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

Pompe disease: Unmet needs and emerging therapies

Pompe disease is a debilitating and life-threatening disease caused by aberrant accumulation of glycogen resulting from reduced acid alpha-glucosidase activity. The first treatment for Pompe disease, the enzyme replacement therapy, Myozyme® (recombinant human acid alpha-glucosidase, alglucosidase alfa), is a lifesaving treatment for the most severe form of the disease and provided clinically meaningful benefits to patients with milder phenotypes. Nonetheless, many patients display suboptimal responses or clinical decline following years of alglucosidase alfa treatment. The approval of avalglucosidase alfa (Nexviazyme®) and cipaglucosidase alfa (Pombiliti®) with miglustat (Opfolda®) represents a new generation of enzyme replacement therapies seeking to further improve patient outcomes beyond alglucosidase alfa. However, the emergence of a complicated new phenotype with central nervous system involvement following long-term treatment, coupled with known and anticipated unmet needs of patients receiving enzyme replacement therapy, has prompted development of innovative new treatments. This review provides an overview of the challenges of existing treatments and a summary of emerging therapies currently in preclinical or clinical development for Pompe disease and related lysosomal storage disorders. Key treatments include tissue-targeted enzyme replacement therapy, which seeks to enhance enzyme concentration in target tissues such as the central nervous system; substrate reduction therapy, which reduces intracellular glycogen concentrations via novel mechanisms; and gene therapy, which may restore endogenous production of deficient acid alpha-glucosidase. Each of these proposed treatments shows promise as a future therapeutic option to improve quality of life in Pompe disease by more efficiently treating the underlying cause of disease progression: glycogen accumulation.

Preclinical lentiviral hematopoietic stem cell gene therapy corrects Pompe disease-related muscle and neurological manifestations

Pompe disease, a rare genetic neuromuscular disorder, is caused by a deficiency of acid alpha-glucosidase (GAA), leading to an accumulation of glycogen in lysosomes, and resulting in the progressive development of muscle weakness. The current standard treatment, enzyme replacement therapy (ERT), is not curative and has limitations such as poor penetration into skeletal muscle and both the central and peripheral nervous systems, a risk of immune responses against the recombinant enzyme, and the requirement for high doses and frequent infusions. To overcome these limitations, lentiviral vector-mediated hematopoietic stem and progenitor cell (HSPC) gene therapy has been proposed as a next-generation approach for treating Pompe disease. This study demonstrates the potential of lentiviral HSPC gene therapy to reverse the pathological effects of Pompe disease in a preclinical mouse model. It includes a comprehensive safety assessment via integration site analysis, along with single-cell RNA sequencing analysis of central nervous tissue samples to gain insights into the underlying mechanisms of phenotype correction.

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.

Severe CNS involvement in a subset of long-term treated children with infantile-onset Pompe disease

INTRODUCTION

The standard of care for patients with infantile-onset Pompe disease (IOPD) is enzyme replacement therapy (ERT), which does not cross the blood brain barrier. While neuromuscular manifestations of IOPD are well-described, central nervous system (CNS) manifestations of this disorder are far less characterized. Here we describe severe CNS-related neurological manifestations including seizures and encephalopathy in six individuals with IOPD.

METHOD

We identified six children with IOPD who developed CNS manifestations such as seizures and/or encephalopathy. We studied their brain magnetic resonance imaging scans (MRIs) and graded the severity of white matter hyperintensities (WMHI) using the Fazekas scale scoring system as previously published. Longitudinal cognitive measures were available from 4/6 children.

RESULTS

All six IOPD patients (4 males/2 females) had been treated with ERT for 12-15 years. Seizures and/or encephalopathy were noted at a median age at onset of 11.9 years (range 9-15 years). All were noted to have extensive WMHI in the brain MRIs and very high Fazekas scores which preceded the onset of neurological symptoms. Longitudinal IQ scores from four of these children suggested developmental plateauing.

DISCUSSION

Among a subset of IOPD patients on long-term ERT, CNS manifestations including hyperreflexia, encephalopathy and seizures may become prominent, and there is likely an association between these symptoms and significant WMHI on MRI. Further study is needed to identify risk factors for CNS deterioration among children with IOPD and develop interventions to prevent neurological decline.

Lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a group of inherited metabolic diseases caused by dysfunction of the lysosomal system, with subsequent progressive accumulation of macromolecules, activation of inflammatory response, and cell death. Neurologic damage is almost always present, and it is usually degenerative. White matter (WM) involvement may be primary or secondary. Diseases with primary WM involvement are leukodystrophies, demyelinating (Krabbe disease and metachromatic leukodystrophy), and hypomyelinating leukodystrophies (free sialic acid storage disease, fucosidosis, and mucolipidosis type IV). LSDs with secondary WM involvement are classified as leukoencephalopathies and include gangliosidosis, mucopolysaccharidosis (MPS), ceroid neuronal lipofuscinosis, multiple sulfatase deficiency, alpha-mannosidosis, Pompe disease, and Fabry disease. Neurologic manifestations may overlap among LSDs and include developmental delays, motor, cognitive and speech impairments, seizures, visual failure, ataxia, and extrapyramidal signs. Most of LSDs are typically present in early or late infancy, but juvenile and adult forms also exist and are associated with predominantly neuropsychiatric and behavioral symptoms. The outcome of these disorders is generally poor and specific treatments (enzyme replacement therapy, hematopoietic stem cell transplantation, or gene therapy) are only available in a small number of them.

Gene and Cellular Therapies for Leukodystrophies

Leukodystrophies are a heterogenous group of inherited, degenerative encephalopathies, that if left untreated, are often lethal at an early age. Although some of the leukodystrophies can be treated with allogeneic hematopoietic stem cell transplantation, not all patients have suitable donors, and new treatment strategies, such as gene therapy, are rapidly being developed. Recent developments in the field of gene therapy for severe combined immune deficiencies, Leber's amaurosis, epidermolysis bullosa, Duchenne's muscular dystrophy and spinal muscular atrophy, have paved the way for the treatment of leukodystrophies, revealing some of the pitfalls, but overall showing promising results. Gene therapy offers the possibility for overexpression of secretable enzymes that can be released and through uptake, allow cross-correction of affected cells. Here, we discuss some of the leukodystrophies that have demonstrated strong potential for gene therapy interventions, such as X-linked adrenoleukodystrophy (X-ALD), and metachromatic leukodystrophy (MLD), which have reached clinical application. We further discuss the advantages and disadvantages of ex vivo lentiviral hematopoietic stem cell gene therapy, an approach for targeting microglia-like cells or rendering cross-correction. In addition, we summarize ongoing developments in the field of in vivo administration of recombinant adeno-associated viral (rAAV) vectors, which can be used for direct targeting of affected cells, and other recently developed molecular technologies that may be applicable to treating leukodystrophies in the future.

[Research progress of nervous system damage in Pompe disease]

Pompe disease, also known as glycogen storage disease type Ⅱ, is a rare autosomal recessive disease. With the application of enzyme replacement therapy, more and more patients with Pompe disease can survive to adulthood, and nervous system-related clinical manifestations gradually emerge. Nervous system involvement seriously affects the quality of life of patients with Pompe disease, and a systematic understanding of the clinical manifestations, imaging features and pathological changes of nervous system injury in Pompe disease is of great significance for the early identification and intervention of Pompe disease. This article reviews the research progress of neurological damage in Pompe disease.

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

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

Combined targeted and untargeted high-resolution mass spectrometry analyses to investigate metabolic alterations in pompe disease

INTRODUCTION

Pompe disease is a rare, lysosomal disorder, characterized by intra-lysosomal glycogen accumulation due to an impaired function of α-glucosidase enzyme. The laboratory testing for Pompe is usually performed by enzyme activity, genetic test, or urine glucose tetrasaccharide (Glc4) screening by HPLC. Despite being a good preliminary marker, the Glc4 is not specific for Pompe.

OBJECTIVE

The purpose of the present study was to develop a simple methodology using liquid chromatography-high resolution mass spectrometry (LC-HRMS) for targeted quantitative analysis of Glc₄ combined with untargeted metabolic profiling in a single analytical run to search for complementary biomarkers in Pompe disease.

METHODS

We collected 21 urine specimens from 13 Pompe disease patients and compared their metabolic signatures with 21 control specimens.

RESULTS

Multivariate statistical analyses on the untargeted profiling data revealed Glc₄, creatine, sorbitol/mannitol, L-phenylalanine, N-acetyl-4-aminobutanal, N-acetyl-L-aspartic acid, and 2-aminobenzoic acid as significantly altered in Pompe disease. This panel of metabolites increased sample class prediction (Pompe disease versus control) compared with a single biomarker.

CONCLUSION

This study has demonstrated the potential of combined acquisition methods in LC-HRMS for Pompe disease investigation, allowing for routine determination of an established biomarker and discovery of complementary candidate biomarkers that may increase diagnostic accuracy, or improve the risk stratification of patients with disparate clinical phenotypes.

Evaluating brain white matter hyperintensity, IQ scores, and plasma neurofilament light chain concentration in early-treated patients with infantile-onset Pompe disease

PURPOSE

The study aimed to describe central nervous system (CNS) progression in patients with infantile-onset Pompe disease (IOPD) and explore the potential clinical impact and predictors.

METHODS

Patients with IOPD treated with enzyme replacement therapy were longitudinally followed with brain magnetic resonance imaging (MRI) and evaluation for IQ scores from 2004 to 2021. Investigation of CNS involvement focused on white matter (WM) abnormalities and was quantified using a scoring system for metachromatic leukodystrophy. MRI scores were correlated with plasma neurofilament light chain (NfL) concentration and IQ scores.

RESULTS

A total of 19 patients who started enzyme replacement therapy at a mean age of 26 days were analyzed; the median age at last examination was 12.1 (range = 1.7-19) years. MRI abnormalities were found in all patients, from supratentorial central WM to U-fibers, then to infratentorial WM, and eventually to gray matter. MRI scores progressed (n = 16) at variable rates (range = 0.8-2.7/y) and were positively correlated with age (n = 16) and negatively correlated with IQ scores (n = 8). Plasma NfL concentration was positively correlated with MRI scores (r² = 0.8569; P < .001; n = 13).

CONCLUSION

Our results suggest that the progression of CNS involvement in IOPD may be associated with neuroaxonal injury and decreased IQ scores. NfL could serve as a biomarker for CNS involvement in IOPD.

Gene Therapy Developments for Pompe Disease

Pompe disease is an inherited neuromuscular disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). The most severe form is infantile-onset Pompe disease, presenting shortly after birth with symptoms of cardiomyopathy, respiratory failure and skeletal muscle weakness. Late-onset Pompe disease is characterized by a slower disease progression, primarily affecting skeletal muscles. Despite recent advancements in enzyme replacement therapy management several limitations remain using this therapeutic approach, including risks of immunogenicity complications, inability to penetrate CNS tissue, and the need for life-long therapy. The next wave of promising single therapy interventions involves gene therapies, which are entering into a clinical translational stage. Both adeno-associated virus (AAV) vectors and lentiviral vector (LV)-mediated hematopoietic stem and progenitor (HSPC) gene therapy have the potential to provide effective therapy for this multisystemic disorder. Optimization of viral vector designs, providing tissue-specific expression and GAA protein modifications to enhance secretion and uptake has resulted in improved preclinical efficacy and safety data. In this review, we highlight gene therapy developments, in particular, AAV and LV HSPC-mediated gene therapy technologies, to potentially address all components of the neuromuscular associated Pompe disease pathology.

Cell type-selective targeted delivery of a recombinant lysosomal enzyme for enzyme therapies

Lysosomal diseases are a class of genetic disorders predominantly caused by loss of lysosomal hydrolases, leading to lysosomal and cellular dysfunction. Enzyme replacement therapy (ERT), where recombinant enzyme is given intravenously, internalized by cells, and trafficked to the lysosome, has been applied to treat several lysosomal diseases. However, current ERT regimens do not correct disease phenotypes in all affected organs because the biodistribution of enzyme uptake does not match that of the affected cells that require the enzyme. We present here targeted ERT, an approach that utilizes antibody-enzyme fusion proteins to target the enzyme to specific cell types. The antibody moiety recognizes transmembrane proteins involved in lysosomal trafficking and that are also preferentially expressed in those cells most affected in disease. Using Pompe disease (PD) as an example, we show that targeted ERT is superior to ERT in treating the skeletal muscle phenotypes of PD mice both as a protein replacement therapeutic and as a gene therapy.

Skeletal muscle magnetic resonance imaging in Pompe disease

Pompe disease is characterized by a deficiency of acid alpha-glucosidase that results in muscle weakness and a variable degree of disability. There is an approved therapy based on enzymatic replacement that has modified disease progression. Several reports describing muscle magnetic resonance imaging (MRI) features of Pompe patients have been published. Most of the studies have focused on late-onset Pompe disease (LOPD) and identified a characteristic pattern of muscle involvement useful for the diagnosis. In addition, quantitative MRI studies have shown a progressive increase in fat in skeletal muscles of LOPD over time and they are increasingly considered a good tool to monitor progression of the disease. The studies performed in infantile-onset Pompe disease patients have shown less consistent changes. Other more sophisticated muscle MRI sequences, such as diffusion tensor imaging or glycogen spectroscopy, have also been used in Pompe patients and have shown promising results.

Novel approaches to quantify CNS involvement in children with Pompe disease

OBJECTIVE

To characterize the extent of CNS involvement in children with Pompe disease using brain MRI and developmental assessments.

METHODS

The study included 14 children (ages 6-18 years) with infantile Pompe disease (IPD) (n = 12) or late-onset Pompe disease (LOPD) (n = 2) receiving enzyme replacement therapy. White matter (WM) hyperintense foci seen in the brain MRIs were systematically quantified using the Fazekas scale (FS) grading system with a novel approach: the individual FS scores from 10 anatomical areas were summed to yield a total FS score (range absent [0] to severe [30]) for each child. The FS scores were compared to developmental assessments of cognition and language obtained during the same time period.

RESULTS

Mild to severe WM hyperintense foci were seen in 10/12 children with IPD (median age 10.6 years) with total FS scores ranging from 2 to 23. Periventricular, subcortical, and deep WM were involved. WM hyperintense foci were seen throughout the path of the corticospinal tracts in the brain in children with IPD. Two children with IPD had no WM hyperintense foci. Children with IPD had relative weaknesses in processing speed, fluid reasoning, visual perception, and receptive vocabulary. The 2 children with LOPD had no WM hyperintense foci, and high scores on most developmental assessments.

CONCLUSION

This study systematically characterized WM hyperintense foci in children with IPD, which could serve as a benchmark for longitudinal follow-up of WM abnormalities in patients with Pompe disease and other known neurodegenerative disorders or leukodystrophies in children.

Treating lysosomal storage disorders: What have we learnt?

The first enzyme replacement therapy (ERT) for a lysosomal storage disorder (LSD) was approved in 1991 and we now have more than 25 years of experience of treating patients with type 1 Gaucher disease. Because of the remarkable success of this therapy, enormous effort and resource has gone into developing other ERTs, for Gaucher (where three different enzyme preparations have now been approved) and for other LSDs. We now have more than 10 years of clinical experience in using ERT to treat Gaucher, Fabry, Pompe and MPS I, II, and VI. This article aims to assess the real-life experience of a selection of these innovative and expensive treatments to see if they have met the high expectations which were set for them when they launched.

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.

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.

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.

Neuroimaging Findings in Lysosomal Disorders: 2018 Update

Lysosomal storage disorders are a heterogeneous group of genetic diseases characterized by defective function in one of the lysosomal enzymes. In this review paper, we describe neuroradiological findings and clinical characteristics of neuronopathic lysosomal disorders with a focus on differential diagnosis. New insights regarding pathogenesis and therapeutic perspectives are also briefly discussed.

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.

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.