diagnosis, treatment and clinical monitoring of patients with juvenile and adult Pompe disease

ABSTRACT Pompe disease (PD) is a potentially lethal illness involving irreversible muscle damage resulting from glycogen storage in muscle fiber and activation of autophagic pathways. A promising therapeutic perspective for PD is enzyme replacement therapy (ERT) with the human recombinant enzyme acid alpha-glucosidase (Myozyme®). The need to organize a diagnostic flowchart, systematize clinical follow-up, and establish new therapeutic recommendations has become vital, as ERT ensures greater patient longevity. A task force of experienced clinicians outlined a protocol for diagnosis, monitoring, treatment, genetic counseling, and rehabilitation for PD patients. The study was conducted under the coordination of REBREPOM, the Brazilian Network for Studies of PD. The meeting of these experts took place in October 2013, at L’Hotel Port Bay in São Paulo, Brazil. In August 2014, the text was reassessed and updated. Given the rarity of PD and limited high-impact publications, experts submitted their views.

Familial Pompe Disease

Introduction:

Pompe disorder is a rare glycogen storage disorder that is due to a deficiency of the lysosomal alpha glycosidase enzyme. The heart, skeletal muscle, liver and nervous system can be affected from the lysosomal glycogen accumulation. Symptoms such as muscle weakness, hypotony, myopathy and respiratory failure develop. The onset may be at the infantile, adolescent or adult period depending on the enzyme level. The CK level is high in almost all patients. The diagnosis is made with enzyme level measurement and genetic analysis.

Case report:

We present a family with Pompe disease consisting of the asymptomatic mother and two siblings who presented with muscle weakness and respiratory failure and who had been followed-up with a diagnosis of muscular dystrophy for a long time.

Diagnosis and treatment of late-onset Pompe disease in the Middle East and North Africa region: consensus recommendations from an expert group

Background

Pompe disease is a rare autosomal recessive disorder caused by a deficiency of the lysosomal enzyme alpha-glucosidase responsible for degrading glycogen. Late-onset Pompe disease has a complex multisystem phenotype characterized by a range of symptoms.

Methods

An expert panel from the Middle East and North Africa (MENA) region met to create consensus-based guidelines for the diagnosis and treatment of late-onset Pompe disease for the MENA region, where the relative prevalence of Pompe disease is thought to be high but there is a lack of awareness and diagnostic facilities.

Results

These guidelines set out practical recommendations and include algorithms for the diagnosis and treatment of late-onset Pompe disease. They detail the ideal diagnostic workup, indicate the patients in whom enzyme replacement therapy should be initiated, and provide guidance on appropriate patient monitoring.

Conclusions

These guidelines will serve to increase awareness of the condition, optimize patient diagnosis and treatment, reduce disease burden, and improve patient outcomes.

Correcting Neuromuscular Deficits With Gene Therapy in Pompe Disease

OBJECTIVE

We have recently reported on the pathology of the neuromuscular junction (NMJ) in Pompe disease, reflecting disruption of neuronal and muscle homeostasis as a result of glycogen accumulation. The aim of this study was to examine how the alteration of NMJ physiology contributes to Pompe disease pathology; we performed molecular, physiological, and histochemical analyses of NMJ-related measures of the tibialis anterior muscles of young-, mid-, and late-stage alpha-glucosidase (GAA)-deficient mice.

METHODS

We performed intramuscular injection of an adeno-associated virus (AAV)9 vector expressing GAA (AAV9-hGAA) into the tibialis anterior muscle of Gaa(-/-) mice at early, mid, and severe pathological time points. We analyzed expression of NMJ-related genes, in situ muscle force production, and clearance of glycogen in conjunction with histological assessment of the NMJ.

RESULTS

Our data demonstrate that AAV9-hGAA is able to replace GAA to the affected tissue and modify AChR mRNA expression, muscle force production, motor endplate area, and innervation status. Importantly, the degree of restoration for these outcomes is limited by severity of disease. Early restoration of GAA activity was most effective, whereas late correction of GAA expression was not effective in modifying parameters reflecting NMJ structure and function nor in force restoration despite resolution of glycogen storage in muscle.

INTERPRETATION

Our data provide new mechanistic insight into the pathology of Pompe disease and suggest that early systemic correction to both neural and muscle tissues may be essential for successful correction of neuromuscular function in Pompe disease. Ann Neurol 2015;78:222-234.

Should patients with asymptomatic pompe disease be treated? A nationwide study in France

INTRODUCTION

Acid α-glucosidase deficiency, that is, Pompe disease, is a glycogenosis for which enzyme replacement therapy (ERT) is available. It is not known whether patients diagnosed at an asymptomatic stage should be treated to prevent progression of the disease.

METHODS

We investigated 7 patients with asymptomatic Pompe disease identified from the French Pompe registry.

RESULTS

The patients had a mean age of 45 (range 24-75) years, a median follow-up duration of 2 (range 1-22) years, and normal clinical examination, pulmonary function tests (PFTs), and echocardiography. All presented with at least 1 subclinical abnormality, including hyperCKemia, vacuolar myopathy, and muscle MRI abnormalities, suggesting that subclinical myopathy was present in all cases.

CONCLUSIONS

Asymptomatic Pompe disease may remain clinically silent for decades, and affected patients should be monitored closely for overt myopathy using clinical examination, PFTs, and muscle MRI to determine when to start ERT.

Pompe disease: literature review and case series

Pompe disease is a rare multi-systemic metabolic myopathy caused by autosomal recessive mutations in the acidic alpha glucosidase (GAA) gene. Significant progress had been made in the diagnosis and management of patients with Pompe disease. Here, we describe our experience with 12 patients with various forms of Pompe disease including 4 potentially pathogenic, novel GAA variants. We also review the recent the recent advances in the pathogenesis, diagnosis, and treatment of individuals with Pompe disease.