Prevalence of lysosomal storage diseases in Portugal

Acid sphingomyelinase deficiency: Laboratory diagnosis, genetic and epidemiologic aspects of a 50-year French cohort

OBJECTIVES

Laboratory diagnosis of acid sphingomyelinase (ASM) deficiency (ASMD) was implemented in France in the early 1970s. The aims of this study were (i) to review the combined use of successively developed strategies - enzyme measurement, genetic testing, and biomarkers analysis - and (ii) to describe the mutational spectrum and epidemiological characteristics of a large patient cohort followed in French hospitals.

RESULTS

During the 1974-2023 period, 271 patients with ASMD (238 families) were diagnosed. The chronic visceral form (historical Niemann-Pick type B) constituted 68 % of the cases, the infantile neurovisceral (type A) form 23 %, and the chronic neurovisceral (type AB) form 9 %. Profoundly deficient ASM activities were constantly observed in the neuronopathic forms. Elevated plasma concentrations of LysoSM and LysoSM-509/PPCS proved useful to comfort interpretation of ASM activities near cut-off found in leukocytes or dried blood spots of some patients with ASMD type B. Although not specific, LysoSM-509/PPCS appeared as the most sensitive biomarker. The spectrum of SMPD1 variants was investigated in 183 families. A total of 93 different SMPD1 variants (26 novel ones) was identified (58 % missense, 19 % frameshift, and 12 % nonsense ones). The proportion of null variants was much larger in ASMD type A (63 %) than in type B (24 %). In type AB, c.1177 T > G (p.Trp393Gly) contributed 32 % of the mutant alleles, most patients having Romani or Northwestern-Balkanic roots, while c.880C > A (p.Gln294Lys) only accounted for 9 %. Homoallelic variants in neuronopathic patients allowed genotype/phenotype correlations. In type B, c.1829_1831delGCC (p.Arg610del) represented 57 % of alleles, with a wide diversity of other variants. Among type B families, approximately one-third had a North African origin, and this variant accounted for 91 % alleles in this subgroup, compared to 40 % in non-North-African families. In patients homozygous for p.Arg610del (n = 69), the age at biological diagnosis was significantly higher (34.0 years; IQR 7.4-45.3) than in patients with either one (n = 41) [4.3 years; IQR 2.77-18.30] or no such allele (n = 43) [6.3 years; IQR 2.2-31.7]. A further observation was the proportional increase in the number of type B patients diagnosed after the age of 30 years since 2015. This nearly complete national cohort allowed a tentative evaluation of (minimal) incidences at birth as follows: ASMD (all clinical forms): 0.70/100,000; type B: 0.48/100,000; neuronopathic types (A and AB): 0.22/100,000.

CONCLUSIONS

This comprehensive cohort (i) summarizes the real-life experience of laboratory diagnosis of ASMD in two expert centres, (ii) confirms the high frequency of the p.Arg610del allele in France and discloses some characteristics of patients homozygous for this variant; (iii) provides for the first time data on the distribution, mutational spectrum and tentative incidence at birth of the three clinical phenotypes of ASMD in France.

Medically Actionable Secondary Findings from Whole-Exome Sequencing (WES) Data in a Sample of 3972 Individuals

The application of whole-exome sequencing (WES) for diagnostic purposes has the potential to unravel secondary findings unrelated with the primary reason of testing. Some of those might be of high clinical utility and comprise disease-causing variants in genes, related to life-threatening and clinically actionable diseases. Clarifying the allelic frequencies of such variants in specific populations is a crucial step for the large-scale deployment of genomic medicine. We analysed medically relevant variants in the 81 genes from the American College of Medical Genetics and Genomics (ACMG) v3.2 list of actionable loci, using WES data from a diagnostic laboratory cohort of 3972 persons, tentatively resampled to represent the Portuguese population geographic distribution. We identified medically actionable variants in 6.2% of our cohort, distributed across several disease domains: cardiovascular disorders (3.0%), cancer predisposition (2.0%), miscellaneous disorders (1.1%), and metabolic disorders (0.1%). Additionally, we estimated a frequency of heterozygotes for recessive disease alleles of 11.1%. Overall, our results suggest that medically actionable findings can be identified in approximately 6.2% of persons from our population. This is the first study estimating medically actionable findings in Portugal. These results provide valuable insight for patients, healthcare providers, and policymakers involved in advancing genomic medicine at the national and international level.

Cultured Macrophage Models for the Investigation of Lysosomal Glucocerebrosidase and Gaucher Disease

Macrophages are specialised cells that degrade a range of substrates during their lifetime. In inherited lysosomal storage disorders, particularly the sphingolipidoses, macrophages transform into storage cells and contribute to pathology. An appropriate cultured macrophage model is desired for fundamental research and the assessment of considered therapeutic interventions. We compared commonly used macrophage cell lines, RAW264.7, J774A.1, and THP-1 cells, with human monocyte-derived macrophages (HMDMs) isolated from peripheral blood. Specific lysosomal glucosidases were analysed by enzymatic activity measurements and visualised with fluorescent activity-based probes. Special attention was given to lysosomal glucocerebrosidase (GBA1), the enzyme deficient in Gaucher disease in which lipid-laden macrophages are a hallmark. In macrophage cell lines and HMDMs, various (glyco)sphingolipids relevant to GBA1 activity were determined. Finally, the feasibility of inactivation of GBA1 with a cell-permeable suicide inhibitor was established, as well as the monitoring of uptake of therapeutic recombinant human GBA1. Major differences among various cell lines were noted in terms of morphology, lysosomal enzyme expression, and glycosphingolipid content. HMDMs appear to be the most suitable model for investigations into GBA1 and Gaucher disease. Moreover, they serve as a valuable model for mannose-receptor mediated uptake of therapeutic human GBA1, effectively mimicking enzyme replacement therapy for Gaucher disease.

The Birth Prevalence of Mucopolysaccharidosis Types I, II, III, IVA, VI, and VII in the Republic of Kazakhstan Between 1984 and 2023

Objectives: Mucopolysaccharidoses (MPSs) are a group of a rare inherited lysosomal storage diseases caused by a deficiency or complete lack of lysosomal enzymes participating in glycosaminoglycan (GAG) degradation, which leads to multisystemic impairment and early mortality. This study aimed to determine the birth prevalence of MPS type I, II, III, IVA, VI, and VII in the Republic of Kazakhstan. Methods: Retrospective epidemiological calculations were carried out on all enzymatically and genetically confirmed MPS cases diagnosed between 1984 and 2023 in the Republic of Kazakhstan. Birth prevalence was calculated by dividing the number of patients diagnosed with MPS by the total number of live births in the same period, recalculated for every 100,000 live births. Results: The overall birth prevalence of MPS was 0.77 per 100,000 live births. The highest birth prevalence was MPS II with 0.36 (47% of all diagnosed MPS types), followed by MPS I with 0.16 (21%), MPS VI with 0.12 (16%), MPS IVA with 0.09 (11%), MPS IIIB with 0.03 (4%), and MPS VII (which is the rarest type) with 0.007 (1%). Conclusions: The most common MPS type in the Republic of Kazakhstan is MPS II (Hunter syndrome).

Ecological study to estimate the prevalence of patients with acid sphingomyelinase deficiency in Spain. PREVASMD study

BACKGROUND AND OBJECTIVE

Prevalence studies of acid sphingomyelinase deficiency (ASMD) are scarce and different in Spain. The objective of the present study was to determine the estimated prevalence of patients diagnosed with ASMD (types A/B and B) in Spain.

MATERIAL AND METHODS

PREVASMD was a descriptive, multicenter, and ecological study involving 21 physicians from different specialties (mainly Internal Medicine, Paediatrics and Hematology), of different autonomous communities, with experience in ASMD management.

RESULTS

Between March and April 2022, specialists were attending a total of 34 patients with ASMD diagnosis, 10 paediatric patients under 18 years of age (29.4%) and 24 adult patients (70.6%). The estimated prevalence of patients (paediatric and adult) diagnosed with ASMD was 0.7 per 1,000,000 inhabitants (95% confidence interval, 95% CI: 0.5-1.0), 1.2 per 1,000,000 (95% CI: 0.6-2.3) in the paediatric population and 0.6 per 1,000,000 inhabitants (95% CI: 0.4-0.9) in the adult population. The most frequent symptoms that led to suspicion of ASMD were: splenomegaly (reported by 100.0% of specialists), hepatomegaly (66.7%), interstitial lung disease (57.1%), and thrombocytopenia (57.1%). According to the specialists, laboratory and routine tests, and assistance in Primary Care were the most relevant healthcare resources in the management of ASMD.

CONCLUSIONS

This first study carried out in Spain shows an estimated prevalence of patients of 0.7 per 1,000,000 inhabitants: 1.2 per 1,000,000 inhabitants in the paediatric population and 0.6 per 1,000,000 inhabitants in the adult population.

Clinical and molecular characteristics of 20 Chinese probands with Mucolipidosis type II and III alpha/beta

BACKGROUND

Mucolipidosis (ML) II and III alpha/beta are lysosomal disorders caused by mutations in the GNPTAB gene which encodes the alpha and beta subunits of the heterohexameric enzyme, N-acetylglucosamine-1-phosphotransferase.

METHOD

To explore the clinical and molecular characteristics of the 20 ML II and III alpha/beta patients, clinical data was collected and GNPTAB gene was analyzed by nest PCR and direct Sanger-sequencing. The activity of several lysosomal enzymes was measured in the plasma.

RESULTS

Among the 20 ML II and III alpha/beta patients, 6 patients were classified as ML II and 14 as ML III alpha/beta. The main clinical manifestations were joint stiffness, skeletal deformity, mental retardation and short stature. Bone X-ray examination showed radiological changes. The plasma arylsulfatase A and hexosaminidase A enzyme activities increased significantly. Urinary glycosaminoglycan values were normal. We detected mutations in GNPTAB in 35 of 40 alleles (87.5%). Mutation c.2715 + 1G > A and c.2404 C > T (p.Gln802Ter) were the most prevalent variants, accounting for 14.3% and 11.4%, respectively. Five novel mutations c.3335 + 5G > A, c.1284 + 1G > A, c.571 + 4 A > G, c.1634_1635delAA (p.Lys545Serfs*16) and c.1582T > C(p.Cys528Arg) were identified.

CONCLUSION

Our study expands the spectrum of GNPTAB gene in China. Mutation c.2715 + 1G > A was the most prevalent mutation in our study. The novel mutation c.1284 + 1G > A might be a severe mutation associated with ML II.

Global birth prevalence of Pompe disease: A systematic review and meta-analysis

BACKGROUND

Pompe disease, also known as Glycogen storage disease type II, is an autosomal recessive disorder caused by defects in alpha-glucosidase, resulting in abnormal glycogen accumulation.

METHODS

To conduct a systematic review and meta-analysis of birth prevalence of Pompe disease, the MEDLINE and EMBASE databases were searched for original research articles on the epidemiology of Pompe disease from inception until July 01, 2024. Meta-analysis was performed to estimate global birth prevalence of Pompe disease. The funnel plot was used to describe potential publication bias.

RESULTS

Twenty-two studies, screened out of 945 records, were included for data extraction. Studies that fulfilled inclusion criteria involved 15 areas/countries. Global birth prevalence of Pompe disease was 2.0 cases (95% CI: 1.5-2.4) per 100,000 live births. Global birth prevalence of infantile-onset Pompe disease was 1.0 cases (95% CI: 0.5-1.5) per 100,000 live births. Global birth prevalence of late-onset Pompe disease was 2.4 cases (95% CI: 1.8-3.0) per 100,000 live births. The main limitations are that no study was assessed as high-quality and approximately half of the studies were from Europe.

CONCLUSIONS

Quantitative data on the global epidemiology of Pompe disease could be the fundamental to evaluate the global efforts on building a better world for Pompe disease patients.

Acid sphingomyelinase deficiency in France: a retrospective survival study

BACKGROUND

Acid sphingomyelinase deficiency (ASMD) or Niemann-Pick disease types A, A/B, and B is a progressive, life-limiting, autosomal recessive disorder caused by sphingomyelin phosphodiesterase 1 (SMPD1) gene mutations. There is a need to increase the understanding of morbidity and mortality across children to adults diagnosed with ASMD.

METHODS

This observational retrospective survey analysed medical records of patients with ASMD with retrievable data from 27 hospitals in France, diagnosed/followed up between 1st January 1990 and 31st December 2020. Eligible records were abstracted to collect demographic, medical/developmental history, and mortality data. Survival outcomes were estimated from birth until death using Kaplan-Meier survival analyses; standardised mortality ratio (SMR) was also explored.

RESULTS

A total of 118 medical records of patients with ASMD (type B [n = 94], type A [n = 15], and type A/B [n = 9]) were assessed. The majority of patients were males (63.6%); the median [range] age at diagnosis was 8.0 [1.0-18.0] months (type A), 1.0 [0-3] year (type A/B), and 5.5 [0-73] years (type B). Overall, 30 patients were deceased at the study completion date; the median [range] age at death for patients with ASMD type A (n = 14) was 1 [0-3.6] year, type A/B (n = 6) was 8.5 [3.0-30.9] years, and type B (n = 10) was 57.6 [3.4-74.1] years. The median [95% confidence interval (CI)] survival age from birth in patients with ASMD type A and type A/B was 2.0 [1.8-2.7] years and 11.4 [5.5-18.5] years, respectively. Survival analysis in ASMD type B was explored using SMR [95% CI] analysis (3.5 [1.6-5.9]), which showed that age-specific deaths in the ASMD type B population were 3.5 times more frequent than those in the general French population. The causes of death were mostly severe progressive neurodegeneration (type A: 16.7%), cancer (type B: 16.7%), or unspecified (across groups: 33.3%).

CONCLUSIONS

This study illustrated a substantial burden of illness with high mortality rates in patients with ASMD, including adults with ASMD type B, in France.

Experiences of patients with metachromatic leukodystrophy, adrenoleukodystrophy, or Krabbe disease and the experiences of their family members: a qualitative systematic review

OBJECTIVE

This review aimed to synthesize the experiences of patients with metachromatic leukodystrophy, adrenoleukodystrophy, or Krabbe disease and the experiences of their families.

INTRODUCTION

Leukodystrophies are metabolic diseases caused by genetic mutations. There are multiple forms of the disease, varying in age of onset and symptoms. The progression of leukodystrophies worsens central nervous system symptoms and significantly affects the lives of patients and their families.

INCLUSION CRITERIA

Qualitative studies on the experiences of patients with leukodystrophies and their family members were included. These experiences included treatments such as enzyme replacement therapy and hematopoietic stem cell transplantation; effects of tracheostomy and gastrostomy; burdens on the family, coordinating care within the health care system, and family planning due to genetic disorders. This review considered studies in any setting.

METHODS

MEDLINE (Ovid), CINAHL Plus (EBSCOhost), APA PsycINFO (EBSCOhost), Scopus, and MedNar databases were searched on November 18, 2022. Study selection, critical appraisal, data extraction, and data synthesis were conducted in accordance with the JBI methodology for systematic reviews of qualitative evidence, and synthesized findings were evaluated according to the ConQual approach.

RESULTS

Eleven studies were eligible for synthesis, and 45 findings were extracted corresponding with participants' voices. Of these findings, 40 were unequivocal and 5 were credible. The diseases in the included studies were metachromatic leukodystrophy and adrenoleukodystrophy; no studies were identified for patients with Krabbe disease and their families. These findings were grouped into 11 categories and integrated into 3 synthesized findings, including i) providing care by family members and health care providers as physical symptoms progress, which relates to the effects of the characteristics of progressive leukodystrophies; ii) building medical teamwork to provide appropriate support services, comprising categories related to the challenges experienced with the health care system for patients with leukodystrophy and their families; and iii) coordinating family functions to accept and cope with the disease, which included categories related to family psychological difficulties and role divisions within the family. According to the ConQual criteria, the second synthesized finding had a low confidence level, and the first and third synthesized findings had a very low confidence level.

CONCLUSIONS

The synthesized findings of this review provide evidence on the experiences of patients with metachromatic leukodystrophy or adrenoleukodystrophy and their families. These findings indicate that there are challenges in managing a patient's physical condition and coordinating the health care system and family functions.

REVIEW REGISTRATION

PROSPERO CRD42022318805.

SUPPLEMENTAL DIGITAL CONTENT

A Japanese-language version of the abstract of this review is available [ http://links.lww.com/SRX/A49 ].

The top 100 most cited articles on mucopolysaccharidoses: a bibliometric analysis

Background: Bibliometrics can trace general research trends in a particular field. Mucopolysaccharidoses (MPS), as a group of rare genetic diseases, seriously affect the quality of life of patients and their families. Scholars have devoted themselves to studying MPS's pathogenesis and treatment modalities and have published many papers. Therefore, we conducted a bibliometric and visual study of the top 100 most highly cited articles to provide researchers with an indication of the current state of research and potential directions in the field. Methods: The Web of Science Core Collection was searched for articles on MPS from 1 January 1900, to 8 November 2023, and the top 100 most cited articles were screened. The title, year of publication, institution, country, and first author of the articles were extracted and statistically analyzed using Microsoft Excel 2007. Keyword co-occurrence and collaborative networks were analyzed using VOSviewer 1.6.16. Results: A total of 9,273 articles were retrieved, and the top 100 most cited articles were filtered out. The articles were cited 18,790 times, with an annual average of 188 citations (122-507). Forty-two journals published these articles, with Molecular Genetics and Metabolism and Proceedings of the National Academy of Sciences of the United States being the most published journal (N = 8), followed by Pediatrics (N = 7), Blood (N = 6). The United States (N = 68), the UK (N = 25), and Germany (N = 20) were the top contributing countries. The Royal Manchester Children's Hospital (N = 20) and the University of North Carolina (N = 18) were the most contributing institutions. Muenzer J was the most prolific author (N = 14). Conclusion: We conducted a bibliometric and visual analysis of the top 100 cited articles in MPS. This study identifies the most influential articles currently available in the field of MPS, which provides a good basis for a better understanding of the disease and informs future research directions.

Impact on physical, social, and family functioning of patients with metachromatic leukodystrophy and their family members in Japan: A qualitative study

Metachromatic leukodystrophy is a rare autosomal recessive disease. There are three forms of this disease, all of which result in cognitive and motor dysfunctions. Although enzyme replacement and gene therapies have been developed, they are not expected to be effective in patients with advanced diseases. Therefore, it is important to focus on treatment effects and patients' quality of life; however, qualitative findings on the experiences of patients and their families have not been adequately reported. Interviews were conducted with the family members of patients with metachromatic leukodystrophy in Japan. Verbatim transcripts were analyzed using a qualitative content analysis approach. We interviewed the mothers of five patients. Verbatim interview transcripts were classified into 81 codes. The codes were then aggregated into 15 categories and 3 themes: challenges of life for the patients, challenges in the healthcare system, and challenges of family function. Disease progression greatly affects patients' lives. Moreover, social systems supporting patients and their families are inadequate, especially as the disease progresses. Family members face life restrictions and role changes because of the patient's diagnosis. Patients with metachromatic leukodystrophy and their families require comprehensive support.

A systematic review on the birth prevalence of metachromatic leukodystrophy

BACKGROUND

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease caused by deficiency in arylsulfatase A (ASA) activity arising primarily from ASA gene (ARSA) variants. Late-infantile, juvenile and adult clinical subtypes are defined by symptom onset at ≤ 2.5, > 2.5 to < 16 and ≥ 16 years, respectively. Epidemiological data were sought to address knowledge gaps and to inform decisions regarding the clinical development of an investigational drug.

METHODS

To synthesize all available estimates of MLD incidence and birth prevalence worldwide and in selected countries, Ovid MEDLINE and Embase were searched systematically (March 11, 2022) using a population, intervention, comparator, outcome, time and setting framework, complemented by pragmatic searching to reduce publication bias. Where possible, results were stratified by clinical subtype. Data were extracted from non-interventional studies (clinical trials, non-clinical studies and case reports were excluded; reviews were used for snowballing only).

RESULTS

Of the 31 studies included, 14 reported birth prevalence (13 countries in Asia-Pacific, Europe, the Middle East, North America and South America), one reported prevalence and none reported incidence. Birth prevalence per 100,000 live births ranged from 0.16 (Japan) to 1.85 (Portugal). In the three European studies with estimates stratified by clinical subtypes, birth prevalence was highest for late-infantile cases (0.31-1.12 per 100,000 live births). The distribution of clinical subtypes reported in cases diagnosed over various time periods in 17 studies varied substantially, but late-infantile and juvenile MLD accounted for at least two-thirds of cases in most studies.

CONCLUSIONS

This review provides a foundation for further analysis of the regional epidemiology of MLD. Data gaps indicate the need for better global coverage, increased use of epidemiological measures (e.g. prevalence estimates) and more stratification of outcomes by clinical and genetic disease subtype.

Description of clinical and genetic features of 122 patients included in the Spanish Pompe registry

Pompe disease is a rare genetic disorder with an estimated prevalence of 1:60.000. The two main phenotypes are Infantile Onset Pompe Disease (IOPD) and Late Onset Pompe Disease (LOPD). There is no published data from Spain regarding the existing number of cases, regional distribution, clinical features or, access and response to the treatment. We created a registry to collect all these data from patients with Pompe in Spain. Here, we report the data of the 122 patients registered including nine IOPD and 113 LOPD patients. There was a high variability in how the diagnosis was obtained and how the follow-up was performed among different centres. Seven IOPD patients were still alive being all treated with enzymatic replacement therapy (ERT) at last visit. Ninety four of the 113 LOPD patients had muscle weakness of which 81 were receiving ERT. We observed a progressive decline in the results of muscle function tests during follow-up. Overall, the Spanish Pompe Registry is a valuable resource for understanding the demographics, patient's journey and clinical characteristics of patients in Spain. Our data supports the development of agreed guidelines to ensure that the care provided to the patients is standardized across the country.

Uncovering a New Family Cluster of Gaucher Disease: A Case Report

Gaucher disease (GD) is a recessive autosomal lysosomal storage disorder caused by a deficiency in glucocerebrosidase, leading to the accumulation of undigested glycolipids in the lysosomes of monocytes and macrophages. Patients with GD exhibit a spectrum of phenotypic heterogeneity and are broadly classified into three subtypes. Type 1 is the most common and is not associated with neurological damage, while types 2 and 3 are more severe, presenting with acute neuropathic and subacute neuropathic symptoms, respectively. A thorough accurate initial multisystemic assessment is crucial for evaluating the damage to all potentially affected organs and determining the disease burden. This case report highlights the intricacies of GD type 1 by providing a thorough exploration of the clinical presentation and showcasing valuable insights into the unique manifestations of the disease. The key feature was his individual and family medical history, which allowed the identification and treatment of another case within the community.

Safety outcomes and patients' preferences for home-based intravenous enzyme replacement therapy (ERT) in pompe disease and mucopolysaccharidosis type I (MPS I) disorder: COVID-19 and beyond

BACKGROUND

The Italian Medicines Agency (AIFA) demands precise information on benefit/risk profile of home-based enzyme replacement therapy (ERT) for the treatment of patients with Pompe disease and Mucopolysaccharidosis type I (MPS I). This passage is necessary to obtain the authorization for ERT home therapy, even after the coronavirus disease-19 (COVID-19) pandemic period. This research intends to evaluate the safety, treatment satisfaction, and compliance of MPS I patients treated with laronidase (Aldurazyme®) and Pompe Disease patients treated with alglucosidase alfa (Myozyme®) in a homecare setting.

RESULTS

We report herein an early interim analysis of the HomERT (Home infusions of ERT) study, a multicenter, non-interventional, double-cohort study that retrospectively analyzed 38 patients from 14 sites in Italy: cohort A (Pompe disease - 32 patients) and cohort B (MPS I - 6 patients). Among the selected patients who started home therapy before enrollment, the average number of missed home-based infusions was 0.7 (1.3) in cohort A and 3.8 (6.4) in cohort B with no return to the hospital setting. Irrespective of the treatment location, 3 prior ADRs per cohort were reported. The majority of patients preferred home-based infusions (cohort A: 96.9%; cohort B: 100%): the main reason was attributed to treatment convenience (cohort A: 81.3%; cohort B: 83.3%). Despite the underlying conditions, most patients self-evaluated their health as "good" (cohort A: 50%; cohort B: 83.3%).

CONCLUSIONS

Evidence of favorable safety profile, improved treatment compliance and personal satisfaction validates the use of ERT with laronidase and alglucosidase alfa as a strong candidate for home therapy.

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.

Variant Classification for Pompe disease; ACMG/AMP specifications from the ClinGen Lysosomal Diseases Variant Curation Expert Panel

Accurate determination of the clinical significance of genetic variants is critical to the integration of genomics in medicine. To facilitate this process, the NIH-funded Clinical Genome Resource (ClinGen) has assembled Variant Curation Expert Panels (VCEPs), groups of experts and biocurators which provide gene- and disease- specifications to the American College of Medical Genetics & Genomics and Association for Molecular Pathology's (ACMG/AMP) variation classification guidelines. With the goal of classifying the clinical significance of GAA variants in Pompe disease (Glycogen storage disease, type II), the ClinGen Lysosomal Diseases (LD) VCEP has specified the ACMG/AMP criteria for GAA. Variant classification can play an important role in confirming the diagnosis of Pompe disease as well as in the identification of carriers. Furthermore, since the inclusion of Pompe disease on the Recommended Uniform Screening Panel (RUSP) for newborns in the USA in 2015, the addition of molecular genetic testing has become an important component in the interpretation of newborn screening results, particularly for asymptomatic individuals. To date, the LD VCEP has submitted classifications and supporting data on 243 GAA variants to public databases, specifically ClinVar and the ClinGen Evidence Repository. Here, we describe the ACMG/AMP criteria specification process for GAA, an update of the GAA-specific variant classification guidelines, and comparison of the ClinGen LD VCEP's GAA variant classifications with variant classifications submitted to ClinVar. The LD VCEP has added to the publicly available knowledge on the pathogenicity of variants in GAA by increasing the number of expert-curated GAA variants present in ClinVar, and aids in resolving conflicting classifications and variants of uncertain clinical significance.

A Comprehensive Update on Late-Onset Pompe Disease

Pompe disease (PD) is an autosomal recessive disorder caused by mutations in the GAA gene that lead to a deficiency in the acid alpha-glucosidase enzyme. Two clinical presentations are usually considered, named infantile-onset Pompe disease (IOPD) and late-onset Pompe disease (LOPD), which differ in age of onset, organ involvement, and severity of disease. Assessment of acid alpha-glucosidase activity on a dried blood spot is the first-line screening test, which needs to be confirmed by genetic analysis in case of suspected deficiency. LOPD is a multi-system disease, thus requiring a multidisciplinary approach for efficacious management. Enzyme replacement therapy (ERT), which was introduced over 15 years ago, changes the natural progression of the disease. However, it has limitations, including a reduction in efficacy over time and heterogeneous therapeutic responses among patients. Novel therapeutic approaches, such as gene therapy, are currently under study. We provide a comprehensive review of diagnostic advances in LOPD and a critical discussion about the advantages and limitations of current and future treatments.

Mucopolysaccharidosis type IIIC in chinese mainland: clinical and molecular characteristics of ten patients and report of six novel variants in the HGSNAT gene

BACKGROUND

Mucopolysaccharidosis type IIIC (MPS IIIC; Sanfilippo syndrome C) is a rare lysosomal storage disease caused by mutations in the heparan-α-glucosaminide N-acetyltransferase (HGSNAT) gene, resulting in the accumulation of heparan sulfate. MPS IIIC is characterized by severe neuropsychiatric symptoms and mild somatic symptoms.

METHODS

Our study analyzed the clinical presentation and biochemical characteristics of ten Chinese MPS IIIC patients from eight families. Whole exome sequencing was applied to identify the variants in HGSNAT gene. In one patient with only one mutant allele identified firstly, whole genome sequencing was applied. The pathogenic effect of novel variants was evaluated in silico.

RESULTS

The mean age at the onset of clinical symptoms was 4.2 ± 2.5 years old, and the mean age of diagnosis was 7.6 ± 4.5 years old, indicating a delay of diagnosis. The most common onset symptoms were speech deterioration, and the most frequent presenting symptoms are speech deterioration, mental deterioration, hyperactivity and hepatomegaly, sequentially. All mutant alleles of 10 patients have been identified. There were eleven different HGSNAT variants, and the most common one was a previously reported variant c.493 + 1G > A. There were six novel variants, p.R124T, p.G290A, p.G426E, c.743 + 101_743 + 102delTT, c.851 + 171T > A and p.V582Yfs*18 in our cohort. Extraordinarily, two deep intron variants were identified in our cohort, with the variant c.851 + 171T > A identified by whole genome sequencing.

CONCLUSION

This study analyzed the clinical, biochemical, and genetic characteristics of ten Chinese MPS IIIC patients, which would assist in the early diagnosis and genetic counselling of MPS IIIC.

Leukocyte Imbalances in Mucopolysaccharidoses Patients

Mucopolysaccharidoses (MPSs) are rare inherited lysosomal storage diseases (LSDs) caused by deficient activity in one of the enzymes responsible for glycosaminoglycans lysosomal degradation. MPS II is caused by pathogenic mutations in the IDS gene, leading to deficient activity of the enzyme iduronate-2-sulfatase, which causes dermatan and heparan sulfate storage in the lysosomes. In MPS VI, there is dermatan sulfate lysosomal accumulation due to pathogenic mutations in the ARSB gene, leading to arylsulfatase B deficiency. Alterations in the immune system of MPS mouse models have already been described, but data concerning MPSs patients is still scarce. Herein, we study different leukocyte populations in MPS II and VI disease patients. MPS VI, but not MPS II patients, have a decrease percentage of natural killer (NK) cells and monocytes when compared with controls. No alterations were identified in the percentage of T, invariant NKT, and B cells in both groups of MPS disease patients. However, we discovered alterations in the naïve versus memory status of both helper and cytotoxic T cells in MPS VI disease patients compared to control group. Indeed, MPS VI disease patients have a higher frequency of naïve T cells and, consequently, lower memory T cell frequency than control subjects. Altogether, these results reveal MPS VI disease-specific alterations in some leukocyte populations, suggesting that the type of substrate accumulated and/or enzyme deficiency in the lysosome may have a particular effect on the normal cellular composition of the immune system.

Consensus clinical management guidelines for acid sphingomyelinase deficiency (Niemann-Pick disease types A, B and A/B)

BACKGROUND

Acid Sphingomyelinase Deficiency (ASMD) is a rare autosomal recessive disorder caused by mutations in the SMPD1 gene. This rarity contributes to misdiagnosis, delayed diagnosis and barriers to good care. There are no published national or international consensus guidelines for the diagnosis and management of patients with ASMD. For these reasons, we have developed clinical guidelines that defines standard of care for ASMD patients.

METHODS

The information contained in these guidelines was obtained through a systematic literature review and the experiences of the authors in their care of patients with ASMD. We adopted the Appraisal of Guidelines for Research and Evaluation (AGREE II) system as method of choice for the guideline development process.

RESULTS

The clinical spectrum of ASMD, although a continuum, varies substantially with subtypes ranging from a fatal infantile neurovisceral disorder to an adult-onset chronic visceral disease. We produced 39 conclusive statements and scored them according to level of evidence, strengths of recommendations and expert opinions. In addition, these guidelines have identified knowledge gaps that must be filled by future research.

CONCLUSION

These guidelines can inform care providers, care funders, patients and their carers about best clinical practice and leads to a step change in the quality of care for patients with ASMD with or without enzyme replacement therapy (ERT).

Experiences of patients and their family members with metachromatic leukodystrophy, adrenoleukodystrophy, and Krabbe disease: a qualitative systematic review protocol

OBJECTIVE

The objective of this review is to synthesize the experiences of patients with metachromatic leukodystrophy (MLD), adrenoleukodystrophy (ALD), and Krabbe disease and the experiences of their family members.

INTRODUCTION

MLD, ALD, and Krabbe disease are rare disorders that are classified as lysosomal storage or peroxisomal disorders, with similar presentations as leukodystrophy. As these diseases cause cognitive and neurological decline due to the progression of leukodystrophy associated with demyelination, they have significant impact on the lives of patients and their families. It is important to identify the impact and challenges of these diseases on patients' lives and on their families, as well as to synthesize qualitative studies regarding their experiences.

INCLUSION CRITERIA

We will consider studies including patients with MLD, ALD, or Krabbe disease and their family members. These experiences will include the challenges, dissatisfactions, and frustrations with symptoms and treatments; complications of hematopoietic stem cell transplantation; and the increased caregiver burden with disease progression. This is important since the impacts of disease progression are experienced in a variety of settings beyond the hospital, such as in the community and at home.

METHODS

The search strategy will follow JBI methodology and be conducted in 3 steps: an initial limited search, a comprehensive database search, and a reference search of the included articles. MEDLINE, CINAHL Plus, PsycINFO, and Scopus will be searched with no restriction on language or publication dates. The study selection, critical appraisal, data extraction, and data synthesis will be performed according to JBI guidelines for systematic reviews of qualitative research. Final syntheses will be assessed using the ConQual approach.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42022318805.

Cyclodextrins applied to the treatment of lysosomal storage disorders

Cyclodextrin (CD), a cyclic oligosaccharide, is a pharmaceutical additive that improves the solubility of hydrophobic compounds. Recent research has focused on the potential active pharmaceutical abilities of CD. Lysosomal storage diseases are inherited metabolic diseases characterized by lysosomal dysfunction and abnormal lipid storage. Niemann-Pick disease type C (NPC) is caused by mutations in cholesterol transporter genes (NPC1, NPC2) and is characterized by cholesterol accumulation in lysosomes. A biocompatible cholesterol solubilizer 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was recently used in NPC patients for compassionate use and in clinical trials. HP-β-CD is an attractive drug candidate for NPC; however, its adverse effects, such as ototoxicity, should be solved. In this review, we discuss the current use of HP-β-CD in basic and clinical research and discuss alternative CD derivatives that may outperform HP-β-CD, which should be considered for clinical use. The potential of CD therapy for the treatment of other lysosomal storage diseases is also discussed.

Mucopolysaccharidoses and the blood-brain barrier

Mucopolysaccharidoses comprise a set of genetic diseases marked by an enzymatic dysfunction in the degradation of glycosaminoglycans in lysosomes. There are eight clinically distinct types of mucopolysaccharidosis, some with various subtypes, based on which lysosomal enzyme is deficient and symptom severity. Patients with mucopolysaccharidosis can present with a variety of symptoms, including cognitive dysfunction, hepatosplenomegaly, skeletal abnormalities, and cardiopulmonary issues. Additionally, the onset and severity of symptoms can vary depending on the specific disorder, with symptoms typically arising during early childhood. While there is currently no cure for mucopolysaccharidosis, there are clinically approved therapies for the management of clinical symptoms, such as enzyme replacement therapy. Enzyme replacement therapy is typically administered intravenously, which allows for the systemic delivery of the deficient enzymes to peripheral organ sites. However, crossing the blood-brain barrier (BBB) to ameliorate the neurological symptoms of mucopolysaccharidosis continues to remain a challenge for these large macromolecules. In this review, we discuss the transport mechanisms for the delivery of lysosomal enzymes across the BBB. Additionally, we discuss the several therapeutic approaches, both preclinical and clinical, for the treatment of mucopolysaccharidoses.

Clinical Characteristics, Renal Involvement, and Therapeutic Options of Pediatric Patients With Fabry Disease

Inherited renal diseases represent 20% of the causes of end-stage renal diseases. Fabry disease, an X-linked lysosomal storage disorder, results from α-galactosidase A deficient or absent activity followed by globotriaosylceramide (Gb3) accumulation and multiorgan involvement. In Fabry disease, kidney involvement starts early, during intrauterine life by the Gb3 deposition. Even if chronic kidney disease (CKD) is discovered later in adult life in Fabry disease patients, a decline in glomerular filtration rate (GFR) can occur during adolescence. The first clinical sign of kidney involvement is represented by albuminuria. So, early and close monitoring of kidneys function is required: albuminuria and proteinuria, urinary albumin-to-creatinine ratio, serum creatinine, or cystatin C to estimate GFR, while urinary sediment with phase-contrast microscopy under polarized light may be useful in those cases where leucocyte α-Gal A activity and GLA genotyping are not available. Children with Fabry disease and kidney involvement should receive enzyme replacement therapy and nephroprotective drugs (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) to prevent or slow the progressive loss of kidney functions. Early diagnosis of Fabry disease is important as enzyme replacement therapy reduces symptoms, improves clinical features and biochemical markers, and the quality of life. More importantly, early treatment could slow or stop progressive organ damage in later life.

Secondary Hyperparathyroidism in Children with Mucolipidosis Type II (I-Cell Disease): Irish Experience

Mucolipidosis type II (ML II) is an autosomal recessive lysosomal targeting disorder that may present with features of hyperparathyroidism. The aim of this study was to describe in detail the clinical cases of ML II presenting to a tertiary referral centre with biochemical and/or radiological features of hyperparathyroidism. There were twenty-three children diagnosed with ML II in the Republic of Ireland from July 1998 to July 2021 inclusive (a 23-year period). The approximate incidence of ML II in the Republic of Ireland is, therefore, 1 per 64,000 live births. Medical records were available and were reviewed for 21 of the 23 children. Five of these had been identified as having biochemical and/or radiological features of hyperparathyroidism. Of these five, three children were born to Irish Traveller parents and two to non-Traveller Irish parents. All five children had radiological features of hyperparathyroidism (on skeletal survey), with evidence of antenatal fractures in three cases and an acute fracture in one. Four children had biochemical features of secondary hyperparathyroidism. Three children received treatment with high dose Vitamin D supplements and two who had antenatal/acute fractures were managed with minimal handling. We observed resolution of secondary hyperparathyroidism in all cases irrespective of treatment. Four of five children with ML II and hyperparathyroidism died as a result of cardiorespiratory failure at ages ranging from 10 months to 7 years. Biochemical and/or radiological evidence of hyperparathyroidism is commonly identified at presentation of ML II. Further studies are needed to establish the pathophysiology and optimal management of hyperparathyroidism in this cohort. Recognition of this association may improve diagnostic accuracy and management, facilitate family counseling and is also important for natural history data.

Prevalence of lysosomal storage disorders in Australia from 2009 to 2020

Background

Lysosomal storage disorders (LSD) are a family of genetic diseases that have a devastating impact on the patient and family with a concomitant health burden. Although considered rare disorders, improved diagnostic capabilities, newborn screening programs and public awareness has witnessed the frequency of many LSD increase considerably over recent years. To quantify their footprint, the number of LSD diagnosed in the multicultural Australian population in a 12-year period was determined. The principle objective was to yield contemporary prevalence figures to inform public health policies.

Methods

From the national referral laboratory for LSD diagnoses in Australia, retrospective data from patient referrals and prenatal testing for the period January 1 2009 to December 31 2020 were collated. Diagnosis was established biochemically by enzyme activity and/or metabolite determinations, as well as molecular genetic testing. The incidence of each disorder was determined by dividing the number of postnatal diagnoses by the number of births with prevalence including prenatal diagnoses.

Findings

During this 12-year period 766 diagnosis of LSD were confirmed inclusive of 32 prenatal outcomes representing 38 individual disorders. Total diagnosis per 100,000 live births averaged 21 per year (range 16 – 26) with Fabry disease the most prevalent representing 34% of all diagnoses in the current (up to 2020) report.

Interpretation

The combined prevalence of LSD for this study period at 1 per 4,800 live births is considerably higher than 1 per 7,700 reported for a 17-year period up to 1996. Additionally, more adults were diagnosed than children, implying that LSD are more common in adulthood than childhood. These data highlight the requirements for physicians to consider LSD in symptomatic adults and should refigure public health policies steering newborn screening programs in the direction of adult-onset conditions.

Funding

No funding was received for this study.

Molecular analysis and novel variation identification of Chinese pedigrees with mucopolysaccharidosis using targeted next-generation sequencing

BACKGROUND

Mucopolysaccharidosis (MPS) refers to a group of lysosomal storage disorders for which seven types and 11 subtypes are currently recognized. Targeted next-generation sequencing (NGS) offers an important method of disease typing, diagnosis, prenatal diagnosis, and treatment.

METHODS

Gene variations in 48 Chinese MPS patients were evaluated using NGS, and the pathogenicity of the DNA alterations was evaluated using PolyPhen2, SIFT, and Mutation Taster. The effect of amino acid substitution on protein structure was also assessed.

RESULTS

Four pedigrees with MPS I (8.3%), 28 with MPS II (58.3%), two with MPS IIIA (4.2%), two with MPS IIIB (4.2%), six with MPS IVA (12.5%), one with MPS IVB (2.1%), and five with MPS VI (10.4%) were identified. Of the 69 variations identified, 11 were novel variants (three in IDUA, five in IDS, and three in GALNS), all of which were predicted to be disease-causing except for one, and were associated with impaired protein structure and function.

CONCLUSIONS

Targeted NGS technology is effective for the gene-based testing of MPS disorders, which show high allelic heterogeneity. MPS II was the predominant form in Chinese. Our study expands the existing variation spectrum of MPS, which is important for disease management and genetic counseling.

Searching, Structural Determination, and Diagnostic Performance Evaluation of Biomarker Molecules for Niemann-Pick Disease Type C Using Liquid Chromatography/Tandem Mass Spectrometry

Niemann-Pick disease type C (NPC) is an autosomal recessive disorder that is characterized by progressive neuronal degeneration. Patients with NPC have a wide age of onset and various clinical symptoms. Therefore, the discovery and diagnosis of NPC are very difficult. Conventional laboratory tests are complicated and time consuming. In this context, biomarker searches have recently been performed. Our research group has previously also investigated NPC biomarkers based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) and related techniques. To identify biomarker candidates, nontargeted analysis with high-resolution MS and MS/MS scanning is commonly used. Structural speculation has been performed using LC/MS/MS fragmentation and chemical derivatization, while identification is performed by matching authentic standards and sample specimens. Diagnostic performance evaluation was performed using the validated LC/MS/MS method and analysis of samples from patients and control subjects. NPC biomarkers, which have been identified and evaluated in terms of performance, are various classes of lipid molecules. Oxysterols, cholenoic acids, and conjugates are cholesterol-derived molecules detected in the blood or urine. Plasma lyso-sphingolipids are biomarkers for both NPC and other lysosomal diseases. N-palmitoyl-O-phosphocholine-serine is a novel class of lipid biomarkers for NPC. This article reviews biomarkers for NPC and the analysis methods employed to that end.

Sanfilippo syndrome type B: Analysis of patients diagnosed by the MPS Brazil Network

Mucopolysaccharidosis type IIIB is a rare autosomal recessive disorder characterized by deficiency of the enzyme N-acetyl-alpha-d-glucosaminidase (NAGLU), caused by biallelic pathogenic variants in the NAGLU gene, which leads to storage of heparan sulfate and a series of clinical consequences which hallmark is neurodegeneration. In this study clinical, epidemiological, and biochemical data were obtained from MPS IIIB patients diagnosed from 2004-2019 by the MPS Brazil Network ("Rede MPS Brasil"), which was created with the goal to provide an easily accessible and comprehensive investigation of all MPS types. One hundred and ten MPS IIIB patients were diagnosed during this period. Mean age at diagnosis was 10.9 years. Patients were from all over Brazil, with a few from abroad, with a possible cluster of MPS IIIB identified in Ecuador. All patients had increased urinary levels of glycosaminoglycans and low NAGLU activity in blood. Main clinical symptoms reported at diagnosis were coarse facies and neurocognitive regression. The most common variant was p.Leu496Pro (30% of alleles). MPS IIIB seems to be relatively frequent in Brazil, but patients are diagnosed later than in other countries, and reasons for that probably include the limited awareness about the disease by health professionals and the difficulties to access diagnostic tests, factors that the MPS Brazil Network is trying to mitigate.

Estimated prevalence of Niemann-Pick type C disease in Quebec

Niemann–Pick type C (NP-C) disease is an autosomal recessive disease caused by variants in the NPC1 or NPC2 genes. It has a large range of symptoms depending on age of onset, thus making it difficult to diagnose. In adults, symptoms appear mainly in the form of psychiatric problems. The prevalence varies from 0.35 to 2.2 per 100,000 births depending on the country. The aim of this study is to calculate the estimated prevalence of NP-C in Quebec to determine if it is underdiagnosed in this population. The CARTaGENE database is a unique database that regroups individuals between 40 and 69 years old from metropolitan regions of Quebec. RNA-sequencing data was available for 911 individuals and exome sequencing for 198 individuals. We used a bioinformatic pipeline on those individuals to extract the variants in the NPC1/2 genes. The prevalence in Quebec was estimated assuming Hardy–Weinberg Equilibrium. Two pathogenic variants were used. The variant p.Pro543Leu was found in three heterozygous individuals that share a common haplotype, which suggests a founder French-Canadian pathogenic variant. The variant p.Ile1061Thr was found in two heterozygous individuals. Both variants have previously been reported and are usually associated with infantile onset. The estimated prevalence calculated using those two variants is 0.61:100,000 births. This study represents the first estimate of NP-C in Quebec. The estimated prevalence for NP-C is likely underestimated due to misdiagnosis or missed cases. It is therefore important to diagnose all NP-C patients to initiate early treatment.

Enzyme replacement therapy with galsulfase for mucopolysaccharidosis type VI

BACKGROUND

Mucopolysaccharidosis type VI (MPS VI) or Maroteaux-Lamy syndrome is a rare genetic disorder caused by the deficiency of arylsulphatase B. The resultant accumulation of dermatan sulphate causes lysosomal damage. The clinical symptoms are related to skeletal dysplasia (i.e. short stature and degenerative joint disease). Other manifestations include cardiac disease, impaired pulmonary function, ophthalmological complications, hepatosplenomegaly, sinusitis, otitis, hearing loss and sleep apnea. Intellectual impairment is generally absent. Clinical manifestation is typically by two or three years of age; however, slowly progressive cases may not present until adulthood. Enzyme replacement therapy (ERT) with galsulfase is considered a new approach for treating MPS VI.

OBJECTIVES

To evaluate the effectiveness and safety of treating MPS VI by ERT with galsulfase compared to other interventions, placebo or no intervention.

SEARCH METHODS

Eletronic searches were performed on the Cystic Fibrosis and Genetic Disorders Group's Inborn Errors of Metabolism Trials Register. Date of the latest search:  09 June 2021. Further searches of the following databases were also performed: CENTRAL, MEDLINE, LILACS, the Journal of Inherited Metabolic Disease, the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov. Date of the latest search: 20 August 2021.

SELECTION CRITERIA

Randomized and quasi-randomized controlled clinical studies of ERT with galsulfase compared to other interventions or placebo.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the studies, assessed the risk of bias, extracted data and assessed the certainty of the the evidence using the GRADE criteria.

MAIN RESULTS

One study was included involving 39 participants who received either ERT with galsulfase (recombinant human arylsulphatase B) or placebo. This small study was considered overall to have an unclear risk of bias in relation to the design and implementation of the study, since the authors did not report how both the allocation generation and concealment were performed. Given the very low certainty of the evidence, we are uncertain whether at 24 weeks there was a difference between groups in relation to the 12-minute walk test, mean difference (MD) of 92.00 meters (95% confidence interval (CI) 11.00 to 172.00), or the three-minute stair climb, MD 5.70 (95% CI -0.10 to 11.50). In relation to respiratory tests, we are uncertain whether galsulfase makes any difference as compared to placebo in forced vital capacity in litres (FVC (L) (absolute change in baseline), given the very low certainty of the evidence. Cardiac function was not reported in the included study. We found that galsulfase, as compared to placebo, may decrease urinary glycosaminoglycan levels at 24 weeks, MD -227.00 (95% CI -264.00 to -190.00) (low-certainty evidence). We are uncertain whether there are differences between the galsulfase and placebo groups in relation to adverse events (very low-certainty evidence). In general, the dose of galsulfase was well tolerated and there were no differences between groups. These events include drug-related adverse events, serious and severe adverse events, those during infusion, drug-related adverse events during infusion, and deaths. More infusion-related reactions were observed in the galsulfase group and were managed with interruption or slowing of infusion rate or administration of antihistamines or corticosteroids drugs. No deaths occurred during the study.   AUTHORS' CONCLUSIONS: The results of this review are based only on one small study (a 24-week randomised phase of the study and prior to the open-label extension). We are uncertain whether galsulfase is more effective than placebo, for treating people with MPS VI, in relation to the 12-minute walk test or the three-minute stair climb, as the certainty of the evidence has been assessed as very low. We found that galsulfase may reduce urinary glycosaminoglycans levels. We are also uncertain whether there are any differences between treatment groups in relation to cardiac or pulmonary functions, liver or spleen volume, overnight apnea-hypopnea, height and weight, quality of life and adverse effects. Further studies are needed to obtain more information on the long-term effectiveness and safety of ERT with galsulfase.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Prevalence of patients with lysosomal storage disorders and peroxisomal disorders: A nationwide survey in Japan

INTRODUCTION

Lysosomal storage disorders and peroxisomal disorders are rare diseases caused by the accumulation of substrates of the metabolic pathway within lysosomes and peroxisomes, respectively. Owing to the rarity of these diseases, the prevalence of lysosomal storage disorders and peroxisomal disorders in Japan is unknown. Therefore, we conducted a nationwide survey to estimate the number of patients with lysosomal storage disorders and peroxisomal disorders in Japan.

METHODS

A nationwide survey was conducted following the "Manual of nationwide epidemiological survey for understanding patient number and clinical epidemiology of rare diseases (3rd version)". A questionnaire asking for detailed information, such as disease phenotypes and medical history, was created and sent to 504 institutions with doctors who have experience in treating patients with lysosomal storage disorders and peroxisomal disorders. Result A total of 303 completed questionnaires were collected from 504 institutions (response rate: 60.1%). The number of patients was estimated by calculating the rate/frequency of overlap. The estimated number of patients was 1658 (±264.8) for Fabry disease, 72 (±11.3) for mucopolysaccharidosis I, 275 (±49.9) for mucopolysaccharidosis II, 211 (±31.3) for Gaucher disease, 124 (±25.8) for Pompe disease, 83 (±44.3) for metachromatic leukodystrophy, 57 (±9.4) for Niemann-Pick type C, and 262 (±42.3) for adrenoleukodystrophy. In addition the birth prevalence was calculated using the estimated number of patients and birth year data for each disease, and was 1.25 for Fabry disease, 0.09 for mucopolysaccharidosis I, 0.38 for mucopolysaccharidosis II, 0.19 for Gaucher disease, 0.14 for Pompe disease, 0.16 for metachromatic leukodystrophy, 0.16 for Niemann-Pick type C, and 0.20 for adrenoleukodystrophy.

DISCUSSION

Among the diseases analyzed, the disease with the highest prevalence was Fabry disease, followed by mucopolysaccharidosis II, adrenoleukodystrophy, Gaucher disease and metachromatic leukodystrophy. In particular, the high prevalence of mucopolysaccharidosis II and Gaucher disease type II was a feature characteristic of Japan.

CONCLUSION

We estimated the number of patients with lysosomal storage disorders and peroxisomal disorders in Japan. The details of the age at diagnosis and treatment methods for each disease were clarified, and will be useful for the early diagnosis of these patients and to provide appropriate treatments. Furthermore, our results suggest that supportive care and the development of an environment that can provide optimal medical care is important in the future.

Demographic, clinical, and ancestry characterization of a large cluster of mucopolysaccharidosis IV A in the Brazilian Northeast region

Mucopolysaccharidosis (MPS) IVA is a rare autosomal recessive disease with a highly variable distribution worldwide. Discrepancies in the incidence of MPS IVA among populations of different ethnicities are mostly attributed to founder effects. Demographic and clinical data from 28 MPS IVA patients, followed at a single center, and ancestry (Y chromosome and mitochondrial markers) of a subsample of 17 patients, most with the p.Ser341Arg (c.1023C>G) mutation were analyzed. Parental consanguinity was observed in 15/20 couples; a rare homozygous N-acetylgalactosamine-6-sulfatase (GALNS) mutation was found in 7/16 families with intra-familial phenotypic heterogeneity. Paternal ancestry was 94.2% (16/17) European, 5.8% (1/17) African, and 0% Amerindian. The European paternal haplogroups R1a, R1b, and R* accounted for 94.2% (16/17) of the patients. The R1b haplogroup, identified in 59% (10/17) of the patients, is frequently found in populations from the Iberian Peninsula. European, Amerindian, and African maternal ancestry was observed in 46.9% (8/17), 35.4% (6/17), and 17.7% (3/17) of the patients, respectively. Study of a cluster of MPS IVA patients from Northeastern Brazil, with high parental consanguinity and phenotypic heterogeneity showed predominantly European parental ancestry. This ancestry finding corroborates historical data on the local settlement, formed predominantly by European men.

Epidemiology of mucopolysaccharidoses (MPS) in United States: challenges and opportunities

Background

Mucopolysaccharidoses (MPS) are rare, inherited lysosomal storage disorders characterized by progressive multiorgan involvement. Previous studies on incidence and prevalence of MPS mainly focused on countries other than the United States (US), showing considerable variation by country. This study aimed to identify MPS incidence and prevalence in the US at a national and state level to guide clinicians and policy makers.

Methods

This retrospective study examined all diagnosed cases of MPS from 1995 to 2015 in the US using the National MPS Society database records. Data included year of birth, patient geographic location, and MPS variant type. US population information was obtained from the National Center for Health Statistics. The incidence and prevalence rates were calculated for each disease. Incidence rates were calculated for each state.

Results

We obtained information from 789 MPS patients during a 20-year period. Incidence of MPS in the US was found to be 0.98 per 100,000 live births. Prevalence was found to be 2.67 per 1 million. MPS I, II, and III had the highest incidence rate at birth (0.26/100,000) and prevalence rates of 0.70–0.71 per million. Birth incidences of MPS IV, VI, and VII were 0.14, 0.04 and 0.027 per 100,000 live births.

Conclusions

This is the most comprehensive review of MPS incidence and prevalence rates in the US. Due to the large US population and state fragmentation, US incidence and prevalence were found to be lower than other countries. Nonetheless, state-level studies in the US supported these figures. Efforts should be focused in the establishment of a national rare disease registry with mandated reporting from every state as well as newborn screening of MPS.

Genotype-phenotype studies in a large cohort of Brazilian patients with Hunter syndrome

Mucopolysaccharidosis type II (MPS II) is an X-linked inherited disease caused by pathogenic variants in the IDS gene, leading to deficiency of the lysosomal enzyme iduronate-2-sulfatase and consequent widespread storage of glycosaminoglycans, leading to several clinical consequences, with progressive manifestations which most times includes cognitive decline. MPS II has wide allelic and clinical heterogeneity and a complex genotype-phenotype correlation. We evaluated data from 501 Brazilian patients diagnosed with MPS II from 1982 to 2020. We genotyped 280 of these patients (55.9%), which were assigned to 206 different families. Point mutations were present in 70% of our patients, being missense variants the most frequent. We correlated the IDS pathogenic variants identified with the phenotype (neuronophatic or non-neuronopathic). Except for two half-brothers, there was no discordance in the genotype-phenotype correlation among family members, nor among MPS II patients from different families with the same single base-pair substitution variant. Mothers were carriers in 82.0% of the cases. This comprehensive study of the molecular profile of the MPS II cases in Brazil sheds light on the genotype-phenotype correlation and helps the better understanding of the disease and the prediction of its clinical course, enabling the provision of a more refined genetic counseling to the affected families.

Genome editing in mucopolysaccharidoses and mucolipidoses

Mucopolysaccharidoses (MPS) and mucolipidoses (ML) are disorders that alter lysosome function. While MPS are caused by mutation in enzymes that degrade glycosaminoglycans, the ML are disorders characterized by reduced function in the phosphotransferase enzyme. Multiple clinical features are associated with these diseases and the exact mechanisms that could explain such different clinical manifestations in patients are still unknown. Furthermore, there are no curative treatment for any of MPS and ML conditions so far. Gene editing holds promise as a tool for the creation of cell and animal models to help explain disease pathogenesis, as well as a platform for gene therapy. In this chapter, we discuss the main studies involving genome editing for MPS and the prospect applications for ML.

Carrier frequency and predicted genetic prevalence of Pompe disease based on a general population database

Background

The genetic prevalence of Pompe disease was estimated based on the proportion of individuals who have a causative genotype in a general population database. In addition, clinical severity for causative genotypes was assessed based on currently available locus-specific databases (LSDBs), which contain information on both genotype and clinical severity.

Methods

Genetic variants in the GAA gene in the Genome Aggregation Database (gnomAD) (v2.1.1) were analyzed in combination with LSDBs of ClinVar, ClinGen Evidence Repository, Pompe disease GAA variant database, and the Pompe Registry. Carrier frequency (CF) and predicted genetic prevalence (pGP) were estimated.

Results

Of 7 populations, East Asian and African showed higher proportions of pathogenic or likely pathogenic variants (PLPVs) associated with classic infantile-onset Pompe disease. Total CF and pGP in the overall population were 1.3% (1 in 77) and 1:23,232, respectively. The highest pGP was observed in the East Asian population at 1:12,125, followed by Non-Finnish European (1:13,756), Ashkenazi Jewish (1:22,851), African/African-American (1:26,560), Latino/Admixed American (1:57,620), South Asian (1:93,087), and Finnish (1:1,056,444).

Conclusions

Pompe disease has a higher pGP (1:23,232) than earlier accepted (1:40,000). The pGP for Pompe disease was expectedly wide by population and consistent with previous reports based on newborn screening programs (approximately 1:10,000-1:30,000).

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.

Epidemiology of Mucopolysaccharidoses Update

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by a lysosomal enzyme deficiency or malfunction, which leads to the accumulation of glycosaminoglycans in tissues and organs. If not treated at an early stage, patients have various health problems, affecting their quality of life and life-span. Two therapeutic options for MPS are widely used in practice: enzyme replacement therapy and hematopoietic stem cell transplantation. However, early diagnosis of MPS is crucial, as treatment may be too late to reverse or ameliorate the disease progress. It has been noted that the prevalence of MPS and each subtype varies based on geographic regions and/or ethnic background. Each type of MPS is caused by a wide range of the mutational spectrum, mainly missense mutations. Some mutations were derived from the common founder effect. In the previous study, Khan et al. 2018 have reported the epidemiology of MPS from 22 countries and 16 regions. In this study, we aimed to update the prevalence of MPS across the world. We have collected and investigated 189 publications related to the prevalence of MPS via PubMed as of December 2020. In total, data from 33 countries and 23 regions were compiled and analyzed. Saudi Arabia provided the highest frequency of overall MPS because of regional or consanguineous marriages (or founder effect), followed by Portugal, Brazil, the Netherlands, and Australia. The newborn screening is an efficient and early diagnosis for MPS. MPS I has been approved for newborn screening in the United States. After the newborn screening of MPS I, the frequency of MPS I increased, compared with the past incidence rates. Overall, we conclude that the current identification methods are not enough to recognize all MPS patients, leading to an inaccurate incidence and status. Differences in ethnic background and/or founder effects impact on the frequency of MPS, which affects the prevalence of MPS. Two-tier newborn screening has accelerated early recognition of MPS I, providing an accurate incidence of patients.

Deficiency in the Screening Process of Fabry Disease: Analysis of Chronic Kidney Patients Not on Dialysis

Fabry Disease (FD), a rare and progressive, X-linked lysosomal storage disorder, is caused by mutations in the α-galactosidase A (GLA) gene which leads to enzymatic deficiency of GLA. Misdiagnosed and undiagnosed FD cases are common for the variable FD phenotype, ranging from asymptomatic and/or impairment of single organs, which is typically seen in females and in patients with late-onset mutation, to multiple organ disease, which is frequently found in males with classic GLA mutation. Consequently, for an early diagnosis and an efficient treatment of FD, three different strategies of screening, new-born screening, high-risk screening and familiar screening, have been conducted. However, most of FD screening in the CKD population has been carried out in hemodialysis patients and kidney transplant recipients, for whom the renal damage is already irreversible, so the effectiveness of enzymatic replacement therapy is limited and delayed therapeutic intervention results in worse long-term outcomes. This review investigates the actual strategies of screening initiatives for the identification of FD, examining in detail those performed in CKD patients not on dialysis.

Inherited disorders of lysosomal membrane transporters

Disorders caused by defects in lysosomal membrane transporters form a distinct subgroup of lysosomal storage disorders (LSDs). To date, defects in only 10 lysosomal membrane transporters have been associated with inherited disorders. The clinical presentations of these diseases resemble the phenotypes of other LSDs; they are heterogeneous and often present in children with neurodegenerative manifestations. However, for pathomechanistic and therapeutic studies, lysosomal membrane transport defects should be distinguished from LSDs caused by defective hydrolytic enzymes. The involved proteins differ in function, localization, and lysosomal targeting, and the diseases themselves differ in their stored material and therapeutic approaches. We provide an overview of the small group of disorders of lysosomal membrane transporters, emphasizing discovery, pathomechanism, clinical features, diagnostic methods and therapeutic aspects. We discuss common aspects of lysosomal membrane transporter defects that can provide the basis for preclinical research into these disorders.

Newborn Screening for Pompe Disease: Pennsylvania Experience

Pennsylvania started newborn screening for Pompe disease in February 2016. Between February 2016 and December 2019, 531,139 newborns were screened. Alpha-Glucosidase (GAA) enzyme activity is measured by flow-injection tandem mass spectrometry (FIA/MS/MS) and full sequencing of the GAA gene is performed as a second-tier test in all newborns with low GAA enzyme activity [<2.10 micromole/L/h]. A total of 115 newborns had low GAA enzyme activity and abnormal genetic testing and were referred to metabolic centers. Two newborns were diagnosed with Infantile Onset Pompe Disease (IOPD), and 31 newborns were confirmed to have Late Onset Pompe Disease (LOPD). The incidence of IOPD + LOPD was 1:16,095. A total of 30 patients were compound heterozygous for one pathogenic and one variant of unknown significance (VUS) mutation or two VUS mutations and were defined as suspected LOPD. The incidence of IOPD + LOPD + suspected LOPD was 1: 8431 in PA. We also found 35 carriers, 15 pseudodeficiency carriers, and 2 false positive newborns.

Human iPSC-Based Models for the Development of Therapeutics Targeting Neurodegenerative Lysosomal Storage Diseases

Lysosomal storage diseases (LSDs) are a group of rare genetic conditions. The absence or deficiency of lysosomal proteins leads to excessive storage of undigested materials and drives secondary pathological mechanisms including autophagy, calcium homeostasis, ER stress, and mitochondrial abnormalities. A large number of LSDs display mild to severe central nervous system (CNS) involvement. Animal disease models and post-mortem tissues partially recapitulate the disease or represent the final stage of CNS pathology, respectively. In the last decades, human models based on induced pluripotent stem cells (hiPSCs) have been extensively applied to investigate LSD pathology in several tissues and organs, including the CNS. Neural stem/progenitor cells (NSCs) derived from patient-specific hiPSCs (hiPS-NSCs) are a promising tool to define the effects of the pathological storage on neurodevelopment, survival and function of neurons and glial cells in neurodegenerative LSDs. Additionally, the development of novel 2D co-culture systems and 3D hiPSC-based models is fostering the investigation of neuron-glia functional and dysfunctional interactions, also contributing to define the role of neurodevelopment and neuroinflammation in the onset and progression of the disease, with important implications in terms of timing and efficacy of treatments. Here, we discuss the advantages and limits of the application of hiPS-NSC-based models in the study and treatment of CNS pathology in different LSDs. Additionally, we review the state-of-the-art and the prospective applications of NSC-based therapy, highlighting the potential exploitation of hiPS-NSCs for gene and cell therapy approaches in the treatment of neurodegenerative LSDs.

Otorhinolaryngological manifestations in 61 patients with mucopolysaccharidosis

OBJECTIVES

The mucopolysaccharidoses (MPS) are inherited lysosomal storage disorders with multisystemic and highly variable clinical manifestation. ENT symptoms are common and early signs of MPS. The most common ENT diagnoses are chronic/recurrent rhinosinusitis, acute otitis media, otitis media with effusion, hearing loss and airway obstruction.

METHODS

A single-centre retrospective chart review of 61 patients (36 M/25F) with different MPS subtypes (MPS I (n = 15), MPS II (n = 10), MPS III (n = 17), MPS IV (n = 15) and MPS VI (n = 4)) was conducted. The age of ENT presentation and frequency of ENT symptoms, surgeries and their distribution among MPS subtypes was studied. The relationship between ENT presentation, first ENT surgery and the age of diagnosis was also evaluated.

RESULTS

Median age at the first ENT manifestation was 2.8 years, median age at MPS diagnosis 4.1 years. The great majority of patients (90%) manifested at least one ENT diagnosis; often before the diagnosis of MPS (75%). Chronic/recurrent rhinosinusitis was the most prevalent ENT diagnosis (77%), followed by upper airway obstruction (65%) and hearing loss (53%). Chronic/recurrent rhinosinusitis was the first ENT symptom to appear (median age 2.2 years), followed by otitis media with effusion (3.7 years) and hearing loss (4.5 years). At least one ENT surgery was performed in 57% of patients; in 69% before MPS diagnosis was established. Median age of the first ENT surgery was 4.1 years. ENT symptoms and surgical procedures were earliest present in MPS II.

CONCLUSIONS

Our study documents high and early occurrence of various otolaryngologic symptoms in MPS and thus highlights the role of ENT specialist in prompt diagnosis of these rare diseases and their long-term management.

Novel biomarkers for lysosomal storage disorders: Metabolomic and proteomic approaches

Lysosomal storage disorders (LSDs) are characterized by the accumulation of specific disease substrates inside the lysosomes of various cells, eventually leading to the deterioration of cellular function and multisystem organ damage. With the continuous discovery and validation of novel and advanced therapies for most LSDs, there is an urgent need to discover more versatile and clinically relevant biomarkers. The utility of these biomarkers should ideally extend beyond the screening and diagnosis of LSDs to the evaluation of disease severity and monitoring of therapy. Metabolomic and proteomic approaches provide the means to the discovery and validation of such novel biomarkers. This is achieved mainly through the application of various mass spectrometric techniques to common and easily accessible biological samples, such as plasma, urine and dried blood spots. In this review, we tried to summarize the complexity of the lysosomal disorders phenotypes, their current diagnostic and therapeutic approaches, the various techniques supporting metabolomic and proteomic studies and finally we tried to explore the newly discovered biomarkers for most LSDs and their reported clinical values.

Ultrastructure of spinal anterior horn cells in human Niemann-Pick type C (NPC) patient and mouse model of NPC with retroposon insertion in NPC1 genes

Niemann-Pick disease type C (NPC) is a neurovisceral lipid-storage disease. Although NPC patients show lipid storage in anterior horn cells of the spinal cord, little information is available regarding the electron microscopic analyses of the morphologies of intra-endosomal lipid like-materials in the anterior horn cells of NPC patients. In this study, we elucidated the intra-endosomal ultrastructures in spinal anterior horn cells in an NPC patient, as well as in mutant BALB/c NPC1^-/- mice with a retroposon insertion in the NPC1 gene. These morphologies were classified into four types: vesicle, multiple concentric sphere (MCS), membrane, and rose flower. The percentages of the composition in the NPC patient and NPC1^-/- mice were: vesicle (55.5% and 14.9%), MCS (15.7% and 3.4%), membrane (23.6% and 57.1%), and rose flower (5.2% and 24.6%), respectively. Formation of the intra-endosomal structures could proceed as follows: (i) a vesicle or MCS buds off the endosome into the lumen; (ii) when a vesicle breaks down, a membrane is formed; and (iii) after an MCS breaks down, a rose flower structure is formed. Our new finding in this study is that ultrastructural morphology is the same between the NPC patient and NPC1^-/- mice, although there are differences in the composition.