Arrhythmias in patients receiving enzyme replacement therapy for infantile Pompe disease

In Utero Enzyme-Replacement Therapy for Infantile-Onset Pompe's Disease

Patients with early-onset lysosomal storage diseases are ideal candidates for prenatal therapy because organ damage starts in utero. We report the safety and efficacy results of in utero enzyme-replacement therapy (ERT) in a fetus with CRIM (cross-reactive immunologic material)-negative infantile-onset Pompe's disease. The family history was positive for infantile-onset Pompe's disease with cardiomyopathy in two previously affected deceased siblings. After receiving in utero ERT and standard postnatal therapy, the current patient had normal cardiac and age-appropriate motor function postnatally, was meeting developmental milestones, had normal biomarker levels, and was feeding and growing well at 13 months of age.

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 This article presents unpublished cardiac findings, concomitant medications, and cardiac efficacy and safety outcomes from the ADVANCE study; trajectories of patients with abnormal left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.

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.

A Race Against Time-Changing the Natural History of CRIM Negative Infantile Pompe Disease

We report the clinical course of the first prenatally diagnosed cross-reactive immunologic material (CRIM)-negative infantile Pompe disease (IPD) patient [homozygous for c.2560C>T (p.Arg854X) variant in the GAA gene] to undergo prophylactic immune tolerance induction (ITI) and enzyme replacement therapy (ERT) within the first 2 days of life. Both parents were found to be carriers of the c.2560C>T (p.Arg854X) variant through prenatal carrier screening. Fetal echocardiogram at 31 weeks of gestation showed left ventricular hypertrophy. An echocardiogram on the 1st day of life revealed marked biventricular hypertrophy. Physical exam was significant for macroglossia and hypotonia. A short course of Prophylactic ITI with rituximab, methotrexate, and intravenous immunoglobulin (IVIG) in conjunction with ERT at a dose of 20 mg/kg every other week was started on day 2 of life. The patient completed the ITI protocol safely and complete B-cell recovery, based on CD19 count, was noted by 3 months of age. The patient never developed anti-rhGAA IgG antibodies to ERT. Vaccinations were initiated at 9 months of age, with adequate response noted. Complete recovery of cardiac function and left ventricular mass was seen by 11 weeks of age. At 8 months of age, the patient developmentally measured at 75–90% on the Alberta Infant Motor Scale, walked at 11 months and continues to develop age-appropriately at 50 months of age based on the Early Learning Accomplishment Profile. ERT dosing was increased to 40 mg/kg every 2 weeks at 32 months of age and frequency increased to 40 mg/kg every week at 47 months of age. Patient continues to have undetectable antibody titers, most recently at age 50 months and urine Hex4 has remained normal. To our knowledge, this is the first report of successful early ERT and ITI in a prenatally diagnosed CRIM-negative IPD patient and the youngest IPD patient to receive ITI safely. With the addition of Pompe disease to the Recommended Uniform Screening Panel(RUSP) and its addition to multiple state newborn screening programs, our case highlights the benefits of early diagnosis and timely initiation of treatment in babies with Pompe disease, who represent the most severe end of the disease spectrum.

Long-term outcome and unmet needs in infantile-onset Pompe disease

Infantile-onset Pompe disease (IOPD) is characterized by virtually complete absence of acid alpha-glucosidase (GAA)-activity, resulting in rapidly progressive hypertrophic cardiomyopathy (HCM), profound skeletal muscle weakness, and death usually within the first 12 months of life. Enzyme replacement therapy (ERT) with recombinant GAA in humans started in 1999, and pivotal studies demonstrated that the treatment ameliorated HCM, improved motor function in some patients, and prolonged overall and ventilator-free survival. These outcomes led to the approval of ERT in 2006. Implementation of ERT has uncovered multisystemic character of IOPD, not known in the pre-ERT era. Although ERT has substantially improved the prognosis of IOPD, mortality is still considerable, and decline of motor function with time is frequent in long-term survivors. This review details the new complex IOPD phenotype, outlines problems related to ERT, and highlights unmet needs.

Lysosomal storage disease overview

The lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate. This storage process leads to a broad spectrum of clinical manifestations depending on the specific substrate and site of accumulation. Examples of LSDs include the mucopolysaccharidoses, mucolipidoses, oligosaccharidoses, Pompe disease, Gaucher disease, Fabry disease, the Niemann-Pick disorders, and neuronal ceroid lipofuscinoses. This review summarizes the main clinical features, diagnosis, and management of LSDs with an emphasis on those for which treatment is available.

Lysosomal storage disease overview

The lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate. This storage process leads to a broad spectrum of clinical manifestations depending on the specific substrate and site of accumulation. Examples of LSDs include the mucopolysaccharidoses, mucolipidoses, oligosaccharidoses, Pompe disease, Gaucher disease, Fabry disease, the Niemann-Pick disorders, and neuronal ceroid lipofuscinoses. This review summarizes the main clinical features, diagnosis, and management of LSDs with an emphasis on those for which treatment is available.

Cardiac outcome in classic infantile Pompe disease after 13 years of treatment with recombinant human acid alpha-glucosidase

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.

Management of Confirmed Newborn-Screened Patients With Pompe Disease Across the Disease Spectrum

After a Pompe disease diagnosis is confirmed in infants identified through newborn screening (NBS), when and if to start treatment with enzyme replacement therapy (ERT) with alglucosidase alfa must be determined. In classic infantile-onset Pompe disease, ERT should start as soon as possible. Once started, regular, routine follow-up is necessary to monitor for treatment effects, disease progression, and adverse effects. Decision-making for when or if to start ERT in late-onset Pompe disease (LOPD) is more challenging because patients typically have no measurable signs or symptoms or predictable time of symptom onset at NBS. With LOPD, adequate, ongoing follow-up and assessments for onset or progression of signs and symptoms are important to track disease state and monitor and adjust care before and after treatment is started. Because numerous tests are used to monitor patients at variable frequencies, a standardized approach across centers is lacking. Significant variability in patient assessments may result in missed opportunities for early intervention. Management of Pompe disease requires a comprehensive, multidisciplinary approach with timely disease-specific interventions that target the underlying disease process and symptom-specific manifestations. Regardless of how identified, all patients who have signs or symptoms of the disease require coordinated medical care and follow-up tailored to individual needs throughout their lives. The Pompe Disease Newborn Screening Working Group identifies key considerations before starting and during ERT; summarizes what comprises an indication to start ERT; and provides guidance on how to determine appropriate patient management and monitoring and guide the frequency and type of follow-up assessments for all patients identified through NBS.

Postmortem Findings and Clinical Correlates in Individuals with Infantile-Onset Pompe Disease

Pompe disease (OMIM 232300), a glycogen storage disorder caused by deficiency in the lysosomal enzyme acid alpha-glucosidase (EC 3.2.1.20), results in weakness and cardiomyopathy in infants affected with the classic form. Although the primary disease manifestations are due to glycogen accumulation in skeletal and cardiac muscle, glycogen also accumulates in a variety of additional tissues. To improve our understanding of disease pathogenesis in long-term survivors, we reviewed postmortem results for three infants with the classic form of Pompe disease. We have observed a number of new complications in long-term survivors of infantile-onset Pompe disease, and we focused this postmortem study on pathological correlates. Findings in survivors include cardiac arrhythmias, which may be related to glycogen accumulation in cardiac conduction tissue; urinary incontinence, likely due to glycogen accumulation in smooth muscle; and refractory errors, possibly related to accumulation in ocular structures. These observations provide potential pathophysiologic correlates for complications in long-term survivors of infantile Pompe disease.

Resolution of severe cardiomyopathy in infantile Pompe disease

Infantile Pompe disease is a rare inborn error of metabolism characterized by severe hypertrophic cardiomyopathy and generalised hypotonia occurring in infancy. We present a case of an infant with severe hypertrophic cardiomyopathy that resolved after treatment with enzyme replacement therapy.

Pompe disease results in a Golgi-based glycosylation deficit in human induced pluripotent stem cell-derived cardiomyocytes

Infantile-onset Pompe disease is an autosomal recessive disorder caused by the complete loss of lysosomal glycogen-hydrolyzing enzyme acid α-glucosidase (GAA) activity, which results in lysosomal glycogen accumulation and prominent cardiac and skeletal muscle pathology. The mechanism by which loss of GAA activity causes cardiomyopathy is poorly understood. We reprogrammed fibroblasts from patients with infantile-onset Pompe disease to generate induced pluripotent stem (iPS) cells that were differentiated to cardiomyocytes (iPSC-CM). Pompe iPSC-CMs had undetectable GAA activity and pathognomonic glycogen-filled lysosomes. Nonetheless, Pompe and control iPSC-CMs exhibited comparable contractile properties in engineered cardiac tissue. Impaired autophagy has been implicated in Pompe skeletal muscle; however, control and Pompe iPSC-CMs had comparable clearance rates of LC3-II-detected autophagosomes. Unexpectedly, the lysosome-associated membrane proteins, LAMP1 and LAMP2, from Pompe iPSC-CMs demonstrated higher electrophoretic mobility compared with control iPSC-CMs. Brefeldin A induced disruption of the Golgi in control iPSC-CMs reproduced the higher mobility forms of the LAMPs, suggesting that Pompe iPSC-CMs produce LAMPs lacking appropriate glycosylation. Isoelectric focusing studies revealed that LAMP2 has a more alkaline pI in Pompe compared with control iPSC-CMs due largely to hyposialylation. MALDI-TOF-MS analysis of N-linked glycans demonstrated reduced diversity of multiantennary structures and the major presence of a trimannose complex glycan precursor in Pompe iPSC-CMs. These data suggest that Pompe cardiomyopathy has a glycan processing abnormality and thus shares features with hypertrophic cardiomyopathies observed in the congenital disorders of glycosylation.

The emerging phenotype of long-term survivors with infantile Pompe disease

PURPOSE

Enzyme replacement therapy with alglucosidase alfa for infantile Pompe disease has improved survival creating new management challenges. We describe an emerging phenotype in a retrospective review of long-term survivors.

METHODS

Inclusion criteria included ventilator-free status and age ≤6 months at treatment initiation, and survival to age ≥5 years. Clinical outcome measures included invasive ventilator-free survival and parameters for cardiac, pulmonary, musculoskeletal, gross motor, and ambulatory status; growth; speech, hearing, and swallowing; and gastrointestinal and nutritional status.

RESULTS

Eleven of 17 patients met study criteria. All were cross-reactive immunologic material-positive, alive, and invasive ventilator-free at most recent assessment, with a median age of 8.0 years (range: 5.4-12.0 years). All had marked improvements in cardiac parameters. Commonly present were gross motor weakness, motor speech deficits, sensorineural and/or conductive hearing loss, osteopenia, gastroesophageal reflux, and dysphagia with aspiration risk. Seven of 11 patients were independently ambulatory and four required the use of assistive ambulatory devices. All long-term survivors had low or undetectable anti-alglucosidase alfa antibody titers.

CONCLUSION

Long-term survivors exhibited sustained improvements in cardiac parameters and gross motor function. Residual muscle weakness, hearing loss, risk for arrhythmias, hypernasal speech, dysphagia with risk for aspiration, and osteopenia were commonly observed findings.

Infantile Pompe disease: clinical and genetic characteristics with an experience of enzyme replacement therapy

Pompe disease is an autosomal recessive disorder caused by lysosomal acid α-glucosidase deficiency. Infantile-onset Pompe disease presents with cardiomyopathy and hypotonia, leading to premature death. This article describes 7 infantile Pompe disease cases and provides their molecular bases and clinical outcomes after enzyme replacement therapy for the first time in Korea. Molecular genetic analyses revealed the presence of 9 different mutations, including 5 novel mutations (c.2171C>A, c.2774C>T, c.1582_3de12, c.1261_1263Tms, and c.1322_1326+9de114). The most common mutation in these 7 patients was c.1316T>A (28%). Four patients received intravenous recombinant human acid α-glucosidase therapy for 2 years, on average, without significant side effects during the treatment course. They all exhibited increased muscle power, with considerable improvement in cardiac function. Pompe disease is heterogeneous regarding both clinical features and molecular characteristics. Early identification of Pompe disease is very important, considering that enzyme replacement therapy is a safe and effective treatment for early-onset patients.

Cardiac Pathology in Glycogen Storage Disease Type III

PURPOSE

To investigate the distribution and clinical impact of glycogen accumulation on heart structure and function in individuals with GSD III.

METHODS

We examined cardiac tissue and the clinical records of three individuals with GSD IIIa who died or underwent cardiac transplantation. Of the two patients that died, one was from infection and the other was from sudden cardiac death. The third patient required cardiac transplantation for end-stage heart failure with severe hypertrophic cardiomyopathy.

RESULTS

Macro- and microscopic examination revealed cardiac fibrosis (n = 1), moderate to severe vacuolation of cardiac myocytes (n = 3), mild to severe glycogen accumulation in the atrioventricular (AV) node (n = 3), and glycogen accumulation in smooth muscle cells of intramyocardial arteries associated with smooth muscle hyperplasia and profoundly thickened vascular walls (n = 1).

CONCLUSION

Our findings document diffuse though variable involvement of cardiac structures in GSD III patients. Furthermore, our results also show a potential for serious arrhythmia and symptomatic heart failure in some GSD III patients, and this should be considered when managing this patient population.

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.

Atypical immunologic response in a patient with CRIM-negative Pompe disease

We report the clinical course of a patient with severe infantile onset Pompe disease [cross-reactive immunologic material (CRIM) negative, R854X/R854X] who was diagnosed prenatally and received standard dosing of alglucosidase alfa (Myozyme®) enzyme replacement therapy (ERT) from day 10 of life until she passed away at the age of 3 years 9 months. In the immediate neonatal period there was cardiomegaly on chest X-ray, cardiac hypertrophy by echocardiogram, and development of a wide complex tachycardia. CRIM negative (CN) status was suspected based on her family history, and the available data at the time indicated that CN patients had limited survival even with ERT. However, given the opportunity for very early treatment, the treating provider and family elected to initiate treatment with ERT, without immune modulation. By 9 months of age echocardiogram was normal. Early motor development was within normal limits but by 2 years of age her developmental progress had slowed. She seroconverted by the 4th month of ERT, and anti-rhGAA antibody titers peaked at 25,600 in the 27th month. Immunomodulatory therapy was considered but declined by family. She acquired Influenza A at 2 years 6 months, which led to a prolonged hospitalization with invasive respiratory support, and placement of tracheostomy and gastrostomy tube. Her developmental progress ceased, and she died suddenly at home from a presumed cardiac event at age 3 years 9 months. The poor outcomes observed in CN patients have been attributed to the development of high sustained antibody titers. Although this CN patient's anti-rhGAA response was elevated and sustained, it is unlike any of the 3 patterns that have been previously described: high titer CN, high titer CRIM positive (HTCP), and low titer CP (LTCP) patients. This patient's clinical course, with achievement of 24 months of motor gains, 30 months of ventilator-free survival and 45 month survival, is like that of only a fraction of ERT treated CN patients, yet it is identical to other reported CN patients in its relentless progression and early fatality. The immunologic response (moderate sustained antibody titers) described here has not been previously reported and may have played a role in the overall pattern of developmental decline. In light of proposed universal newborn screening for Pompe disease, there is an urgent need for improved understanding of the interplay between immunologic responses to the only available treatment, ERT, and the relentless nature of this disease in CN patients.

Use of cardiac magnetic resonance imaging to evaluate cardiac structure, function and fibrosis in children with infantile Pompe disease on enzyme replacement therapy

BACKGROUND

Pompe disease (acid α-glucosidase deficiency) is one of several lysosomal storage diseases amenable to treatment with enzyme replacement therapy (ERT). While echocardiography (echo) has been the standard method to evaluate the cardiac response to ERT, cardiac magnetic resonance imaging (CMR) has the advantage of a better tissue definition and characterization of myocardial fibrosis. However, CMR for Pompe disease is not frequently performed due to a high risk of sedation. We report the first use of CMR in a feasible protocol to quantify left ventricular (LV) mass, function, and the presence of myocardial fibrosis in the Pompe population.

METHODS

Children with Pompe disease on ERT were assessed with transthoracic echo and CMR over a 3 year period at a single institution. Echocardiography was performed using standard techniques without sedation. CMR was performed using retrospectively gated and real-time imaging, with and without sedation. LV mass indexed to body surface area (LVMI) and ejection fraction (EF) were measured by both echo and CMR, and evaluated for change over time. Myocardial fibrosis was assessed by CMR with delayed enhancement imaging 5-10 min after gadolinium contrast using single shot inversion recovery sequences with inversion time set to null the signal from normal myocardium.

RESULTS

Seventeen CMR scans were successfully performed in 10 subjects with Pompe disease (median age at first CMR is 9 months, range 1-38 months, 80% male), with sedation only performed in 4 studies. There was a median interval of 5 months (range 0-34 months) from the start of ERT to first CMR (baseline). At baseline, the median indexed LVMI by CMR (140.0 g/m(2), range 43.8-334.0) tended to be lower than that assessed by echo (median 204.0 g/m(2), range 52.0-385.0), but did not reach statistical significance. At baseline, CMR EF was similar to that assessed by echo (55% vs. 55%). Overall, there was no significant decrease in CMR measured LVMI over time (CMR median LVMI at baseline 94 g/m(2) (range 43.8-334) vs. CMR median at most recent study 44.5 g/m(2) (range 34-303), p=0.44). In 5 patients with serial CMR scans over time, LVMI decreased in 2, was similar in 2, and increased in 1 patient with high sustained antibodies to exogenous enzyme. Delayed enhancement was noted in only l separate patient who also had high sustained antibodies to exogenous enzyme.

CONCLUSION

CMR is an imaging tool that is feasible to use to serially follow LVMI and EF in children with Pompe disease on ERT. Real-time imaging is adequate for quantification purposes in these patients and minimizes the need for sedation. Quantitative CMR LVMI is generally lower than echo derived LVMI. Delayed enhancement appears to be a rare finding by CMR in Pompe disease. A further follow-up is necessary to better understand the long term effects of ERT in infantile Pompe survivors, especially those with high sustained antibody titers or advanced cardiac disease at treatment outset.