Cardiac evaluation in children and adults with Pompe disease sharing the common c.−32-13T>G genotype rarely reveals abnormalities

Pompe disease ascertained through The Lantern Project, 2018-2021: Next-generation sequencing and enzymatic testing to overcome obstacles to diagnosis

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.

Early clinical phenotype of late onset Pompe disease: Lessons learned from newborn screening

PURPOSE

Thoroughly phenotype children with late-onset Pompe disease (LOPD) diagnosed via newborn screening (NBS) to provide guidance for long-term follow up.

METHODS

Twenty infants ages 6-21 months with LOPD diagnosed by NBS underwent systematic clinical evaluation at Duke University including cardiac imaging, biomarker testing, physical therapy evaluation, and speech-language pathology evaluation.

RESULTS

Of the 20 infants, four were homozygous for the "late-onset" IVS1 splice site variant c.-32-13 T > G, fourteen were compound heterozygous, and two did not have any copies of this variant. None of the patients had evidence of cardiomyopathy or cardiac rhythm disturbances. Biomarker testing showed an increase in CK, AST, and ALT in 8 patients (40%) and increase in Glc4 in two patients (10%). All patients demonstrated postural and kinematic concerns. Three patients (17%) scored below the 10%ile on the Alberta Infant Motor Scale (AIMS) and 15 patients (83%) scored above the 10%ile. Speech-language pathology assessments were normal in all patients and mild feeding/swallowing abnormalities were noted in nine patients (45%).

CONCLUSION

Our data show high variability among children with LOPD diagnosed via NBS. Careful physical therapy evaluation is necessary to monitor for subtle musculoskeletal signs that may reflect early muscle involvement. Patients should be monitored closely for symptom progression.

Cardiac responses in paediatric Pompe disease in the ADVANCE patient cohort

Pompe disease results from lysosomal acid α-glucosidase deficiency, which leads to cardiomyopathy in all infantile-onset and occasional late-onset patients. Cardiac assessment is important for its diagnosis and management. This article presents unpublished cardiac findings, concomitant medications, and cardiac efficacy and safety outcomes from the ADVANCE study; trajectories of patients with abnormal left ventricular mass z score at enrolment; and post hoc analyses of on-treatment left ventricular mass and systolic blood pressure z scores by disease phenotype, GAA genotype, and "fraction of life" (defined as the fraction of life on pre-study 160 L production-scale alglucosidase alfa). ADVANCE evaluated 52 weeks' treatment with 4000 L production-scale alglucosidase alfa in ≥1-year-old United States of America patients with Pompe disease previously receiving 160 L production-scale alglucosidase alfa. M-mode echocardiography and 12-lead electrocardiography were performed at enrolment and Week 52. Sixty-seven patients had complete left ventricular mass z scores, decreasing at Week 52 (infantile-onset patients, change -0.8 ± 1.83; 95% confidence interval -1.3 to -0.2; all patients, change -0.5 ± 1.71; 95% confidence interval -1.0 to -0.1). Patients with "fraction of life" <0.79 had left ventricular mass z score decreasing (enrolment: +0.1 ± 3.0; Week 52: -1.1 ± 2.0); those with "fraction of life" ≥0.79 remained stable (enrolment: -0.9 ± 1.5; Week 52: -0.9 ± 1.4). Systolic blood pressure z scores were stable from enrolment to Week 52, and no cohort developed systemic hypertension. Eight patients had Wolff-Parkinson-White syndrome. Cardiac hypertrophy and dysrhythmia in ADVANCE patients at or before enrolment were typical of Pompe disease. Four-thousand L alglucosidase alfa therapy maintained fractional shortening, left ventricular posterior and septal end-diastolic thicknesses, and improved left ventricular mass z score.Trial registry: ClinicalTrials.gov Identifier: NCT01526785 https://clinicaltrials.gov/ct2/show/NCT01526785.Social Media Statement: Post hoc analyses of the ADVANCE study cohort of 113 children support ongoing cardiac monitoring and concomitant management of children with Pompe disease on long-term alglucosidase alfa to functionally improve cardiomyopathy and/or dysrhythmia.

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.

Cardiovascular disease in non-classic Pompe disease: A systematic review

Pompe disease is a rare inherited metabolic and neuromuscular disorder, presenting as a spectrum, with the classic infantile form on one end and the more slowly progressive non-classic form on the other end. While being a hallmark in classic infantile Pompe disease, cardiac involvement in non-classic Pompe disease seems rare. Vascular abnormalities, such as aneurysms and arterial dolichoectasia, likely caused by glycogen accumulation in arterial walls, have been reported in non-classic Pompe patients. With this first systematic review on cardiovascular disease in non-classic Pompe disease, we aim to gain insight in the prevalence and etiology of cardiovascular disease in these patients. Forty-eight studies (eight case-control studies, 15 cohort studies and 25 case reports/series) were included. Fourteen studies reported cardiac findings, 25 studies described vascular findings, and nine studies reported both cardiac and vascular findings. Severe cardiac involvement in non-classic Pompe disease patients has rarely been reported, particularly in adult-onset patients carrying the common IVS1 mutation. There are indications that intracranial dolichoectasia and aneurysms are more prevalent in non-classic Pompe patients compared to the general population. To further investigate the prevalence of cardiovascular disease in non-classic Pompe patients, larger case-control studies that also study established cardiovascular risk factors should be conducted.

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.

Severe Cardiac Involvement Is Rare in Patients with Late-Onset Pompe Disease and the Common c.-32-13T>G Variant: Implications for Newborn Screening

Based on a review of a large patient cohort, published literature, and 3 newborn screening cohorts, we concluded that children diagnosed through newborn screening with late-onset Pompe disease and the common heterozygous c.-32-13T>G variant require frequent cardiac follow-up with electrocardiography for arrhythmias. However, there is limited evidence for performing repeated echocardiography for cardiomyopathy.

Perioperative management of children with glycogen storage disease type II-Pompe disease

BACKGROUND

Pompe disease is a rare metabolic disorder caused by a deficiency of the lysosomal enzyme acid α-glucosidase. Glycogen accumulation damages skeletal, cardiac, and smooth muscles, causing a progressive and debilitating muscle weakness and cardiomyopathy. As life expectancy has much improved since the introduction of enzyme replacement therapy an increasing number of patients are referred for surgical procedures. Due to the potential cardiopulmonary complications, these patients form a high-risk group for the anesthesiologist.

AIMS

In this study, we investigated the incidence of perioperative complications in children with Pompe disease treated in our hospital since the introduction of enzyme replacement therapy.

METHODS

Anesthetic and perioperative data of children with Pompe disease treated between 1999 and 2015 in the Erasmus MC-Sophia Children's Hospital, University Medical Centre, Rotterdam, The Netherlands, were collected, retrospectively.

RESULTS

Of the 65 children with Pompe disease, 34 patients underwent in total 77, mostly low-risk, surgical procedures. Twenty-one children had the classic infantile form and 13 had a nonclassic presentation of Pompe disease. In 13 (16.8%) procedures, 1 or more perioperative complications occurred. Perioperative desaturation was the main complication (12.9%), followed by arrhythmia (3.8%) and heart failure requiring diuretic treatment (2.6%). One child died 2 days postoperatively, but this was considered unrelated to the procedure.

CONCLUSION

Despite the potentially high anesthetic risk for children with Pompe disease under enzyme replacement therapy, the incidence of perioperative complications in our study was relatively low. Our data suggest that with proper precautionary measures and a critical choice of timing of the operation, general anesthesia in children with Pompe disease could be relatively safe nowadays.

GAA Deficiency in Pompe Disease Is Alleviated by Exon Inclusion in iPSC-Derived Skeletal Muscle Cells

Pompe disease is a metabolic myopathy caused by deficiency of the acid α-glucosidase (GAA) enzyme and results in progressive wasting of skeletal muscle cells. The c.-32-13T>G (IVS1) GAA variant promotes exon 2 skipping during pre-mRNA splicing and is the most common variant for the childhood/adult disease form. We previously identified antisense oligonucleotides (AONs) that promoted GAA exon 2 inclusion in patient-derived fibroblasts. It was unknown how these AONs would affect GAA splicing in skeletal muscle cells. To test this, we expanded induced pluripotent stem cell (iPSC)-derived myogenic progenitors and differentiated these to multinucleated myotubes. AONs restored splicing in myotubes to a similar extent as in fibroblasts, suggesting that they act by modulating the action of shared splicing regulators. AONs targeted the putative polypyrimidine tract of a cryptic splice acceptor site that was part of a pseudo exon in GAA intron 1. Blocking of the cryptic splice donor of the pseudo exon with AONs likewise promoted GAA exon 2 inclusion. The simultaneous blocking of the cryptic acceptor and cryptic donor sites restored the majority of canonical splicing and alleviated GAA enzyme deficiency. These results highlight the relevance of cryptic splicing in human disease and its potential as therapeutic target for splicing modulation using AONs.

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.

Pattern and prognostic value of cardiac involvement in patients with late-onset pompe disease: a comprehensive cardiovascular magnetic resonance approach

BACKGROUND

Pompe disease is an autosomal recessive disorder caused by deficiency of the lysosomal α-1,4-glucosidase leading to accumulation of glycogen in target tissues with progressive organ failure. While the early infantile-onset form is characterized by early severe hypertrophic cardiomyopathy with cardiac and respiratory failure, clinically relevant cardiomyopathy seems to be uncommon in patients with late-onset Pompe disease, and the prevalence and nature of myocardial abnormalities are still to be clarified.

METHODS

Seventeen patients with genetically proven late-onset Pompe disease (50 ± 18 years, 11 male) and 18 age- and gender-matched healthy controls (44 ± 10 year, 12 male) underwent comprehensive cardiovascular magnetic resonance (CMR) including conventional and advanced techniques: cine and feature tracking-based strain imaging for depiction of (even subtle) systolic LV dysfunction as well as late gadolinium enhancement (LGE) and myocardial extracellular volume fraction (ECV) quantification for focal and diffuse fibrosis detection.

RESULTS

All patients had normal left ventricular (LV) and right ventricular (RV) volumes and normal LV and RV ejection fraction. In comparison to healthy controls, neither conventional cine nor advanced feature-tracking based-strain imaging could depict any (subclinical) myocardial systolic dysfunction. Three (18%) of the patients had non-ischemic LGE in the basal inferolateral wall and 21% demonstrated elevated global ECV values suggestive of interstitial myocardial fibrosis. Non-specific abnormalities such as left atrial (LA) dilatation were present in two patients, while LV hypertrophy was seen only in one. Two of the three LGE-positive patients were also hypertensive and demonstrated high global ECV values (>30%) in addition to dilated LA. After a median follow-up of 25 (11-29) months, only one cardiovascular event occurred: one of the LGE-positive patients with a high cardiovascular risk profile suffered an acute coronary syndrome.

CONCLUSION

In contrast to the early infantile-onset form of Pompe disease, mild and rather non-specific cardiac abnormalities can be detected by CMR only in a small proportion of patients with late-onset Pompe disease. The observed structural abnormalities seem to result from an interplay between the storage disease and other comorbidities and they did not affect short-term to mid-term prognosis in adult Pompe patients.

Prospective exploratory muscle biopsy, imaging, and functional assessment in patients with late-onset Pompe disease treated with alglucosidase alfa: The EMBASSY Study

BACKGROUND

Late-onset Pompe disease is characterized by progressive skeletal myopathy followed by respiratory muscle weakness, typically leading to loss of ambulation and respiratory failure. In this population, enzyme replacement therapy (ERT) with alglucosidase alfa has been shown to stabilize respiratory function and improve mobility and muscle strength. Muscle pathology and glycogen clearance from skeletal muscle in treatment-naïve adults after ERT have not been extensively examined.

METHODS

This exploratory, open-label, multicenter study evaluated glycogen clearance in muscle tissue samples collected pre- and post- alglucosidase alfa treatment in treatment-naïve adults with late-onset Pompe disease. The primary endpoint was the quantitative reduction in percent tissue area occupied by glycogen in muscle biopsies from baseline to 6months. Secondary endpoints included qualitative histologic assessment of tissue glycogen distribution, secondary pathology changes, assessment of magnetic resonance images (MRIs) for intact muscle and fatty replacement, and functional assessments.

RESULTS

Sixteen patients completed the study. After 6months of ERT, the percent tissue area occupied by glycogen in quadriceps and deltoid muscles decreased in 10 and 8 patients, respectively. No changes were detected on MRI from baseline to 6months. A majority of patients showed improvements on functional assessments after 6months of treatment. All treatment-related adverse events were mild or moderate.

CONCLUSIONS

This exploratory study provides novel insights into the histopathologic effects of ERT in late-onset Pompe disease patients. Ultrastructural examination of muscle biopsies demonstrated reduced lysosomal glycogen after ERT. Findings are consistent with stabilization of disease by ERT in treatment-naïve patients with late-onset Pompe disease.

Elevated Plasma Cardiac Troponin T Levels Caused by Skeletal Muscle Damage in Pompe Disease

Background—

Elevated plasma cardiac troponin T (cTnT) levels in patients with neuromuscular disorders may erroneously lead to the diagnosis of acute myocardial infarction or myocardial injury.

Methods and Results—

In 122 patients with Pompe disease, the relationship between cTnT, cardiac troponin I, creatine kinase (CK), CK-myocardial band levels, and skeletal muscle damage was assessed. ECG and echocardiography were used to evaluate possible cardiac disease. Patients were divided into classic infantile, childhood-onset, and adult-onset patients. cTnT levels were elevated in 82% of patients (median 27 ng/L, normal values <14 ng/L). Cardiac troponin I levels were normal in all patients, whereas CK-myocardial band levels were increased in 59% of patients. cTnT levels correlated with CK levels in all 3 subgroups ( P <0.001). None of the abnormal ECGs recorded in 21 patients were indicative of acute myocardial infarction, and there were no differences in cTnT levels between patients with and without (n=90) abnormalities on ECG (median 28 ng/L in both groups). The median left ventricular mass index measured with echocardiography was normal in all the 3 subgroups. cTnT mRNA expression in skeletal muscle was not detectable in controls but was strongly induced in patients with Pompe disease. cTnT protein was identified by mass spectrometry in patient-derived skeletal muscle tissue.

Conclusions—

Elevated plasma cTnT levels in patients with Pompe disease are associated with skeletal muscle damage, rather than acute myocardial injury. Increased cTnT levels in Pompe disease and likely other neuromuscular disorders should be interpreted with caution to avoid unnecessary cardiac interventions.

Small-fiber neuropathy in pompe disease: first reported cases and prospective screening of a clinic cohort

Case series

Patient: Male, 11 • Female, 49

Final Diagnosis: Small fiber neuropathy

Symptoms: —

Medication: —

Clinical Procedure: Skin biopsy

Specialty: Neurology

Methods of diagnosis of patients with Pompe disease: Data from the Pompe Registry

Pompe disease is a rare, autosomal recessive disorder characterized by deficiency of lysosomal acid alpha-glucosidase and accumulation of lysosomal glycogen in many tissues. The variable clinical manifestations, broad phenotypic spectrum, and overlap of signs and symptoms with other neuromuscular diseases make diagnosis challenging. In the past, the diagnosis of Pompe disease was based on enzyme activity assay in skin fibroblasts or muscle tissue. In 2004, methods for measuring acid alpha-glucosidase activity in blood were published. To compare how diagnostic methods changed over time and whether they differed by geographic region and clinical phenotype, we examined diagnostic methods used for 1059 patients enrolled in the Pompe Registry in three onset categories (Group A: onset of signs/symptoms ≤ 12 months of age with cardiomyopathy; Group B: onset ≤ 12 months without cardiomyopathy and onset >1 year to ≤ 12 years; Group C: onset >12 years). Enzyme activity-based assays were used more frequently than other diagnostic methods. Measuring acid alpha-glucosidase activity in blood (leukocytes, lymphocytes, or dried-blood spot) increased over time; use of muscle biopsy decreased. The increased use of blood-based assays for diagnosis may result in a more timely diagnosis in patients across the clinical spectrum of Pompe disease.

Clinical features and predictors for disease natural progression in adults with Pompe disease: a nationwide prospective observational study

Background

Due partly to physicians’ unawareness, many adults with Pompe disease are diagnosed with great delay. Besides, it is not well known which factors influence the rate of disease progression, and thus disease outcome. We delineated the specific clinical features of Pompe disease in adults, and mapped out the distribution and severity of muscle weakness, and the sequence of involvement of the individual muscle groups. Furthermore, we defined the natural disease course and identified prognostic factors for disease progression.

Methods

We conducted a single-center, prospective, observational study. Muscle strength (manual muscle testing, and hand-held dynamometry), muscle function (quick motor function test), and pulmonary function (forced vital capacity in sitting and supine positions) were assessed every 3–6 months and analyzed using repeated-measures ANOVA.

Results

Between October 2004 and August 2009, 94 patients aged between 25 and 75 years were included in the study. Although skeletal muscle weakness was typically distributed in a limb-girdle pattern, many patients had unfamiliar features such as ptosis (23%), bulbar weakness (28%), and scapular winging (33%). During follow-up (average 1.6 years, range 0.5-4.2 years), skeletal muscle strength deteriorated significantly (mean declines of −1.3% point/year for manual muscle testing and of −2.6% points/year for hand-held dynamometry; both p<0.001). Longer disease duration (>15 years) and pulmonary involvement (forced vital capacity in sitting position <80%) at study entry predicted faster decline. On average, forced vital capacity in supine position deteriorated by 1.3% points per year (p=0.02). Decline in pulmonary function was consistent across subgroups. Ten percent of patients declined unexpectedly fast.

Conclusions

Recognizing patterns of common and less familiar characteristics in adults with Pompe disease facilitates timely diagnosis. Longer disease duration and reduced pulmonary function stand out as predictors of rapid disease progression, and aid in deciding whether to initiate enzyme replacement therapy, or when.

Autopsy findings in late-onset Pompe disease: a case report and systematic review of the literature

BACKGROUND

Late-onset Pompe disease (LOPD) is a rare cause of declining proximal muscle strength and respiratory function that can also affect other organ systems. The development of enzyme replacement therapy has made it one of the few inherited muscle disorders with treatment, but clinical response is difficult to assess due to the variable and often slow progression of illness. A better understanding of the disease's systemic effects can be gleaned through autopsy findings.

PURPOSE

The purpose of this study was to: (1) describe the histological findings observed in LOPD, (2) provide correlations between reported histological and clinical findings, and (3) review the literature on autopsy findings in LOPD.

METHODS

Histological evaluation of autopsy tissues from a 62-year-old woman with LOPD was conducted. A clinical history was obtained by review of the medical records. The literature was reviewed for previously reported histological and clinical findings in LOPD. Based on this case report and information from prior publications, histological and clinical findings for the disease were correlated.

RESULTS

Histologic examination revealed mostly mild vacuolar myopathy typical of glycogen accumulation within skeletal and smooth muscle cells. The most prominent vacuolar myopathy was in quadriceps muscle, which also exhibited chronic myositis with degenerating and regenerating muscle fibers. Transmission electron microscopy disclosed lysosomal glycogen accumulation within skeletal, cardiac, and vascular smooth muscle cells, correlating with published case reports of basilar artery and ascending aortic aneurysms and carotid artery dissection. Organs containing smooth muscle cells (the bladder, intestine, and esophagus) were also affected, explaining reports of symptoms such as urinary incontinence and dysphagia. In addition to glycogen accumulation, there was obvious damage to the contraction apparatus of myofibrils within cardiac and skeletal muscle cells. These histological and ultrastructural findings correlate with the clinical manifestations of LOPD.

CONCLUSIONS

This study is the first to describe histological findings of LOPD utilizing both traditional paraffin-processed tissues and epoxy resin embedded tissues for high-resolution light microscopy. The findings are similar to those seen in previous studies, but with improved morphological detail and glycogen preservation. This patient exhibited histological involvement of multiple organs, correlating with the clinical features of LOPD. With the advent of definitive therapy for Pompe disease, it is important to be aware of these findings and use them to develop methods for tracking therapeutic response.

Cardiovascular abnormalities in late-onset Pompe disease and response to enzyme replacement therapy

PURPOSE

We evaluated the prevalence of cardiovascular abnormalities and the efficacy and safety of enzyme replacement therapy in patients with late-onset Pompe disease.

METHODS

Ninety patients were randomized 2:1 to enzyme replacement therapy or placebo in a double-blinded protocol. Electrocardiograms and echocardiograms were obtained at baseline and scheduled intervals during the 78-week study period. Baseline cardiovascular abnormalities, and efficacy and safety of enzyme replacement therapy were described. Three pediatric patients were excluded.

RESULTS

Eighty-seven patients were included. Median age was 44 years; 51% were men. At baseline, a short PR interval was present in 10%, 7% had decreased left ventricular systolic function, and 5% had elevated left ventricular mass on echocardiogram (all in mild range). There was no change in cardiovascular status associated with enzyme replacement therapy. No significant safety concerns related to enzyme replacement therapy were identified.

CONCLUSIONS

Although some patients with late-onset Pompe disease had abnormalities on baseline electrocardiogram or echocardiogram, those classically seen in infantile Pompe disease, such as significant ventricular hypertrophy, were not noted. Cardiovascular parameters were not impacted by enzyme replacement therapy, and there were no cardiovascular safety concerns. The cardiovascular abnormalities identified may be related to Pompe disease or other comorbid conditions.

Rate of progression and predictive factors for pulmonary outcome in children and adults with Pompe disease

Respiratory insufficiency is a serious threat to patients with Pompe disease, a neuromuscular disorder caused by lysosomal acid alpha-glucosidase deficiency. Innovative therapeutic options which may stabilize pulmonary function have recently become available. We therefore determined proportion and severity of pulmonary involvement in patients with Pompe disease, the rate of progression of pulmonary dysfunction, and predictive factors for poor respiratory outcome. In a single-center, prospective, cohort study, we measured vital capacity (VC) in sitting and supine positions, as well as maximum inspiratory (MIP) and expiratory (MEP) mouth pressures, and end expiratory CO(2) in 17 children and 75 adults with Pompe disease (mean age 42.7 years, range 5-76 years). Seventy-four percent of all patients, including 53% of the children, had some degree of respiratory dysfunction. Thirty-eight percent had obvious diaphragmatic weakness. Males appeared to have more severe pulmonary involvement than females: at a group level, their mean VC was significantly lower than that of females (p<0.001), they used mechanical ventilation more often than females (p=0.042) and the decline over the course of the disease was significantly different between males and females (p=0.003). Apart from male gender, severe skeletal muscle weakness and long disease duration were the most important predictors of poor respiratory status. During follow-up (average 1.6 years, range 0.5-4.2 years), three patients became ventilator dependent. Annually, there were average decreases in VC in upright position of 0.9% points (p=0.09), VC in supine position of 1.2% points (p=0.049), MIP of 3.2% points (p=0.018) and MEP of 3.8% points (p<0.01). We conclude that pulmonary dysfunction in Pompe disease is much more common than generally thought. Males, patients with severe muscle weakness, and those with advanced disease duration seem most at risk.