Epidemiology and diagnosis of lysosomal storage disorders; challenges of screening

Natural history of acid sphingomyelinase deficiency among European patients during childhood and adolescence: A retrospective observational study

Acid sphingomyelinase deficiency (ASMD) is a rare, lysosomal storage disease with limited evidence on its natural history. This retrospective, medical record abstraction study aimed to characterize the natural history of ASMD (types B and A/B) during childhood and adolescence. Recruiting sites were European centers (i.e., France, Germany, Italy, and the United Kingdom) from the ASCEND-Peds trial (NCT02292654); these sites were targeted because of the rarity of ASMD and specialized care provided at these centers. The study population comprised ASMD trial patients (before exposure to treatment) and ASMD non-trial participants who were managed at the same trial sites. Overall, 18 patients were included (11 trials; 7 non-trials; median [Q1;Q3] age at ASMD diagnosis: 2.5 [1.0;4.0] years). Median follow-up duration was 10.0 years. Frequently reported medical conditions were hepatobiliary (17 [94.4%]) and blood and lymphatic system disorders (16 [88.9%]). Adenoidectomy (3 [16.7%]) was the most commonly reported surgical procedures; gastroenteritis (5 [27.8%]) was the most frequently reported infections, and epistaxis (6 [33.3%]) was the most commonly reported bleeding events. Abnormal spleen (16 [88.9%]) and liver (15 [83.3%]) size and respiratory function (8 [44.4%]) were commonly reported during physical examination. Overall, 11 (61.1%) patients were hospitalized; 6 (33.3%) patients had emergency room visits. Findings were consistent with published literature and support the current understanding of natural history of ASMD.

Development, validation and application of single molecule molecular inversion probe based novel integrated genetic screening method for 29 common lysosomal storage disorders in India

BACKGROUND

Current clinical diagnosis pathway for lysosomal storage disorders (LSDs) involves sequential biochemical enzymatic tests followed by DNA sequencing, which is iterative, has low diagnostic yield and is costly due to overlapping clinical presentations. Here, we describe a novel low-cost and high-throughput sequencing assay using single-molecule molecular inversion probes (smMIPs) to screen for causative single nucleotide variants (SNVs) and copy number variants (CNVs) in genes associated with 29 common LSDs in India.

RESULTS

903 smMIPs were designed to target exon and exon-intron boundaries of targeted genes (n = 23; 53.7 kb of the human genome) and were equimolarly pooled to create a sequencing library. After extensive validation in a cohort of 50 patients, we screened 300 patients with either biochemical diagnosis (n = 187) or clinical suspicion (n = 113) of LSDs. A diagnostic yield of 83.4% was observed in patients with prior biochemical diagnosis of LSD. Furthermore, diagnostic yield of 73.9% (n = 54/73) was observed in patients with high clinical suspicion of LSD in contrast with 2.4% (n = 1/40) in patients with low clinical suspicion of LSD. In addition to detecting SNVs, the assay could detect single and multi-exon copy number variants with high confidence. Critically, Niemann-Pick disease type C and neuronal ceroid lipofuscinosis-6 diseases for which biochemical testing is unavailable, could be diagnosed using our assay. Lastly, we observed a non-inferior performance of the assay in DNA extracted from dried blood spots in comparison with whole blood.

CONCLUSION

We developed a flexible and scalable assay to reliably detect genetic causes of 29 common LSDs in India. The assay consolidates the detection of multiple variant types in multiple sample types while having improved diagnostic yield at same or lower cost compared to current clinical paradigm.

A retrospective study of morbidity and mortality of chronic acid sphingomyelinase deficiency in Germany

BACKGROUND

Acid sphingomyelinase deficiency (ASMD) is a rare, progressive, potentially fatal lysosomal storage disease that exhibits a broad spectrum of clinical phenotypes. There is a need to expand the knowledge of disease mortality and morbidity in Germany because of limited information on survival analysis in patients with chronic ASMD (type B or type A/B).

METHODS

This observational, multicentre, retrospective cohort study was conducted using medical records of patients with the first symptom onset/diagnosis of ASMD type B or type A/B between 1st January 1990 and 31st July 2021 from four German medical centres. Eligible medical records were abstracted to collect data on demographic characteristics, medical history, hospitalisation, mortality, and causes of death from disease onset to the last follow-up/death. Survival outcomes were estimated using the Kaplan-Meier analysis. Standardised mortality ratio (SMR) was also explored.

RESULTS

This study included 33 chart records of patients with ASMD type B (n = 24) and type A/B (n = 9), with a median (interquartile range [IQR]) age of 8.0 [3.0-20.0] years and 1.0 [1.0-2.0] years, respectively, at diagnosis. The commonly reported manifestations were related to spleen (100.0%), liver (93.9%), and respiratory (77.4%) abnormalities. Nine deaths were reported at a median [IQR] age of 17.0 [5.0-25.0] years, with 66.7% of overall patients deceased at less than 18 years of age; the median [IQR] age at death for patients with ASMD type B (n = 4) and type A/B (n = 5) was 31.0 [11.0-55.0] and 9.0 [4.0-18.0] years, respectively. All deaths were ASMD-related and primarily caused by liver or respiratory failures or severe progressive neurodegeneration (two patients with ASMD type A/B). The median (95% confidence interval [CI]) overall survival age since birth was 45.4 (17.5-65.0) years. Additionally, an SMR [95% CI] analysis (21.6 [9.8-38.0]) showed that age-specific deaths in the ASMD population were 21.6 times more frequent than that in the general German population.

CONCLUSIONS

This study highlights considerable morbidity and mortality associated with ASMD type B and type A/B in Germany. It further emphasises the importance of effective therapy for chronic ASMD to reduce disease complications.

Diagnostic odyssey for patients with acid sphingomyelinase deficiency (ASMD): Exploring the potential indicators of diagnosis using quantitative and qualitative data

Acid sphingomyelinase deficiency (ASMD) is a rare, progressive, and potentially fatal lysosomal storage disease. This two-part international study aimed to understand physician, patient, and caregivers' experiences during the ASMD diagnostic journey. Qualitative interviews were conducted with patients with ASMD type B or A/B, caregivers (for patients <18 years), and physicians (January 2018-May 2019). A quantitative patient chart review was then performed by physicians (1-3 charts per physician) (April to May 2020). Overall, 12 physicians and 27 patients (self-reported, n = 11; caregiver-reported, n = 16) completed qualitative interviews. Symptoms first presented at approximately 2 years, with physician visits 2 months-1 year later. On average, diagnosis took 3 years and average age at diagnosis was 5 years. During childhood, all patients reported abdominal enlargement and 67% had respiratory issues. Adult patients frequently reported fatigue (64%) and heart problems (36%). In the quantitative study, 86 physicians reviewed 193 ASMD patient charts. At initial presentation, most patients reported abdominal enlargement (pediatric, 55%; adolescents/adults, 39%). Time to diagnosis ranged 0-10 years for patients with ASMD type A/B or type B, and most patients (85%) received an incorrect initial diagnosis. Diagnosis of ASMD can be challenging, and is often delayed due to disease heterogeneity and misdiagnoses.

Survival of patients with chronic acid sphingomyelinase deficiency (ASMD) in the United States: A retrospective chart review study

Background

Acid sphingomyelinase deficiency (ASMD), historically known as Niemann-Pick disease type A, A/B, and B, is a rare lysosomal storage pathology with multisystemic clinical manifestations. The aims of this study were to estimate the survival probability in patients in the United States with chronic ASMD (ASMD types B and A/B), and to describe the disease characteristics of these patients.

Methods

This observational retrospective study included medical chart records of patients with chronic ASMD with retrievable data abstracted by 69 participating physicians from 25 medical centers in the United States. Included patients had a date of ASMD diagnosis or first presentation to a physician for ASMD symptoms (whichever occurred first) between January 01, 1990, and February 28, 2021. Medical chart records were excluded if patients were diagnosed with ASMD type A. Eligible medical chart records were abstracted to collect demographic, medical and developmental history, and mortality data. Survival outcomes were analyzed using Kaplan-Meier survival analyses from birth until death.

Results

The overall study population (N = 110) included 69 patients with ASMD type B, nine with type A/B, and 32 with ASMD "non-type A" (ASMD subtype was unknown, but patients were confirmed as not having ASMD type A). The majority of patients were male with a median age at diagnosis of 3.8 years. Thirty-eight patients died during the study observation period, at a median age of 6.8 years. The median (95% confidence interval) survival age from birth was 21.3 (10.2; 60.4) years. At diagnosis or first presentation, 42.7% patients had ≥1 ASMD-related complication; splenic (30.0%) and hepatobiliary (20.9%) being the most common, and 40.9% required ≥1 medical visit due to complications.

Conclusion

Patients with chronic ASMD in the United States have poor survival and significant burden of illness.

Real-life impacts of olipudase alfa: The experience of patients and families taking an enzyme replacement therapy for acid sphingomyelinase deficiency

BACKGROUND

Acid Sphingomyelinase Deficiency (ASMD) is an ultra-rare autosomal recessive lysosomal storage disorder characterized by intracellular lipid accumulation resulting from reduced function of acid sphingomyelinase. Olipudase alfa, an enzyme replacement therapy, was recently approved in several countries for the treatment of the non-neurologic manifestations of ASMD. Studies demonstrate improvement in organomegaly, pulmonary function and lipid profiles with olipudase alfa, yet little is known about its impact on quality of life (QoL) for patients and caregivers. The purpose of this study is to better understand the real-life impact of ASMD on patients and caregivers and assess how olipudase alfa impacts QoL for pediatric patients and their caregivers.

METHODS

Caregivers of pediatric patients (≤ 18 years of age) with a confirmed diagnosis of ASMD that received olipudase alfa for at least 12 months were recruited in early 2022 through national patient organizations to participate in a global online questionnaire followed by semi-structured interviews. Ten caregivers of patients with ASMD who utilized olipudase alfa as an experimental therapy for pediatric patients participated in the study. Quantitative analysis of the results was undertaken, and qualitative data was analyzed using an inductive thematic approach.

RESULTS

Ten eligible participants completed questionnaires, and 8 of the 10 went on to participate in structured interviews. Symptom burden of ASMD and impact on symptomatology and quality of life after olipudase alfa use are reported here. Five themes emerged from analysis: (1) ASMD is a systemic disease with a wide array of manifestations that significantly impact QoL; (2) Olipudase alfa was associated with improvements in all non-neurologic manifestations of ASMD; (3) Participants perceived the risk associated with olipudase alfa to be low and the benefits to greatly outweigh any risk or burden; (4) Participants reported an unmet need to treat the neurologic manifestations of the disease despite the benefits of olipudase alfa in the management of non-neurological symptoms; (5) Participants felt all patients with ASMD need access to olipudase alfa based on the life-changing experience they perceived.

CONCLUSIONS

These findings highlight the sustained positive impact olipudase alfa had in many domains that are deemed important to patients and families living with ASMD and outline the extensive unmet need for patients and families living with ASMD.

Sphingolipidoses in Morocco: Chemical profiling for an affordable and rapid diagnosis strategy

Sphingolipidoses are a group of metabolic diseases in which lysosomal hydrolases dysfunction disrupt normal sphingolipids' metabolism, leading to excess accumulation in cellular compartments and excretion in urine. These pathologies represent a significant burden among Moroccan population, for which an easy access to enzymatic assays and genetic tests is not guaranteed. Parallel analytical methods thus have to be developed for preliminary screening. In this study, 107 patients were addressed to the metabolic platform of the Marrakesh Faculty of Medicine for diagnosis confirmation. Thin-Layer Chromatography was used as a first step to perform chemical profiling of the patients' urinary lipids, allowing 36% of the patients to be efficiently oriented towards the adequate enzymatic assay. UPLC-MS/MS analyses of urinary sulfatides excreted in urines patient had been used to control the reliability of TLC analysis and to obtain more accurate information related to the sulfatides isoforms. This analytical process combining TLC with UPLC-MS/MS has enabled rapid and appropriate patient management in a reduced time and with reduced resources.

Curated incidence of lysosomal storage diseases from the Taiwan Biobank

Lysosomal storage diseases (LSDs) are a group of metabolic disorders resulting from a deficiency in one of the lysosomal hydrolases. Most LSDs are inherited in an autosomal or X-linked recessive manner. As LSDs are rare, their true incidence in Taiwan remains unknown. In this study, we used high-coverage whole-genome sequencing data from 1,495 Taiwanese individuals obtained from the Taiwan Biobank. We found 3826 variants in 71 genes responsible for autosomal recessive LSDs. We first excluded benign variants by allele frequency and other criteria. As a result, 270 variants were considered disease-causing. We curated these variants using published guidelines from the American College of Medical Genetics and Genomics (ACMG). Our results revealed a combined incidence rate of 13 per 100,000 (conservative estimation by pathologic and likely pathogenic variants; 95% CI 6.92-22.23) to 94 per 100,000 (extended estimation by the inclusion of variants of unknown significance; 95% CI 75.96-115.03) among 71 autosomal recessive disease-associated genes. The conservative estimations were similar to those in published clinical data. No disease-causing mutations were found for 18 other diseases; thus, these diseases are likely extremely rare in Taiwan. The study results are important for designing screening and treatment methods for LSDs in Taiwan and demonstrate the importance of mutation curation to avoid overestimating disease incidences from genomic data.

Omics-Based Approaches for the Characterization of Pompe Disease Metabolic Phenotypes

Lysosomal storage disorders (LSDs) constitute a large group of rare, multisystemic, inherited disorders of metabolism, characterized by defects in lysosomal enzymes, accessory proteins, membrane transporters or trafficking proteins. Pompe disease (PD) is produced by mutations in the acid alpha-glucosidase (GAA) lysosomal enzyme. This enzymatic deficiency leads to the aberrant accumulation of glycogen in the lysosome. The onset of symptoms, including a variety of neurological and multiple-organ pathologies, can range from birth to adulthood, and disease severity can vary between individuals. Although very significant advances related to the development of new treatments, and also to the improvement of newborn screening programs and tools for a more accurate diagnosis and follow-up of patients, have occurred over recent years, there exists an unmet need for further understanding the molecular mechanisms underlying the progression of the disease. Also, the reason why currently available treatments lose effectiveness over time in some patients is not completely understood. In this scenario, characterization of the metabolic phenotype is a valuable approach to gain insights into the global impact of lysosomal dysfunction, and its potential correlation with clinical progression and response to therapies. These approaches represent a discovery tool for investigating disease-induced modifications in the complete metabolic profile, including large numbers of metabolites that are simultaneously analyzed, enabling the identification of novel potential biomarkers associated with these conditions. This review aims to highlight the most relevant findings of recently published omics-based studies with a particular focus on describing the clinical potential of the specific metabolic phenotypes associated to different subgroups of PD patients.

Experimental pharmacology: Targeting metabolic pathways

Since the discovery of the treatment for Wilson disease a growing number of treatable inherited dystonias have been identified and their search and treatment have progressively been implemented in the clinics of patients with dystonia. While waiting for gene therapy to be more widely and adequately translated into the clinical setting, the efforts to divert the natural course of dystonia reside in unveiling its pathogenesis. Specific metabolic treatments can rewrite the natural history of the disease by preventing neurotoxic metabolite accumulation or interfering with the cell accumulation of damaging metabolites, restoring energetic cell fuel, supplementing defective metabolites, and supplementing the defective enzyme. A metabolic derangement of cell homeostasis is part of the progression of many non-metabolic genetic lesions and could be the target for possible metabolic approaches. In this chapter, we provided an update on treatment strategies for treatable inherited dystonias and an overview of genetic dystonias with new experimental therapeutic approaches available or close to clinical translation.

Expert opinion on patient journey, diagnosis and clinical monitoring in acid sphingomyelinase deficiency in Turkey: a pediatric metabolic disease specialist's perspective

This review by a panel of pediatric metabolic disease specialists aimed to provide a practical and implementable guidance document to assist clinicians in best clinical practice in terms of recognition, diagnosis and management of patients with acid sphingomyelinase deficiency (ASMD). The participating experts consider the clinical suspicion of ASMD by the physician to be of utmost importance in the prevention of diagnostic delay and strongly suggest the use of a diagnostic algorithm including/starting with dried blood spots assay in the timely diagnosis of ASMD in patients presenting with hepatosplenomegaly and a need for increased awareness among physicians in this regard to consider ASMD in the differential diagnosis. In anticipation of the introduction of enzyme replacement therapy, raising awareness of the disease among physicians to prevent diagnostic delay and further investigation addressing natural history of ASMD across the disease spectrum, potential presenting characteristics with a high index of suspicion, as well as biomarkers and genotype-phenotype correlations suggestive of poor prognosis seem important in terms of implementation of best practice patterns.

Identifying the genetic causes of phenotypically diagnosed Pakistani mucopolysaccharidoses patients by whole genome sequencing

Background: Lysosomal storage disorders (LSDs) are a group of inherited metabolic diseases, which encompass more than 50 different subtypes of pathologies. These disorders are caused by defects in lysosomal enzymes, transporters, and other non-lysosomal proteins. Mucopolysaccharidosis (MPS) is the most common subgroup of lysosomal storage disorders in which the body is unable to properly breakdown mucopolysaccharides. The aim of the present study was to identify novel genes and pathogenic variants in families from diverse regions of Pakistan with clinically diagnosed mucopolysaccharidosis type I and mucopolysaccharidosis type II.

Methods: Clinical diagnosis identified 12 with mucopolysaccharidosis I and 2 with mucopolysaccharidosis II in 14 families and whole genome sequencing (WGS) was performed to identify the causative variations in 15 affected individuals. Twenty-two unaffected individuals including parents or normal siblings of patients were also sequenced. Putative causal variants were identified by co-segregation and functional annotation.

Results: Analysis of whole genome sequencing data revealed ten novel and six previously reported variants in lysosomal storage disorders-associated genes (IDUA, GALNS, SGSH, GAA, IDS, ALDOB, TRAPPC4, MASP1, SMARCAL, KIAA1109, HERC1, RRAS2) and a novel candidate gene (ABCA5) for lysosomal storage disorder-like phenotypes, which has previously been associated with symptoms strongly related with lysosomal storage disorder in animal models.

Conclusion: Multigenic inheritance was found in several families highlighting the importance of searching for homozygous pathogenic variants in several genes also in families with a high degree of consanguinity.

Acid sphingomyelinase deficiency (ASMD): addressing knowledge gaps in unmet needs and patient journey in Italy-a Delphi consensus

Acid sphingomyelinase deficiency (ASMD) is an ultra-rare disease, and several gaps of knowledge on various issues remain, particularly at a regional/national level. Expert opinions collected through well-defined consensus methodologies are increasingly used to make available reliable information in the context of rare/ultra-rare diseases. With the aim to provide indications on infantile neurovisceral ASMD (also formerly known as Niemann-Pick disease type A), chronic neurovisceral ASMD (formerly known as Niemann-Pick disease type A/B) and chronic visceral ASMD (formerly known as Niemann-Pick disease type B) in Italy, we conducted a Delphi consensus of experts focused on five main areas: (i) patients and disease characteristics; (ii) unmet needs and quality of life; (iii) diagnostic issues; (iv) treatment-related aspects; and (v) patient journey. Pre-specified, objective criteria were used to outline the multidisciplinary panel, based on 19 Italian experts in ASMD in paediatric and adult patients from different Italian Regions, including both clinicians (n = 16) and ASMD patients' advocacy or payors with expertise in rare diseases (n = 3). During two Delphi rounds, a high ratio of agreement was found on several topics related to ASMD characteristics, diagnosis, management and disease burden. Our findings may provide valuable indications for management of ASMD at a public health level in Italy.

Enzyme replacement therapy for children with acid sphingomyelinase deficiency in the real world: A single center experience in Taiwan

Background

Acid sphingomyelinase deficiency (ASMD) is a lysosomal storage disease with multi-systemic involvement, with no disease-modifying treatment available. Olipudase alfa is an investigational enzyme product developed to replace the deficient acid sphingomyelinase in ASMD patients. Several clinical trials have reported promising safety and efficacy results in adult and pediatric patients. However, no data have been reported outside of the clinical trial setting yet. This study aimed to evaluate major outcomes in pediatric chronic ASMD patients receiving olipudase alfa in the real-world setting.

Materials and methods

Two children with type A/B (chronic neuropathic) ASMD have received olipudase alfa treatment since May 2021. Clinical parameters, including height, weight, complete blood count, liver function tests, lipid profiles, biomarkers, abdominal ultrasonography with shear wave elastography, chest computed tomography, nerve conduction studies, neurodevelopmental evaluations, and six-minute walk tests, were checked at baseline and every three to six months in the first year of enzyme replacement therapy (ERT) to assess its efficacy and safety.

Results

The two patients in our study started olipudase alfa treatment at the age of 5 years and 8 months and 2 years and 6 months. During the first year of treatment, both patients saw a reduction in their hepatic and splenic volumes as well as liver stiffness. Height z-score, weight z-score, lipid profiles, biomarker levels, interstitial lung disease scores, and bone mineral densities also improved over time. The six-minute walk test showed a gradual increase in walking distance in both patients. There were no obvious improvements or deterioration in neurocognitive function and peripheral nerve conduction velocities after treatment. No severe infusion-associated reactions were noted during the first year of treatment. One patient had two episodes of transient but significantly elevated liver enzymes during the dose-escalation phase. The patient was asymptomatic, and the impaired liver function resolved spontaneously within two weeks.

Conclusion

Our results provide real-world experience that olipudase alfa is safe and effective in improving major systemic clinical outcomes for pediatric chronic ASMD patients. Monitoring of liver stiffness by shear wave elastography is a noninvasive procedure that can monitor treatment efficacy during ERT.

Similarities and differences between Gaucher disease and acid sphingomyelinase deficiency: An algorithm to support the diagnosis

Lysosomal storage disorders are a group of inborn errors of metabolism due to defects in proteins crucial for lysosomal function. Gaucher disease is the most common autosomal recessive lysosomal storage disorder due to mutations in the GBA1 gene, resulting in the lysosomal deficiency of glucocerebrosidase activity. Gaucher disease is characterized by the toxic accumulation of glucosylceramide in the reticuloendothelial system. Acid sphingomyelinase deficiency (ASMD), previously known as Niemann Pick A/B disease, is also an autosomal recessive lysosomal storage disorder due to mutations in the SMPD1 gene, which result in acid sphingomyelinase deficiency and the accumulation of sphingomyelin in mononuclear phagocytic system and hepatocytes. The phenotypic expression of Gaucher disease type 1 (GD1), the most common type, and chronic visceral ASMD may overlap for several signs or symptoms. Splenomegaly is detectable in approximately 90% of the patients in both conditions; however, since GD1 is more frequent than ASMD, clinicians are more prone to suspect it, often neglecting the diagnosis of ASMD. Based on previous experience, a group of experts in the clinical and laboratory diagnosis, management, and treatment of lysosomal storage disorders developed an algorithm for both GD1 and ASMD to support physicians, including primary care providers, internists, and specialists (e.g., hepatologists, hematologists, and pulmonologists) to suspect and differentiate GD1 and ASMD and to provide the appropriate referral.

Successful Outcome of Pregnancy in Niemann-Pick Disease Type B: A Case Report and Review of Literature

Niemann-Pick (NPD) is a rare autosomal recessive disease, caused by deficiency of acid sphingomyelinase enzyme leading to accumulation of lipids mainly in the reticuloendothelial system and lungs. We describe the case of a 29-year-old primigravida, recently diagnosed with NPD type B. At initial evaluation, her platelets were normal, liver enzymes slightly elevated and splenomegaly on scan. Pregnancy care was by a multidisciplinary team which routinely monitored her liver and pulmonary functions along with platelets. Labor was induced at 37 + 1 weeks of gestation because of fetal growth restriction. She underwent an cesarean section for failed induction and delivered a healthy male baby. Conclusion: Successful outcomes in such pregnancies depend upon close monitoring by a multidisciplinary team.

Quantification of lysosphingomyelin and lysosphingomyelin-509 for the screening of acid sphingomyelinase deficiency

BACKGROUND

Acid sphingomyelinase deficiency (ASMD) is a lysosomal disorder caused by deficiency of acid sphingomyelinase (ASM) leading to the accumulation of sphingomyelin (SM) in a variety of cell types. Lysosphingomyelin (LysoSM) is the de-acetylated form of SM and it has been shown as a biomarker for ASMD in tissues, plasma, and dried blood spots (DBS) and lysosphingomyelin-509 (LysoSM509) is the carboxylated analogue of LysoSM. High levels of Lysosphingomyelin 509 (LysoSM509) have also been shown in ASMD patients. In this study, we report the utility of the quantification of LysoSM and LysoSM509 in DBS of patients from Latin America with ASMD by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS).

RESULTS

DBS samples from 14 ASMD patients were compared with 15 controls, and 44 general newborns. All patients had their diagnosis confirmed by the quantification of ASM and the measurement of the activity of chitotriosidase. All patients had significantly higher levels of lysoSM and lysoSM509 compared to controls and general newborns.

CONCLUSIONS

The quantification of lysosphingolipids in DBS is a valuable tool for the diagnosis of ASMD patients and lysoSM can be useful in the differential diagnosis with NPC. This method is also valuable in the ASMD newborn screening process.

Convergent molecular mechanisms underlying cognitive impairment in mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder caused by pathogenic variants in the iduronate-2-sulfatase gene (IDS), responsible for the degradation of glycosaminoglycans (GAGs) heparan and dermatan sulfate. IDS enzyme deficiency results in the accumulation of GAGs within cells and tissues, including the central nervous system (CNS). The progressive neurological outcome in a representative number of MPSII patients (neuronopathic form) involves cognitive impairment, behavioral difficulties, and regression in developmental milestones. In an attempt to dissect part of the influence of axon guidance instability over the cognitive impairment presentation in MPS II, we used brain expression data, network propagation, and clustering algorithm to prioritize in the human interactome a disease module associated with the MPS II context. We identified new candidate genes and pathways that act in focal adhesion, integrin cell surface, laminin interactions, ECM proteoglycans, cytoskeleton, and phagosome that converge into functional mechanisms involved in early neural circuit formation defects and could indicate clues about cognitive impairment in patients with MPSII. Such molecular changes during neurodevelopment may precede the morphological and clinical evidence, emphasizing the importance of an early diagnosis and directing the development of potential drug leads. Furthermore, our data also support previous hypotheses pointing to shared pathogenic mechanisms in some neurodegenerative diseases.

Glial Dysfunction and Its Contribution to the Pathogenesis of the Neuronal Ceroid Lipofuscinoses

While significant efforts have been made in developing pre-clinical treatments for the neuronal ceroid lipofuscinoses (NCLs), many challenges still remain to bring children with NCLs a cure. Devising effective therapeutic strategies for the NCLs will require a better understanding of pathophysiology, but little is known about the mechanisms by which loss of lysosomal proteins causes such devastating neurodegeneration. Research into glial cells including astrocytes, microglia, and oligodendrocytes have revealed many of their critical functions in brain homeostasis and potential contributions to neurodegenerative diseases. Genetically modified mouse models have served as a useful platform to define the disease progression in the central nervous system across NCL subtypes, revealing a wide range of glial responses to disease. The emerging evidence of glial dysfunction questions the traditional “neuron-centric” view of NCLs, and would suggest that directly targeting glia in addition to neurons could lead to better therapeutic outcomes. This review summarizes the most up-to-date understanding of glial pathologies and their contribution to the pathogenesis of NCLs, and highlights some of the associated challenges that require further research.

Advancing the Research and Development of Enzyme Replacement Therapies for Lysosomal Storage Diseases

With the increasing interest in developing gene therapies for rare diseases, it is easy to overlook that there are numerous rare lysosomal storage diseases (LSD) with treatments that have been approved by regulatory agencies in the United States and Europe. These primarily consist of enzyme replacement therapies (ERT), which are recombinant human proteins that are delivered for the life of the patient via different routes and may have distinct safety and distribution advantages over gene therapies. The research and development of ERT is a lengthy and expensive process, which is usually performed in academic laboratories before transfer to pharmaceutical companies and is hence a process ripe for disruption. There may still be considerable scientific and investment potential for ERT, however we need to develop a pipeline of proteins analogous to what has been created in some open science efforts as well as apply technologies to decrease manufacturing costs. In this Perspective, we illustrate the opportunity to fill the rare LSD treatment gap with ERTs while gene therapies are in development for these life-shortening diseases.

Acid Sphingomyelinase Deficiency: Sharing Experience of Disease Monitoring and Severity in France

Acid sphingomyelinase deficiency (ASMD) is a rare inherited lipid storage disorder caused by a deficiency in lysosomal enzyme acid sphingomyelinase which results in the accumulation of sphingomyelin, predominantly within cells of the reticuloendothelial system located in numerous organs, such as the liver, spleen, lungs, and central nervous system. Although all patients with ASMD share the same basic metabolic defect, a wide spectrum of clinical presentations and outcomes are observed, contributing to treatment challenges. While infantile neurovisceral ASMD (also known as Niemann-Pick disease type A) is rapidly progressive and fatal in early childhood, and the more slowly progressive chronic neurovisceral (type A/B) and chronic visceral (type B) forms have varying clinical phenotypes and life expectancy. The prognosis of visceral ASMD is mainly determined by the association of hepatosplenomegaly with secondary thrombocytopenia and lung disease. Early diagnosis and appropriate management are essential to reduce the risk of complications and mortality. The accessibility of the new enzyme replacement therapy olipudase alfa, a recombinant human ASM, has been expedited for clinical use based on positive clinical data in children and adult patients, such as improved respiratory status and reduced spleen volume. The aim of this article is to share the authors experience on monitoring ASMD patients and stratifying the severity of the disease to aid in care decisions.

Renal involvement in a patient with the chronic visceral subtype of acid sphingomyelinase deficiency resembles Fabry disease

Acid sphingomyelinase deficiency (ASMD) is a lysosomal storage disease (LSD) in which sphingomyelin accumulates due to deficient acid sphingomyelinase. In the chronic visceral subtype, organ manifestations are generally limited to the spleen, liver, and lungs. We report a male patient with the chronic visceral subtype who developed proteinuria and renal insufficiency at the age of 49. In renal tissue, foam cells were observed in the glomeruli as well as sphingomyelin accumulation within podocytes, mesangial cells, endothelial cells, and tubular epithelial cells. Although macrophages are the primary storage cells in both ASMD and Gaucher disease, comparison to the histopathological findings in Gaucher and Fabry disease revealed a diffuse storage pattern in multiple renal cell types, closer resembling the pattern found in Fabry disease.

Mucopolysaccharidosis Type I-Associated Corneal Disease: A Clinicopathologic Study

PURPOSE

To report the anterior segment clinical features and histopathologic and histochemical characteristics of explanted corneas from the largest reported cohort of patients with Hurler syndrome and other variants of mucopolysaccharidosis (MPS) I undergoing corneal transplantation.

DESIGN

Retrospective observational case series.

METHODS

This institutional study reviewed 15 corneas from 9 patients with MPS I spectrum disease who underwent corneal transplant to treat corneal clouding between May 2011 and October 2020. We reviewed the clinical data, hematoxylin-eosin-stained sections, and histochemical stains, including those for mucopolysaccharides (Alcian blue and/or colloidal iron). The main outcome measures were pathology observed under light microscopy and postsurgical clinical outcomes.

RESULTS

Nine patients underwent 15 corneal transplants for corneal clouding (14/15 procedures were deep anterior lamellar keratoplasty). All corneas had mucopolysaccharide deposition visible on hematoxylin-eosin-stained sections, which was highlighted in blue with histochemical stains. All corneas also showed alterations in Bowman's layer and the majority also showed epithelial abnormalities.

CONCLUSION

MPS I shows significant corneal clouding that is successfully treated with deep anterior lamellar keratoplasty. The excised corneas show characteristic epithelial changes, disruption or breaks in Bowman's membrane, and amphophilic collections of stromal granular mucopolysaccharides which are visible on hematoxylin-eosin-stained sections and highlighted by special histochemical stains (Alcian blue and collodial iron). These changes, although subtle, should alert the pathologist to the possibility of an underlying lysosomal storage disorder.

A Comprehensive, Targeted NGS Approach to Assessing Molecular Diagnosis of Lysosomal Storage Diseases

With over 60 different disorders and a combined incidence occurring in 1:5000-7000 live births, lysosomal storage diseases (LSDs) represent a major public health problem and constitute an enormous burden for affected individuals and their families. Several reasons make the diagnosis of LSDs an arduous task for clinicians, including the phenotype and penetrance variability, the shared signs and symptoms, and the uncertainties related to biochemical enzymatic assay results. Developing a powerful diagnostic tool based on next generation sequencing (NGS) technology may help reduce the delayed diagnostic process for these families, leading to better outcomes for current therapies and providing the basis for more appropriate genetic counseling. Herein, we employed a targeted NGS-based panel to scan the coding regions of 65 LSD-causative genes. A reference group sample (n = 26) with previously known genetic mutations was used to test and validate the entire workflow. Our approach demonstrated elevated analytical accuracy, sensitivity, and specificity. We believe the adoption of comprehensive targeted sequencing strategies into a routine diagnostic route may accelerate both the identification and management of LSDs with overlapping clinical profiles, producing a significant reduction in delayed diagnostic response with beneficial results in the treatment outcome.

Prevalence of Cancer in Acid Sphingomyelinase Deficiency

Acid sphingomyelinase deficiency (ASMD) is an inherited lysosomal disease characterised by a diffuse accumulation of sphingomyelin that cannot be catabolised into ceramide and phosphocholine. We studied the incidence of cancer in ASMD patients. We retrospectively reviewed the medical records of the adult chronic visceral ASMD patients in our cohort. Thirty-one patients (12 females, 19 males) were included with a median age of 48.7 y. (IQ: 30.3–55.1). Five cancers were observed in 1 female (breast cancer) and 4 males (two lung cancers, one thyroid cancer and one bladder cancer), resulting in a prevalence of 16.1%. The existence of cancer was associated with a more severe ASMD characterised by a larger spleen (25 cm (22.5–25) vs. 18 cm (17–20); p = 0.042); lower diffusing capacity of the lung for carbon monoxide (DLCO; 29.5 % (17.8–43.0) vs. 58.5 % (49.8–69.5%); p = 0.01) and tobacco use (100% vs. 45%; p = 0.04). Three patients died, all from cancer (p = 0.002). The prevalence of cancer appeared to be strikingly elevated in our cohort of patients, without any specificity in the type of cancer. Systematic screening for cancer should be performed, and carcinogenic substances such as tobacco should be avoided in patients with ASMD.

Impact and burden of acid sphingomyelinase deficiency from a patient and caregiver perspective

Acid sphingomyelinase deficiency (ASMD), historically known as Niemann–Pick disease (NPD) types A, A/B, and B, is a rare, progressive, potentially fatal lysosomal storage disease with a spectrum of phenotypes. Little is known about how ASMD symptoms affect the lives of patients and their caregivers. In a cross-sectional qualitative study conducted in the US and UK, and in collaboration with the National Niemann–Pick Disease Foundation (US) and Niemann–Pick UK, we investigated the symptom experience of patients with ASMD types B and A/B and explored how the disease impacts their and their caregivers’ lives. The study included 17 adult patients (mean age 38.7 years, 12 female), three caregivers of adults with ASMD, 12 pediatric/adolescent patients with ASMD (mean age 10.5 years, six female), and 12 caregivers of pediatric/adolescent patients with ASMD. The most commonly reported disease manifestations were respiratory (n = 26, 89.7%), abdominal (n = 25, 86.2%), and musculoskeletal symptoms (n = 23, 79.3%); excessive bleeding or bruising (n = 20, 69%); fatigue (n = 20, 69%); gastrointestinal symptoms (n = 18, 62.1%); and headache (n = 15, 51.7%). ASMD was reported to negatively impact patients’ physical function (n = 23, 79.3%), self-esteem (n = 18, 62.1%), emotions (n = 16, 55.2%), social function and relationships (n = 16, 55.2%), and personal care (n = 9, 31%). Providing care for individuals with ASMD negatively affected caregivers’ emotional well-being (n = 12, 80%), social function (n = 4, 26.7%), relationships (n = 6, 40%), and financial security (n = 7, 46.7%). The physical toll of providing care, the need for lifestyle changes, and the responsibility for making medical decisions added to the burden for caregivers. Alternatively, some caregivers noted that caring for a loved one enhanced their spirituality, providing them with a different outlook on life and a deeper personal resolve. This study showed that ASMD is a substantial burden for patients and caregivers, with long-term physical, emotional, social, and financial impacts. The study confirmed commonly known manifestations of ASMD, especially respiratory problems, but also identified less recognized ones, such as dermatological complications. The data collected and insight gained from this study should enhance clinical care, help evaluate new treatments, and inform health care decision making for patients with ASMD.

Focal hepatic lesions in acid sphingomyelinase deficiency: Differential diagnosis between foamy macrophages aggregates and malignancy

Acid sphingomyelinase deficiency (ASMD) is a rare metabolic disorder due to biallelic mutation in the SMPD1 gene. The defect leads to the accumulation of sphingomyelin within the cells of the reticulo-endothelial system, particularly in the spleen, liver, lungs, and bone marrow causing hepato-splenomegaly, lung disease and hematological abnormalities. At present, data on abdominal imaging in ASMD are limited. Here we describe the characteristics of focal liver lesions observed in a 30 years old female. During the Magnetic Resonance follow up an increase in number and size of the lesions, showing T1 hypointensity and T2 hyperintensity with contrast enhancement, was observed. Contrast enhanced ultrasound evidenced rapid wash-in and steady isoecogenicity without appreciable wash-out at 80 seconds. The main lesion was biopsied to rule out the presence of a hepatocellular carcinoma, and showed to be a benign foamy macrophages aggregate. In this report, we discuss the possible pathogenesis of focal hepatic lesions in ASMD and their differential diagnosis.

Design and Validation of a Custom NGS Panel Targeting a Set of Lysosomal Storage Diseases Candidate for NBS Applications

Lysosomal storage diseases (LSDs) are a heterogeneous group of approximately 70 monogenic metabolic disorders whose diagnosis represents an arduous challenge for clinicians due to their variability in phenotype penetrance, clinical manifestations, and high allelic heterogeneity. In recent years, the approval of disease-specific therapies and the rapid emergence of novel rapid diagnostic methods has opened, for a set of selected LSDs, the possibility for inclusion in extensive national newborn screening (NBS) programs. Herein, we evaluated the clinical utility and diagnostic validity of a targeted next-generation sequencing (tNGS) panel (called NBS_LSDs), designed ad hoc to scan the coding regions of six genes (GBA, GAA, SMPD1, IDUA1, GLA, GALC) relevant for a group of LSDs candidate for inclusion in national NBS programs (MPSI, Pompe, Fabry, Krabbe, Niemann Pick A-B and Gaucher diseases). A standard group of 15 samples with previously known genetic mutations was used to test and validate the entire flowchart. Analytical accuracy, sensitivity, and specificity, as well as turnaround time and costs, were assessed. Results showed that the Ion AmpliSeq and Ion Chef System-based high-throughput NBS_LSDs tNGS panel is a fast, accurate, and cost-effective process. The introduction of this technology into routine NBS procedures as a second-tier test along with primary biochemical assays will allow facilitating the identification and management of selected LSDs and reducing diagnostic delay.

Prospective study of the natural history of chronic acid sphingomyelinase deficiency in children and adults: eleven years of observation

Background

Acid sphingomyelinase deficiency (ASMD) (also known as Niemann-Pick disease types A and B) is a rare and debilitating lysosomal storage disorder. This prospective, multi-center, multinational longitudinal study aimed to characterize the clinical features of chronic forms of ASMD and disease burden over time in children and adults.

Results

Fifty-nine patients (31 males/28 females) ranging in age from 7 to 64 years with chronic ASMD types A/B and B and at least two disease symptoms participated from 5 countries. Disease characteristics were assessed at baseline, after 1 year, and at the final visit (ranging from 4.5 to 11 years). Thirty patients (51%) were < 18 years at baseline (median age 12 years), and 29 were adults (median age 32 years). Overall, 32/59 patients completed the final visit, 9 died, 9 discontinued, and 9 were lost to follow up. Common clinical characteristics that tended to worsen gradually with time were splenomegaly, hepatomegaly, interstitial lung disease, lung diffusion capacity (DL_CO), and dyslipidemia. Spleen volumes ranged from 4 to 29 multiples of normal at baseline, and splenomegaly was moderate or severe in 86%, 83%, and 90% of individuals at baseline, year 1, and final visits, respectively. The proportion of all individuals with interstitial lung disease was 66% (39/59) at baseline and 78% (25/32) at the final visit, while median % predicted DL_CO decreased by > 10% from baseline to the final visit. Nine patients died (15%), eight of causes related to ASMD (most commonly pneumonia); of these eight patients, five (63%) had symptom onset at or before age 2. Overall, six of the nine deaths occurred before age 50 with three occurring before age 20. Individuals with either severe splenomegaly or prior splenectomy were ten times more likely to have died during the follow-up period than those with smaller or intact spleens (odds ratio 10.29, 95% CI 1.7, 62.7). Most children had growth deficits that persisted into adulthood.

Conclusions

This study provides important information about the natural history of chronic ASMD and provides a longitudinal view of the spectrum of disease manifestations and major morbidities in children and adults and supports the selection of clinically meaningful endpoints in therapeutic trials.

Sphingolipid lysosomal storage diseases: from bench to bedside

Johann Ludwig Wilhelm Thudicum described sphingolipids (SLs) in the late nineteenth century, but it was only in the past fifty years that SL research surged in importance and applicability. Currently, sphingolipids and their metabolism are hotly debated topics in various biochemical fields. Similar to other macromolecular reactions, SL metabolism has important implications in health and disease in most cells. A plethora of SL-related genetic ailments has been described. Defects in SL catabolism can cause the accumulation of SLs, leading to many types of lysosomal storage diseases (LSDs) collectively called sphingolipidoses. These diseases mainly impact the neuronal and immune systems, but other systems can be affected as well. This review aims to present a comprehensive, up-to-date picture of the rapidly growing field of sphingolipid LSDs, their etiology, pathology, and potential therapeutic strategies. We first describe LSDs biochemically and briefly discuss their catabolism, followed by general aspects of the major diseases such as Gaucher, Krabbe, Fabry, and Farber among others. We conclude with an overview of the available and potential future therapies for many of the diseases. We strive to present the most important and recent findings from basic research and clinical applications, and to provide a valuable source for understanding these disorders.

Opinions of adults affected with later-onset lysosomal storage diseases regarding newborn screening: A qualitative study

Lysosomal storage diseases (LSDs) are a heterogeneous group of conditions causing substrate accumulation leading to progressive organ damage. Newborn screening (NBS) for several LSDs has become available in recent years due to advances in technology and treatment availability. While early initiation of treatment is lifesaving for those with infantile presentations, controversy continues regarding diagnosis of milder, later-onset diseases in infancy, including creation of pre-symptomatic populations of 'patients-in-waiting', the potential for medicalization, stigmatization, and/or discrimination. In-depth interviews were conducted with 36 adults [11 with Fabry disease (FD), 8 with Gaucher disease (GD), and 17 with late-onset Pompe disease (LOPD)], to determine their perspectives on NBS for their respective conditions. Thirty-four of 36 participants were in favor of NBS; both participants not in favor had GD1. Emergent themes influencing participants favorably toward NBS included earlier age of onset, a long diagnostic odyssey, less efficacious treatment, and the desire to have made different life decisions (e.g., relationships, career, or lifestyle) with the knowledge of their diagnosis. Concerns about insurance discrimination and psychological or physical burdens were associated with less favorable opinions of NBS. The ability for parents to make future reproductive decisions based their child's NBS result was considered favorably by some participants and unfavorably by others. Participants' specific condition (GD1, FD, or LOPD) contributed to these experiences differently. Participants with LOPD and FD favored NBS to initiate earlier treatment and prevent irreversible organ damage, whereas fewer patients with GD1 mentioned this benefit. Participants with LOPD had the longest diagnostic odyssey, while those with FD were more likely to report feeling misunderstood and experiencing accusations of malingering, both contributing to favorable views of NBS. Results expand prior quantitative findings by illuminating how participants' lived experiences can shape opinions about NBS. By understanding how currently affected individuals perceive the lifelong impact of a NBS result, genetic counselors can provide better anticipatory guidance to the parents of individuals diagnosed with a later-onset LSD by NBS.

One-year results of a clinical trial of olipudase alfa enzyme replacement therapy in pediatric patients with acid sphingomyelinase deficiency

Purpose

To assess olipudase alfa enzyme replacement therapy for non–central nervous system manifestations of acid sphingomyelinase deficiency (ASMD) in children.

Methods

This phase 1/2, international, multicenter, open-label trial (ASCEND-Peds/NCT02292654) administered intravenous olipudase alfa every 2 weeks with intrapatient dose escalation to 3 mg/kg. Primary outcome was safety through week 64. Secondary outcomes included pharmacokinetics, spleen and liver volumes, lung diffusing capacity (DL_CO), lipid profiles, and height through week 52.

Results

Twenty patients were enrolled: four adolescents (12–17 years), nine children (6–11 years), and seven infants/early child (1–5 years). Most adverse events were mild or moderate, including infusion-associated reactions (primarily urticaria, pyrexia, and/or vomiting) in 11 patients. Three patients had serious treatment-related events: one with transient asymptomatic alanine aminotransferase increases, another with urticaria and rash (antidrug antibody positive [ADA+]), and a third with an anaphylactic reaction (ADA+) who underwent desensitization and reached the 3 mg/kg maintenance dose. Mean splenomegaly and hepatomegaly improved by >40% (p < 0.0001). Mean % predicted DL_CO improved by 32.9% (p = 0.0053) in patients able to perform the test. Lipid profiles and elevated liver transaminase levels normalized. Mean height Z-scores improved by 0.56 (p < 0.0001).

Conclusion

In this study in children with chronic ASMD, olipudase alfa was generally well-tolerated with significant, comprehensive improvements in disease pathology across a range of clinically relevant endpoints.

Exploiting the Potential of Drosophila Models in Lysosomal Storage Disorders: Pathological Mechanisms and Drug Discovery

Lysosomal storage disorders (LSDs) represent a complex and heterogeneous group of rare genetic diseases due to mutations in genes coding for lysosomal enzymes, membrane proteins or transporters. This leads to the accumulation of undegraded materials within lysosomes and a broad range of severe clinical features, often including the impairment of central nervous system (CNS). When available, enzyme replacement therapy slows the disease progression although it is not curative; also, most recombinant enzymes cannot cross the blood-brain barrier, leaving the CNS untreated. The inefficient degradative capability of the lysosomes has a negative impact on the flux through the endolysosomal and autophagic pathways; therefore, dysregulation of these pathways is increasingly emerging as a relevant disease mechanism in LSDs. In the last twenty years, different LSD Drosophila models have been generated, mainly for diseases presenting with neurological involvement. The fruit fly provides a large selection of tools to investigate lysosomes, autophagy and endocytic pathways in vivo, as well as to analyse neuronal and glial cells. The possibility to use Drosophila in drug repurposing and discovery makes it an attractive model for LSDs lacking effective therapies. Here, ee describe the major cellular pathways implicated in LSDs pathogenesis, the approaches available for their study and the Drosophila models developed for these diseases. Finally, we highlight a possible use of LSDs Drosophila models for drug screening studies.

Elevated Dipeptidyl Peptidase IV (DPP-IV) Activity in Plasma from Patients with Various Lysosomal Diseases

Increased activity of dipeptidyl peptidase IV (DPP-IV) was reported earlier in patients with different types of mucopolysaccharidoses. DPP-IV (also known as CD26 lymphocyte T surface antigen) is a transmembrane protein showing protease activity. This enzyme displays various functions in the organism and plays an important role in multiple processes like glucose metabolism, nociception, cell-adhesion, psychoneuroendocrine regulation, immune response and cardiovascular adaptation. In order to evaluate DPP-IV in lysosomal storage diseases (LSD), we examined its activity in plasma samples from 307 patients affected with 24 different LSDs and in 75 control persons. Our results revealed elevated DPP-IV activity especially in individuals affected with mucolipidosis II/III, alpha-mannosidosis, and mucopolysaccharidoses types III, II, and I (p < 0.05). In other LSDs the DPP-IV activity was still significantly increased, but to a lesser extent. In patients with Gaucher disease, ceroid lipofuscinosis type 1 (CLN1), Niemann-Pick disease type C and A, Krabbe and Pompe diseases, gangliosidosis GM2 and metachromatic leukodystrophy discreet or no changes in DPP-IV activity were observed. DPP-IV may serve as a first-tier diagnostic procedure or additional biochemical analysis in recognizing patients with some LSDs. DPP-IV may become an object of basic research for a better understanding of LSDs.

Transplantation of Stem Cells as a Potential Therapeutic Strategy in Neurodegenerative Disorders

Stem cells are considered to have significant capacity to differentiate into various cell types in humans and animals. Unlike specialized cells, these cells can proliferate several times to produce millions of cells. Nowadays, pluripotent stem cells are important candidates to provide a renewable source for the replacement of cells in tissues of interest. The damage to neurons and glial cells in the brain or spinal cord is present in neurological disorders such as Amyotrophic lateral sclerosis, stroke, Parkinson's disease, multiple sclerosis, Alzheimer's disease, Huntington's disease, spinal cord injury, lysosomal storage disorder, epilepsy, and glioblastoma. Therefore, stem cell transplantation can be used as a novel therapeutic approach in cases of brain and spinal cord damage. Recently, researchers have generated neuron-like cells and glial-like cells from embryonic stem cells, mesenchymal stem cells, and neural stem cells. In addition, several experimental studies have been performed for developing stem cell transplantation in brain tissue. Herein, we focus on stem cell therapy to regenerate injured tissue resulting from neurological diseases and then discuss possible differentiation pathways of stem cells to the renewal of neurons.

Temporospatial Development of Neuropathologic Findings in a Canine Model of Mucopolysaccharidosis IIIB

Mucopolysaccharidosis (MPS) IIIB is a neuropathic lysosomal storage disease characterized by the deficient activity of a lysosomal enzyme obligate for the degradation of the glycosaminoglycan (GAG) heparan sulfate (HS). The pathogenesis of neurodegeneration in MPS IIIB is incompletely understood. Large animal models are attractive for pathogenesis and therapeutic studies due to their larger size, outbred genetics, longer lifespan, and naturally occurring MPS IIIB disease. However, the temporospatial development of neuropathologic changes has not been reported for canine MPS IIIB. Here we describe lesions in 8 brain regions, cervical spinal cord, and dorsal root ganglion (DRG) in a canine model of MPS IIIB that includes dogs aged from 2 to 26 months of age. Pathological changes in the brain included early microscopic vacuolation of glial cells initially observed at 2 months, and vacuolation of neurons initially observed at 10 months. Inclusions within affected cells variably stained positively with PAS and LFB stains. Quantitative immunohistochemistry demonstrated increased glial expression of GFAP and Iba1 in dogs with MPS IIIB compared to age-matched controls at all time points, suggesting neuroinflammation occurs early in disease. Loss of Purkinje cells was initially observed at 10 months and was pronounced in 18- and 26-month-old dogs with MPS IIIB. Our results support the dog as a replicative model of MPS IIIB neurologic lesions and detail the pathologic and neuroinflammatory changes in the spinal cord and DRG of MPS IIIB-affected dogs.

Periodontal condition and treatment in a patient with rare systemic condition: A case report for acid sphingomyelinase deficiency

BACKGROUND

Acid sphingomyelinase deficiency (ASMD) is a rare group of autosomal recessive disorders. This report provides the first detailed description of the periodontal condition and treatment response in a patient with chronic visceral ASMD.

CASE DESCRIPTION

A 49-year-old white woman with ASMD showed elevated visible plaque index (VPI), gingival bleeding index (GBI), and bleeding on probing (BOP) at 100% of sites. Periodontal pocket depths (PPD) were mostly shallow to moderate (at 96% of sites), whereas the loss of clinical attachment (CAL) was moderate to severe (54% and 46% of sites, respectively, at 4-6 mm and ≥7 mm categories). Periapical radiographs revealed the presence of furcation involvement and intra-bony defects. The periodontal diagnosis was periodontitis stage IV, generalized, grade C. Ninety days after the end of the supra and subgingival control (e.g., cause-related therapy), marked reduction was observed for all periodontal indicators: VPI (-83%), GBI (-79%), BOP (-85%), elimination of sites PPD ≥7 mm, 27% increase in sites PPD 1-3 mm (from 64% to 91%), and gain of clinical attachment (gain of 11% CAL 1-3 mm and 25% CAL 4-6 mm; and a reduction of 36% CAL ≥7 mm).

PRACTICAL IMPLICATIONS

Despite the severity of the initial periodontal condition, the patient with chronic visceral ASMD responded well to the non-surgical periodontal treatment.

Oral, dental, and craniofacial features in chronic acid sphingomyelinase deficiency

The aim of this study was to evaluate the oral, dental, and craniofacial features of individuals affected by the chronic forms of acid sphingomyelinase deficiency (ASMD). This study comprised a sample of adult and pediatric patients (n = 8) with chronic ASMD. The individuals underwent oral examinations to evaluate the occurrence of caries, as well as full-mouth periodontal examinations, to assess the occurrence and severity of periodontal diseases. Panoramic and profile radiographs were obtained to analyze dental conditions and craniofacial parameters. Participants also answered questionnaires to identify systemic impairment, parafunctional habits, and bruxism. Dental anomalies of size, shape, and number were found, with agenesis and microdontia being the predominant findings. The average of caries experience was 11.75 (±8.1). Only one patient had periodontal health and all adult individuals had periodontitis at different stages and degrees. Bruxism was found in 87.5% of the sample. The convex profile and maxillary and mandibular retrusion were the most relevant findings in the cephalometric analysis. It is concluded that individuals with chronic ASMD, in addition to several systemic manifestations, present significant modifications in their oral health, from a greater occurrence of dental anomalies, caries, periodontal disease, in addition to skeletal changes.

Highlights on Genomics Applications for Lysosomal Storage Diseases

Lysosomal storage diseases (LSDs) are a heterogeneous group of rare multisystem genetic disorders occurring mostly in infancy and childhood, characterized by a gradual accumulation of non-degraded substrates inside the lysosome. Although the cellular pathogenesis of LSDs is complex and still not fully understood, the approval of disease-specific therapies and the rapid emergence of novel diagnostic methods led to the implementation of extensive national newborn screening (NBS) programs in several countries. In the near future, this will help the development of standardized workflows aimed to more timely diagnose these conditions. Hereby, we report an overview of LSD diagnostic process and treatment strategies, provide an update on the worldwide NBS programs, and discuss the opportunities and challenges arising from genomics applications in screening, diagnosis, and research.

Chemical inhibition of β-glucocerebrosidase does not affect phagocytosis and early containment of Leishmania by murine macrophages

Gaucher disease is a lysosomal storage disease in which a genetic deficiency in β-glucocerebrosidase leads to the accumulation of glycosphingolipids in lysosomes. Macrophages are amongst the cells most severely affected in Gaucher disease patients. One phenotype associated with Gaucher macrophages is the impaired capacity to fight bacterial infections. Here, we investigate whether inhibition of β-glucocerebrosidase activity affects the capacity of macrophages to phagocytose and act on the early containment of human pathogens of the genus Leishmania. Towards our aim, we performed in vitro infection assays on macrophages derived from the bone marrow of C57BL/6 mice. To mimic Gaucher disease, macrophages were incubated with the β-glucocerebrosidase inhibitor, conduritol B epoxide (CBE), prior to contact with Leishmania. This treatment guaranteed that β-glucocerebrosidase was fully inhibited during the contact of macrophages with Leishmania, its enzymatic activity being progressively recovered along the 48 h that followed removal of the inhibitor. Infections were performed with L. amazonensis, L. infantum, or L. major, so as to explore potential species-specific responses in the context of β-glucocerebrosidase inactivation. Parameters of infection, recorded immediately after phagocytosis, as well as 24 and 48 h later, revealed no noticeable differences in the infection parameters of CBE-treated macrophages relative to non-treated controls. We conclude that blocking β-glucocerebrosidase activity during contact with Leishmania does not interfere with the phagocytic capacity of macrophages and the early onset of leishmanicidal responses.

Biochemical and imaging parameters in acid sphingomyelinase deficiency: Potential utility as biomarkers

Acid Sphingomyelinase Deficiency (ASMD), or Niemann-Pick type A/B disease, is a rare lipid storage disorder leading to accumulation of sphingomyelin and its precursors primarily in macrophages. The disease has a broad phenotypic spectrum ranging from a fatal infantile form with severe neurological involvement (the infantile neurovisceral type) to a primarily visceral form with different degrees of pulmonary, liver, spleen and skeletal involvement (the chronic visceral type). With the upcoming possibility of treatment with enzyme replacement therapy, the need for biomarkers that predict or reflect disease progression has increased. Biomarkers should be validated for their use as surrogate markers of clinically relevant endpoints. In this review, clinically important endpoints as well as biochemical and imaging markers of ASMD are discussed and potential new biomarkers are identified. We suggest as the most promising biomarkers that may function as surrogate endpoints in the future: diffusion capacity measured by spirometry, spleen volume, platelet count, low-density lipoprotein cholesterol, liver fibrosis measured with a fibroscan, lysosphingomyelin and walked distance in six minutes. Currently, no biomarkers have been validated. Several plasma markers of lipid-laden cells, fibrosis or inflammation are of high potential as biomarkers and deserve further study. Based upon current guidelines for biomarkers, recommendations for the validation process are provided.

Lipid-based biomarkers for CVD, COPD, and aging - A translational perspective

For many diseases, there is an unmet need for new or better biomarkers for improved disease risk assessment and monitoring, as available markers lack sufficient specificity. Lipids are drawing major interest as potential candidates for filling these gaps. This has recently been demonstrated by the identification of selective ceramides for prediction of cardiovascular mortality, enabling improved risk assessment of cardiovascular disease compared with conventional clinical markers. In this review, we discuss current lipid biomarker findings and the possible connection between cardiovascular disease, chronic obstructive pulmonary disease, and aging. Moreover, we discuss how to overcome the current roadblocks facing lipid biomarker research. We stress the need for improved quantification, standardization of methodologies, and establishment of initial reference values to allow for an efficient transfer path of research findings into the clinical landscape, and, ultimately, to put newly identified biomarkers into practical use.

A perspective on research, diagnosis, and management of lysosomal storage disorders in Colombia

Lysosomal storage diseases (LSDs) are a group of about 50 inborn errors of metabolism characterized by the lysosomal accumulation of partially or non-degraded molecules due to mutations in proteins involved in the degradation of macromolecules, transport, lysosomal biogenesis or modulators of lysosomal environment. Significant advances have been achieved in the diagnosis, management, and treatment of LSDs patients. In terms of approved therapies, these include enzyme replacement therapy (ERT), substrate reduction therapy, hematopoietic stem cell transplantation, and pharmacological chaperone therapy. In this review, we summarize the Colombian experience in LSDs thorough the evidence published. We identified 113 articles published between 1995 and 2019 that included Colombian researchers or physicians, and which were mainly focused in Mucopolysaccharidoses, Pompe disease, Gaucher disease, Fabry disease, and Tay-Sachs and Sandhoff diseases. Most of these articles focused on basic research, clinical cases, and mutation reports. Noteworthy, implementation of the enzyme assay in dried blood samples, led to a 5-fold increase in the identification of LSD patients, suggesting that these disorders still remain undiagnosed in the country. We consider that the information presented in this review will contribute to the knowledge of a broad spectrum of LSDs in Colombia and will also contribute to the development of public policies and the identification of research opportunities.

Neuropathophysiology of Lysosomal Storage Diseases: Synaptic Dysfunction as a Starting Point for Disease Progression

About two thirds of the patients affected with lysosomal storage diseases (LSD) experience neurological manifestations, such as developmental delay, seizures, or psychiatric problems. In order to develop efficient therapies, it is crucial to understand the neuropathophysiology underlying these symptoms. How exactly lysosomal storage affects biogenesis and function of neurons is still under investigation however recent research highlights a substantial role played by synaptic defects, such as alterations in synaptic spines, synaptic proteins, postsynaptic densities, and synaptic vesicles that might lead to functional impairments in synaptic transmission and neurodegeneration, finally culminating in massive neuronal death and manifestation of cognitive symptoms. Unveiling how the synaptic components are affected in neurological LSD will thus enable a better understanding of the complexity of disease progression as well as identify crucial targets of therapeutic relevance and optimal time windows for targeted intervention.

A mutation map for human glycoside hydrolase genes

Glycoside hydrolases (GHs) are found in all domains of life, and at least 87 distinct genes encoding proteins related to GHs are found in the human genome. GHs serve diverse functions from digestion of dietary polysaccharides to breakdown of intracellular oligosaccharides, glycoproteins, proteoglycans and glycolipids. Congenital disorders of GHs (CDGHs) represent more than 30 rare diseases caused by mutations in one of the GH genes. We previously used whole-exome sequencing of a homogenous Danish population of almost 2000 individuals to probe the incidence of deleterious mutations in the human glycosyltransferases (GTs) and developed a mutation map of human GT genes (GlyMAP-I). While deleterious disease-causing mutations in the GT genes were very rare, and in many cases lethal, we predicted deleterious mutations in GH genes to be less rare and less severe given the higher incidence of CDGHs reported worldwide. To probe the incidence of GH mutations, we constructed a mutation map of human GH-related genes (GlyMAP-II) using the Danish WES data, and correlating this with reported disease-causing mutations confirmed the higher prevalence of disease-causing mutations in several GH genes compared to GT genes. We identified 76 novel nonsynonymous single-nucleotide variations (nsSNVs) in 32 GH genes that have not been associated with a CDGH phenotype, and we experimentally validated two novel potentially damaging nsSNVs in the congenital sucrase-isomaltase deficiency gene, SI. Our study provides a global view of human GH genes and disease-causing mutations and serves as a discovery tool for novel damaging nsSNVs in CDGHs.

Setup and Validation of a Targeted Next-Generation Sequencing Approach for the Diagnosis of Lysosomal Storage Disorders

Lysosomal storage disorders (LSDs) are monogenic diseases, due to accumulation of specific undegraded substrates into lysosomes. LSD diagnosis could take several years because of both poor knowledge of these diseases and shared clinical features. The diagnostic approach includes clinical evaluations, biochemical tests, and genetic analysis of the suspected gene. In this study, we evaluated an LSD targeted sequencing panel as a tool capable to potentially reverse this classic diagnostic route. The panel includes 50 LSD genes and 230 intronic sequences conserved among 33 placental mammals. For the validation phase, 56 positive controls, 13 biochemically diagnosed patients, and nine undiagnosed patients were analyzed. Disease-causing variants were identified in 66% of the positive control alleles and in 62% of the biochemically diagnosed patients. Three undiagnosed patients were diagnosed. Eight patients undiagnosed by the panel were analyzed by whole exome sequencing: for two of them, the disease-causing variants were identified. Five patients, undiagnosed by both panel and exome analyses, were investigated through array comparative genomic hybridization: one of them was diagnosed. Conserved intronic fragment analysis, performed in cases unresolved by the first-level analysis, evidenced no candidate intronic variants. Targeted sequencing has low sequencing costs and short sequencing time. However, a coverage >60× to 80× must be ensured and/or Sanger validation should be performed. Moreover, it must be supported by a thorough clinical phenotyping.

Laboratory Diagnosis of Lysosomal Diseases: Newborn Screening to Treatment

The goal of screening programs for inborn errors of metabolism (IEM) is early detection and timely intervention to significantly reduce morbidity, mortality and associated disabilities. Phenylketonuria exemplifies their success as neonates are identified at birth and then promptly treated allowing normal neurological development. Lysosomal diseases comprise about 50 IEM arising from a deficiency in a protein required for proper lysosomal function. Typically, these defects are in lysosomal enzymes with the concomitant accumulation of the enzyme's substrate as the cardinal feature. None of the lysosomal diseases are screened at birth in Australia and in the absence of a family history, traditional laboratory diagnosis of the majority, involves demonstrating a deficiency of the requisite enzyme. Diagnostic confusion can arise from interpretation of the degree of residual enzyme activity causative of disease and is impractical when the disorder is not due to an enzyme deficiency per se. Advances in mass spectrometry technologies has enabled simultaneous measurement of the enzymes' substrates and their metabolites which facilitates the efficiency of diagnosis. Employing urine chemistry as a reflection of multisystemic disease, individual lysosomal diseases can be identified by a characteristic substrate pattern complicit with the enzyme deficiency. Determination of lipids in plasma allows the diagnosis of a further class of lysosomal disorders, the sphingolipids. The ideal goal would be to measure biomarkers for each specific lysosomal disorder in the one mass spectrometry-based platform to achieve a diagnosis. Confirmation of the diagnosis is usually by identifying pathogenic variants in the underlying gene, and although molecular genetic technologies can provide the initial diagnosis, the biochemistry will remain important for interpreting molecular variants of uncertain significance.