Cognitive outcome of patients with classic infantile Pompe disease receiving enzyme therapy

Long term survival in patients with classic infantile Pompe disease reveals a spectrum with progressive brain abnormalities and changes in cognitive functioning

The aim of this longitudinal cohort study, is to provide more insight into the pattern of brain abnormalities, and possible consequences for cognitive functioning, in patients with classic infantile Pompe disease. We included 19 classic infantile Pompe patients (median age last assessment 8.9 years, range 1.5-22.5 years; 5/19 CRIM negative), treated with ERT. Using MR imaging of the brain (T1, T2, and FLAIR acquisitions), we classified progression of brain abnormalities on a 12-point rating scale at multiple time points throughout follow-up. Additionally we noted specific white matter patterns and examined atrophy. Cognitive development was studied using Wechsler IQ assessments obtained by certified neuropsychologists. The association between age and cognitive functioning, and MRI ratings and cognitive functioning was assessed by linear regression models. All but one patient developed brain abnormalities. The abnormalities progressed in a similar pattern throughout the brain, with early involvement of periventricular white matter, later followed by subcortical white matter, gray matter structures, and juxtacortical U-fibers. We found a significant decline (p < 0.01), with increasing age for full scale IQ, performance IQ and processing speed, but not for verbal IQ (p = 0.17). Each point increment in the 12-point MRI rating scale was associated with a significant decline (3.1-6.0 points) in all the IQ index scores (p < 0.05). The majority of long-term surviving patients in our cohort develop incremental brain MRI abnormalities and decline in cognitive functioning. This highlights the need for new therapies that can cross the blood-brain barrier in order to treat this CNS phenotype.

Lentiviral gene therapy with IGF2-tagged GAA normalizes the skeletal muscle proteome in murine Pompe disease

Pompe disease is a lysosomal storage disorder caused by deficiency of acid alpha-glucosidase (GAA), resulting in glycogen accumulation with profound pathology in skeletal muscle. We recently developed an optimized form of lentiviral gene therapy for Pompe disease in which a codon-optimized version of the GAA transgene (LV-GAAco) was fused to an insulin-like growth factor 2 (IGF2) peptide (LV-IGF2.GAAco), to promote cellular uptake via the cation-independent mannose-6-phosphate/IGF2 receptor. Lentiviral gene therapy with LV-IGF2.GAAco showed superior efficacy in heart, skeletal muscle, and brain of Gaa -/- mice compared to gene therapy with untagged LV-GAAco. Here, we used quantitative mass spectrometry using TMT labeling to analyze the muscle proteome and the response to gene therapy in Gaa -/- mice. We found that muscle of Gaa -/- mice displayed altered levels of proteins including those with functions in the CLEAR signaling pathway, autophagy, cytoplasmic glycogen metabolism, calcium homeostasis, redox signaling, mitochondrial function, fatty acid transport, muscle contraction, cytoskeletal organization, phagosome maturation, and inflammation. Gene therapy with LV-GAAco resulted in partial correction of the muscle proteome, while gene therapy with LV-IGF2.GAAco resulted in a near-complete restoration to wild type levels without inducing extra proteomic changes, supporting clinical development of lentiviral gene therapy for Pompe disease. SIGNIFICANCE: Lysosomal glycogen accumulation is the primary cause of Pompe disease, and leads to a cascade of pathological events in cardiac and skeletal muscle and in the central nervous system. In this study, we identified the proteomic changes that are caused by Pompe disease in skeletal muscle of a mouse model. We showed that lentiviral gene therapy with LV-IGF2.GAAco nearly completely corrects disease-associated proteomic changes. This study supports the future clinical development of lentiviral gene therapy with LV-IGF2.GAAco as a new treatment option for Pompe disease.

Impaired Neurodevelopment in Children with 5q-SMA - 2 Years After Newborn Screening

OBJECTIVE

Numerous studies have consistently found that reduced SMN protein expression does not severely affect cognitive function in SMA patients. However, the average intelligence quotient of SMA patients has ranged above to below average in different studies. The cognitive development of SMA patients identified through newborn screening remains largely unknown.

METHODS

40 of 47 eligible SMA patients (23 females/17 males) from 39 families identified through newborn screening between January 2018 and December 2020 underwent developmental testing using Bayley III (BSID) after the 2 years of age. The mean age was 29.25 months (23-42 months). 17 patients had 2, 11 patients had 3 and 12 patients had ≥4 copies of SMN2.

RESULTS

cognitive scale: mean 94.55 (SD 24.01); language scale: mean 86.09 (SD 26.41); motor scale: 81.28 (SD 28.07). Overall, the cognitive scales show that 14 children were below average, 20 children were average and 6 children were above average. 10/14 children with below average scores had 2 SMN2 copies. The post-hoc pairwise comparisons showed that the cognition main scale was significantly more sensitive to the number of SMN2 copies than the motor main scale of the BSID (MΔ= 10.27, p = 0.014). There is also evidence that cognition scored higher than the language main scale (MΔ= 7.11, p = 0.090).

CONCLUSION

The impaired cognitive development of SMA children with 2 SMN2 copies, despite early initiation of therapy, underscores the critical role of the SMN protein in the early stages of brain development.

Long-Term Outcome of Infantile Onset Pompe Disease Patients Treated with Enzyme Replacement Therapy - Data from a German-Austrian Cohort

BACKGROUND

Enzyme replacement therapy (ERT) with recombinant human alglucosidase alfa (rhGAA) was approved in Europe in 2006. Nevertheless, data on the long-term outcome of infantile onset Pompe disease (IOPD) patients at school age is still limited.

OBJECTIVE

We analyzed in detail cardiac, respiratory, motor, and cognitive function of 15 German-speaking patients aged 7 and older who started ERT at a median age of 5 months.

RESULTS

Starting dose was 20 mg/kg biweekly in 12 patients, 20 mg/kg weekly in 2, and 40 mg/kg weekly in one patient. CRIM-status was positive in 13 patients (86.7%) and negative or unknown in one patient each (6.7%). Three patients (20%) received immunomodulation. Median age at last assessment was 9.1 (7.0-19.5) years. At last follow-up 1 patient (6.7%) had mild cardiac hypertrophy, 6 (42.9%) had cardiac arrhythmias, and 7 (46.7%) required assisted ventilation. Seven patients (46.7%) achieved the ability to walk independently and 5 (33.3%) were still ambulatory at last follow-up. Six patients (40%) were able to sit without support, while the remaining 4 (26.7%) were tetraplegic. Eleven patients underwent cognitive testing (Culture Fair Intelligence Test), while 4 were unable to meet the requirements for cognitive testing. Intelligence quotients (IQs) ranged from normal (IQ 117, 102, 96, 94) in 4 patients (36.4%) to mild developmental delay (IQ 81) in one patient (9.1%) to intellectual disability (IQ 69, 63, 61, 3x <55) in 6 patients (54.5%). White matter abnormalities were present in 10 out of 12 cerebral MRIs from 7 patients.

CONCLUSION

Substantial motor, cardiac, respiratory, and cognitive deficits are frequent in IOPD long-term survivors who started ERT before 2016. The findings of this study can be valuable as comparative data when evaluating the impact of newer treatment strategies including higher enzyme dosage, immunomodulation, modified enzymes, or early start of treatment following newborn screening.

Long-term follow-up of 64 children with classical infantile-onset Pompe disease since 2004: A French real-life observational study

BACKGROUND

Classical infantile-onset Pompe disease (IOPD) is the most severe form of Pompe disease. Enzyme replacement therapy (ERT) has significantly increased survival but only a few studies have reported long-term outcomes.

METHODS

We retrospectively analyzed the outcomes of classical IOPD patients diagnosed in France between 2004 and 2020.

RESULTS

Sixty-four patients were identified. At diagnosis (median age 4 months) all patients had cardiomyopathy and most had severe hypotonia (57 of 62 patients, 92%). ERT was initiated in 50 (78%) patients and stopped later due to being ineffective in 10 (21%). Thirty-seven (58%) patients died during follow-up, including all untreated and discontinued ERT patients, and 13 additional patients. Mortality was higher during the first 3 years of life and after the age of 12 years. Persistence of cardiomyopathy during follow-up and/or the presence of heart failure were highly associated with an increased risk of death. In contrast, cross-reactive immunologic material (CRIM)-negative status (n = 16, 26%) was unrelated to increased mortality, presumably because immunomodulation protocols prevent the emergence of high antibody titers to ERT. Besides survival, decreased ERT efficacy appeared after the age of 6 years, with a progressive decline in motor and pulmonary functions for most survivors.

CONCLUSIONS

This study reports the long-term follow-up of one of the largest cohorts of classical IOPD patients and demonstrates high long-term mortality and morbidity rates with a secondary decline in muscular and respiratory functions. This decreased efficacy seems to be multifactorial, highlighting the importance of developing new therapeutic approaches targeting various aspects of pathogenesis.

Longitudinal developmental profile of newborns and toddlers treated for spinal muscular atrophy

Background

Spinal muscular atrophy (SMA) results from a loss-of-function mutation in the SMN1 gene. SMA patients suffer progressive motor disability, although no intellectual impairments have been described. Three drugs have been recently approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). These drugs result in longer life expectancy for SMA type 1 (SMA1) patients.

Objective

The objective of the study was to assess longitudinally the psychomotor development of patients with SMA1 treated after the symptom onset and of patients treated presymptomatically.

Design

Longitudinal, monocentric, noninterventional, prospective study.

Methods

Our study included 11 SMA1 patients and seven presymptomatic SMA patients. The SMA1 patients were treated with an approved drug beginning after onset of symptoms; treatment for the presymptomatic patients was begun before symptom onset. They were longitudinally evaluated between September 2018 and January 2022 using the Bayley Scales of Infant and Toddler Development™ - Third Edition.

Results

At each time point, all patients treated presymptomatically scored above those treated postsymptomatically on the motor scale. The cognitive scores of six of the seven patients treated presymptomatically were average; one patient was in the low average range. In the 11 postsymptomatically treated patients, four scored either in the low average or the abnormal range on the cognitive scale, but a positive trend was observed during the follow-up.

Conclusion

A significant proportion of patients treated postsymptomatically scored below average on cognitive and communicative scales, with most significant concerns raised about the age of 1 year. Our study indicates that intellectual development should be considered as an important outcome in treated SMA1 patients. Cognitive and communicative evaluations should be performed as part of standard of care, and guidance should be provided to parents for optimal stimulation.

Long-term outcomes of very early treated infantile-onset Pompe disease with short-term steroid premedication: experiences from a nationwide newborn screening programme

BACKGROUND

Starting enzyme replacement therapy (ERT) before severe irreversible muscular damage occurs is important in infantile-onset Pompe disease (IOPD). This long-term follow-up study demonstrates our diagnostic and treatment strategies for IOPD and compares our clinical outcomes with those of other medical centres.

METHODS

In this long-term follow-up study, we analysed the outcomes of very early ERT with premedication hydrocortisone in patients with IOPD. Out of 1 228 539 infants screened between 1 January 2010 and 28 February 2021, 33 newborns had confirmed IOPD in Taipei Veterans General Hospital. Twenty-six were regularly treated and monitored at Taipei Veterans General Hospital. Echocardiographic parameters, biomarkers, IgG antibodies against alglucosidase alpha, pulmonary function variables and developmental status were all assessed regularly over an average follow-up duration of 6.18±3.14 years. We compared the long-term treatment outcomes of our patients with those of other research groups.

RESULTS

The average age at ERT initiation was 9.75±3.17 days for patients with classic IOPD. The average of the latest antialglucosidase alpha IgG titre was 669.23±1159.23. All enrolled patients had normal heart sizes, motor milestones, cognitive function and pulmonary function that were near-normal to normal. Compared with patients in other studies, our patients had better outcomes in all aspects.

CONCLUSION

Very early ERT using our rapid diagnostic and treatment strategy enabled our patients with IOPD to have better outcomes than patients in other medical centres.

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

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

Hearing characteristics of infantile-onset Pompe disease after early enzyme-replacement therapy

BACKGROUND

Studies suggest that enzyme-replacement therapy (ERT) is crucial to the survival of patients with infantile-onset Pompe disease (IOPD). Hearing impairment (HI) is one of the clinical sequelae observed in long-term survivors. However, the benefits of early ERT for hearing outcomes have not yet been reported. This study aimed to investigate the impact of early ERT on IOPD patients.

METHODS

This retrospective longitudinal study recruited IOPD patients who were referred by newborn screening for confirmatory diagnosis based on our rapid diagnostic criteria and received early ERT treatment between January 1, 2010, and January 31, 2018. The hearing test battery included a tympanogram, otoacoustic emission, auditory brainstem evoked response (ABR), pure-tone audiometry or conditioned play audiometry.

RESULTS

Nineteen patients with IOPD were identified, 6 of whom had hearing impairment (HI); 1 had conductive HI, 2 had sensorineural HI (one had bilateral mild HI and one had mild HI in a single ear) and 1 had moderate mixed-type HI. Two patients failed the newborn screening test and had mild HI in the ABR. The mean age of the initial time to ERT was 11.05 ± 4.31 days, and the HI rate was 31.6% (6/19).

CONCLUSION

Our study is the largest cohort to show the characteristic hearing outcomes of IOPD patients after ERT. Early ERT within 2 weeks after birth may contribute to better hearing outcomes. Clinicians should be vigilant in testing for the hearing issues associated with IOPD and should intervene early if any HI is detected.

Behavioral, social and school functioning in children with Pompe disease

Purpose

To improve our understanding of the behavioral, social, and emotional functioning of children and adolescents with Pompe disease.

Method

Parents/guardians of 21 children (age 5-18y) with infantile (IPD) or late-onset (LOPD) Pompe disease on long-term enzyme replacement therapy completed three standardized checklists regarding their child's behavior: the Child Behavior Checklist (CBCL), Conners 3 Parent (Conners-3), Behavior Rating Inventory of Executive Function-2 (BRIEF2), and a survey of their child's educational services.

Results

Descriptive statistics were used to summarize the findings for each behavior checklist. Age standard scores from each checklist were reported for the IPD (n = 17, 9 females, mean age = 9y, 4 mo; SD = 3y, 8mo) and LOPD (n = 4, 1 female; mean = 11y, 2mo; SD = 2y, 1mo) groups. The majority of children with Pompe exhibited age-appropriate behavior and emotional functioning on these standardized checklists. However, negative mood symptoms, learning problems, decreased participation in structured social activities, and attentional difficulties were more frequently reported in children with IPD in comparison to same-aged peers. Parents of children with LOPD reported fewer problematic behaviors but endorsed negative mood symptoms and difficulties with peer relations. Most children received accommodations in regular education classrooms at school.

Conclusions

These standardized behavior checklists are useful screening tools for the early identification and treatment of behavior, emotional, and social concerns in children with Pompe disease.

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Parents of children with Pompe disease completed standardized behavior checklists.

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Most children with Pompe exhibited age appropriate behavior and emotional functioning.

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Negative mood, learning, and attentional problems reported in infantile Pompe group.

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Negative mood and concerns about peer interactions reported in late-onset Pompe group.

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Most children with Pompe attend and succeed at school, with classroom accommodations.

Using human Pompe disease-induced pluripotent stem cell-derived neural cells to identify compounds with therapeutic potential

Pompe disease (OMIM # 232300) is a glycogen storage disease caused by autosomal recessive mutations of the gene encoding alpha-1,4-glucosidase (GAA; EC 3.2.1.20). Despite the relatively effective employment of enzyme replacement therapy, some critical medical issues still exist in patients with this disease, including the persistence of abnormalities in the central nervous system (CNS), probably because of the inability of the recombinant GAA to pass through the blood-brain barrier. To address this issue, identification of more therapeutic agents that target the CNS of patients with Pompe disease may be required. In this study, we derived neuronal cells from Pompe disease-induced pluripotent stem cells (Pom-iPSCs) and proved that they are able to recapitulate the hallmark cellular and biochemical phenotypes of Pompe disease. Using the Pom-iPSC-derived neurons as an in vitro drug-testing model, we then identified three compounds, ebselen, wortmannin and PX-866, with therapeutic potential to alleviate Pompe disease-associated pathological phenotypes in the neurons derived from Pom-iPSCs. We confirmed that all three compounds were able to enhance the GAA activity in the Pom-iPSC-derived neurons. Moreover, they were able to enhance the GAA activity in several important internal organs of GAA-deficient mice when co-injected with recombinant human GAA, and we found that intraperitoneal injection of ebselen was able to promote the GAA activity of the GAA-heterozygous mouse brain. Our results prove the usefulness of Pom-iPSC-derived neuronal populations for identifying new compounds with therapeutic potential.

Lentiviral Hematopoietic Stem Cell Gene Therapy Corrects Murine Pompe Disease

Pompe disease is an autosomal recessive lysosomal storage disorder characterized by progressive muscle weakness. The disease is caused by mutations in the acid α-glucosidase (GAA) gene. Despite the currently available enzyme replacement therapy (ERT), roughly half of the infants with Pompe disease die before the age of 3 years. Limitations of ERT are immune responses to the recombinant enzyme, incomplete correction of the disease phenotype, lifelong administration, and inability of the enzyme to cross the blood-brain barrier. We previously reported normalization of glycogen in heart tissue and partial correction of the skeletal muscle phenotype by ex vivo hematopoietic stem cell gene therapy. In the present study, using a codon-optimized GAA (GAAco), the enzyme levels resulted in close to normalization of glycogen in heart, muscles, and brain, and in complete normalization of motor function. A large proportion of microglia in the brain was shown to be GAA positive. All astrocytes contained the enzyme, which is in line with mannose-6-phosphate receptor expression and the key role in glycogen storage and glucose metabolism. The lentiviral vector insertion site analysis confirmed no preference for integration near proto-oncogenes. This correction of murine Pompe disease warrants further development toward a cure of the human condition.

Language, speech, and oromotor function in children with Pompe disease

Advances in the treatment of Pompe disease have improved life expectancy and quality of life, but speech and oromotor function remain significantly affected. The purpose of this study was to expand on existing data and present new findings of speech acoustic and physiologic outcomes in Pompe disease. A retrospective analysis was carried out on results of speech, language and oromotor tests carried out in 14 children diagnosed with Pompe disease. The assessment battery included standardized tests of language, picture naming, maximum performance tests, and oromotor resistance tasks. Speech production was scored with respect to intelligibility, hypernasality, and articulatory accuracy. Language delays ranged from mild to severe in 1/3 of the children. Reduced speech intelligibility, disordered articulation, and hypernasality were present in at least 2/3 of the children. Maximum performance tests all fell at least 1 SD below normative means. Significant correlations were identified between maximum phonation time and articulation and between the S/Z ratio and intelligibility. Positive correlations were also found between tongue strength and articulation. Results confirm previous reports of speech and language function in Pompe disease. Clinical acoustic measures provide important insights into the speech deficits in this group of children and suggest possible treatment strategies.

Airway abnormalities in very early treated infantile-onset Pompe disease: A large-scale survey by flexible bronchoscopy

Early enzyme replacement therapy (ERT) improve long-term outcomes in patients with infantile-onset Pompe disease (IOPD). Our cohort of patients with IOPD at Taipei Veterans General Hospital (TVGH) joined Taiwan Pompe newborn screening program from 2008, testing more than one million newborns until 2018. By 2010, we had established rapid diagnostic strategies. Now, the average age of ERT initiation starts at an average age of <10 days-old, the earliest group in the world. However, they still presented some airway problems. We present a retrospective study focused on airway abnormalities in these patients along 8 years of observation. Fifteen patients with IOPD, who received very early treatment at a mean age of 8.94 ± 3.75 days, underwent flexible bronchoscopy (FB) for dynamic assessment of the whole airway. Long-term clinical outcomes and relevant symptoms of the upper airway were assessed. All patients in the study had varying degrees of severity of upper airway abnormalities and speech disorders. The three oldest children (Age 94, 93, and 88 months, respectively) had poor movement of the vocal cords with reduced abduction and adduction and had silent aspiration of saliva through the glottis during respiration. This is the largest cohort study presented to date about airway abnormalities in very early treated patients with IOPD patients by FB. Despite very early treatment, we observed upper airway abnormalities in these IOPD patients. In IOPD, upper airway abnormalities seem inevitable over time. We suggest early and continuous monitoring for all IOPD patients, even with early and regular treatment.

Novel GAA Variants and Mosaicism in Pompe Disease Identified by Extended Analyses of Patients with an Incomplete DNA Diagnosis

Pompe disease is a metabolic disorder caused by a deficiency of the glycogen-hydrolyzing lysosomal enzyme acid α-glucosidase (GAA), which leads to progressive muscle wasting. This autosomal-recessive disorder is the result of disease-associated variants located in the GAA gene. In the present study, we performed extended molecular diagnostic analysis to identify novel disease-associated variants in six suspected Pompe patients from four different families for which conventional diagnostic assays were insufficient. Additional assays, such as a generic-splicing assay, minigene analysis, SNP array analysis, and targeted Sanger sequencing, allowed the identification of an exonic deletion, a promoter deletion, and a novel splicing variant located in the 5′ UTR. Furthermore, we describe the diagnostic process for an infantile patient with an atypical phenotype, consisting of left ventricular hypertrophy but no signs of muscle weakness or motor problems. This led to the identification of a genetic mosaicism for a very severe GAA variant caused by a segmental uniparental isodisomy (UPD). With this study, we aim to emphasize the need for additional analyses to detect new disease-associated GAA variants and non-Mendelian genotypes in Pompe disease where conventional DNA diagnostic assays are insufficient.

Gene therapy for glycogen storage diseases

The focus of this review is the development of gene therapy for glycogen storage diseases (GSDs). GSD results from the deficiency of specific enzymes involved in the storage and retrieval of glucose in the body. Broadly, GSDs can be divided into types that affect liver or muscle or both tissues. For example, glucose-6-phosphatase (G6Pase) deficiency in GSD type Ia (GSD Ia) affects primarily the liver and kidney, while acid α-glucosidase (GAA) deficiency in GSD II causes primarily muscle disease. The lack of specific therapy for the GSDs has driven efforts to develop new therapies for these conditions. Gene therapy needs to replace deficient enzymes in target tissues, which has guided the planning of gene therapy experiments. Gene therapy with adeno-associated virus (AAV) vectors has demonstrated appropriate tropism for target tissues, including the liver, heart and skeletal muscle in animal models for GSD. AAV vectors transduced liver and kidney in GSD Ia and striated muscle in GSD II mice to replace the deficient enzyme in each disease. Gene therapy has been advanced to early phase clinical trials for the replacement of G6Pase in GSD Ia and GAA in GSD II (Pompe disease). Other GSDs have been treated in proof-of-concept studies, including GSD III, IV and V. The future of gene therapy appears promising for the GSDs, promising to provide more efficacious therapy for these disorders in the foreseeable future.

An emerging phenotype of central nervous system involvement in Pompe disease: from bench to bedside and beyond

Pompe disease (PD) is a lysosomal storage disorder caused by deficiency of the lysosomal enzyme acid-alpha glucosidase (GAA). Pathogenic variants in the GAA gene lead to excessive accumulation of lysosomal glycogen primarily in the cardiac, skeletal, and smooth muscles. There is growing evidence of central nervous system (CNS) involvement in PD. Current research is focused on determining the true extent of CNS involvement, its effects on behavior and cognition, and effective therapies that would correct the disease in both muscle and the CNS. This review article summarizes the CNS findings in patients, highlights the importance of research on animal models, explores the probable success of gene therapy in reversing CNS pathologies as reported by some breakthrough preclinical studies, and emphasizes the need to follow patients and monitor for CNS involvement over time. Lessons learned from animal models (bench) and from the literature available to date on patients will guide future clinical trials in patients (bedside) with PD. Our preliminary studies in infantile PD show that some patients are susceptible to early and extensive CNS pathologies, as assessed by neuroimaging and developmental assessments. This article highlights the importance of neuroimaging which could serve as useful tools to diagnose and monitor certain CNS pathologies such as white matter hyperintense foci (WMF) in the brain. Longitudinal studies with large sample sizes are warranted at this time to better understand the emergence, progression and consequences of CNS involvement in patients with PD.

Newborn screening: Taiwanese experience

Newborn screening (NBS) aims to diagnose patients with Pompe disease earlier so that timely treatment can be applied. We describe the evolution of the screening methods in Taiwan with a population in which a pseudodeficiency variant is prevalent. We review and update the outcome of NBS-identified patients and discuss the limitations of the current therapy. We also address the challenges associated with caring for the babies with diagnosed acid alpha-glucosidase deficiency but yet without significant clinical manifestations. Further modifications of the current treatment and better predictive biomarkers should be explored.

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.

Restoring the regenerative balance in neuromuscular disorders: satellite cell activation as therapeutic target in Pompe disease

Skeletal muscle is capable of efficiently regenerating after damage in a process mediated by tissue-resident stem cells called satellite cells. This regenerative potential is often compromised under muscle-degenerative conditions. Consequently, the damage produced during degeneration is not efficiently repaired and the balance between repair and damage is lost. Here we review recent progress on the role of satellite cell-mediated repair in neuromuscular disorders with a focus on Pompe disease, an inherited metabolic myopathy caused by deficiency of the lysosomal enzyme acid alpha glucosidase (GAA). Studies performed in patient biopsies as well as in Pompe disease mouse models demonstrate that muscle regeneration activity is compromised despite progressing muscle damage. We describe disease-specific mechanisms of satellite cell dysfunction to highlight the differences between Pompe disease and muscle dystrophies. The mechanisms involved provide possible targets for therapy, such as modulation of autophagy, muscle exercise, and pharmacological modulation of satellite cell activation. Most of these approaches are still experimental, although promising in animal models, still warrant caution with respect to their safety and efficiency profile.

Comparison of recent pivotal recommendations for the diagnosis and treatment of late-onset Pompe disease using diagnostic nodes-the Pompe disease burden scale

Pompe disease is a rare autosomal-recessive disorder characterised by limb-girdle myopathy and respiratory weakness in the late-onset form (LOPD). Various mutations in the acid alpha-glucosidase gene lead to toxic lysosomal and extra-lysosomal glycogen accumulation in all organs due to ineffective glycogen clearance by the encoded enzyme. Only one randomized trial demonstrated beneficial effects of respiratory function and meters walked in the 6-min walking test with enzyme replacement therapy (ERT). These results were confirmed in several retrospective and prospective observations and in meta-analyses. Due to a potential lifelong therapy, moderate efficacy and high treatment costs time of ERT initiation and cessation is an ongoing matter of debate. So far, several national and international recommendations have been published with different criteria concerning diagnosis, initiation and cessation of ERT in LOPD. We therefore formally analysed recent published recommendations and consensus statements of LOPD using diagnostic nodes (DODES) as a special software tool. With DODES, an objective analysis becomes possible if the content of the recommendations is represented as algorithms using cross-compatible elements. This analysis formally disclosed both, areas of great heterogeneity and concordance for the diagnosis and management of LOPD and paved the way for a Pompe disease burden scale focussing on ERT initiation. According to this investigation further clinical research should concentrate on ERT in pre-symptomatic and severely affected LOPD patients and on cessation criteria for ERT as these issues are areas of international uncertainty and discordance.

Advances in imaging of brain abnormalities in neuromuscular disease

Brain atrophy, white matter abnormalities, and ventricular enlargement have been described in different neuromuscular diseases (NMDs). We aimed to provide a comprehensive overview of the substantial advancement of brain imaging in neuromuscular diseases by consulting the main libraries (Pubmed, Scopus and Google Scholar) including the more common forms of muscular dystrophies such as dystrophinopathies, dystroglycanopathies, myotonic dystrophies, facioscapulohumeral dystrophy, limb-girdle muscular dystrophy, congenital myotonia, and congenital myopathies. A consistent, widespread cortical and subcortical involvement of grey and white matter was found. Abnormalities in the functional connectivity in brain networks and metabolic alterations were observed with positron emission tomography (PET) and single photon emission computed tomography (SPECT). Pathological brain changes with cognitive dysfunction seemed to be frequently associated in NMDs. In particular, in congenital muscular dystrophies (CMDs), skeletal muscular weakness, severe hypotonia, WM abnormalities, ventricular dilatation and abnormalities in cerebral gyration were observed.

In dystroglycanopathy 2I subtype (LGMD2I), adult patients showed subcortical atrophy and a WM periventricular involvement, moderate ventriculomegaly, and enlargement of subarachnoid spaces. Correlations with clinical features have been observed with brain imaging characteristics and alterations were prominent in congenital or childhood onset cases. In myotonic dystrophy type 2 (DM2) symptoms seem to be less severe than in type 1 (DM1).

In Duchenne and Becker muscular dystrophies (DMD, BMD) cortical atrophy is associated with minimal ventricular dilatation and WM abnormalities.

Late-onset glycogenosis type II (GSD II) or Pompe infantile forms are characterized by delayed myelination. Only in a few cases of oculopharyngeal muscular dystrophy (OPMD) central nervous system involvement has been described and associated with executive functions impairment.

Classic infantile Pompe patients approaching adulthood: a cohort study on consequences for the brain

AIM

To examine the long-term consequences of glycogen storage in the central nervous system (CNS) for classic infantile Pompe disease using enzyme replacement therapy.

METHOD

Using neuropsychological tests and brain magnetic resonance imaging (MRI), we prospectively assessed a cohort of 11 classic infantile Pompe patients aged up to 17 years.

RESULTS

From approximately age 2 years onwards, brain MRI showed involvement of the periventricular white matter and centrum semiovale. After 8 years of age, additional white-matter abnormalities occurred in the corpus callosum, internal and external capsule, and subcortical areas. From 11 years of age, white-matter abnormalities were also found in the brainstem. Although there seemed to be a characteristic pattern of involvement over time, there were considerable variations between patients, reflected by variations in neuropsychological development. Cognitive development ranged from stable and normal to declines that lead to intellectual disabilities.

INTERPRETATION

As treatment enables patients with classic infantile Pompe disease to reach adulthood, white-matter abnormalities are becoming increasingly evident, affecting the neuropsychological development. Therefore, we advise follow-up programs are expanded to capture CNS involvement in larger, international patient cohorts, to incorporate our findings in the counselling of parents before the start of treatment, and to include the brain as an additional target in the development of next-generation therapeutic strategies for classic infantile Pompe disease.

WHAT THIS PAPER ADDS

In our long-term survivors treated intravenously with enzyme replacement therapy, we found slowly progressive symmetric white-matter abnormalities. Cognitive development varied from stable and normal to declines towards intellectual disabilities.

Long term clinical history of an Italian cohort of infantile onset Pompe disease treated with enzyme replacement therapy

Background

Enzyme replacement therapy (ERT) has deeply modified the clinical history of Infantile Onset Pompe Disease (IOPD). However, its long-term effectiveness is still not completely defined. Available data shows a close relationship between clinical outcome and patients’ cross-reactive immunological status (CRIM), being CRIM-negative status a negative prognostic factor. At the same time limited data are available on the long-term treatment in CRIM-positive infants.

Methods

A retrospective multicentre observational study was designed to analyse the long-term effectiveness of ERT in IOPD. Thirteen Italian centres spread throughout the country were involved and a cohort of 28 patients (15 females, 13 males, born in the period: February 2002–January 2013) was enrolled. IOPD diagnosis was based on clinical symptoms, enzymatic and molecular analysis. All patients received ERT within the first year of life. Clinical, laboratory, and functional data (motor, cardiac and respiratory) were collected and followed for a median period of 71 months (5 years 11 months).

Results

Median age at onset, diagnosis and start of ERT were 2, 3 and 4 months, respectively. CRIM status was available for 24/28 patients: 17/24 (71%) were CRIM-positive. Nineteen patients (67%) survived > 2 years: 4 were CRIM-negative, 14 CRIM-positive and one unknown. Six patients (5 CRIM-positive and one unknown) never needed ventilation support (21,4%) and seven (6 CRIM-positive and one unknown: 25%) developed independent ambulation although one subsequently lost this function. Brain imaging study was performed in 6 patients and showed peri-ventricular white matter abnormalities in all of them. Clinical follow-up confirmed the better prognosis for CRIM-positive patients, though a slow, progressive worsening of motor and/or respiratory functions was detected in 8 patients.

Conclusions

These data are the result of the longest independent retrospective study on ERT in IOPD reported so far outside clinical trials. The data obtained confirmed the better outcome of the CRIM-positive patients but at the same time, showed the inability of the current therapeutic approach to reverse or stabilize the disease progression. The results also evidenced the involvement of central nervous system in Pompe disease. To better understand the disease clinical history and to improve treatment efficacy larger multicentre studies are needed as well as the development of new therapeutic approaches.

Neuroimaging findings in infantile Pompe patients treated with enzyme replacement therapy

BACKGROUND

Recombinant human acid α-glucosidase (rhGAA) enzyme replacement therapy (ERT) has prolonged survival in infantile Pompe disease (IPD), but has unmasked central nervous system (CNS) changes.

METHODS

Brain imaging, consisting of computed tomography (CT) and/or magnetic resonance imaging (MRI), was performed on 23 patients with IPD (17 CRIM-positive, 6 CRIM-negative) aged 2-38months. Most patients had baseline neuroimaging performed prior to the initiation of ERT. Follow-up neuroimaging was performed in eight.

RESULTS

Sixteen patients (70%) had neuroimaging abnormalities consisting of ventricular enlargement (VE) and/or extra-axial cerebrospinal fluid accumulation (EACSF) at baseline, with delayed myelination in two. Follow-up neuroimaging (n=8) after 6-153months showed marked improvement, with normalization of VE and EACSF in seven patients. Two of three patients imaged after age 10years demonstrated white matter changes, with one noted to have a basilar artery aneurysm.

CONCLUSIONS

Mild abnormalities on brain imaging in untreated or newly treated patients with IPD tend to resolve with time, in conjunction with ERT. However, white matter changes are emerging as seen in Patients 1 and 3 which included abnormal periventricular white matter changes with subtle signal abnormalities in the basal ganglia and minimal, symmetric signal abnormalities involving the deep frontoparietal cerebral white matter, respectively. The role of neuroimaging as part of the clinical evaluation of IPD needs to be considered to assess for white matter changes and cerebral aneurysms.

The humanistic burden of Pompe disease: are there still unmet needs? A systematic review

BACKGROUND

Humanistic burden considers the impact of an illness on a patient's health-related quality of life (HRQoL), activities of daily living (ADL), caregiver health, and caregiver QoL. Humanistic burden also considers treatment satisfaction and adherence to treatment regimens. Pompe disease is an autosomal recessive, progressive, multisystemic neuromuscular disease. Approval of enzyme-replacement therapy (ERT) markedly improved prognosis for patients, but considerable morbidity and a substantial humanistic burden remain. This article characterizes the humanistic burden of Pompe disease through a systematic literature review.

METHODS

A systematic search of MEDLINE® and Embase® with back-referencing and supplementary literature searches was performed to retrieve data from interventional and non-interventional studies on the humanistic burden of Pompe disease. Publications were screened according to predefined criteria, extracted, and assessed for quality. Extracted data were narratively synthesized.

RESULTS

No publications on the humanistic burden of infantile-onset Pompe disease (IOPD) were identified. As such, of 17 publications included here, all are in patients with late-onset Pompe disease (LOPD). Thirteen publications were initiated after approval of ERT, two were initiated before, and two overlapped the approval of ERT. The review shows that LOPD patients have a significantly lower HRQoL than the general population, even if treated with ERT. On transitioning to ERT, treatment was associated with improvement in the physical component score of the SF-36 and fatigue, although the SF-36 mental component score remained stable. Physical HRQoL remained below population norms after 4 years of ERT. Significantly more ERT-treated patients reported pain than controls, and bodily pain worsened in later years following ERT initiation. Treatment-naïve LOPD patients had significantly poorer ADL functioning compared with the general population, although ERT stabilized deteriorating functioning impairment. ERT studies showed caregivers provide 17.7 h/week informal care on average. Fifty percent, 40% and <20% of caregivers reported mental health, physical health, and financial/relational problems, respectively. In ERT-naïve patients, wheelchair use and home ventilatory support was associated with lower physical HRQoL and ADL functioning. In ERT-treated patients, key factors predicting worse HRQoL and ADL functioning were higher respiratory distress, poorer sleep quality, greater pain, and more fatigue.

CONCLUSIONS

Pompe disease has a substantial humanistic burden, with strong inter-relationships among and between humanistic burden parameters and clinical progression.

High dose IVIG successfully reduces high rhGAA IgG antibody titers in a CRIM-negative infantile Pompe disease patient

Alglucosidase alfa (rhGAA) has altered the course of an otherwise fatal outcome in classic infantile Pompe disease (IPD), which presents with cardiomyopathy and severe musculoskeletal involvement. However, the response to therapy is determined by several factors including the development of high and sustained antibody titers (HSAT) to rhGAA. Cross-reactive immunologic material (CRIM) negative patients are at the highest risk for development of HSAT. Immune tolerance induction (ITI) with methotrexate, rituximab, and intravenous immunoglobulin (IVIG) has been largely successful in preventing the immune response and in achieving tolerance when done in conjunction with enzyme replacement therapy (ERT) initiation. Reducing antibody titers in cases with an entrenched immune response remains a challenge in the field despite the use of multiple immunomodulatory agents. Success has been shown with addition of bortezomib to the ITI regimen, yet the prolonged course and potential risks with the use of such agents' demands caution. We present here a 7-year-old CRIM-negative IPD patient who was not successfully tolerized by an ITI regimen with rituximab, methotrexate, and IVIG due to intolerability to the regimen and recurrent infections. She went on to develop HSAT, with significant clinical decline, loss of all motor abilities, and a fragile medical state, which made it challenging to institute the bortezomib based regimen to reduce HSAT. She had severe developmental delay, respiratory failure with invasive ventilation and tracheostomy, persistent hypotonia, ptosis of eyelids, diffuse severe osteopenia, contractures, and was completely G-tube fed. As a rescue mechanism, we treated her with high dose and high frequency IVIG in an attempt to reduce rhGAA IgG antibody titers (antibody titers; titers). Her titers saw a steady decline on weekly IVIG doses at 1g/kg for 20weeks. Subsequently when the IVIG regimen was altered to 1g/kg every month, rising titers were detected and therefore the regimen was changed to a biweekly regimen. High dose IVIG resulted in an eightfold decrease in antibody titers. Clinically, she showed improvement with partial recovery of previously lost motor abilities, especially hand movements and better head and neck control than before. The regimen was safely tolerated with no hospitalizations. The effectiveness of IVIG as a single agent, in this case with multiple comorbidities and fragile clinical status, was lifesaving and may represent an effective, perhaps lifesaving rescue approach to reduce antibody titers.

Rapidly Progressive White Matter Involvement in Early Childhood: The Expanding Phenotype of Infantile Onset Pompe?

Glycogen accumulation in the central nervous system of patients with classical infantile onset Pompe disease (IOPD) has been a consistent finding on the few post-mortems performed. While delays in myelination and a possible reduction in processing speed have previously been noted, it has only been recently that the potential for clinically significant progressive white matter disease has been noted. The limited reports thus far published infer that in some IOPD patients, this manifests as intellectual decline in the second decade of life. We present a CRIM negative patient, immunomodulated with rituximab and methotrexate at birth, who despite an initial good clinical response to ERT, at the age of just under 4 years, presented with evolving spasticity in the lower limbs. The investigation of which revealed progressive central nervous system involvement. Given both the earlier onset of the symptoms and consanguineous familial pedigree, extensive biochemical and genetic investigation was undertaken to ensure no alternative pathology was elucidated. In light of these findings, we review the radiology and post-mortems of previous cases and discuss the potential mechanisms that may underlie this presentation.

Cognitive and academic outcomes in long-term survivors of infantile-onset Pompe disease: A longitudinal follow-up

This study examines the long-term cognitive and academic outcomes of 11 individuals with infantile onset Pompe disease (IOPD) (median age=11years, 1month, range=5years, 6months through 17years of age) treated with enzyme replacement therapy from an early age. All participants (7 males, 4 females) were administered individual intelligence tests (Wechsler or Leiter scales or both), a measure of their academic skill levels (Woodcock-Johnson Tests of Achievement), and a screening measure of visual-motor integration ability (Beery-Buktenica). Consistent with our earlier findings, median IQ scores for the entire group on the Wechsler (median=84) and Leiter (median=92) scales continue to fall at the lower end of the average range compared to same-aged peers. The median scores for the group on a measure of visual-motor integration (median=76), visual perception (median=74) and motor coordination (median=60) were below average. Two distinct subgroups emerged based on participants' average or below average performance on the majority of academic subtests. Those participants with below average academic skills (n=6) demonstrated average nonverbal cognitive abilities on the Leiter, but had weaknesses in speech and language skills and greater medical involvement. Their profiles were more consistent with a learning disability diagnosis than an intellectual disability. Two of these participants showed a significant decline (15 and 23 points, respectively) on repeated Wechsler scales, but one continued to earn average scores on the Leiter scales where the verbal and motor demands are minimal. Participants with average academic skills (n=5) demonstrated average cognitive abilities (verbal and nonverbal) on the Wechsler scales and less medical involvement. Their speech and language skills appeared to be more intact. However, both groups earned below average median scores on the Beery-Buktenica motor coordination task. This study highlights the importance of using appropriate tests to capture both verbal and nonverbal abilities, considering each individual's motor skills, speech and language abilities, hearing status and native language. This will allow for a more accurate assessment of whether there is a learning disability or an intellectual disability. Long-term outcomes may be related to the stability of an individual's expressive and/or receptive language abilities over time. Changes in the speech and language domain may account for the decline in IQ observed in some IOPD long-term survivors, reflecting a learning disability rather than a decline in overall cognition or an intellectual disability. These observations, in conjunction with neuroimaging, will further our understanding of the neurocognitive profile of long-term IOPD survivors.

Longitudinal follow-up to evaluate speech disorders in early-treated patients with infantile-onset Pompe disease

BACKGROUND

Patients with infantile-onset Pompe disease (IOPD) can be treated by recombinant human acid alpha glucosidase (rhGAA) replacement beginning at birth with excellent survival rates, but they still commonly present with speech disorders. This study investigated the progress of speech disorders in these early-treated patients and ascertained the relationship with treatments.

METHODS

Speech disorders, including hypernasal resonance, articulation disorders, and speech intelligibility, were scored by speech-language pathologists using auditory perception in seven early-treated patients over a period of 6 years. Statistical analysis of the first and last evaluations of the patients was performed with the Wilcoxon signed-rank test.

RESULTS

A total of 29 speech samples were analyzed. All the patients suffered from hypernasality, articulation disorder, and impairment in speech intelligibility at the age of 3 years. The conditions were stable, and 2 patients developed normal or near normal speech during follow-up. Speech therapy and a high dose of rhGAA appeared to improve articulation in 6 of the 7 patients (86%, p = 0.028) by decreasing the omission of consonants, which consequently increased speech intelligibility (p = 0.041). Severity of hypernasality greatly reduced only in 2 patients (29%, p = 0.131).

CONCLUSION

Speech disorders were common even in early and successfully treated patients with IOPD; however, aggressive speech therapy and high-dose rhGAA could improve their speech disorders.

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

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

Cognitive Development in Infantile-Onset Pompe Disease Under Very Early Enzyme Replacement Therapy

Most patients with infantile-onset Pompe disease die in early infancy before beginning enzyme replacement therapy, which has made it difficult to evaluate the impact of Pompe disease on cognitive development. Patients with infantile-onset Pompe disease can survive with enzyme replacement therapy, and physicians can evaluate cognitive development in these patients. We established an effective newborn screening program with quick clinical diagnostic criteria. Cognitive and motor development were evaluated using the Bayley Scales of Infant and Toddler Development-Third Edition at 6, 12, and 24 months of age. The patients who were treated very early demonstrate normal cognitive development with no significant change in cognition during this period (P = .18 > .05). The cognitive development was positively correlated with motor development (r = 0.533, P = .011). The results indicated that very early enzyme replacement therapy could protect cognitive development in patients with infantile-onset Pompe disease up to 24 months of age.

From Cryptic Toward Canonical Pre-mRNA Splicing in Pompe Disease: a Pipeline for the Development of Antisense Oligonucleotides

While 9% of human pathogenic variants have an established effect on pre-mRNA splicing, it is suspected that an additional 20% of otherwise classified variants also affect splicing. Aberrant splicing includes disruption of splice sites or regulatory elements, or creation or strengthening of cryptic splice sites. For the majority of variants, it is poorly understood to what extent and how these may affect splicing. We have identified cryptic splicing in an unbiased manner. Three types of cryptic splicing were analyzed in the context of pathogenic variants in the acid α-glucosidase gene causing Pompe disease. These involved newly formed deep intronic or exonic cryptic splice sites, and a natural cryptic splice that was utilized due to weakening of a canonical splice site. Antisense oligonucleotides that targeted the identified cryptic splice sites repressed cryptic splicing at the expense of canonical splicing in all three cases, as shown by reverse-transcriptase-quantitative polymerase chain reaction analysis and by enhancement of acid α-glucosidase enzymatic activity. This argues for a competition model for available splice sites, including intact or weakened canonical sites and natural or newly formed cryptic sites. The pipeline described here can detect cryptic splicing and correct canonical splicing using antisense oligonucleotides to restore the gene defect.

Very Early Treatment for Infantile-Onset Pompe Disease Contributes to Better Outcomes

OBJECTIVE

To evaluate whether very early treatment in our patients would result in better clinical outcomes and to compare these data with other infantile-onset Pompe disease (IOPD) cohort studies.

METHODS

In this nationwide program, 669,797 newborns were screened for Pompe disease. We diagnosed IOPD in 14 of these newborns, and all were treated and followed in our hospital.

RESULTS

After 2010, the mean age at first enzyme-replacement therapy (ERT) was 11.92 days. Our patients had better biological, physical, and developmental outcomes and lower anti-rh acid α-glucosidase antibodies after 2 years of treatment, even compared with one group that began ERT just 10 days later than our cohort. No patient had a hearing disorder or abnormal vision. The mean age for independent walking was 11.6 ± 1.3 months, the same age as normal children.

CONCLUSIONS

ERT for patients with IOPD should be initiated as early as possible before irreversible damage occurs. Our results indicate that early identification of patients with IOPD allows for the very early initiation of ERT. Starting ERT even a few days earlier may lead to better patient outcomes.

Ten years of the international Pompe survey: patient reported outcomes as a reliable tool for studying treated and untreated children and adults with non-classic Pompe disease

Pompe disease is a rare, progressive lysosomal storage disorder for which enzyme therapy (ERT) became available in 2006. Four years earlier, the IPA/Erasmus MC survey, an international longitudinal prospective survey, was established to collect information on the natural course of the disease and its burden on patients. The survey is a collaboration between Erasmus MC University Medical Center and the International Pompe Association (IPA) and comprises an annual questionnaire that was specifically designed to assess the symptoms and problems of the disease. Here we review our results of over 10 years of follow-up, and discuss the survey's contribution to the field. Tracking 408 Pompe patients between 2002 and 2013, the cumulative data reveals the broad range of clinical manifestations that interfere with patients' lives. The survey allowed us to quantify the rate of disease progression and the positive effects of ERT on patients' quality of life, fatigue, and participation in daily life. Furthermore, it showed for the first time that survival is reduced in adult Pompe disease and improved by ERT. Our results show that a patient survey can serve as a valuable and reliable tool for obtaining quantifiable information on the natural course of a rare disease and on the effects of therapy in a large cohort over a very long time. Most importantly, by working with patient reported outcomes, the survey provides the data that is truly relevant to the patient and complementary to clinical datasets.

Cognitive profile of patients with glycogen storage disease type III: a clinical description of seven cases

BACKGROUND

Glycogen storage disease type III (GSDIII) is a rare autosomal recessive disorder due to glycogen debranching enzyme (GDE) deficiency. It results in a multisystemic disease with predominant hepatic and myopathic symptoms. While frequent social maladjustment has been observed in our clinical practice, cognitive and psychological disturbances have never been assessed. The aim of this pilot study was to examine and characterize the cognitive profile of patients with GSDIII.

METHODS

Seven patients (six women and one man, mean age: 38.7 ± 11.6 years) with GSDIII underwent a neuropsychological set of tests assessing global cognitive efficiency, executive functions, social cognition, apathy, and episodic memory.

RESULTS

All patients presented previous psychopathological history. We observed attention fluctuations for each patient, and impaired global cognitive efficiency with deficiencies in executive functions in 5/7 patients. Emotional skills (social cognition) were impaired in five patients. Memory was mostly preserved.

CONCLUSION

The impairment in social cognition (recognition of emotions and ability to attribute mental states to others) and executive functions observed could be a consequence of orbito-frontal dysfunction due to the abnormal glycogen metabolism characteristic of the underlying disease. These results are consistent with the hypothesis of a central nervous system involvement in patients with GSDIII, but need to be confirmed in future research. This could explain the social and economic difficulties, and the lack of compliance to the medical follow-up presented by these patients. It suggests that these disturbances need to be taken into account when planning the medical management of patients with GSDIII.

Long-term prognosis of patients with infantile-onset Pompe disease diagnosed by newborn screening and treated since birth

OBJECTIVE

To determine the benefit of newborn screening for the long-term prognosis of patients with classic infantile-onset Pompe disease (IOPD).

STUDY DESIGN

A cohort of patients with classic IOPD were diagnosed by newborn screening, treated with recombinant human acid α-glucosidase (rhGAA), and followed prospectively. Outcome measurements included survival, left ventricular mass, serum creatinine kinase, motor function, mental development, and systemic manifestations.

RESULTS

Ten patients who presented with left ventricular hypertrophy at diagnosis received rhGAA infusions starting at a median age of 16 days (6-34 days). All patients were cross-reactive immunologic material-positive. After a median treatment time of 63 months (range 28-90 months), all could walk independently, and none required mechanical ventilation. All patients had motor capability sufficient for participating in daily activities, but muscle weakness over the pelvic girdle appeared gradually after 2 years of age. Ptosis was present in one-half of the patients, and speech disorders were common. Anti-rhGAA antibody titers were low (median maximal titer value 1:1600, range: undetectable ∼ 1:12,800).

CONCLUSION

By studying patients treated since birth who have no significant anti-rhGAA antibody interference, this prospective study demonstrates that the efficacy of rhGAA therapy is high and consistent for the treatment of classic IOPD. This study also exposes limitations of rhGAA treatment. The etiology of the manifestations in these early-treated patients will require further study.

Premature pubarche in children with Pompe disease

Pompe disease (PD), or glycogen storage disease type II, results from deficiency of acid α-glucosidase. Patients with infantile-onset PD die by early childhood if untreated. Patient survival has improved with enzyme replacement therapy. We report a case series of 8 patients with infantile-onset PD on enzyme replacement therapy with premature pubarche.

Pompe disease: literature review and case series

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

Spectrum of metabolic myopathies

Metabolic myopathies are disorders of utilization of carbohydrates or fat in muscles. The acute nature of energy failure is manifested either by a metabolic crisis with weakness, sometimes associated with respiratory failure, or by myoglobinuria. A typical disorder where permanent weakness occurs is glycogenosis type II (GSDII or Pompe disease) both in infantile and late-onset forms, where respiratory insufficiency is manifested by a large number of cases. In GSDII the pathogenetic mechanism is still poorly understood, and has to be attributed more to structural muscle alterations, possibly in correlation to macro-autophagy, rather than to energetic failure. This review is focused on recent advances about GSDII and its treatment, and the most recent notions about the management and treatment of other metabolic myopathies will be briefly reviewed, including glycogenosis type V (McArdle disease), glycogenosis type III (debrancher enzyme deficiency or Cori disease), CPT-II deficiency, and ETF-dehydrogenase deficiency (also known as riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency or RR-MADD). The discovery of the genetic defect in ETF dehydrogenase confirms the etiology of this syndrome. Other metabolic myopathies with massive lipid storage and weakness are carnitine deficiency, neutral lipid storage-myopathy (NLSD-M), besides RR-MADD. Enzyme replacement therapy is presented with critical consideration and for each of the lipid storage disorders, representative cases and their response to therapy is included. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Treatment of lysosomal storage disorders: successes and challenges

Treatment options for a number of lysosomal storage disorders have rapidly expanded and currently include enzyme replacement therapy, substrate reduction, chaperone treatment, hematopoietic stem cell transplantation, and gene-therapy. Combination treatments are also explored. Most therapies are not curative but change the phenotypic expression of the disease. The effectiveness of treatment varies considerably between the different diseases, but also between sub-groups of patients with a specific lysosomal storage disorder. The heterogeneity of the patient populations complicates the prediction of benefits of therapy, specifically in patients with milder disease manifestations. In addition, there is a lack of data on the natural history of diseases and disease phenotypes. Initial trial data show benefits on relevant short-term endpoints, but the real world situation may reveal different outcomes. Collaborative international studies are much needed to study the long-term clinical efficacy of treatments, and to detect new complications or associated conditions of the diseases. This review summarizes the available treatment modalities for lysosomal storage disorders and the challenges associated with long term clinical care for these patients.

New insights in the field of muscle glycogenoses

PURPOSE OF REVIEW

This review highlights recent contributions regarding clinical heterogeneity, pathogenic mechanisms, therapeutic trials, and animal models of the muscle glycogenoses.

RECENT FINDINGS

Most recent publications have dealt with the clinical effects of enzyme replacement therapy (ERT) in glycogenosis type II (Pompe disease), including the cognitive development of children with the infantile form who have reached school age. Standardized exercise testing has shown the similarity between McArdle disease and one of the most recently described muscle glycogenoses, phosphoglucomutase deficiency. Cycle ergometry in patients with glycogenosis type III (debrancher deficiency) without overt weakness has documented exercise intolerance relieved by glucose infusion, consistent with the glycogenolytic block. A mouse model of McArdle disease faithfully recapitulates most features of the human disease and will prove valuable for a better understanding of pathogenesis and therapeutic modalities. Polyglucosan body myopathy with cardiomyopathy has been associated with mutations in RBCK1, a ubiquitin ligase, which have also been reported in children with early-onset immune disorder. The role of polyglucosan storage in muscle and in both central and peripheral nervous systems has been confirmed in the infantile and late-onset forms of glycogenosis type IV (brancher enzyme deficiency). Additional novel findings include the involvement of the heart in one patient with phosphofructokinase (PFK) deficiency and the presence of tubular aggregates in a manifesting heterozygote with phosphoglycerate mutase deficiency.

SUMMARY

Important recent developments in the field of muscle glycogenoses include a new disease entity, a new animal model of McArdle disease, and better knowledge of the pathogenesis in some glycogenoses and of the long-term effects of enzyme replacement therapy in Pompe disease.

New innovations: therapeutic opportunities for intellectual disabilities

Intellectual disability is common and is associated with significant morbidity. Until the latter half of the 20th century, there were no efficacious treatments. Following initial breakthroughs associated with newborn screening and metabolic corrections, little progress was made until recently. With improved understanding of genetic and cellular mechanisms, novel treatment options are beginning to appear for a number of specific conditions. Fragile X and tuberous sclerosis offer paradigms for the development of targeted therapeutics, but advances in understanding of other disorders such as Down syndrome and Rett syndrome, for example, are also resulting in promising treatment directions. In addition, better understanding of the underlying neurobiology is leading to novel developments in enzyme replacement for storage disorders and adjunctive therapies for metabolic disorders, as well as potentially more generalizable approaches that target dysfunctional cell regulation via RNA and chromatin. Physiologic therapies, including deep brain stimulation and transcranial magnetic stimulation, offer yet another direction to enhance cognitive functioning. Current options and evolving opportunities for the intellectually disabled are reviewed and exemplified.

The brain in late-onset glycogenosis II: a structural and functional MRI study

BACKGROUND

Late-onset glycogenosis type II (GSD II) is a rare, multisystem disorder mainly affecting limb and respiratory muscles due to acid alpha glucosidase deficiency. Despite evidence at autopsy of glycogen accumulation in the brain, no study exploring brain functions is yet available.

OBJECTIVE

Our objective in this study was to assess brain changes in late-onset GSD II.

METHODS

Each patient underwent a standardized neuropsychological assessment, regional grey-matter (GM) atrophy, and resting-state functional magnetic resonance imaging (RS-fMRI). Functional connectivity maps of the salience (SN) and default-mode (DMN) networks were considered. A group of age- and gender-matched healthy controls was enrolled for MRI comparisons. P values family-wise error (FWE) cluster level corrected inferior to 0.05 were considered.

RESULTS

Nine GSD II patients (age 46.6 ± 8.0; 55% male) were recruited. No significant GM atrophy was found in patients compared with controls (n = 18; age 48.0 ± 9.8,;40% male). Functional connectivity within the SN was selectively reduced in patients, and cingulate gyrus and medial frontal cortex were mainly involved. Accordingly, patients had significant impairment of executive functions (as measured by Wisconsin Card Sorting test), whereas other cognitive domains were within mean normal ranges.

CONCLUSIONS

Our findings extend the clinical spectrum of GSD II by indicating that brain changes occur in this muscular disorder. Above all, these results should lead to better examinations of therapeutic approaches and perspectives for the affected patients. Further studies evaluating in depth these issues are warranted.

Enzyme replacement in neuronal storage disorders in the pediatric population

OPINION STATEMENT

In the past 15 years, for select lysosomal storage diseases, there has been a shift from symptom management to disease modification in terms of treatment strategy, mainly related to use of enzyme replacement therapy (ERT). Yet the application of ERT is for very few diseases, and while beneficial, ERT does not represent a cure. For some disorders, the advent of ERT has made a dramatic impact, while for others, benefits have been much more modest. Understanding of the long-term effects as well as the appropriate time for initiation of ERT is under exploration in a number of diseases, while the feasibility of ERT is still being established for others. No definite effects of ERT on central nervous system manifestations of lysosomal storage diseases have been observed for any disease to date. New strategies, including intrathecal enzyme replacement, gene therapy and substrate reduction therapy are being developed in animal models and clinical trials, which hopefully will begin a new era of nervous system disease modification in neuronal storage disorders.

Therapeutic advances in the management of Pompe disease and other metabolic myopathies

The world of metabolic myopathies has been dramatically modified by the advent of enzyme replacement therapy (ERT), the first causative treatment for glycogenosis type II (GSDII) or Pompe disease, which has given new impetus to research into that disease and also other pathologies. This article reviews new advances in the treatment of GSDII, the consensus about ERT, and its limitations. In addition, the most recent knowledge regarding the pathophysiology, phenotype, and genotype of the disease is discussed. Pharmacological, immunotherapy, nutritional, and physical/rehabilitative treatments for late-onset Pompe disease and other metabolic myopathies are covered, including treatments for defects in glycogen metabolism, such as glycogenosis type V (McArdle disease), and glycogenosis type III (debrancher enzyme deficiency), and defects in lipid metabolism, such as carnitine palmitoyltransferase II deficiency and electron transferring flavoprotein dehydrogenase deficiency, or riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency.