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ObjectiveTo investigate the clinical features and genetic characteristics of patients with late-onset Pompe disease(LOPD).MethodsA total of 13 patients diagnosed with LOPD in the First Affiliated Hospital of Zhejiang University School of Medicine from September 2020 to December 2023 were selected, and all patients were subjected to clinical investigation, GAA activity detection and GAA gene testing.ResultsAmong the 13 patients, 7 were males and 6 were females; 5 were family patients and 8 were sporadic patients; and the median age of onset was 17 years(8-52 years), the median age of presentation was 24 years(10-52 years), and the median age of diagnosis was 31 years(14-58 years). In terms of the first symptoms, 10 patients presented with limb weakness and 3 patients presented with dyspnea. The average serum creatine kinase level was 552 U/L(55-1084 U/L), and the serum creatine kinase level was normal in one patient. All patients had scoliosis and different degrees of restrictive ventilatory dysfunction. Neuroelectrophysiological examinations of 9 patients showed myogenic damage, and 8 of them had muscle tonic discharge. The mean value of GAA activity was 0.3 μmol/(L·h)[0.17-0.5 μmol/(L·h)]. A total of 13 mutations were detected in GAA gene, and the most common mutation was c.2238G > C(p.W746C).There were five new variant sites: c.543del(p.F181Lfs*40), c.839_840insCC(p.R281Pfs*34), c.1800_1823del(p.S601_ R608del), c.2296T > C(p.Y766H) and c.995C > A(p.S332*).ConclusionsLOPD is a rare disease that tends to delay diagnosis. Proximal limb weakness, decreased respiratory function, mild-to-moderate elevation of creatine kinase, scoliosis, and clinical inferior tonic discharge on electromyography are high-risk images of LOPD. c.2238G > C(p.W746C)is a hotspot mutation, and the discovery of five new mutations enriches the GAA gene mutations lineage.

Background: Pompe Disease (PD) is a metabolic myopathy caused by variants in the GAA gene, resulting in deficient enzymatic activity. We aimed to characterize the clinical features and related genetic variants in a series of Mexican patients. Methods: We performed a retrospective study of clinical records of patients diagnosed with LOPD, IOPD or pseudodeficiency. Results: Twenty‐nine patients were included in the study, comprising these three forms. Overall, age of symptom onset was 0.1 to 43 years old. The most frequent variant identified was c.‐32‐13T>G, which was detected in 14 alleles. Among the 23 different variants identified in the GAA gene, 14 were classified as pathogenic, 5 were likely pathogenic, and 1 was a variant of uncertain significance. Two variants were inherited in cis arrangement and 2 were pseudodeficiency‐related benign alleles. We identified two novel variants (c.1615 G>A and c.1076‐20_1076‐4delAAGTCGGCGTTGGCCTG). Conclusion: To the best of our knowledge, this series represent the largest phenotypic and genotypic characterization of patients with PD in Mexico. Patients within our series exhibited a combination of LOPD and IOPD associated variants, which may be related to genetic diversity within Mexican population. Further population‐wide studies are required to better characterize the incidence of this disease in Mexican population. [ABSTRACT FROM AUTHOR]

Glycogenosis type II (GSDII) is a rare autosomal disorder that is caused by the deficiency of alpha-glucosidase, a lysosomal enzyme that hydrolyzes glycogen to glucose. Autophagy dysregulation plays a critical role. Importantly, since 2006, both patients with infantile (classic Pompe disease) and adult GSDII (late-onset Pompe disease or LOPD) have been treated with enzyme replacement therapy (ERT). To support this use, several double-blind and observational studies including large cohorts of GSDII patients have been undertaken and have shown ERT to be effective in modifying the natural course of disease. Indeed, most LOPD cases improve in the first 20 months of treatment in a six-minute walk test (6MWT), while those who are untreated do not; instead, their response declines over time. The author reviews avalglucosidase alpha, a therapy approved by both the FDA and European regulatory agencies. Herein, the author considers the pathophysiological approaches such as the role of enzyme entry, autophagy, and the response to ERT treatment of motor and respiratory components. There has been a notable drive toward the research of various aspects of this disease regarding the role of new enzyme penetration and immune adverse events. Consequently, avalglucosidase alpha might be a further step forward. [ABSTRACT FROM AUTHOR]

Abstract Background Pompe Disease (PD) is a metabolic myopathy caused by variants in the GAA gene, resulting in deficient enzymatic activity. We aimed to characterize the clinical features and related genetic variants in a series of Mexican patients. Methods We performed a retrospective study of clinical records of patients diagnosed with LOPD, IOPD or pseudodeficiency. Results Twenty‐nine patients were included in the study, comprising these three forms. Overall, age of symptom onset was 0.1 to 43 years old. The most frequent variant identified was c.‐32‐13T>G, which was detected in 14 alleles. Among the 23 different variants identified in the GAA gene, 14 were classified as pathogenic, 5 were likely pathogenic, and 1 was a variant of uncertain significance. Two variants were inherited in cis arrangement and 2 were pseudodeficiency‐related benign alleles. We identified two novel variants (c.1615 G>A and c.1076‐20_1076‐4delAAGTCGGCGTTGGCCTG). Conclusion To the best of our knowledge, this series represent the largest phenotypic and genotypic characterization of patients with PD in Mexico. Patients within our series exhibited a combination of LOPD and IOPD associated variants, which may be related to genetic diversity within Mexican population. Further population‐wide studies are required to better characterize the incidence of this disease in Mexican population.

Abstract Background Pompe disease is a rare glycogen storage disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA), leading to glycogen deposition in multiple tissues. Infantile-onset Pompe disease (IOPD) patients present within the first year of life with profound hypotonia and hypertrophic cardiomyopathy. Treatment with enzyme replacement therapy (ERT) has significantly improved survival for this otherwise lethal disorder. This study aims to describe the clinical and molecular spectrum of Malaysian IOPD patients, and to analyze their long term treatment outcomes. Methods Seventeen patients diagnosed with IOPD between 2000 and 2020 were included in this retrospective cohort study. Clinical and biochemical data were collated and analyzed using descriptive statistics. GAA enzyme levels were performed on dried blood spots. Molecular analysis of the GAA gene was performed by polymerase chain reaction and Sanger sequencing. Structural modelling was used to predict the effect of the novel mutations on enzyme structure. Results Our cohort had a median age of presentation of 3 months and median age of diagnosis of 6 months. Presenting features were hypertrophic cardiomyopathy (100%), respiratory insufficiency (94%), hypotonia (88%), failure to thrive (82%), feeding difficulties (76%), and hepatomegaly (76%). Fourteen different mutations in the GAA gene were identified, with three novel mutations, c.1552-14_1552-1del, exons 2–3 deletion and exons 6–10 deletion. The most common mutation identified was c.1935C > A p.(D645E), with an allele frequency of 33%. Sixteen patients received ERT at the median age of 7 months. Overall survival was 29%. Mean age of death was 17.5 months. Our longest surviving patient has atypical IOPD and is currently 20 years old. Conclusions This is the first study to analyze the genotype and phenotype of Malaysian IOPD patients, and has identified the c.1935C > A p.(D645E) as the most common mutation. The three novel mutations reported in this study expands the mutation spectrum for IOPD. Our low survival rate underscores the importance of early diagnosis and treatment in achieving better treatment outcomes.

Background: Pompe disease is a rare glycogen storage disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA), leading to glycogen deposition in multiple tissues. Infantile-onset Pompe disease (IOPD) patients present within the first year of life with profound hypotonia and hypertrophic cardiomyopathy. Treatment with enzyme replacement therapy (ERT) has significantly improved survival for this otherwise lethal disorder. This study aims to describe the clinical and molecular spectrum of Malaysian IOPD patients, and to analyze their long term treatment outcomes. Methods: Seventeen patients diagnosed with IOPD between 2000 and 2020 were included in this retrospective cohort study. Clinical and biochemical data were collated and analyzed using descriptive statistics. GAA enzyme levels were performed on dried blood spots. Molecular analysis of the GAA gene was performed by polymerase chain reaction and Sanger sequencing. Structural modelling was used to predict the effect of the novel mutations on enzyme structure. Results: Our cohort had a median age of presentation of 3 months and median age of diagnosis of 6 months. Presenting features were hypertrophic cardiomyopathy (100%), respiratory insufficiency (94%), hypotonia (88%), failure to thrive (82%), feeding difficulties (76%), and hepatomegaly (76%). Fourteen different mutations in the GAA gene were identified, with three novel mutations, c.1552-14_1552-1del, exons 2–3 deletion and exons 6–10 deletion. The most common mutation identified was c.1935C > A p.(D645E), with an allele frequency of 33%. Sixteen patients received ERT at the median age of 7 months. Overall survival was 29%. Mean age of death was 17.5 months. Our longest surviving patient has atypical IOPD and is currently 20 years old. Conclusions: This is the first study to analyze the genotype and phenotype of Malaysian IOPD patients, and has identified the c.1935C > A p.(D645E) as the most common mutation. The three novel mutations reported in this study expands the mutation spectrum for IOPD. Our low survival rate underscores the importance of early diagnosis and treatment in achieving better treatment outcomes. [ABSTRACT FROM AUTHOR]

Pompe disease (PD) is caused by mutations in the GAA gene, which encodes the lysosomal enzyme acid alpha-glucosidase, causing lysosomal glycogen accumulation, mainly in muscular tissue. Autophagic buildup is considered the main factor affecting skeletal muscle, although other processes are also involved. Uncovering how these mechanisms are interconnected could be an approximation to address long-lasting concerns, like the differential skeletal and cardiac involvement in each clinical phenotype. In this sense, a network reconstruction based on a comprehensive literature review of evidence found in PD enriched with the STRING database and other scientific articles is presented. The role of autophagic lysosome reformation, PGC-1α, MCOLN1, calcineurin, and Keap1 as intermediates between the events involved in the pathologic cascade is discussed and contextualized within their relationship with mTORC1/AMPK. The intermediates and mechanisms found open the possibility of new hypotheses and questions that can be addressed in future experimental studies of PD. [ABSTRACT FROM AUTHOR]

Identification of variants in the acid α-glucosidase (GAA) gene in Pompe disease provides valuable insights and systematic overviews are needed. We report on the number, nature, frequency, and geographic distribution of GAA sequence variants listed in the Pompe Registry, a long-term, observational program and the largest global repository of Pompe disease data. Variant information was reviewed and compared with publicly available GAA databases/resources. Among 1,079 eligible patients, 2,075 GAA variants (80 unique novel) were reported. Variants were listed by groups representing Pompe disease phenotypes. Patients were classified as Group A: Symptom onset ≤ 12 months of age with cardiomyopathy; Group B: Symptom onset ≤ 12 years of age (includes patients with symptom onset ≤ 12 months of age without cardiomyopathy); or Group C: Symptom onset > 12 years of age. Likely impact of novel variants was predicted using bioinformatics algorithms. Variants were classified by pathogenicity using ACMG guidelines. Data reported from the Pompe Registry provide new information about the distribution of GAA variants globally and across the clinical spectrum, add to the number and diversity of GAA variants registered in public databases through published data sharing, provide a first indication of the severity of novel variants, and assist in diagnostic practice and outcome prediction.

Enzyme replacement therapy (ERT) is the current standard treatment for Pompe disease, a lysosomal storage disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). ERT has shown to be lifesaving in patients with classic infantile Pompe disease. However, a major drawback is the development of neutralizing antibodies against ERT. Hematopoietic stem and progenitor cell-mediated lentiviral gene therapy (HSPC-LVGT) provides a novel, potential lifelong therapy with a single intervention and may induce immune tolerance. Here, we investigated whether ERT can be safely applied as additional or alternative therapy following HSPC-LVGT in a murine model of Pompe disease. We found that lentiviral expression at subtherapeutic dose was sufficient to induce tolerance to the transgene product, as well as to subsequently administered ERT. Immune tolerance was established within 4–6 weeks after gene therapy. The mice tolerated ERT doses up to 100 mg/kg, allowing ERT to eliminate glycogen accumulation in cardiac and skeletal muscle and normalizing locomotor function. The presence of HSPC-derived cells expressing GAA in the thymus suggested the establishment of central immune tolerance. These findings demonstrate that lentiviral gene therapy in murine Pompe disease induced robust and long-term immune tolerance to GAA either expressed by a transgene or supplied as ERT.

BACKGROUND: Pompe disease is a genetic disorder of glycogen metabolism due to the deficiency of the enzyme acid alpha-glucosidase, causing progressive muscle weakness, respiratory distress and life-threatening heart condition. Patients treated with enzyme replacement therapy (ERT) with alglucosidase alfa need to have follow up and assess the response to treatment. CLINICAL CASE: This paper reports the case of three women with Pompe disease, 32, 41 and 31 years old, who started with symptoms between 12-16 years old, but were diagnosed at the age of 30, 39, and 29 years, respectively. They were homozygous c.1082c> T, two sisters and a cousin. All three received enzyme replacement therapy 6-20 months earlier. Functionality improved after the start of enzyme replacement therapy; two of the patients were unable to walk and needed oxygen, and now they can walk and climb stairs, although only one successfully completed the 6-min-walk and 3-min-stairs tests. Two patients were dependent on oxygen before the enzyme replacement therapy and subsequently maintained saturations above 90% without oxygen. CONCLUSIONS: Enzyme replacement therapy improved movement and functionality, as well as oxygen saturation in 3 patients with Pompe disease in a hospital in the northeast of Mexico. [ABSTRACT FROM AUTHOR]

Late-onset Pompe disease (LOPD) is caused by a genetic deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA), leading to progressive limb-girdle weakness and respiratory impairment. The insidious onset of non-specific early symptoms often prohibits timely diagnosis. This study aimed to validate the high-risk screening criteria for LOPD in the Chinese population. A total of 726 patients were included, including 96 patients under 14 years of age. Dried blood spots (DBS) and tandem mass spectrometry (MS/MS) were employed to evaluate serum GAA activity. Forty-four patients exhibited a decreased GAA activity, 16 (2.2%) of which were confirmed as LOPD by genetic testing. Three previously unreported GAA mutations were also identified. The median diagnostic delay was shortened to 3 years, which excelled the previous retrospective studies. At diagnosis, most patients exhibited impaired respiratory function and/or limb-girdle weakness. Elevated serum creatine kinase (CK) levels were more frequently observed in patients who manifested before age 16. Overall, high-risk screening is a feasible and efficient method to identify LOPD patients at an early stage. Patients over 1 year of age with either weakness in axial and/or proximal limb muscles, or unexplained respiratory distress shall be subject to GAA enzymatic test, while CK levels above 2 times the upper normal limit shall be an additional criterion for patients under 16. This modified high-risk screening criteria for LOPD requires further validation in larger Chinese cohorts., (© 2024 SSIEM.)

Pompe disease (PD) is an autosomal recessive disorder by a deficiency of acid α‐glucosidase (GAA) with intralysosomal glycogen accumulation in multiple tissues. We present the case of a 5‐month‐old male with hypertrophic cardiomyopathy, hypotony, feeding difficulties, and oxygen requirement since birth. At 3 months of age, he develops heart failure, respiratory impairment, and neurological deterioration. The echocardiogram revealed concentric hypertrophic cardiomyopathy with left‐diastolic dysfunction. We found increased creatine‐phosphokinase, lactate dehydrogenase, and urinary glucose tetrasaccharide levels, 50% of PAS‐positive vacuolated lymphocytes in the peripheral blood smear, and low GAA activity. Sequencing of coding exons and flanking intronic sequences revealed a novel homozygous 4 bp deletion in exon 15 of the GAA gene (c.2066_2069delAGCC/p.Glu689Glyfs*6). IOPD was diagnosed. At 5 months old, we started enzyme replacement therapy with an alpha‐alglucosidase of 20 mg/kg weekly and immunomodulation with intravenous immunoglobulin. He developed two cardiorespiratory arrests with subsequent neurologic deterioration, convulsive crisis, and respiratory failure and died at 9 months old. We found the usual PD hallmarks in the heart, striated muscle, and liver but also we found neuronal lesions characterized by cytoplasm vacuolization with PAS‐positive granules in the central nervous system and myenteric plexus. We describe a novel GAA gene pathogenic variant with a particular phenotype characterized by classic IOPD and neurologic histopathological findings. Enhancing the knowledge of lysosomal diseases is critical to improving the diagnosis and treatment of these patients. [ABSTRACT FROM AUTHOR]

Abstract Pompe disease (PD) is an autosomal recessive disorder by a deficiency of acid α‐glucosidase (GAA) with intralysosomal glycogen accumulation in multiple tissues. We present the case of a 5‐month‐old male with hypertrophic cardiomyopathy, hypotony, feeding difficulties, and oxygen requirement since birth. At 3 months of age, he develops heart failure, respiratory impairment, and neurological deterioration. The echocardiogram revealed concentric hypertrophic cardiomyopathy with left‐diastolic dysfunction. We found increased creatine‐phosphokinase, lactate dehydrogenase, and urinary glucose tetrasaccharide levels, 50% of PAS‐positive vacuolated lymphocytes in the peripheral blood smear, and low GAA activity. Sequencing of coding exons and flanking intronic sequences revealed a novel homozygous 4 bp deletion in exon 15 of the GAA gene (c.2066_2069delAGCC/p.Glu689Glyfs*6). IOPD was diagnosed. At 5 months old, we started enzyme replacement therapy with an alpha‐alglucosidase of 20 mg/kg weekly and immunomodulation with intravenous immunoglobulin. He developed two cardiorespiratory arrests with subsequent neurologic deterioration, convulsive crisis, and respiratory failure and died at 9 months old. We found the usual PD hallmarks in the heart, striated muscle, and liver but also we found neuronal lesions characterized by cytoplasm vacuolization with PAS‐positive granules in the central nervous system and myenteric plexus. We describe a novel GAA gene pathogenic variant with a particular phenotype characterized by classic IOPD and neurologic histopathological findings. Enhancing the knowledge of lysosomal diseases is critical to improving the diagnosis and treatment of these patients.

Pompe disease is a lysosomal storage disorder caused by malfunctions of the acid alpha-glucosidase (GAA) enzyme with a consequent toxic accumulation of glycogen in cells. Muscle wasting and hypertrophic cardiomyopathy are the most common clinical signs that can lead to cardiac and respiratory failure within the first year of age in the more severe infantile forms. Currently available treatments have significant limitations and are not curative, highlighting a need for the development of alternative therapies. In this study, we investigated the use of a clinically relevant lentiviral vector to deliver systemically GAA through genetic modification of hematopoietic stem and progenitor cells (HSPCs). The overexpression of GAA in human HSPCs did not exert any toxic effect on this cell population, which conserved its stem cell capacity in xenograft experiments. In a murine model of Pompe disease treated at young age, we observed phenotypic correction of heart and muscle function with a significant reduction of glycogen accumulation in tissues after 6 months of treatment. These findings suggest that lentiviral-mediated HSPC gene therapy can be a safe alternative therapy for Pompe disease.

Pompe disease is caused by the deficiency of lysosomal acid α-glucosidase (GAA) leading to progressive myopathy. Enzyme replacement therapy (ERT) with recombinant human (rh) GAA has limitations, including inefficient uptake of rhGAA in skeletal muscle linked to low cation-independent mannose-6-phosphate receptor (CI-MPR) expression. To test the hypothesis that antihypertensive agents causing muscle hypertrophy by increasing insulin-like growth factor 1 expression can increase CI-MPR-mediated uptake of recombinant enzyme with therapeutic effects in skeletal muscle. Three such agents were evaluated in mice with Pompe disease (carvedilol, losartan, and propranolol), either with or without concurrent ERT. Carvedilol, a selective β-blocker, increased muscle strength but reduced biochemical correction from ERT. Administration of drugs alone had minimal effect, with the exception of losartan that increased glycogen storage and mortality either by itself or in combination with ERT. The β-blocker carvedilol had beneficial effects during ERT in mice with Pompe disease, in comparison with propranolol or losartan. Caution is warranted when prescribing antihypertensive drugs in Pompe disease. [ABSTRACT FROM AUTHOR]

A major obstacle to enzyme replacement therapy (ERT) with recombinant human acid-α-glucosidase (rhGAA) for Pompe disease is the development of high titers of anti-rhGAA antibodies in a subset of patients, which often leads to a loss of treatment efficacy. In an effort to induce sustained immune tolerance to rhGAA, we supplemented the rhGAA therapy with a weekly intravenous injection of synthetic vaccine particles carrying rapamycin (SVP-Rapa) during the first 3 weeks of a 12-week course of ERT in GAA-KO mice, and compared this with three intraperitoneal injections of methotrexate (MTX) per week for the first 3 weeks. Empty nanoparticles (NP) were used as negative control for SVP-Rapa. Co-administration of SVP-Rapa with rhGAA resulted in more durable inhibition of anti-rhGAA antibody responses, higher efficacy in glycogen clearance in skeletal muscles, and greater improvement of motor function than mice treated with empty NP or MTX. Body weight loss was observed during the MTX-treatment but not SVP-Rapa-treatment. Our data suggest that co-administration of SVP-Rapa may be an innovative and safe strategy to induce durable immune tolerance to rhGAA during the ERT in patients with Pompe disease, leading to improved clinical outcomes.

Cross-reactive immunological material (CRIM) status is an important prognostic factor in patients with infantile Pompe disease (IPD) being treated with enzyme replacement therapy. Western blot analysis of cultured skin fibroblast lysates has been the gold standard for determining CRIM status. Here, we evaluated CRIM status using peripheral blood mononuclear cell (PBMC) protein. For 6 of 33 patients (18%) CRIM status determination using PBMC was either indeterminate or discordant with GAA genotype or fibroblast CRIM analysis results. While the use of PBMCs for CRIM determination has the advantage of a faster turnaround time, further evaluation is needed to ensure the accuracy of CRIM results.

Abstract Background Cardiac failure is the main cause of death in untreated classic infantile Pompe disease, an inheritable metabolic myopathy characterized by progressive hypertrophic cardiomyopathy. Since the introduction of enzyme replacement therapy (ERT), survival has increased significantly due to reduced cardiac hypertrophy and improved cardiac function. However, little is known about ERT's long-term effects on the heart. Methods Fourteen patients were included in this prospective study. Cardiac dimensions, function, conduction and rhythm disturbances were evaluated at baseline and at regular intervals thereafter. Results Treatment duration ranged from 1.1 to 13.9 years (median 4.8 years). At baseline, all patients had increased left ventricular mass index (LVMI) (median LVMI 226 g/m2, range 98 to 599 g/m2, Z-score median 7, range 2.4–12.4). During the first four weeks, LVMI continued to increase in six patients. Normalization of LVMI was observed in 13 patients (median 30 weeks; range 3 to 660 weeks). After clinical deterioration, LVMI increased again slightly in one patient. At baseline, PR interval was shortened in all patients; it normalized in only three. A delta-wave pattern on ECG was seen in six patients and resulted in documented periods of supraventricular tachycardias (SVTs) in three patients, two of whom required medication and/or ablation. One patient had severe bradycardia (35 beats/min). Conclusion This study shows that ERT significantly reduced LVMI, and sustained this effect over a period of 13.9 years. The risk for rhythm disturbances remains. Regular cardiac evaluations should be continued, also after initially good response to ERT. Highlights • ERT significantly reduced cardiac hypertrophy in classic infantile Pompe patients. • This significant improvement of LVMI is sustained over 14 years. • After start of treatment LVMI may initially increase, before starting to decline. • The risk for rhythm disturbances remains and warrants follow-up. [ABSTRACT FROM AUTHOR]

Myozyme is a recombinant human acid alpha-glucosidase (rhGAA) that is currently the only drug approved for treating Pompe disease, and its low efficacy means that a high dose is required. Mannose-6-phosphate (M6P) glycosylation on rhGAA is a key factor influencing lysosomal enzyme targeting and the efficacy of enzyme replacement therapy (ERT); however, its complex structure and relatively small quantity still remain to be characterized. This study investigated M6P glycosylation on rhGAA using liquid chromatography (LC)–electrospray ionization (ESI)–high-energy collisional dissociation (HCD) tandem mass spectrometry (MS/MS). The glycans released from rhGAA were labeled with procainamide to improve mass ionization efficiency and the sensitivity of MS/MS. The relative quantities (%) of 78 glycans were obtained, and 1.0% of them were glycans containing M6P (M6P glycans). These were categorized according to their structure into 4 types: 3 newly found ones, comprising high-mannose-type M6P glycans capped with N -acetylglucosamine (GlcNAc) (2 variants, 17.5%), hybrid-type M6P glycans (2 variants, 11.2%), and hybrid-type M6P glycans capped with GlcNAc (3 variants, 6.9%), as well as high-mannose-type M6P glycans (3 variants, 64.4%). HCD-MS/MS spectra identified six distinctive M6P-derived oxonium ions. The glycopeptides obtained from protease-digested rhGAA were analyzed using nano-LC-ESI-HCD-MS/MS, and the extracted-ion chromatograms of M6P-derived oxonium ions confirmed three M6P glycosylation sites comprising Asn 140, Asn 233 (newly found), and Asn 470 attached heterogeneously to nine M6P glycans (two types), eight M6P glycans (four types), and seven M6P glycans (two types), respectively. This is the first study of rhGAA to differentiate M6P glycans and identify their attachment sites, despite rhGAA already being an approved drug for Pompe disease. [ABSTRACT FROM AUTHOR]

Background Pompe disease is caused by a deficiency of acid alpha-glucosidase. Its prevalence varies depending on ethnicity, and is less prevalent in Japan as compared with other countries. Because of the wide spectrum of clinical features in late-onset cases, some patients might be misdiagnosed with another myopathy, thus the actual prevalence in Japan might not be accurately reported. Aim To clarify the actual prevalence of late-onset Pompe disease, we investigated acid alpha-glucosidase activity in patients with undiagnosed myopathies. Methods Of 42 patients with undiagnosed myopathies, 41 underwent assessment of acid alpha-glucosidase enzyme activity using dried blood spot analysis. As a second step, reassessment of acid alpha-glucosidase activity was carried out using cultured skin fibroblasts. We also determined acid alpha-glucosidase activity in biopsied muscle tissue obtained from the one other patient, who had previously undergone a muscle biopsy. Finally, gene analysis was carried out to confirm diagnosis. Results Four patients showed reduced acid alpha-glucosidase activity in dried blood spot findings, of whom one possessed a pseudo-deficiency allele. Furthermore, one patient who showed reduced acid alpha-glucosidase activity in a biopsied muscle specimen was diagnosed with late-onset Pompe disease based on gene analysis. Conclusions Of the present 42 patients, only one patient was diagnosed with late-onset Pompe disease. The prevalence of Pompe disease in Japan does not seem to be as high as in other countries, though a certain number of patients might exist among those with undiagnosed myopathies. A larger and more systematic survey is necessary to elucidate the actual prevalence of late-onset Pompe disease in Japan. [ABSTRACT FROM AUTHOR]

The Lantern Project is an ongoing complimentary diagnostic program for patients in the United States sponsored by Sanofi and implemented by PerkinElmer Genomics. It combines specific enzymatic, biomarker, and genetic testing to facilitate rapid, accurate laboratory diagnosis of Pompe disease and several other lysosomal storage diseases, and a multigene next-generation sequencing panel including Pompe disease, LGMD, and other neuromuscular disorders. This article reports data for Pompe disease collected from October 2018 through December 2021, including acid α-glucosidase (GAA) enzyme assay and GAA sequencing (standard or expedited for positive newborn screening [NBS] to rule out infantile-onset Pompe disease [IOPD]) and the Focused Neuromuscular Panel, which includes GAA. One hundred forty patients (12 received only GAA enzyme testing, 128 had GAA sequencing alone or in addition to enzyme assay) have been confirmed with Pompe disease in this project. Eight of the 140 had a variant of unknown significance, but GAA activity ≤2.10 μmol/L/h, thus were confirmed with Pompe disease. Three diagnosed patients 0–2 years old had cross-reactive immunologic material (CRIM)-negative GAA variants and thus IOPD. One additional infant with presumptive IOPD had a homozygous frameshift c.1846del, likely CRIM-negative; symptoms were not provided. Among the 128 patients with molecular results, the c.-32-13T>G splice variant was homozygous in 11, compound-heterozygous in 98, and absent in 19. Proximal muscle weakness (58 patients) was the most common sign reported at testing; elevated creatine kinase (29 patients) was the most common laboratory result. The most common symptom categories were muscular (73 patients), musculoskeletal (13 patients), and respiratory (23 patients). Clinical information was not available for 42 samples, and 17 infants had only "abnormal NBS" or "low GAA" reported. Cardiac symptoms in 7 included potentially age-related conditions in five c.-32-13T>G-compound-heterozygous adults (myocardial infarction, heart murmur/palpitations, congestive heart failure: 1 each; 2 with atrial fibrillation) and hypertrophic cardiomyopathy in 2 children (1 and 2 years old) with presumptive IOPD. One novel GAA variant was observed in a patient with enzyme activity 0.31 μmol/L/h: c.1853_1854ins49, a frameshift pathogenic variant. The Lantern Project demonstrates the combinatorial utility of enzyme assay, targeted single-gene testing, and a focused neuromuscular next-generation sequencing panel in diagnosing Pompe disease. • Lantern Project provides enzyme, molecular, and NGS panel options for Pompe disease. • In 2018–21, 6473 panel tests and 1339 targeted tests have been conducted. • 140 patients received a laboratory diagnosis of Pompe disease. • Enzyme activity informed several VUS alleles; one novel frameshift allele reported. • One patient each had an DMD or ANO5 variant along with GAA pathogenic/VUS alleles. [ABSTRACT FROM AUTHOR]

Pompe disease is a metabolic myopathy, due to deficiency of alpha glucosidase, with a wide clinical spectrum. Enzyme replacement therapy is the only available treatment to improve morbidity and mortality, especially in infantile-onset form. However, some patients experience infusion-associated reactions, which may restrict their access to this treatment. We report on two patients (respectively 12 and 3 months old) with infantile-onset Pompe disease and severe cardiomyopathy, that presented with severe reactions during infusion of enzyme replacement therapy and were successfully desensitized with a new individualized protocol. Our protocol, using microdilution and a premedication with antihistamines, corticosteroids, and tranexamic acid, seems safe and effective and it may allow the continuation of therapy in Pompe patients resulting in the reduction of morbidity and mortality related to this disease. [ABSTRACT FROM AUTHOR]

Objective PRKAG2 syndrome, an autosomal dominant disorder, is characterized by severe infantile hypertrophic cardiomyopathy and heart rhythm disturbances to cases with a later presentation and a spectrum of manifestations including cardiac manifestations, myopathy and seizures. The cardiac features of PRKAG2 resemble the cardiac manifestations of Pompe disease. We present a patient who was initially diagnosed with Pompe disease and treated with alglucosidase-alfa enzyme replacement therapy (ERT); however, he was eventually diagnosed to carrying a PRKAG2 pathogenic gene mutation; he did not have Pompe disease instead he was a carrier for the common adult leaky splice site mutation in the GAA gene. Case report At 2.5 months, the patient had hypotonia/generalized muscle weakness, a diagnosis of non-classic infantile Pompe disease was made based on low acid alpha-glucosidase activity and the patient started on ERT at 11 months. However, 1 month later, the patient began to have seizures. As the patient's medical history was somewhat unusual for infantile Pompe disease, further evaluation was initiated and included a glycogen storage disease sequencing panel which showed that the patient had a pathogenic mutation in PRKAG2 which had been reported previously. ERT was discontinued and patient had a progression of motor deficits. ERT was reinitiated by the treating physician, and a clinical benefit was noted. Conclusion This report outlines the benefits of ERT with alglucosidase alfa in a patient with PRKAG2 syndrome, the decline in his condition when the ERT infusions were discontinued, and the significant positive response when ERT was reinitiated. [ABSTRACT FROM AUTHOR]

Pompe disease is a rare autosomal recessive hereditary disease caused by genetic defects of acid maltase. This disease could be divided into two forms: infantile and late-onset, which mainly affect cardiac, respiratory, and skeletal muscle systems. Late-onset patients mainly show symptoms of skeletal muscle involvement, but recent reports have found that the central nervous system was also affected in some patients. Herein, we report a case of a female, adolescent-onset Pompe patient, who was diagnosed with complicated intracranial aneurysm in adulthood. [ABSTRACT FROM AUTHOR]

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Antibodies formed against the therapeutic protein are a life-threatening complication that arises during enzyme replacement therapy for Pompe disease (acid α-glucosidase deficiency; GAA). To provide an effective alternative to current practices, we investigated the capacity of anti-B-cell activating factor (BAFF) as a novel drug candidate to prevent antibody formation in a Pompe disease mouse model. A BAFF-neutralizing antibody was administered prophylactically and with maintenance doses in association with enzyme replacement therapy using recombinant human GAA in Gaa −/− mice. BAFF blockade delayed antibody production and increased GAA activity within tissues with protection from anaphylaxis. Anti-BAFF also resolved antibody formation during an immune response and precluded the maturation of antibody secreting cells from entering the bone marrow compartment. This treatment modality may therefore be a viable alternative for the clinical management of antibody formation for Pompe disease and has potential use against antibody formation in other protein replacement therapies. [ABSTRACT FROM AUTHOR]

Background: Mutations in the acid alpha-glucosidase (GAA) gene usually lead to reduced GAA activity. In this study, we analyzed the mutations of GAA and GAA enzyme activity from one sibling suspected Pompe disease and their first-degree relatives. Materials and Methods: In this cross-sectional study, GAA enzyme activity assay was assessed using tandem mass spectrometry. Polymerase chain reaction and Sanger sequencing were performed for GAA analysis. Results: GAA enzyme activity was significantly decreased in patients compared to the normal range (P = 0.02). Two individuals showed ten alterations in the GAA sequence, in which one of them (c. 1650del G) has not been previously described in the literature. A single Guanine deletion (del-G) was detected at codon 551 in exon 12. Conclusion: According to the literature, the detected change is a novel mutation. We hypothesized that the discovered deletion in the GAA might lead to a reduced activity of the gene product.

Background: Mutations in the acid alpha-glucosidase (GAA) gene usually lead to reduced GAA activity. In this study, we analyzed the mutations of GAA and GAA enzyme activity from one sibling suspected Pompe disease and their first-degree relatives. Materials and Methods: In this cross-sectional study, GAA enzyme activity assay was assessed using tandem mass spectrometry. Polymerase chain reaction and Sanger sequencing were performed for GAA analysis. Results: GAA enzyme activity was significantly decreased in patients compared to the normal range (P = 0.02). Two individuals showed ten alterations in the GAA sequence, in which one of them (c. 1650del G) has not been previously described in the literature. A single Guanine deletion (del-G) was detected at codon 551 in exon 12. Conclusion: According to the literature, the detected change is a novel mutation. We hypothesized that the discovered deletion in the GAA might lead to a reduced activity of the gene product. [ABSTRACT FROM AUTHOR]

Pompe disease is a lysosomal storage disorder associated with systemic deficiency of acid α-glucosidase (GAA). Respiratory-related problems in Pompe disease include hypoventilation and upper airway dysfunction. Although these problems have generally been attributed to muscular pathology, recent work has highlighted the potential role of central nervous system (CNS) neuropathology in Pompe motor deficiencies. We used a murine model of Pompe disease to test the hypothesis that systemic GAA deficiency is associated with hypoglossal (XII) motoneuron pathology and altered XII motor output during breathing. Brainstem tissue was harvested from adult Gaa-/- mice and the periodic acid Schiff (PAS) method was used to examine neuronal glycogen accumulation. Semi-thin (2 µm) plastic sections showed widespread medullary neuropathology with extensive cytoplasmic glycogen accumulation in XII motoneuron soma. We next recorded efferent XII bursting in anesthetized and ventilated Gaa-/- and B6/129 mice both before and after bilateral vagotomy. The coefficient of variation of respiratory cycle duration was greater in Gaa-/- compared to B6/129 mice (P < 0.01). Vagotomy caused a robust increase in XII inspiratory burst amplitude in B6/129 mice (239 ± 44 %baseline; P < 0.01) but had little impact on burst amplitude in Gaa-/- mice (130 ± 23 %baseline; P > 0.05). We conclude that CNS GAA deficiency results in substantial glycogen accumulation in XII motoneuron cell bodies and altered XII motor output. Therapeutic strategies targeting the CNS may be required to fully correct respiratory-related deficits in Pompe disease.

A recently proposed therapeutic approach for lysosomal storage disorders (LSDs) relies upon the ability of transcription factor EB (TFEB) to stimulate autophagy and induce lysosomal exocytosis leading to cellular clearance. This approach is particularly attractive in glycogen storage disease type II [a severe metabolic myopathy, Pompe disease (PD)] as the currently available therapy, replacement of the missing enzyme acid alpha-glucosidase, fails to reverse skeletal muscle pathology. PD, a paradigm for LSDs, is characterized by both lysosomal abnormality and dysfunctional autophagy. Here, we show that TFEB is a viable therapeutic target in PD: overexpression of TFEB in a new muscle cell culture system and in mouse models of the disease reduced glycogen load and lysosomal size, improved autophagosome processing, and alleviated excessive accumulation of autophagic vacuoles. Unexpectedly, the exocytosed vesicles were labelled with lysosomal and autophagosomal membrane markers, suggesting that TFEB induces exocytosis of autophagolysosomes. Furthermore, the effects of TFEB were almost abrogated in the setting of genetically suppressed autophagy, supporting the role of autophagy in TFEB-mediated cellular clearance. [ABSTRACT FROM AUTHOR]

Introduction: Pompe disease is an autosomal recessive disorder caused by a deficiency of acid-α-glucosidase (GAA), an enzyme responsible for hydrolyzing lysosomal glycogen. A lack of GAA leads to accumulation of glycogen in the lysosomes of cardiac, skeletal, and smooth muscle cells, as well as in the central and peripheral nervous system. Enzyme replacement therapy has been the standard of care for 15 years and slows disease progression, particularly in the heart, and improves survival. However, there are limitations of ERT success, which gene therapy can overcome., Areas Covered: Gene therapy offers several advantages including prolonged and consistent GAA expression and correction of skeletal muscle as well as the critical CNS pathology. We provide a systematic review of the preclinical and clinical outcomes of adeno-associated viral mediated gene therapy and alternative gene therapy strategies, highlighting what has been successful., Expert Opinion: Although the preclinical and clinical studies so far have been promising, barriers exist that need to be addressed in gene therapy for Pompe disease. New strategies including novel capsids for better targeting, optimized DNA vectors, and adjuctive therapies will allow for a lower dose, and ameliorate the immune response.

Abstract: Enzyme replacement therapy (ERT) with recombinant human acid α-glucosidase (rhGAA) has improved clinical outcomes in patients with Pompe disease; however, the response of skeletal muscle and the central nervous system to ERT has been attenuated. The poor response of skeletal muscle to ERT has been attributed to the low abundance of the cation-independent mannose-6-phosphate receptor (CI-MPR), which mediates receptor-mediated uptake of rhGAA. Hence the ability of adjunctive therapy with β2-agonists to increase CI-MPR expression in skeletal muscle was evaluated during ERT in murine Pompe disease with regard to reversal of neuromuscular involvement. Mice with Pompe disease were treated with weekly rhGAA injections (20mg/kg) and a selective β2-agonist, either albuterol (30mg/l in drinking water) or low-dose clenbuterol (6mg/l in drinking water). Biochemical correction was enhanced by β2-agonist treatment in both muscle and the cerebellum, indicating that adjunctive therapy could enhance efficacy from ERT in Pompe disease with regard to neuromuscular involvement. Intriguingly, clenbuterol slightly reduced muscle glycogen content independent of CI-MPR expression, as demonstrated in CI-MPR knockout/GAA knockout mice that were otherwise resistant to ERT. Thus, adjunctive therapy with β2 agonists might improve the efficacy of ERT in Pompe disease and possibly other lysosomal storage disorders through enhancing receptor-mediated uptake of recombinant lysosomal enzymes. [Copyright &y& Elsevier]

Abstract: Pompe disease is caused by a deficiency of acid alpha-glucosidase (GAA) that results in glycogen accumulation, primarily in muscle. Newborn screening (NBS) for Pompe disease has been initiated in Taiwan and is reportedly successful. However, the comparatively high frequency of pseudodeficiency allele makes NBS for Pompe disease complicated in Taiwan. To investigate the feasibility of NBS for Pompe disease in Japan, we obtained dried blood spots (DBSs) from 496 healthy Japanese controls, 29 Japanese patients with Pompe disease, and five obligate carriers, and assayed GAA activity under the following conditions: (1) total GAA measured at pH 3.8, (2) GAA measured at pH 3.8 in the presence of acarbose, and (3) neutral glucosidase activity (NAG) measured at pH 7.0 without acarbose. The % inhibition and NAG/GAA ratio were calculated. For screening, samples with GAA<8% of the normal mean, % inhibition>60%, and NAG/GAA ratio>30 were considered to be positive. Two false positive cases (0.3%) were found, one was a healthy homozygote of pseudodeficiency allele (c.1726G>A). The low false-positive rate suggests that NBS for Pompe disease is feasible in Japan. [Copyright &y& Elsevier]

Abstract: Enzyme replacement therapy (ERT) with acid α-glucosidase has become available for Pompe disease; however, the response of skeletal muscle, as opposed to the heart, has been attenuated. The poor response of skeletal muscle has been attributed to the low abundance of the cation-independent mannose-6-phosphate receptor (CI-MPR) in skeletal muscle compared to heart. To further understand the role of CI-MPR in Pompe disease, muscle-specific CI-MPR conditional knockout (KO) mice were crossed with GAA-KO (Pompe disease) mice. We evaluated the impact of CI-MPR-mediated uptake of GAA by evaluating ERT in CI-MPR-KO/GAA-KO (double KO) mice. The essential role of CI-MPR was emphasized by the lack of efficacy of ERT as demonstrated by markedly reduced biochemical correction of GAA deficiency and of glycogen accumulations in double KO mice, in comparison with the administration of the same therapeutic doses in GAA-KO mice. Clenbuterol, a selective β2-agonist, enhanced the CI-MPR expression in skeletal tissue and also increased efficacy from GAA therapy, thereby confirming the key role of CI-MPR with regard to enzyme replacement therapy in Pompe disease. Biochemical correction improved in both muscle and non-muscle tissues, indicating that therapy could be similarly enhanced in other lysosomal storage disorders. In summary, enhanced CI-MPR expression might improve the efficacy of enzyme replacement therapy in Pompe disease through enhancing receptor-mediated uptake of GAA. [Copyright &y& Elsevier]