Mucopolysaccharidosis VI

Mucopolysaccharidosis-Plus Syndrome: Is This a Type of Mucopolysaccharidosis or a Separate Kind of Metabolic Disease?

Several years ago, dozens of cases were described in patients with symptoms very similar to mucopolysaccharidosis (MPS). This new disease entity was described as mucopolysaccharidosis-plus syndrome (MPSPS). The name of the disease indicates that in addition to the typical symptoms of conventional MPS, patients develop other features such as congenital heart defects and kidney and hematopoietic system disorders. The symptoms are highly advanced, and patients usually do not survive past the second year of life. MPSPS is inherited in an autosomal recessive manner and is caused by a homozygous-specific mutation in the gene encoding the VPS33A protein. To date, it has been described in 41 patients. Patients with MPSPS exhibited excessive excretion of glycosaminoglycans (GAGs) in the urine and exceptionally high levels of heparan sulfate in the plasma, but the accumulation of substrates is not caused by a decrease in the activity of any lysosomal enzymes. Here, we discuss the pathomechanisms and symptoms of MPSPS, comparing them to those of MPS. Moreover, we asked the question whether MPSPS should be classified as a type of MPS or a separate disease, as contrary to 'classical' MPS types, despite GAG accumulation, no defects in lysosomal enzymes responsible for degradation of these compounds could be detected in MPSPS. The molecular mechanism of the appearance of GAG accumulation in MPSPS is suggested on the basis of results available in the literature.

Real-world pharmacovigilance analysis of galsulfase: a study based on the FDA adverse event reporting system (FAERS) database

Background

Associated with enzyme deficiencies causing glycosaminoglycans (GAGs) accumulation, mucopolysaccharidosis type VI (MPS VI) is lysosomal storage disorder. In the treatment of MPS VI, galsulfase (Naglazyme) is commonly used as an enzyme replacement therapy (ERT). There remains a need for comprehensive real-world data on its safety and associated adverse events (AEs).

Objective

An analysis of the FDA Adverse Event Reporting System (FAERS) database will be conducted to identify potential risks and adverse reactions associated with galsulfase in real-life settings.

Methods

The FAERS database was used to extract data from Q2 2005 to Q4 2023. A total of 20,281,876 reports were analyzed after duplicate elimination, with 3,195 AE reports related to galsulfase identified. The association between galsulfase and AEs was investigated by utilizing four algorithms: reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network (BCPNN), and multi-item gamma Poisson shrinker (MGPS). The analysis focused on the timing of onset, signs of AEs, and clinical significance.

Results

Twenty seven organ systems were involved, and significant system organ classes (SOCs) included respiratory, thoracic and mediastinal disorders, and infections and infestations. At the PT level, 72 PTs corresponding to 15 SOCs were identified, with some AEs not previously mentioned in the product label. AEs associated with galsulfase had a median onset time of 1,471 days, with over half of the cases occurred within the first 5 years of treatment initiation.

Conclusion

This investigation delivers an exhaustive and indicative assessment of galsulfase's safety profile, grounded in authentic, real-world evidence. The findings emphasis the importance of continuous safety surveillance and the emergence of new AEs. The identification of previously unreported urologic adverse events, such as glomerulonephritis membranous and nephritic syndrome, warrants further investigation. The study emphasizes the need for enhanced pharmacovigilance to ensure patient safety and the effectiveness of galsulfase treatment.

REMOVER-PITCh: microhomology-assisted long-range gene replacement with highly multiplexed CRISPR-Cas9

A variety of CRISPR-Cas9-based gene editing technologies have been developed, including gene insertion and gene replacement, and applied to the study and treatment of diseases. While numerous studies have been conducted to improve the efficiency of gene insertion and to expand the system in various ways, there have been relatively few reports on gene replacement technology; therefore, further improvements are still needed in this context. Here, we developed the REMOVER-PITCh system to establish an efficient long-range gene replacement method and demonstrated its utility at two genomic loci in human cultured cells. REMOVER-PITCh depends on microhomology-assisted gene insertion technology called PITCh with highly multiplexed CRISPR-Cas9. First, we achieved gene replacement of about 20-kb GUSB locus using this system. Second, by applying the previously established knock-in-enhancing platform, the LoAD system, along with REMOVER-PITCh, we achieved the replacement of a longer gene region of about 200 kb at the ARSB locus. Our REMOVER-PITCh system will make it possible to remove and incorporate a variety of sequences from and into the genome, respectively, which will facilitate the generation of various disease and humanized models.

Elucidating the functional impact of G137V and G144R variants in Maroteaux Lamy's Syndrome by Molecular Dynamics Simulation

Mucopolysaccharidoses VI (Maroteaux Lamy syndrome) is a metabolic disorder due to the loss of enzyme activity of N-acetyl galactosamine-4-sulphatase arising from mutations in the ARSB gene. The mutated ARSB is the origin for the accumulation of GAGs within the lysosome leading to severe growth deformities, causing lysosomal storage disease. The main focus of this study is to identify the deleterious variants by applying bioinformatics tools to predict the conservation, pathogenicity, stability, and effect of the ARSB variants. We examined 170 missense variants, of which G137V and G144R were the resultant variants predicted detrimental to the progression of the disease. The native along with G137V and G144R structures were fixed as the receptors and subjected to Molecular docking with the small molecule Odiparcil to analyze the binding efficiency and the varied interactions of the receptors towards the drug. The interaction resulted in similar docking scores of - 7.3 kcal/mol indicating effective binding and consistent interactions of the drug with residues CYS117, GLN118, THR182, and GLN517 for native, along with G137V and G144R structures. Molecular Dynamics were conducted to validate the stability and flexibility of the native and variant structures on ligand binding. The overall study indicates that the drug has similar therapeutic towards the native and variant based on the higher binding affinity and also the complexes show stability with an average of 0.2 nm RMS value. This can aid in the future development therapeutics for the Maroteaux Lamy syndrome.

Consensus-based expert recommendations on the management of MPS IVa and VI in Saudi Arabia

BACKGROUND

Mucopolysaccharidosis type IVa (Morquio A syndrome) and mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome) are rare inherited lysosomal storage diseases associated with significant functional impairment and a wide spectrum of debilitating clinical manifestations. These conditions are thought to have higher-than-average prevalence rates in Saudi Arabia due to high rates of consanguineous marriage in the country. There are several unmet needs associated with the management of these diseases in Saudi Arabia.

MAIN BODY

The aim of this manuscript is to contextualize unmet management needs and provide recommendations to optimize diagnosis, multidisciplinary care delivery, and local data generation in this disease area. An expert panel was assembled comprising seven consultant geneticists from across Saudi Arabia. The Delphi methodology was used to obtain a consensus on statements relating to several aspects of mucopolysaccharidosis types IVa and VI. A consensus was reached for all statements by means of an online, anonymized voting system. The consensus statements pertain to screening and diagnosis, management approaches, including recommendations pertaining to enzyme replacement therapy, and local data generation.

CONCLUSION

The consensus statements presented provide specific recommendations to improve diagnostic and treatment approaches, promote multidisciplinary care and data sharing, and optimize the overall management of these rare inherited diseases in Saudi Arabia.

Proteogenomics in cerebrospinal fluid and plasma reveals new biological fingerprint of cerebral small vessel disease

Cerebral small vessel disease (cSVD) is a leading cause of stroke and dementia with no specific mechanism-based treatment. We used Mendelian randomization to combine a unique cerebrospinal fluid (CSF) and plasma pQTL resource with the latest European-ancestry GWAS of MRI-markers of cSVD (white matter hyperintensities, perivascular spaces). We describe a new biological fingerprint of 49 protein-cSVD associations, predominantly in the CSF. We implemented a multipronged follow-up, across fluids, platforms, and ancestries (Europeans and East-Asian), including testing associations of direct plasma protein measurements with MRI-cSVD. We highlight 16 proteins robustly associated in both CSF and plasma, with 24/4 proteins identified in CSF/plasma only. cSVD-proteins were enriched in extracellular matrix and immune response pathways, and in genes enriched in microglia and specific microglial states (integration with single-nucleus RNA sequencing). Immune-related proteins were associated with MRI-cSVD already at age twenty. Half of cSVD-proteins were associated with stroke, dementia, or both, and seven cSVD-proteins are targets for known drugs (used for other indications in directions compatible with beneficial therapeutic effects. This first cSVD proteogenomic signature opens new avenues for biomarker and therapeutic developments.

Causes of death in mucopolysaccharidoses

Mucopolysaccharidoses are inherited metabolic diseases caused by mutations in genes encoding enzymes required for degradation of glycosaminoglycans. A lack or severe impairment of activity of these enzymes cause accumulation of GAGs which is the primary biochemical defect. Depending on the kind of the deficient enzyme, there are 12 types and subtypes of MPS distinguished. Despite the common primary metabolic deficit (inefficient GAG degradation), the course and symptoms of various MPS types can be different, though majority of the diseases from the group are characterized by severe symptoms and significantly shortened live span. Here, we analysed the frequency of specific, direct causes of death of patients with different MPS types, the subject which was not investigated comprehensively to date. We examined a total of 1317 cases of death among MPS patients, including 393 cases of MPS I, 418 cases of MPS II, 232 cases of MPS III, 45 cases of MPS IV, 208 cases of MPS VI, and 22 cases of MPS VII. Our analyses indicated that the most frequent causes of death differ significantly between MPS types, with cardiovascular and respiratory failures being predominant in MPS I, MPS II, and MPS VI, neurological deficits in MPS III, respiratory issues in MPS IV, and hydrops fetalis in MPS VII. Results of such studies suggest what specific clinical problems should be considered with the highest priority in specific MPS types, apart from attempts to correct the primary causes of the diseases, to improve the quality of life of patients and to prolong their lives.

Lung Diseases and Rare Disorders: Is It a Lysosomal Storage Disease? Differential Diagnosis, Pathogenetic Mechanisms and Management

Pulmonologists may be involved in managing pulmonary diseases in children with complex clinical pictures without a diagnosis. Moreover, they are routinely involved in the multidisciplinary care of children with rare diseases, at baseline and during follow-up, for lung function monitoring. Lysosomal storage diseases (LSDs) are a group of genetic diseases characterised by a specific lysosomal enzyme deficiency. Despite varying pathogen and organ involvement, they are linked by the pathological accumulation of exceeding substrates, leading to cellular toxicity and subsequent organ damage. Less severe forms of LSDs can manifest during childhood or later in life, sometimes being underdiagnosed. Respiratory impairment may stem from different pathogenetic mechanisms, depending on substrate storage in bones, with skeletal deformity and restrictive pattern, in bronchi, with obstructive pattern, in lung interstitium, with altered alveolar gas exchange, and in muscles, with hypotonia. This narrative review aims to outline different pulmonary clinical findings and a diagnostic approach based on key elements for differential diagnosis in some treatable LSDs like Gaucher disease, Acid Sphingomyelinase deficiency, Pompe disease and Mucopolysaccharidosis. Alongside their respiratory clinical aspects, which might overlap, we will describe radiological findings, lung functional patterns and associated symptoms to guide pediatric pulmonologists in differential diagnosis. The second part of the paper will address follow-up and management specifics. Recent evidence suggests that new therapeutic strategies play a substantial role in preventing lung involvement in early-treated patients and enhancing lung function and radiological signs in others. Timely diagnosis, driven by clinical suspicion and diagnostic workup, can help in treating LSDs effectively.

Dental Profile of Brazilian Patients with Rare Skeletal Genetic Disorders: Clinical Features and Associated Factors

The aim of this study is to compare the dental profiles of Brazilian patients with rare genetic skeletal disorders and normotypical patients. A cross-sectional study was carried out with 210 individuals aged between 2 and 54 years old [105 with rare diseases (Mucopolysaccharidosis/MPS n = 27 and Osteogenesis Imperfecta/OI n = 78) and 105 without rare diseases] and their parents/caregivers. The parents/caregivers answered a questionnaire about individual aspects of their child and the dental profile was identified from questions related to dental history and the presence/absence of dental problems. The patients' oral cavity was also examined by three examiners for dental caries, malocclusion, gingivitis, and dental anomalies. The average age of individuals with a rare disease was 14.1 years (±12.2) and the median was 9.5 years. Participants who had already used the public health system (SUS) dental care services had a 2.24 times higher chance of belonging to the group with a rare disease (OR = 2.24; 95% CI: 1.07-4.89). Patients with rare diseases are 14.86 times more likely to have difficulty receiving dental treatment (OR = 14.86; 95% CI: 5.96-27.03) and 10.38 times more likely to have one or more dental problems (OR = 10.38; 95% CI: 1.95-35.17). Individuals with rare disorders have a greater history of difficulty in accessing dental treatment, using the SUS, and were diagnosed with more dental problems compared to normotypical individuals.

Biomarkers of Glycosaminoglycans (GAG) accumulation in patients with mucopolysaccharidosis type VI-LeukoGAG, Corneal Opacification (COM) and Carotid Intima Media Thickening (CIMT)

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive lysosomal storage disorder characterized by deficient activity of arylsulfatase B enzyme (ASB) resulting in cellular accumulation of dermatan sulfate (DS) and chondroitin sulfate (CS) that leads to cell injury. Urinary glycosaminoglycans (GAG) are often used as a biomarker in MPS diseases for diagnosis and to monitor treatment efficacy. This study evaluated leukocyte GAGs (leukoGAG) and skin GAGs as alternate biomarkers representing intracellular GAG changes in patients with MPS VI and treated with enzyme replacement therapy (ERT). In addition, we evaluated corneal opacification measurements (COM) and carotid intima media thickness (CIMT) as indicators of GAG accumulation and tissue injury. The study was performed in a serial two-step design in a single center. A quantitative method to measure leukoGAG levels in leukocytes was developed in Study 1 to compare the GAG levels between MPS VI patients and a control group and to assess correlations between leukoGAG and urineGAG. Study 2 validated the leukoGAG measurement, assessed the effect of ERT infusion on leukoGAG and ASB activity in leukocytes, identified correlations between leukoGAG and other biomarkers, and assessed differences in GAG accumulation between MPS VI patients and control subjects. In Study 1, leukoCS and leukoDS levels were significantly higher in the MPS VI group than the control group (leukoCS: 37.9 ± 10.2 and 2.9 ± 1.5 μg/μg protein, respectively, p = 0.005; leukoDS: 0.26 ± 0.2 and 0.0 ± 0.0 μg/μg protein, respectively, p = 0.028) with positive correlations between leukoCS and urine CS and leukoDS and urineDS. In Study 2, leukoCS (32.0 ± 11.8 vs 6.9 ± 3.1 μg/mg protein, p = 0.005) and leukoDS (0.4 ± 0.1 and 0.2 ± 0.1 μg/mg protein, p = 0.020) were significantly higher compared with control subjects. Thus, these results highlight the potential of leukoGAG as a new biomarker representing intracellular GAG accumulation in MPS VI patients and may be valuable for patient management.

Psychobehavioral factors and family functioning in mucopolysaccharidosis: preliminary studies

Introduction

Mucopolysaccharidoses (MPS) constitute a group of progressive and multisystemic inherited metabolic diseases that profoundly affect both the mental health of patients and the wellbeing of their families. This study aims to evaluate the impact of MPS on family functioning and related factors.

Methods and results

Twenty-five patients with MPS, including types I (n = 4), II (n = 11), IIIB (n = 2), IVA (n = 3), and VI (n = 5), and their families participated in this study. The mean patient age was 13 years [standard deviation (SD): 7.7 years]. Behavioral and emotional problems were noted in 9.1% of all patients. While the type of MPS did not directly influence mental problems, the presence of neuronal involvement did (p = 0.006). Patients with MPS III exhibited difficulties primarily in emotional areas, conduct, hyperactivity, and peer problems. Importantly, both patients with MPS II and those with MPS III experienced a significant impact on communication [mean scores for communication domain: MPS II, 35.6 (SD: 24.3); MPS III, 35.0 (SD: 22.6)]; poorer communication was directly linked to worse adaptive behavior (p = 0.012), and worse adaptive behavior was associated with lower quality of life (p = 0.001). Quality of life and caregiver burden among family members did not significantly differ across MPS types; however, higher caregiver burden was negatively associated with quality of life (p = 0.002). Concerning family functioning, the most impacted domains included independence, intellectual/cultural orientation, activity/recreation, and expressiveness. Domain scores did not vary based on MPS type, treatment, or neurological involvement. Quality-of-life scores were positively associated with the cultural/intellectual domain score.

Conclusion

The impacts of quality of life and family extend beyond clinical characteristics and MPS type, strongly influenced by patient cognition and communication, as well as type of family functioning, especially those with greater cultural/intellectual skills of their family members. A multidisciplinary approach addressing the broader needs of individuals with MPS becomes essential. Techniques aimed at improving communication, including prompt interventions such as speech therapy and augmentative and alternative communication strategies, can contribute to overall family functioning improvement.

Skeletal phenotype amelioration in mucopolysaccharidosis VI requires intervention at the earliest stages of postnatal development

Mucopolysaccharidosis VI (MPS VI) is a rare lysosomal disease arising from impaired function of the enzyme arylsulfatase B (ARSB). This impairment causes aberrant accumulation of dermatan sulfate, a glycosaminoglycan (GAG) abundant in cartilage. While clinical severity varies along with age at first symptom manifestation, MPS VI usually presents early and strongly affects the skeleton. Current enzyme replacement therapy (ERT) does not provide effective treatment for the skeletal manifestations of MPS VI. This lack of efficacy may be due to an inability of ERT to reach affected cells or to the irreversibility of the disease. To address the question of reversibility of skeletal phenotypes, we generated a conditional by inversion (COIN) mouse model of MPS VI, ArsbCOIN/COIN, wherein Arsb is initially null and can be restored to WT using Cre. We restored Arsb at different times during postnatal development, using a tamoxifen-dependent global Cre driver. By restoring Arsb at P7, P21, and P56-P70, we determined that skeletal phenotypes can be fully rescued if Arsb restoration occurs at P7, while only achieving partial rescue at P21 and no significant rescue at P56-P70. This work has highlighted the importance of early intervention in patients with MPS VI to maximize therapeutic impact.

The clinical and genotypic-phenotypic findings of mucopolysaccharidosis VI patients: an Iraqi single-study descriptive study

Background

Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI; MPS VI) is a chronic illness that causes progressive enlargement, inflammation, or scarring of several tissues and organs until their collapse. In most cases, an infant with MPS VI shows no symptoms. The early signs and symptoms of MPS VI in children often develop in the first few months of life. MPS VI affects various systems in the body, including the skeletal, cardiac, and respiratory systems. The authors aim in our study to describe the clinical and genotypic-phenotypic findings of MPS VI patients in 'children Welfare Teaching Hospital, Medical City Complex.'

Methods

The single-center study was conducted at the 'children Welfare Teaching Hospital, Medical City Complex' from November 2016 to May 2022. The research recruited 72 MPS VI patients from Iraq, all under 20. The authors investigated the sociodemographic characteristics, hematological lab results, gene-phenotype findings, and clinical features and evaluated the severity and progression of the MPS 6 disease.

Results

Seventy-two Iraqi MPS VI patients were involved in the study, and the average age of the study sample was 6.38±3.4 (0.3-19). The consanguinity rate was 94.4%. In the research, females comprised 56.9% of the patients, and the Z-scores for body mass index and occipital-frontal head circumference were -2.66 and 1.2. The fascial features at diagnosis, 'coarse facies' (90.3%), dysostosis multiplex (93%), short stature (94.4%), and recurrent respiratory infections (91.6%), were the most common clinical features among the enrolled patients. The most frequent mutation was (complementary DNA: c.753C>G, protein effect: p.(Tyr2*) or p.(Tyr251Term), and the codon cross-tabulation: premature stop codon, or homozygous stop nonsense mutation/exon N.3) (33/69 (47.82%)). Furthermore, a statistically significant correlation existed between lower weight and height readings and the progressed and severe stages of the MPS VI illness.

Conclusion

As the first research in Iraq with a sufficient sample size of MPS VI patients, the investigation presented important clinical and gene-phenotype findings and revealed the necessity for enhancing the diagnosis of MPS VI, including the updated molecular analysis and monitoring the multisystem parameters, aberrant comorbidities, and the progression and severity.

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.

Neurological Disease Modeling Using Pluripotent and Multipotent Stem Cells: A Key Step towards Understanding and Treating Mucopolysaccharidoses

Despite extensive research, the links between the accumulation of glycosaminoglycans (GAGs) and the clinical features seen in patients suffering from various forms of mucopolysaccharidoses (MPSs) have yet to be further elucidated. This is particularly true for the neuropathology of these disorders; the neurological symptoms are currently incurable, even in the cases where a disease-specific therapeutic approach does exist. One of the best ways to get insights on the molecular mechanisms driving that pathogenesis is the analysis of patient-derived cells. Yet, not every patient-derived cell recapitulates relevant disease features. For the neuronopathic forms of MPSs, for example, this is particularly evident because of the obvious inability to access live neurons. This scenario changed significantly with the advent of induced pluripotent stem cell (iPSC) technologies. From then on, a series of differentiation protocols to generate neurons from iPSC was developed and extensively used for disease modeling. Currently, human iPSC and iPSC-derived cell models have been generated for several MPSs and numerous lessons were learnt from their analysis. Here we review most of those studies, not only listing the currently available MPS iPSC lines and their derived models, but also summarizing how they were generated and the major information different groups have gathered from their analyses. Finally, and taking into account that iPSC generation is a laborious/expensive protocol that holds significant limitations, we also hypothesize on a tempting alternative to establish MPS patient-derived neuronal cells in a much more expedite way, by taking advantage of the existence of a population of multipotent stem cells in human dental pulp to establish mixed neuronal and glial cultures.

Mucopolysaccharidosis Type VI with Recurrent Chest Infection

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome) is a progressive multi-systemic autosomal recessive disease resulting from a deficiency of arylsulfatase B (N-acetylgalactosamine-4-sulfatase). Here we report the case of a three-year-old male child born full-term via normal vaginal delivery. He had frequent admissions due to a chest infection that started at two months of age. At the age of 23 months, he was admitted after complaining of shortness of breath (SOB) due to asthma and aspiration pneumonia; additionally, dysmorphic features were noticed (single palmar crease, short round toes, coarse facial features such as a flat nose, big lips). A genetic study showed mucopolysaccharidosis VI (MPS VI). At three years of age, he was complaining of cough and SOB. Examination showed wheezing all over the chest, normal first and second heart sounds (S1 and S2), a murmur with no clicks, hepatosplenomegaly, and a palpable left kidney. However, the central nervous system (CNS) and eye examinations were normal. Echocardiography revealed a thickened bicuspid aortic valve, mild aortic regurgitation, and mitral regurgitation. Therefore, the patient presented with different clinical symptoms of MPS VI. It is important to increase the physicians' awareness about MPS by focusing on increasing the probability of MPS as a differential diagnosis whenever patients present with abnormal appearance, limb deformities, and recurrent unexplained infections; hence, making early diagnosis and treatment decisions, leading to a slowing down of the progression of the disease and enhancing the patient's quality of life.

Successful combined umbilical cord blood and bone marrow transplantation from an HLA-matched sibling for MPS VI: a case report

Mucopolysaccharidosis type VI (MPS VI), also known as Maroteaux-Lamy syndrome, polydystrophic dwarfism, and arysulfatase B (ASB) deficiency, is a lysosomal storage disorder with autosomal recessive inheritance characterized by progressive multisystem involved that causes many tissues and organs to enlarge and become inflamed. Skeletal deformities are common that progress and worsen in varying degrees thus affecting quality of life and life expectancy. Many studies have shown that allogeneic hematopoietic stem cell transplantation can reduce morbidity and enhance the survival and quality of life in such patients. We present a case of a 6-year-old girl diagnosed with MPS VI at the age of 3 years. Thereafter the patient developed various complications of the disease causing morbidity. She was then treated with combined umbilical cord blood (UCB) and bone marrow (BM) transplantation from complete human leukocyte antigen-matched (6/6) donor which was her younger sibling. The transplant was successful without any serious adverse effects. No additional treatments such as enzyme replacement therapy (ERT) were required. The transplantation of UCB along with BM can be considered as an effective treatment approach for this rare disease.

Plain language summary

Case of MPS VI treated with stem cell transplantation: This article reports a case of a 6-year-old girl who was diagnosed with mucopolysaccharidosis type VI also known as MPS VI, an autosomal recessive disorder that caused her arysulfatase B (ASB) deficiency. This disorder affects growth velocity, gives coarse facial features, gives rise to skeletal deformities, frequent upper-airway infections, enlarged liver and spleen, hearing loss, and joint stiffness. However, very few studies have reported definitive ways to treat or cure MPS VI. To help her combat this disorder, combined umbilical cord blood and bone marrow transplantation was done. This transplant alleviated her symptoms, and the patient did not need any further treatment. Follow-up, 4 years after transplantation, shows normal enzyme level, no complications, and improved quality of life.

Facial and Cephalometric Features of Individuals With Mucopolysaccharidosis: A Cross-Sectional Study

OBJECTIVE

The aim was to assess craniofacial features through facial anthropometric and lateral cephalometry measurements of individuals with mucopolysaccharidosis (MPS) and compare them with individuals without MPS.

DESIGN

Cross-sectional study.

PATIENTS

A total of 14 individuals with MPS and 28 non-MPS age- and sex-matched were enrolled in this study.

METHODS

A clinical facial analysis to evaluate the soft tissues and cephalometric analysis that comprised linear and angular measurements were performed. The calculation of the method error suggested no systematic errors (p > .05). Random errors for linear and angular measurements were low (less than 0.5° and 1.6 mm). Chi-square test and independent t-test were performed.

RESULTS

Most individuals with MPS were dolichofacial, presented altered facial proportions with an increased anterior lower facial height (ALFH) and lip incompetence (all p < .05), when compared with non-MPS individuals. Six angular measurements (1s.Na, 1s.NB, FMA, IMPA, AFI, and Po.Or_Go.Me; all p < .05) were significantly increased among individuals with MPS, and two (1s.1i and Ba.N-Ptm.Gn, all p < .05) were significantly decreased among them. Four linear measurements were significantly increased among individuals with MPS (1s-NA, 1i-NB, S-UL, and S-LL; all p < .05) and five (PogN-Perp, Co-A, Co-Gn, Nfa-Nfp, and overbite; all p < .05) were significantly decreased among them.

CONCLUSION

In summary, most individuals with MPS were dolichofacial with increased ALFH. Proclined upper and lower incisors, reduced nasopharyngeal space, and reduced overbite was also noted.

Understanding the challenges, unmet needs, and expectations of mucopolysaccharidoses I, II and VI patients and their caregivers in France: a survey study

BACKGROUND

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage diseases caused by defective enzyme activity involved in the catalysis of glycosaminoglycans. Published data on adult patients with MPS remains scarce. Therefore, the present qualitative survey study was aimed at understanding knowledge of the disease, unmet needs, expectations, care, and overall medical management of adult/adolescent patients with MPS I, II and VI and their caregivers in France.

RESULTS

A total of 25 patients (MPS I, n_p = 11; MPS II, n_p = 9; MPS VI, n_p = 5) were included and about 36 in-depth interviews (caregivers alone, n_c = 8; patients-caregiver pair, n_c+p = 22; patients alone, n_p = 6) were conducted. Except one (aged 17 years), all patients were adults (median age: 29 years [17-50]) and diagnosed at median age of 4 years [0.4-30], with mainly mothers as caregivers (n_c = 16/19). Patients were classified into three groups: Group A, Patients not able to answer the survey question because of a severe cognitive impairment (n_p = 8); Group B, Patients able to answer the survey question with low or no cognitive impairment and high motor disability (n_p = 10); and Group C, Patients able to answer the survey question with low or no cognitive impairment and low motor disability (n_p = 7). All groups were assessed for impact of disease on their daily lives based on a scale of 0-10. Caregivers in Group A were found to be most negatively affected by the disease, except for professional activity, which was most significantly impacted in Group B (4.7 vs. 5.4). The use of orthopaedic/medical equipments, was more prevalent in Groups A and B, versus Group C. Pain management was one of the global unmet need expressed by all groups. Group A caregivers expected better support from childcare facilities, disability clinics, and smooth transition from paediatric care to adult medicine. Similarly, Group B caregivers expected better specialised schools, whereas Group C caregivers expected better psychological support and greater flexibility in weekly infusion schedules for their patients.

CONCLUSIONS

The survey concluded that more attention must be paid to the psychosocial status of patients and caregivers. The preference for reference centre for follow-up and treatment, hospitalizations and surgeries were evident. The most significant needs expressed by the patients and caregivers include better understanding of the disease, pain management, monitoring of complications, flexibility in enzyme replacement therapy, home infusions especially for attenuated patients, and improved transitional support from paediatric to adult medicine.

Early enzyme replacement therapy prevents dental and craniofacial abnormalities in a mouse model of mucopolysaccharidosis type VI

Mucopolysaccharidosis VI (MPS VI) is a hereditary lysosomal storage disease caused by the absence of the enzyme arylsulfatase B (ARSB). Craniofacial defects are common in MPS VI patients and manifest as abnormalities of the facial bones, teeth, and temporomandibular joints. Although enzyme replacement therapy (ERT) is the treatment of choice for MPS VI, the effects on the craniofacial and dental structures are still poorly understood. In this study, we used an Arsb-deficient mouse model (Arsbm/m) that mimics MPS VI to investigate the effects of ERT on dental and craniofacial structures and compared these results with clinical and radiological observations from three MPS VI patients. Using micro-computed tomography, we found that the craniofacial phenotype of the Arsbm/m mice was characterized by bone exostoses at the insertion points of the masseter muscles and an overall increased volume of the jaw bone. An early start of ERT (at 4 weeks of age for 20 weeks) resulted in a moderate improvement of these jaw anomalies, while a late start of ERT (at 12 weeks of age for 12 weeks) showed no effect on the craniofacial skeleton. While teeth typically developed in Arsbm/m mice, we observed a pronounced loss of tooth-bearing alveolar bone. This alveolar bone loss, which has not been described before in MPS VI, was also observed in one of the MPS VI patients. Interestingly, only an early start of ERT led to a complete normalization of the alveolar bone in Arsbm/m mice. The temporomandibular joints in Arsbm/m mice were deformed and had a porous articular surface. Histological analysis revealed a loss of physiological cartilage layering, which was also reflected in an altered proteoglycan content in the cartilage of Arsbm/m mice. These abnormalities could only be partially corrected by an early start of ERT. In conclusion, our results show that an early start of ERT in Arsbm/m mice achieves the best therapeutic effects for tooth, bone, and temporomandibular joint development. As the MPS VI mouse model in this study resembles the clinical findings in MPS VI patients, our results suggest enzyme replacement therapy should be started as early as possible.

Comparison of growth dynamics in different types of MPS: an attempt to explain the causes

Background

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by deficient activity of enzymes responsible for the catabolism of glycosaminoglycans (GAGs), resulting in progressive damage to various tissues and organs. Affected individuals present with skeletal deformities, bone growth impairment, joint stiffness and frequently mental retardation.

Results

The objective of the study was to summarise over 30 years of observations of the growth dynamics in patients with different types of MPS, performed at the Children’s Memorial Health Institute (CMHI, Warsaw, Poland). A retrospective analysis of anthropometric data collected from 1989 to 2020 was performed for 195 patients with MPS I, MPS II, MPS III, MPS IVA and MPS VI. Mean values for birth body length were statistically significantly greater than in the general population. The mean z-scores for other MPS groups showed that until the 24th month of life, the growth pattern for all patients was similar, and the average z-scores for body height were greater than in reference charts. Afterwards, growth patterns began to differentiate for MPS groups.

Conclusions

The long-term follow up showed that the growth pattern in patients with all types of mucopolysaccharidoses significantly deviates from the general population. Patients with MPS IVA had the most severe growth impairments compared to other patients in the study group. Neuropathic MPS I and II demonstrated severe growth impairments compared to other patients in this study. Patients with MPS III showed the mildest growth impairments compared to other MPS patients and reached the 3rd percentile last.

Generation of a novel disease model mouse for mucopolysaccharidosis type VI via c. 252T>C human ARSB mutation knock-in

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive lysosomal disorder caused by a mutation in the ARSB gene, which encodes arylsulfatase B (ARSB), and is characterized by glycosaminoglycan accumulation. Some pathogenic mutations have been identified in or near the substrate-binding pocket of ARSB, whereas many missense mutations present far from the substrate-binding pocket. Each MPS VI patient shows different severity of clinical symptoms. To understand the relationship between mutation patterns and the severity of MPS VI clinical symptoms, mutations located far from the substrate-binding pocket must be investigated using mutation knock-in mice. Here, I generated a knock-in mouse model of human ARSB Y85H mutation identified in Japanese MPS VI patients using a CRISPR-Cas9-mediated approach. The generated mouse model exhibited phenotypes similar to those of MPS VI patients, including facial features, mucopolysaccharide accumulation, and smaller body size, suggesting that this mouse will be a valuable model for understanding MPS VI pathology.

•

We generated a mouse model of the Y85H ARSB mutation in humans using CRISPR-Cas9.

•

The knock-in mice exhibited phenotypes similar to those of MPS VI patients.

•

The mice showed facial features, mucopolysaccharide build-up, and smaller bodies.

•

The model could successfully show the correlation between genotype and phenotype.

•

These mice could serve as a useful model for novel therapeutic approaches.

Dose-dependent effects of a brain-penetrating iduronate-2-sulfatase on neurobehavioral impairments in mucopolysaccharidosis II mice

Deposition of heparan sulfate (HS) in the brain of patients with mucopolysaccharidosis II (MPS II) is believed to be the leading cause of neurodegeneration, resulting in several neurological signs and symptoms, including neurocognitive impairment. We recently showed that pabinafusp alfa, a blood-brain-barrier-penetrating fusion protein consisting of iduronate-2-sulfatase and anti-human transferrin receptor antibody, stabilized learning ability by preventing the deposition of HS in the CNS of MPS II mice. We further examined the dose-dependent effect of pabinafusp alfa on neurological function in relation to its HS-reducing efficacy in a mouse model of MPS II. Long-term intravenous treatment with low (0.1 mg/kg), middle (0.5 mg/kg), and high (2.0 mg/kg) doses of the drug dose-dependently decreased HS concentration in the brain and cerebrospinal fluid (CSF). A comparable dose-dependent effect in the prevention of neuronal damage in the CNS, and dose-dependent improvements in neurobehavioral performance tests, such as gait analysis, pole test, Y maze, and Morris water maze, were also observed. Notably, the water maze test performance was inversely correlated with the HS levels in the brain and CSF. This study provides nonclinical evidence substantiating a quantitative dose-dependent relationship between HS reduction in the CNS and neurological improvements in MPS II.

Misdiagnosis in mucopolysaccharidoses

Mucopolysaccharidosis (MPS) is a group of 13 hereditary metabolic diseases identified in humans (or 14 diseases if considering one MPS type described to date only in mice) in which an enzymatic defect results in the accumulation of glycosaminoglycans (GAG) in the lysosomes of cells. First of all, as a result of GAG storage, the proper functioning of the lysosome is disturbed; then, the cells, and finally, tissue, organs, and the whole organism malfunctions are observed. Due to the rarity, heterogeneity, and multi-systemic and progressive nature of MPS, they present a major diagnostic challenge. Due to the wide variation in symptoms and their similarity to other diseases, MPS is often misdiagnosed, usually as neurological diseases (like autism spectrum disorders, psychomotor hyperactivity, and intellectual disability) or rheumatology and orthopedic disorders (like juvenile idiopathic arthritis, Perthes disease, rickets, and muscular dystrophy). In this review article, we present the problems associated with the possibility of misdiagnosing MPS, discuss what diseases they can be confused with, and suggest ways to reduce these problems in the future.

A novel approach in diagnosing multiple dentigerous cysts using CBCT illustration indicative of Mucopolysaccharidosis VI - a case report

Mucopolysaccharidosis VI is a genetic disorder affecting multiple organs with sundry clinical presentations. The main etiological factor reflects the disturbances in mucopolysaccharide metabolism leading to deposition of acid mucopolysaccharide in various tissues. The pathognomonic features of the disease include a large head, short neck, corneal opacity, open mouth associated with an enlarged tongue, enlargement of the skull, and long anteroposterior dimension with unerupted dentition, dentigerous cyst-like follicles, condylar defects, and gingival hyperplasia. An 18-year-old boy with Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI) is described in this article, emphasizing the oral manifestations and radiographic illustration of lesions in the jaws. It also emphasizes the essential role of cone-beam computed tomography to identify and analyze multicentric pathologies in the jaws.

Application of a Novel Algorithm for Expanding Newborn Screening for Inherited Metabolic Disorders across Europe

Inherited metabolic disorders (IMDs) are mostly rare, have overlapping symptoms, and can be devastating and progressive. However, in many disorders, early intervention can improve long-term outcomes, and newborn screening (NBS) programmes can reduce caregiver stress in the journey to diagnosis and allow patients to receive early, and potentially pre-symptomatic, treatment. Across Europe there are vast discrepancies in the number of IMDs that are screened for and there is an imminent opportunity to accelerate the expansion of evidence-based screening programmes and reduce the disparities in screening programmes across Europe. A comprehensive list of IMDs was created for analysis. A novel NBS evaluation algorithm, described by Burlina et al. in 2021, was used to assess and prioritise IMDs for inclusion on expanded NBS programmes across Europe. Forty-eight IMDs, of which twenty-one were lysosomal storage disorders (LSDs), were identified and assessed with the novel NBS evaluation algorithm. Thirty-five disorders most strongly fulfil the Wilson and Jungner classic screening principles and should be considered for inclusion in NBS programmes across Europe. The recommended disorders should be evaluated at the national level to assess the economic, societal, and political aspects of potential screening programmes.

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a heterogeneous group of disorders that results in the absence or deficiency of lysosomal enzymes, leading to an inappropriate storage of glycosaminoglycans (GAGs) in various tissues of the body such as bones, cartilage, heart valves, arteries, upper airways, cornea, teeth, liver and nervous system. Clinical manifestations can become progressively exacerbated with age and affect their quality of life. Developments in advanced supportive treatment options such as enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT) may have improved patients' life span. Adult MPS patients require specialist clinical surveillance long-term. In many cases, in addition to the MPS-related health problems, they may develop age-related complications. Considering the complexity of their clinical manifestations and lack of guidelines on the management of adult MPS disorders, multispecialty and multidisciplinary teams' care is essential to diagnose and treat health problems that are likely to be encountered. This review presents non-cardiac clinical manifestations, their pathophysiology, management and long-term outcomes in adult MPS patients.

Addressing the need for patient-friendly medical communications: adaptation of the 2019 recommendations for the management of MPS VI and MPS IVA

BACKGROUND

Patients are the most important stakeholders in the care of any disease and have an educational need to learn about their condition and the treatment they should receive. Considering this need for patient-focused materials, we present a directed approach for mucopolysaccharidosis (MPS) VI and MPS IVA, a pair of rare, inherited diseases that affects multiple organs and parts of the body. Independent guidelines on the treatment of these diseases were recently published, providing evidence- and expertise-driven recommendations to optimize patient management. However, while healthcare providers may have the training and knowledge to understand these guidelines, patients and their caregivers can find the technical content challenging. Hence, we aimed to develop plain language summaries (PLS) of the MPS VI and MPS IVA guidelines with patients as the primary audience.

RESULTS

A review of the guidelines by an expert team identified six domains of information relevant to patients: The multidisciplinary team, regular tests and check-ups, disease-modifying and supportive treatments, general anesthetics, ear-nose-throat/respiratory care, and surgeries. This information was adapted into a series of infographics specific to either MPS VI or MPS IVA, designed to appeal to patients and clearly present information in a concise manner.

CONCLUSIONS

The use of patient-friendly materials, like the infographics we have developed, has the potential to better inform patients and engage them in their care. We issue a "call to arms" to the medical community for the development of similar PLS materials in rare diseases intended to inform and empower patients.

Oral treatment for mucopolysaccharidosis VI: Outcomes of the first phase IIa study with odiparcil

Mucopolysaccharidosis (MPS) disorders are a group of rare, progressive lysosomal storage diseases characterized by the accumulation of glycosaminoglycans (GAGs) and classified according to the deficient enzyme. Enzyme replacement therapy (ERT) of MPS VI has limited effects on ophthalmic, cardiovascular, and skeletal systems. Odiparcil is an orally available small molecule that results in the synthesis of odiparcil-linked GAGs facilitating their excretion and reducing cellular and tissue GAG accumulation. Improve MPS treatment was a Phase 2a study of the safety, pharmacokinetics/pharmacodynamics, and efficacy of two doses of odiparcil in patients with MPS VI. The core study was a 26-week, randomized, double-blind, placebo-controlled trial in patients receiving ERT and an open-label, noncomparative, single-dose cohort not receiving ERT. Patients aged ≥ 16 years receiving ERT were randomized to odiparcil 250 or 500 mg twice daily or placebo. Patients without ERT received odiparcil 500 mg twice daily. Of 20 patients enrolled, 13 (65.0%) completed the study. Odiparcil increased total urine GAGs (uGAGs), chondroitin sulfate, and dermatan sulfate concentrations. A linear increase in uGAG levels and odiparcil exposure occurred with increased odiparcil dose. Odiparcil demonstrated a good safety and tolerability profile. Individual analyses found more improvements in pain, corneal clouding, cardiac, vascular, and respiratory functions in the odiparcil groups vs placebo. This study confirmed the mechanism of action and established the safety of odiparcil with clinical beneficial effects after only a short treatment duration in an advanced stage of disease. Further assessment of odiparcil in younger patients is needed.

Mass spectrometry and two-dimensional electrophoresis in prenatal diagnosis of mucopolysaccharidosis type VI

Background

Mucopolysaccharidosis VI (MPS VI) or Maroteaux–Lamy syndrome is an autosomal recessive lysosomal storage disorder. Clinical manifestations are related to progressive accumulation of dermatan sulfate (DS). Two-dimensional electrophoresis has traditionally been used for the diagnosis of MPS disorders. The method is only qualitative and is time consuming. For prenatal diagnosis of MPS, 6–8 ml of amniotic fluid is required and 5 working days to complete. It needs personal experience to do the test and to interpret the results. Mass spectrometry (MS) is now available as a quantitative method and for prenatal diagnosis of MPS it needs less amniotic fluid and takes only 2 working days. It is more accurate, less person dependent, but it costs more. Our aim was to introduce quantitative determination of dermatan sulfate using mass spectrometry in the prenatal diagnosis of MPS VI in Egypt and to compare this technique to the classical qualitative diagnosis using two-dimensional electrophoresis (2-DEP) of the glycosaminoglycans (GAGs) in amniotic fluid. Thirty pregnant females each with single fetus were subjected to amniocentesis at 16 weeks gestation. Ten with a previously affected MPS VI infant and twenty served as controls. Prenatal diagnosis (PD) was done by both MS and 2-DEP.

Results

MS verified 2-DEP results which showed 5 affected and 5 non-affected fetuses with MPS VI.

Conclusion

Two-dimensional electrophoresis of the GAGs in amniotic fluid is a good qualitative method and MS was an accurate quantitative method for prenatal diagnosis of MPS type VI. Quantitative determination of GAGs in AF by mass spectrometry is quicker. Where prenatal diagnosis is recommended for at risk pregnancies, mass spectrometry could be used more in the future as it gives rapid and accurate results.

Surgical Management of Valvular Heart Disease in Mucopolysaccharidoses: A Review of Literature

Mucopolysaccharidoses are extremely rare diseases that are frequently presenting with structural heart problems of the aortic and mitral valve in combination with myocardial dysfunction. In a substantial proportion, this leads to heart failure and is a leading cause of death in these patients. As this glycosaminoglycan degradation defect is associated with other conditions strongly influencing the perioperative risk and choice of surgical technique, multidisciplinary planning is crucial to improve short- and long-term outcomes. The extensive variance in clinical presentation between different impaired enzymes, and further within subgroups, calls for personalised treatment plans. Enzyme replacement therapies and bone marrow transplantation carry great potential as they may significantly abrogate the progress of the disease and as such reduce the clinical burden and improve life expectancy. Nevertheless, structural heart interventions may be required. We reviewed the existing literature of the less than 50 published cases regarding surgical management, technique, and choice of prostheses. Although improvement in therapy has shown promising results in protecting valvar tissue when initiated in infancy, concerns regarding stability of this effect and durability of biological prostheses remain.

MPS VI associated ocular phenotypes in an MPS VI murine model and the therapeutic effects of odiparcil treatment

Maroteaux - Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a lysosomal storage disease resulting from insufficient enzymatic activity for degradation of the specific glycosaminoglycans (GAG) chondroitin sulphate (CS) and dermatan sulphate (DS). Among the most pronounced MPS VI clinical manifestations caused by cellular accumulation of excess CS and DS are eye disorders, in particular those that affect the cornea. Ocular manifestations are not treated by the current standard of care, enzyme replacement therapy (ERT), leaving patients with a significant unmet need. Using in vitro and in vivo models, we previously demonstrated the potential of the β-D-xyloside, odiparcil, as an oral GAG clearance therapy for MPS VI. Here, we characterized the eye phenotypes in MPS VI arylsulfatase B deficient mice (Arsb^-) and studied the effects of odiparcil treatment in early and established disease models. Severe levels of opacification and GAG accumulation were detected in the eyes of MPS VI Arsb^- mice. Histological examination of MPS VI Arsb^- eyes showed an aggregate of corneal phenotypes, including reduction in the corneal epithelium thickness and number of epithelial cell layers, and morphological malformations in the stroma. In addition, colloidal iron staining showed specifically GAG accumulation in the cornea. Orally administered odiparcil markedly reduced GAG accumulation in the eyes of MPS VI Arsb^- mice in both disease models and restored the corneal morphology (epithelial layers and stromal structure). In the early disease model of MPS VI, odiparcil partially reduced corneal opacity area, but did not affect opacity area in the established model. Analysis of GAG types accumulating in the MPS VI Arsb^- eyes demonstrated major contribution of DS and CS, with some increase in heparan sulphate (HS) as well and all were reduced with odiparcil treatment. Taken together, we further reveal the potential of odiparcil to be an effective therapy for eye phenotypes associated with MPS VI disease.

Fifteen years of enzyme replacement therapy for mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome): a case report

Background

Mucopolysaccharidosis VI, or Maroteaux–Lamy disease, is an autosomal recessive disease characterized by deficiency of the enzyme arylsulfatase B in the lysosomal catabolism of glycosaminoglycans. Due to reduced (or even null) enzyme activity, glycosaminoglycans (mainly dermatan sulfate) accumulates, leading to a multisystemic disease. Mucopolysaccharidosis VI induces reduced growth, coarse face, audiovisual deficits, osteoarticular deformities, and cardiorespiratory issues, hampering the quality of life of the patient. Enzyme replacement therapy with galsulfase (Naglazyme, BioMarin Pharmaceuticals Inc., USA) is the specific treatment for this condition. Although studies have shown that enzyme replacement therapy slows the progression of the disease, the effects of long-term enzyme replacement therapy remain poorly understood.

Case presentation

A 29-year-old, Caucasian, male patient diagnosed with mucopolysaccharidosis VI was treated with enzyme replacement therapy for over 15 years. Enzyme replacement therapy was initiated when patient was 13 years old. The patient evolved multiplex dysostosis, carpal tunnel syndrome, thickened mitral valve, and hearing and visual loss.

Conclusions

Although enzyme replacement therapy did not prevent the main signs of mucopolysaccharidosis VI, it slowed their progression. Additionally, enzyme replacement therapy was associated with a longer survival compared with the untreated affected sibling. Taken together, the results indicate that enzyme replacement therapy positively modified the course of the disease.

Delivering gene therapy for mucopolysaccharide diseases

Mucopolysaccharide diseases are a group of paediatric inherited lysosomal storage diseases that are caused by enzyme deficiencies, leading to a build-up of glycosaminoglycans (GAGs) throughout the body. Patients have severely shortened lifespans with a wide range of symptoms including inflammation, bone and joint, cardiac, respiratory and neurological disease. Current treatment approaches for MPS disorders revolve around two main strategies. Enzyme replacement therapy (ERT) is efficacious in treating somatic symptoms but its effect is limited for neurological functions. Haematopoietic stem cell transplant (HSCT) has the potential to cross the BBB through monocyte trafficking, however delivered enzyme doses limit its use almost exclusively to MPSI Hurler. Gene therapy is an emerging therapeutic strategy for the treatment of MPS disease. In this review, we will discuss the various vectors that are being utilised for gene therapy in MPS as well as some of the most recent gene-editing approaches undergoing pre-clinical and clinical development.

Mucopolysaccharidosis Type VI, an Updated Overview of the Disease

Mucopolysaccharidosis type VI, or Maroteaux-Lamy syndrome, is a rare, autosomal recessive genetic disease, mainly affecting the pediatric age group. The disease is due to pathogenic variants of the ARSB gene, coding for the lysosomal hydrolase N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). The enzyme deficit causes a pathological accumulation of the undegraded glycosaminoglycans dermatan-sulphate and chondroitin-sulphate, natural substrates of ASB activity. Intracellular and extracellular deposits progressively take to a pathological scenario, often severe, involving most organ-systems and generally starting from the osteoarticular apparatus. Neurocognitive and behavioral abilities, commonly described as maintained, have been actually investigated by few studies. The disease, first described in 1963, has a reported prevalence between 0.36 and 1.3 per 100,000 live births across the continents. With this paper, we wish to contribute an updated overview of the disease from the clinical, diagnostic, and therapeutic sides. The numerous in vitro and in vivo preclinical studies conducted in the last 10-15 years to dissect the disease pathogenesis, the efficacy of the available therapeutic treatment (enzyme replacement therapy), as well as new therapies under study are here described. This review also highlights the need to identify new disease biomarkers, potentially speeding up the diagnostic process and the monitoring of therapeutic efficacy.

Bone Biomarkers in Mucopolysaccharidoses

The accumulation of glycosaminoglycans (GAGs) in bone and cartilage leads to progressive damage in cartilage that, in turn, reduces bone growth by the destruction of the growth plate, incomplete ossification, and growth imbalance. The mechanisms of pathophysiology related to bone metabolism in mucopolysaccharidoses (MPS) include impaired chondrocyte function and the failure of endochondral ossification, which leads to the release of inflammatory cytokines via the activation of Toll-like receptors by GAGs. Although improvements in the daily living of patients with MPS have been achieved with enzyme replacement, treatment for the bone disorder is limited. There is an increasing need to identify biomarkers related to bone and cartilage to evaluate the progressive status and to monitor the treatment of MPS. Recently, new analysis methods, such as proteomic analysis, have identified new biomarkers in MPS. This review summarizes advances in clinical bone metabolism and bone biomarkers.

Hyo-Mental Angle and Distance: An Important Adjunct in Airway Assessment of Adult Mucopolysaccharidosis

Background: Mucopolysaccharidosis (MPS) is a rare congenital lysosomal storage disorder with complex airways. High anterior larynx is assessed by thyromental distance (TMD) nasendoscopy. A simpler method to assess this hyoid bone is described. The distance between the central-hyoid and symphysis of the mandible (hyo-mental distance; HMD) and inclination of this line to the horizontal axis (hyo-mental angle; HMA) in neutrally positioned patients is investigated. Methods: HMA, HMD in MPS, and non-MPS were compared, and their correlation with height and weight were assessed. Results: 50 adult MPS patients (M = 32, F = 18, age range = 19–66 years; mean BMI = 26.8 kg/m²) of MPS I, II, III, IV, and VI were compared with 50 non-MPS (M = 25, F = 25; age range = 22–84 years; mean BMI = 26.5 kg/m²). Mean HMA in MPS was 25.72° (−10 to +50) versus 2.42° (−35 to +28) in non-MPS. Mean HMD was 46.5 (25.7–66) millimeters in MPS versus 41.8 (27–60.3) in non-MPS. HMA versus height and weight showed a moderate correlation (r = −0.4, p < 0.05) in MPS and no significant correlation (r < 0.4, p > 0.05) in non-MPS. HMD versus height and weight showed no correlation (r < 0.4, p > 0.05) in both groups. Conclusions: HMA seems more acute in MPS despite nearly the same HMD as non-MPS, signifying a high larynx, which may be missed by TMD.

Clinical and event-based outcomes of patients with mucopolysaccharidosis VI receiving enzyme replacement therapy in Turkey: a case series

Background

The objective of this study was to describe clinical manifestations and events of patients with mucopolysaccharidosis (MPS) VI in Turkey who are treated with galsulfase enzyme replacement therapy (ERT). Clinical data of 14 children with MPS VI who were followed up at the Department of Pediatrics of the Gazi University Faculty of Medicine in Ankara, Turkey were retrospectively collected from the patients’ medical records. Patients were selected based on availability of a pre-ERT baseline and follow-up clinical data for a similar period of time (1.9–3.2 years). Event data (occurrence of acute clinical events, onset of chronic events, surgeries) collected during hospital visits and telemedicine were available for up to 10 years after initiation of ERT (2.5–10 years).

Results

Age at initiation of ERT ranged from 2.8 to 15.8 years (mean age 7.5 years). All patients presented with reduced endurance and skeletal abnormalities (dysostosis multiplex) on radiography. Other common clinical manifestations were cardiac valve disease (N = 13), short stature (N = 11), cranial abnormalities on MRI (N = 10), spinal abnormalities on MRI (N = 7), and mild cognitive impairment (N = 6). School attendance was generally poor, and several patients had urinary incontinence. After 1.9 to 3.2 years of ERT, most patients showed improvements in endurance in the 6-min walk test and 3-min stair climb tests; the frequency of urinary incontinence decreased. ERT did not seem to prevent progression of cardiac valve disease, eye disorders, hearing loss, or bone disease. Long-term event-based data showed a high incidence of respiratory tract infections, adenotonsillectomy/adenoidectomy, reduced sleep quality, sleep apnea, and depression before initiation of ERT. The number of events tended to remain stable or decrease in all patients over 2.5–10 years follow-up. However, the nature of the events shifted over time, with a reduction in the frequency of respiratory tract infections and sleep problems and an increase in ophthalmologic events, ear tube insertions, and depression.

Conclusions

This case series shows the high disease burden of the MPS VI population in Turkey and provides a unique insight into their clinical journey based on real-life clinical and event-based data collected before and after initiation of ERT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02060-4.

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 loss in inherited metabolic disorders: A systematic review

Inherited metabolic disorders (IMDs) have been observed in individuals with hearing loss (HL), but IMDs are rarely the cause of syndromic HL. With early diagnosis, management of HL is more effective and cortical reorganization is possible with hearing aids or cochlear implants. This review describes relationships between IMDs and HL in terms of incidence, etiology of HL, pathophysiology, and treatment. Forty types of IMDs are described in the literature, mainly in case reports. Management and prognosis are noted where existing. We also describe IMDs with HL given age of occurrence of HL. Reviewing the main IMDs that are associated with HL may provide an additional clinical tool with which to better diagnose syndromic HL.

Deep intronic variant in the ARSB gene as the genetic cause for Maroteaux-Lamy syndrome (MPS VI)

Maroteaux-Lamy syndrome (MPS-VI) is a rare autosomal-recessive disorder with a wide spectrum of clinical manifestations, ranging from an attenuated to a rapidly progressive disease. It is caused by variants in ARSB, which encodes the lysosomal arylsulfatase B (ARSB) enzyme, part of the degradation process of glycosaminoglycans in lysosomes. Over 220 variants have been reported so far, with a majority of missense variants. We hereby report two siblings of Bedouin origin with a diagnosis of MPS-VI. Western blots in patient fibroblasts revealed total absence of ARSB protein production. Complete sequencing of the coding region of ARSB did not identify a candidate disease-associated variant. However, deep sequencing of the noncoding region of ARSB by whole genome sequencing (WGS) revealed a c.1142+581A to G variant. The variant is located within intron 5 and fully segregated with the disease in the family. Determination of the genetic cause for these patients enabled targeted treatment by enzyme replacement therapy, along with appropriate genetic counseling and prenatal diagnosis for the family. These results highlight the advantage of WGS as a powerful tool, for improving the diagnostic rate of rare disease-causing variants, and emphasize the importance of studying deep intronic sequence variation as a cause of monogenic disorders.

Airway Abnormalities in Adult Mucopolysaccharidosis and Development of Salford Mucopolysaccharidosis Airway Score

(1) Background: Mucopolysaccharidoses (MPS) are a heterogeneous group of lysosomal storage disorders caused by the absence of enzymes required for degradation of glycosaminoglycans (GAGs). GAGs deposition in tissues leads to progressive airway narrowing and/or tortuosity. Increased longevity of patients has posed newer problems, especially the airway. This study aims to characterise various airway abnormalities in adult MPS from a regional centre and proposes a method to quantify the severity of the airway disease. (2) Methods: Retrospective analysis by case notes review, clinical examination, endoscopy, cross-sectional imaging, 3-dimensional reconstruction, and physiological investigations were used to assess the airway abnormalities. Quantitative assessment of the airway severity was performed a validated questionnaire of 15 parameters to derive Salford Mucopolysaccharidosis Airway Score (SMAS). (3) Results: Thirty-one adult MPS patients (21M/ 9F; median 26.7 years; range 19–42 years) were reviewed. There were 9 MPS I, 12 MPS II, 2 MPS III, 5 MPS IV, 2 MPS VI, and 1 MPS VII. Airway abnormalities in each MPS type are described. Patients scoring more than 35 on SMAS had some form of airway intervention. The area under curve of 0.9 was noted at a score of 25, so SMAS more than 25 may predict a difficult airway and potential to have complications. Pearson’s correlation between SMAS and height, weight, BMI were poor (p < 0.05). (4) Conclusions: Airway abnormalities in adult MPS are varied and complex. Assessment of the airway should be holistic and include multiple parameters. An objective multidimensional score such as SMAS may help to predict and manage difficult airways warranting further investigation and validation.

Open-label phase 1/2 study of vestronidase alfa for mucopolysaccharidosis VII

Vestronidase alfa is an enzyme replacement therapy for mucopolysaccharidosis VII (MPS VII). In this open-label, phase 1/2 study, three subjects with MPS VII received intravenous vestronidase alfa administered every other week (QOW) for 14 weeks (2 mg/kg), followed by 24-week forced-dose titration (1, 4, and 2 mg/kg QOW; 8 weeks each), 36-week continuation (2 mg/kg), and long-term extension (4 mg/kg). Vestronidase alfa was well tolerated and led to dose-responsive, sustained reductions in urinary glycosaminoglycan excretion.

Enzyme Replacement Therapy for Genetic Disorders Associated with Enzyme Deficiency

Mutations in human genes might lead to loss of functional proteins, causing diseases. Among these genetic disorders, a large class is associated with the deficiency in metabolic enzymes, resulting in both an increase in the concentration of substrates and a loss in the metabolites produced by the catalyzed reactions. The identification of therapeutic actions based on small molecules represents a challenge to medicinal chemists because the target is missing. Alternative approaches are biology-based, ranging from gene and stem cell therapy, CRISPR/Cas9 technology, distinct types of RNAs, and enzyme replacement therapy (ERT). This review will focus on the latter approach that since the 1990s has been successfully applied to cure many rare diseases, most of them being lysosomal storage diseases or metabolic diseases. So far, a dozen enzymes have been approved by FDA/EMA for lysosome storage disorders and only a few for metabolic diseases. Enzymes for replacement therapy are mainly produced in mammalian cells and some in plant cells and yeasts and are further processed to obtain active, highly bioavailable, less degradable products. Issues still under investigation for the increase in ERT efficacy are the optimization of enzymes interaction with cell membrane and internalization, the reduction in immunogenicity, and the overcoming of blood-brain barrier limitations when neuronal cells need to be targeted. Overall, ERT has demonstrated its efficacy and safety in the treatment of many genetic rare diseases, both saving newborn lives and improving patients' life quality, and represents a very successful example of targeted biologics.

Disease burden, management patterns and multidisciplinary clinical approaches for patients with MPS IVA and VI in selected Latin American Countries

Background

There is a paucity of real-world epidemiological data on patients with mucopolysaccharidoses (MPS) in Latin America. This real-world study assessed the disease burden, management patterns and multidisciplinary clinical approaches for MPS-IVA and MPS-VI patients in Latin America (Colombia, Ecuador, Mexico, Peru).

Methods

Data were collected from physicians/specialists experienced in treating MPS patients between April–June 2020, via an online patient-diary survey.

Results

Overall, 29 physicians/specialists participated in this study. Data from 98 patients were analyzed (MPS-IVA, 71 patients and MPS-VI, 27 patients). Mean age for MPS-IVA patients was 17.5 years and for MPS-VI patients was 11.6 years, and the majority were females (52% and 78%, respectively). MPS-IVA and VI patients presented a high absenteeism from school (55% and 37%, respectively; <18 years age) and workplace (78% and 100%, respectively; >18 years age), indicating an impact of the disease on some aspects of the patients' quality of life. The onset of the first symptom occurred at the age of 3.1 years for MPS-IVA patients and at 1 year for MPS-VI, with delay in diagnosis (3.5–3.9 years from symptom onset) and enzyme replacement therapy (ERT) initiation (1.1–3.6 years from diagnosis). ERT interruptions were observed for MPS-IVA (48%) and MPS-VI patients (44%), with non-availability of medication recorded as the main reason for non-adherence (46% and 60% patients, respectively). ERT showed noticeable treatment benefits in MPS-IVA/VI patients, with stabilization/reduction in complications or the number of surgeries. A multidisciplinary clinical team approach was used for patient management.

Conclusion

The disease burden for MPS-IVA/VI was high in Latin America, with consistent management, treatment and socio-demographic trends throughout the region.

Compound heterozygous missense mutations in a Chinese mucopolysaccharidosis type VI patient: a case report

BACKGROUND

Mucopolysaccharidosis type VI (MPS VI) is a rare autosomal recessive inherited disease caused by mutations in the arylsulfatase B (ARSB) gene. MPS VI is a multisystemic disease resulting from a deficiency in arylsulfatase B causing an accumulation of glycosaminoglycans in the tissues and organs of the body. In this report, we present the case of a 16-year-old Chinese male who presented with vision loss caused by corneal opacity. MPS VI was confirmed by genetic diagnosis.

CASE PRESENTATION

A 16-year-old Chinese male presented with a one-year history of binocular vision loss. The best-corrected visual acuity was 0.25 in the right eye and 0.5 in the left eye. Although slit-lamp examination revealed corneal opacification in both eyes, the ocular examinations of his parents were normal. At the same time, the patient presented with kyphotic deformity, short stature, joint and skeletal malformation, thick lips, long fingers, and coarse facial features. Genetic assessments revealed that ARSB was the causative gene. Compound heterozygous missense mutations were found in the ARSB gene, namely c.1325G > A (p. Thr442Met) (M1) and c.1197G > C (p. Phe399Leu) (M2). Genetic diagnosis confirmed that the patient had MPS VI.

CONCLUSIONS

This paper reports a case of MPS VI confirmed by genetic diagnosis. MPS VI is a multisystem metabolic disease, with corneal opacity as a concomitant ocular symptom. As it is difficult for ophthalmologists to definitively diagnose MPS VI, genetic testing is useful for disease confirmation.

Long-term outcomes of patients with mucopolysaccharidosis VI treated with galsulfase enzyme replacement therapy since infancy

OBJECTIVE

Long-term outcomes of patients with mucopolysaccharidosis (MPS) VI treated with galsulfase enzyme replacement therapy (ERT) since infancy were evaluated.

METHODS

The study was a multicenter, prospective evaluation using data from infants with MPS VI generated during a phase 4 study (ASB-008; Clinicaltrials.govNCT00299000) and clinical data collected ≥5 years after completion of the study.

RESULTS

Parents of three subjects from ASB-008 (subjects 1, 2, and 4) provided written informed consent to participate in the follow-up study. One subject was excluded as consent was not provided. Subjects 1, 2, and 4 were aged 0.7, 0.3, and 1.1 years, respectively, at initiation of galsulfase and 10.5, 7.9, and 10.5 years, respectively, at follow-up. All subjects had classical MPS VI based on pre-treatment urinary glycosaminoglycans and the early onset of clinical manifestations. At follow-up, subject 4 had normal stature for age; subjects 1 and 2 had short stature, but height remained around the 90th percentile of growth curves for untreated classical MPS VI. Six-minute walk distance was normal for age/height in subjects 1 (550 m) and 4 (506 m), and reduced for subject 2 (340 m). Subject 2 preserved normal respiratory function, while percent predicted forced vital capacity and forced expiratory volume in 1 s decreased over time in the other subjects. Skeletal dysplasia was already apparent in all subjects at baseline and continued to progress. Cardiac valve disease showed mild progression in subject 1, mild improvement in subject 4, and remained trivial in subject 2. All subjects had considerably reduced pinch and grip strength at follow-up, but functional dexterity was relatively normal for age and there was limited impact on activities of daily living. Bruininks-Oseretsky Test of Motor Proficiency (BOT-2) results showed that subjects 2 and 4 had numerous fine and gross motor competencies. Corneal clouding progressed in all subjects, while progression of hearing impairment was variable. Liver size normalized from baseline in subjects 1 and 4, and remained normal in subject 2.

CONCLUSION

Very early and continuous ERT appears to slow down the clinical course of MPS VI, as shown by preservation of endurance, functional dexterity, and several fine and gross motor competencies after 7.7-9.8 years of treatment, and less growth impairment or progression of cardiac disease than could be expected based on the patients' classical phenotype. ERT does not seem to prevent progression of skeletal or eye disease in the long term.

The natural history of neurocognition in MPS disorders: A review

MPS disorders are associated with a wide spectrum of neurocognitive effects, from mild problems with attention and executive functions to progressive and degenerative neuronopathic disease. Studies of the natural history of neurocognition are necessary to determine the profile of abnormality and the rates of change, which are crucial to select endpoints for clinical trials of brain treatments and to make clinical recommendations for interventions to improve patients' quality of life. The goal of this paper is to review neurocognitive natural history studies to determine the current state of knowledge and assist in directing future research in all MPS disorders. There are seven different types of MPS diseases, each resulting from a specific enzyme deficiency and each having a separate natural history. MPS IX, will not be discussed as there are only 4 cases reported in the literature without cognitive abnormality. For MPS IH, hematopoietic cell transplant (HCT) is standard of care and many studies have documented the relationship between age at treatment and neurocognitive outcome, and to a lesser extent, neurocognitive status at baseline. However, the mortality and morbidity associated with the transplant process and residual long-term problems after transplant, have led to renewed efforts to find better treatments. Rather than natural history, new trials will likely need to use the developmental trajectories of the patients with HCT as a comparators. The literature has extensive data regarding developmental trajectories post-HCT. For attenuated MPS I, significant neurocognitive deficits have been documented, but more longitudinal data are needed in order to support a treatment directed at their attention and executive function abnormalities. The neuronopathic form of MPS II has been a challenge due to the variability of the trajectory of the disease with differences in timing of slowing of development and decline. Finding predictors of the course of the disease has only been partially successful, using mutation type and family history. Because of lack of systematic data and clinical trials that precede a thorough understanding of the disease, there is need for a major effort to gather natural history data on the entire spectrum of MPS II. Even in the attenuated disease, attention and executive function abnormalities need documentation. Lengthy detailed longitudinal studies are needed to encompass the wide variability in MPS II. In MPS IIIA, the existence of three good natural history studies allowed a quasi-meta-analysis. In patients with a rapid form of the disease, neurocognitive development slowed up until 42 to 47 months, halted up to about 54 months, then declined rapidly thereafter, with a leveling off at an extremely low age equivalent score below 22 months starting at about chronological age of 6. Those with slower or attenuated forms have been more variable and difficult to characterize. Because of the plethora of studies in IIIA, it has been recommended that data be combined from natural history studies to minimize the burden on parents and patients. Sufficient data exists to understand the natural history of cognition in MPS IIIA. MPS IIIB is quite similar to IIIA, but more attenuated patients in that phenotype have been reported. MPS IIIC and D, because they are so rare, have little documentation of natural history despite the prospects of treatments. MPS IV and VI are the least well documented of the MPS disorders with respect to their neurocognitive natural history. Because, like attenuated MPS I and II, they do not show progression of neurocognitive abnormality and most patients function in the range of normality, their behavioral, attentional, and executive function abnormalities have been ignored to the detriment of their quality of life. A peripheral treatment for MPS VII, extremely rare even among MPS types, has recently been approved with a post-approval monitoring system to provide neurocognitive natural history data in the future. More natural history studies in the MPS forms with milder cognitive deficits (MPS I, II, IV, and VI) are recommended with the goal of improving these patients' quality of life with and without new brain treatments, beyond the benefits of available peripheral enzyme replacement therapy. Recommendations are offered at-a-glance with respect to what areas most urgently need attention to clarify neurocognitive function in all MPS types.

Long-term impact of early initiation of enzyme replacement therapy in 34 MPS VI patients: A resurvey study

Patients with mucopolysaccharidosis type VI (MPS VI) present with a wide range of disease severity and clinical manifestations, with significant functional impairment and shortened lifespan. Enzyme replacement therapy (ERT) with galsulfase has been shown to improve clinical and biochemical parameters including patient survival, quality of life and growth. The present study is a resurvey of 34 Brazilian MPS VI patients with rapidly progressive disease (classical phenotype) who initiated ERT with galsulfase under five years of age and had been on ERT until data collection in 2019, with few exceptions (n = 4 patients who died before 2019). Anthropometric measures, urinary glycosaminoglycans, and data regarding cardiac, orthopedic, neurologic, sleep apnea, hearing and ophthalmologic outcomes were filled in by specialists. Pubertal development, clinical complications, hospitalizations, and surgeries were also assessed. In this resurvey study, treatment with galsulfase has shown to be safe and well tolerated in MPS VI patients who initiated ERT under the age of 5 years and who have been undergoing ERT for approximately 10 years. Mortality rate suggests that early initiation of ERT may have a positive impact on patients' survival, improving but not preventing disease progression and death. MPS VI patients on ERT also showed improved growth velocity and the pubertal development was normal in all surviving patients. Follow-up data on pneumonia and hospitalization suggest that early ERT may have a protective effect against major respiratory complications. Cardiac valve disease progressed since their prior evaluation and spinal cord compression was observed in a large number of patients, suggesting that these disease complications were not modified by ERT.