A basic understanding of mucopolysaccharidosis: Incidence, clinical features, diagnosis, and management

Health service utilization, economic burden and quality of life of patients with mucopolysaccharidosis in China

BACKGROUND

Patients with mucopolysaccharidosis (MPS) often face delayed diagnoses, limited treatment options and high healthcare costs, that may significantly affect patients' quality of life. The objective of this study was to understand medical service utilization related to diagnosis and treatment, economic burden during diagnosis period, and health-related quality of life among MPS patients in China.

METHODS

A series of patients diagnosed with MPS registered in the national patient organization were recruited for a cross-sectional survey from May to July 2019. Information were collected from patients or their parents via phone interview, including demographic data, utilization of services related to diagnosis and treatment, total cost during the period of MPS diagnosis and health-related quality of life (HRQoL). HRQoL was assessed by PedsQL 4.0 Generic Core Scale (PedsQL) and 36-item short-form health survey (SF-36) depending on the age of patients with MPS and compared with the general Chinese population.

RESULTS

A total of 180 MPS patients (50, 67, 15, 46, 1 and 1 for type I, II, III, IV, VI and VII), with a mean age of 9.54 years and 137 (76.11%) males, were included in analysis. The mean age at first visit to a medical doctor for MPS related symptoms was 3.65 ± 2.58 years old, while only 12 patients (6.67%) were diagnosed on their first visit. The mean diagnostic delay, which is defined as the time between the first visit to a medical doctor for MPS related symptoms and the final diagnosis, was 9.42 months, with no significant difference between types. The average number of misdiagnosis was 4.56. Before the confirmed diagnosis, the patients made an average of 6.31 visits and visited 4.3 hospitals. During diagnosis period, the mean of ¥81,086.72 direct medical costs accounted for 63.75% of the total cost. Only 32.78% of the patients had ever received specific treatments. The mean scores of PedsQL and SF-36 of patients were significantly lower than the Chinese norms. Household annual income per person, specific treatment use and MPS subtype were significantly associated HRQoL of patients.

CONCLUSION

The results highlight challenges faced by MPS patients in terms of diagnosis, access to specific treatments, economic burden and low HRQoL. There is an urgent need to improve early detection and diagnosis, create fair and consistent mechanisms to increase access to specialized treatment and reduce the economic burden of MPS patients in China.

CRISPR/Cas9 technology in the modeling of and treatment of mucopolysaccharidosis

Mucopolysaccharidosis (MPS) syndromes are a group of heterogeneous genetic disorders in terms of genetic basis and clinical manifestations, ranging from mild to fatal forms. There are a number of applied or prospective treatment modalities for MPS, including bone marrow transplantation, enzyme replacement therapy, targeted gene therapy and substrate reduction therapy. Recently, CRISPR/Cas9 technology has emerged as a novel tool for several metabolic disorders, such as MPS. This review concentrates on the application of this technique in the treatment of MPS, particularly MPS I, and modeling of disease-causing mutations.

The importance of geographic and sociodemographic aspects in the characterization of mucopolysaccharidoses: a case series from Ceará state (Northeast Brazil)

Geographic and sociodemographic aspects may influence the natural history and epidemiology of mucopolysaccharidoses (MPS). The main objective in this work was to evaluate the clinical, molecular, and geographic profile of MPS in a population from Ceará (Northeast Brazil). For this, we have performed a descriptive cross-sectional study based on clinical evaluation, interviews with patients and/or family members, and review of medical records of 76 MPS patients. MPS II was the most common type, with the most affected individuals presenting missense pathogenic variants. Patients with MPS I proved to be the most severe clinical phenotype, presenting the first symptoms (mean: 7.1 months; SD = 4.5) and being diagnosed earlier (2.2 years; SD = 2.1) in comparison with the other types. In addition, we have shown that 13 individuals with MPS VI were born of consanguineous marriages in small, nearby cities, in a place where geographical isolation, consanguinity, and clusters of genetic diseases were previously reported. Ten of these individuals (at least, seven different families) presented a rare pathogenic variant in the ARSB gene, c.1143-8T > G in homozygosity, previously reported only among Iberian and South American patients. The results presented here provide a comprehensive picture of MPS in an important state of the Brazilian Northeast, a region that concentrates many risk factors for rare genetic diseases, such as endogamy, inbreeding, and reproductive isolation. We discuss the possible evolutionary processes and biosocial dynamics that can help to explain this finding in terms of population medical genetics and public health.

Mucopolysaccharidosis Type IIIE: A Real Human Disease or a Diagnostic Pitfall?

Mucopolysaccharidoses (MPS) comprise a group of 12 metabolic disorders where defects in specific enzyme activities lead to the accumulation of glycosaminoglycans (GAGs) within lysosomes. This classification expands to 13 when considering MPS IIIE. This type of MPS, associated with pathogenic variants in the ARSG gene, has thus far been described only in the context of animal models. However, pathogenic variants in this gene also occur in humans, but are linked to a different disorder, Usher syndrome (USH) type IV, which is sparking increasing debate. This paper gathers, discusses, and summarizes arguments both for and against classifying dysfunctions of arylsulfatase G (due to pathogenic variants in the ARSG gene) in humans as another subtype of MPS, called MPS IIIE. Specific difficulties in diagnostics and the classification of some inherited metabolic diseases are also highlighted and discussed.

Synergistic effects of resveratrol and enzyme replacement therapy in the Mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPS I) is a rare genetic disorder caused by mutations in the IDUA gene, leading to alpha-L-iduronidase enzyme deficiency and resulting in the accumulation of glycosaminoglycans (GAG; heparan and dermatan sulfate) in lysosomes. The consequent GAG accumulation within cells leads to organ dysfunction and a range of debilitating symptoms. Enzyme replacement therapy (ERT) is the prevailing treatment, but its limitations (including high cost, time requirements, inefficiency in treatment of central nervous system (CNS), and immunogenicity) necessitate exploration of alternative therapeutic strategies. This research propose a novel approach leveraging the synergistic effects of ERT and resveratrol-induced autophagy. Resveratrol, with its immunomodulatory and GAG degradation-stimulating properties, holds a promise in mitigating immune responses triggered by ERT. Moreover, its ability to penetrate the blood-brain barrier presents a potential solution for addressing CNS manifestations. This study employed cells from MPS I patients to investigate the combined effects of resveratrol and the enzyme. Evaluation of the therapeutic impact involved assessing GAG accumulation, enzyme testing, and examining lysosome functionality and the autophagy process through fluorescence microscopy and Western blotting. The combined therapy stimulated the lysosomal mannose-6-phosphate receptor (M6PR) and lysosome biogenesis through the transcription factor EB (TFEB). Additionally, initial block of autophagy in autophagosome formation was relieved after the combined therapy and resveratrol alone. Together with increased enzyme activity through stimulation of the receptor, this synergistic therapy can be considered a new potential treatment for MPS I patients, improving their overall quality of life.

Recent advancements and applications of ophthalmic gene therapy strategies: A breakthrough in ocular therapeutics

Over the past twenty years, ocular gene therapy has primarily focused on addressing diseases linked to various genetic factors. The eye is an ideal candidate for gene therapy due to its unique characteristics, such as easy accessibility and the ability to target both corneal and retinal conditions, including retinitis pigmentosa (RP), Leber congenital amaurosis (LCA), age-related macular degeneration (AMD), and Stargardt disease. Currently, literature documents 33 clinical trials in this field, with the most promising results emerging from trials focused on LCA. These successes have catalyzed further research into other ocular conditions such as glaucoma, AMD, RP, and choroideremia. The effectiveness of gene therapy relies on the efficient delivery of genetic material to specific cells, ensuring sustained and optimal gene expression over time. Viral vectors have been widely used for this purpose, although concerns about potential risks such as immune reactions and genetic mutations have led to the development of non-viral vector systems. Preliminary laboratory research and clinical investigations have shown a connection between vector dosage and the intensity of immune response and inflammation in the eye. The method of administration significantly influences these reactions, with subretinal delivery resulting in a milder humoral response compared to the intravitreal route. This review discusses various ophthalmic diseases, including both corneal and retinal conditions, and their underlying mechanisms, highlighting recent advances and applications in ocular gene therapies.

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.

Application of tandem mass spectrometry in the screening and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPSs) are caused by a deficiency in the enzymes needed to degrade glycosaminoglycans (GAGs) in the lysosome. The storage of GAGs leads to the involvement of several systems and even to the death of the patient. In recent years, an increasing number of therapies have increased the treatment options available to patients. Early treatment is beneficial in improving the prognosis, but children with MPSs are often delayed in their diagnosis. Therefore, there is an urgent need to develop a method for early screening and diagnosis of the disease. Tandem mass spectrometry (MS/MS) is an analytical method that can detect multiple substrates or enzymes simultaneously. GAGs are reliable markers of MPSs. MS/MS can be used to screen children at an early stage of the disease, to improve prognosis by treating them before symptoms appear, to evaluate the effectiveness of treatment, and for metabolomic analysis or to find suitable biomarkers. In the future, MS/MS could be used to further identify suitable biomarkers for MPSs for early diagnosis and to detect efficacy.

Engineering Memory T Cells as a platform for Long-Term Enzyme Replacement Therapy in Lysosomal Storage Disorders

Enzymopathy disorders are the result of missing or defective enzymes. Amongst these enzymopathies, mucopolysaccharidosis type I, is a rare genetic lysosomal storage disorder caused by mutations in the gene encoding alpha-L-iduronidase (IDUA), ultimately causes toxic build-up of glycosaminoglycans (GAGs). There is currently no cure and standard treatments provide insufficient relief to the skeletal structure and central nervous system (CNS). Human memory T cells (Tm) migrate throughout the body's tissues and can persist for years, making them an attractive approach for cellular-based, systemic enzyme replacement therapy. Here, we tested genetically engineered, IDUA-expressing Tm as a cellular therapy in an immunodeficient mouse model of MPS I. Our results demonstrate that a single dose of engineered Tm leads to detectable IDUA enzyme levels in the blood for up to 22 weeks and reduced urinary GAG excretion. Furthermore, engineered Tm take up residence in nearly all tested tissues, producing IDUA and leading to metabolic correction of GAG levels in the heart, lung, liver, spleen, kidney, bone marrow, and the CNS. Our study indicates that genetically engineered Tm holds great promise as a platform for cellular-based enzyme replacement therapy for the treatment of mucopolysaccharidosis type I and potentially many other enzymopathies and protein deficiencies.

Fabry Disease: Cardiac Implications and Molecular Mechanisms

PURPOSE OF REVIEW

This review explores the interplay among metabolic dysfunction, oxidative stress, inflammation, and fibrosis in Fabry disease, focusing on their potential implications for cardiac involvement. We aim to discuss the biochemical processes that operate in parallel to sphingolipid accumulation and contribute to disease pathogenesis, emphasizing the importance of a comprehensive understanding of these processes.

RECENT FINDINGS

Beyond sphingolipid accumulation, emerging studies have revealed that mitochondrial dysfunction, oxidative stress, and chronic inflammation could be significant contributors to Fabry disease and cardiac involvement. These factors promote cardiac remodeling and fibrosis and may predispose Fabry patients to conduction disturbances, ventricular arrhythmias, and heart failure. While current treatments, such as enzyme replacement therapy and pharmacological chaperones, address disease progression and symptoms, their effectiveness is limited. Our review uncovers the potential relationships among metabolic disturbances, oxidative stress, inflammation, and fibrosis in Fabry disease-related cardiac complications. Current findings suggest that beyond sphingolipid accumulation, other mechanisms may significantly contribute to disease pathogenesis. This prompts the exploration of innovative therapeutic strategies and underscores the importance of a holistic approach to understanding and managing Fabry disease.

Caries assessment and salivary microbial analysis in patients diagnosed with mucopolysaccharidosis

BACKGROUND AND OBJECTIVES

Mucopolysaccharidosis (MPS) is a group of lysosomal storage disorders that cause the deposition of polysaccharides in cells. This causes systemic and oral manifestations, which can be observed clinically and radiographically. The present study aimed to assess dental caries, the effect of salivary pH, and the change of microflora on teeth in patients diagnosed with MPS.

MATERIALS AND METHODS

The study included children affected with mucopolysaccharidosis (n = 50) and healthy children (n = 50) in the control group between 3 and 15 years of age. The pH of saliva and decayed, missing, and filled teeth/decayed extracted and filled teeth index were noted and recorded. For the microbial analysis, saliva was inoculated into blood agar, MacConkey agar, Candida CHROMagar, and Mitis Salivarius agar, then inspected for colony-forming units, which were counted and recorded based on the colony characteristics and gram staining.

STATISTICAL ANALYSIS

Intergroup comparison of the test parameters was done using the Mann-Whitney test. P < 0.05 was considered statistically significant.

RESULTS

The results showed significantly higher total microbial load (P = 0.00008), streptococcus viridans species (P = 0.00001), and Candida species (P = 0.0038) in the study group. The caries incidence was also higher in the study group for both primary (P = 0.0096) and permanent dentition (P = 0.0251), and salivary pH was more acidic (P = 0.00001) in the patients diagnosed with MPS.

INTERPRETATION AND CONCLUSION

Patients diagnosed with MPS have a higher microbial load, more acidic saliva, and subsequently, a higher caries incidence than normal healthy children. Hence, regular dental evaluation, prevention, and treatment must be integrated into their health-care regimen.

Cellular Organelle-Related Transcriptomic Profile Abnormalities in Neuronopathic Types of Mucopolysaccharidosis: A Comparison with Other Neurodegenerative Diseases

Mucopolysaccharidoses (MPS) are a group of diseases caused by mutations in genes encoding lysosomal enzymes that catalyze reactions of glycosaminoglycan (GAG) degradation. As a result, GAGs accumulate in lysosomes, impairing the proper functioning of entire cells and tissues. There are 14 types/subtypes of MPS, which are differentiated by the kind(s) of accumulated GAG(s) and the type of a non-functional lysosomal enzyme. Some of these types (severe forms of MPS types I and II, MPS III, and MPS VII) are characterized by extensive central nervous system disorders. The aim of this work was to identify, using transcriptomic methods, organelle-related genes whose expression levels are changed in neuronopathic types of MPS compared to healthy cells while remaining unchanged in non-neuronopathic types of MPS. The study was conducted with fibroblast lines derived from patients with neuronopathic and non-neuronopathic types of MPS and control (healthy) fibroblasts. Transcriptomic analysis has identified genes related to cellular organelles whose expression is altered. Then, using fluorescence and electron microscopy, we assessed the morphology of selected structures. Our analyses indicated that the genes whose expression is affected in neuronopathic MPS are often associated with the structures or functions of the cell nucleus, endoplasmic reticulum, or Golgi apparatus. Electron microscopic studies confirmed disruptions in the structures of these organelles. Special attention was paid to up-regulated genes, such as PDIA3 and MFGE8, and down-regulated genes, such as ARL6IP6, ABHD5, PDE4DIP, YIPF5, and CLDN11. Of particular interest is also the GM130 (GOLGA2) gene, which encodes golgin A2, which revealed an increased expression in neuronopathic MPS types. We propose to consider the levels of mRNAs of these genes as candidates for biomarkers of neurodegeneration in MPS. These genes may also become potential targets for therapies under development for neurological disorders associated with MPS and candidates for markers of the effectiveness of these therapies. Although fibroblasts rather than nerve cells were used in this study, it is worth noting that potential genetic markers characteristic solely of neurons would be impractical in testing patients, contrary to somatic cells that can be relatively easily obtained from assessed persons.

Caregiver experiences and observations of intrathecal idursulfase-IT treatment in a phase 2/3 trial in pediatric patients with neuronopathic mucopolysaccharidosis II

BACKGROUND

Approximately two-thirds of patients with mucopolysaccharidosis II (MPS II) have a severe, neuronopathic phenotype, characterized by somatic, cognitive, and behavioral issues. Current standard of care for the treatment of MPS II is enzyme replacement therapy with intravenous recombinant human iduronate-2-sulfatase (idursulfase). To target cognitive manifestations of MPS II, idursulfase has been formulated for intrathecal administration into the cerebrospinal fluid (idursulfase-IT). In accordance with recommendations for patient-focused drug development, semi-structured interviews were conducted to assess caregiver experiences and observations in a 52-week phase 2/3 trial of idursulfase-IT, in addition to intravenous idursulfase in pediatric patients with neuronopathic MPS II, or a substudy which enrolled patients younger than 3 years old, all of whom received idursulfase-IT.

RESULTS

Overall, 46 caregivers providing care for 50 children (mean [range] age 7.9 [3-17] years at interview) took part in a single 60-min exit interview; six of these children had participated in the substudy. Qualitative and quantitative data were obtained demonstrating the burden of MPS II experienced by caregivers and their families. Following participation in the trials, 39 (78%) of the children were reported by their caregivers to have experienced improvements in the symptoms and impact of disease. Of those with improvements, 37 (95%) experienced cognitive improvements and 26 (67%) experienced emotional/behavioral improvements. Overall, 43 children (86%) were rated by caregivers as having moderate or severe symptoms before the trials; after the trials, 28 children (56%) were considered to have mild or no symptoms. For the six children who participated in the substudy, these proportions were 83% and 100%, respectively. Caregivers' qualitative descriptions of trial experiences suggested improvements in children's verbal and non-verbal functioning and spatial and motor skills, as well as a positive impact on family life.

CONCLUSIONS

This study revealed caregiver-reported improvements in children's MPS II symptoms and the impact of the disease on patients and their families. There was a trend for cognitive improvement and a reduction in severity of MPS II symptoms. After many years of extensive review and regulatory discussions of idursulfase-IT, the clinical trial data were found to be insufficient to meet the evidentiary standard to support regulatory filings.

Mucopolysaccharidosis type VII (Sly syndrome) - What do we know?

Mucopolysaccharidosis type VII (MPS VII) is an ultra-rare, life-threatening, progressive disease caused by genetic mutations that affect lysosomal storage/function. MPS VII has an estimated prevalence of <1:1,000,000 and accounts for <3% of all MPS diagnoses. Given the rarity of MPS VII, comprehensive information on the disease is limited and we present a review of the current understanding. In MPS VII, intracellular glycosaminoglycans accumulate due to a deficiency in the lysosomal enzyme that is responsible for their degradation, β-glucuronidase, which is encoded by the GUSB gene. MPS VII has a heterogeneous presentation. Features can manifest across multiple systems and can vary in severity, age of onset and progression. The single most distinguishing clinical feature of MPS VII is non-immune hydrops fetalis (NIHF), which presents during pregnancy. MPS VII usually presents within one month of life and become more prominent at 3 to 4 years of age; key features are skeletal deformities, hepatosplenomegaly, coarse facies, and cognitive impairment, although phenotypic variation is a hallmark. Current treatments include hematopoietic stem cell transplantation and enzyme replacement therapy with vestronidase alfa. Care should be individualized for each patient. Development of consensus guidelines for MPS VII management and treatment is needed, as consolidation of expert knowledge and experience (for example, through the MPS VII Disease Monitoring Program) may provide a significant positive impact to patients.

Specific GAG ratios in the diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) screening is tedious and still performed by analysis of total glycosaminoglycans (GAG) using 1,9-dimethylmethylene blue (DMB) photometric assay, although false positive and negative tests have been reported. Analysis of differentiated GAGs have been pursued classically by gel electrophoresis or more recently by quantitative LC-MS assays. Secondary elevations of GAGs have been reported in urinary tract infections (UTI). In this manuscript, we describe the diagnostic accuracy of urinary GAG measurements by LC-MS for MPS typing in 68 untreated MPS and mucolipidosis (ML) patients, 183 controls and 153 UTI samples. We report age-dependent reference values and cut-offs for chondroitin sulfate (CS), dermatan sulfate (DS), heparan sulfate (HS) and keratan sulfate (KS) and specific GAG ratios. The use of HS/DS ratio in combination to GAG concentrations normalized to creatinine improves the diagnostic accuracy in MPS type I, II, VI and VII. In total 15 samples classified to the wrong MPS type could be correctly assigned using HS/DS ratio. Increased KS/HS ratio in addition to increased KS improves discrimination of MPS type IV by excluding false positives. Some samples of UTI patients showed elevation of specific GAGs, mainly CS, KS and KS/HS ratio and could be misclassified as MPS type IV. Finally, DMB photometric assay performed in MPS and ML samples reveal four false negative tests (sensitivity of 94%). In conclusion, specific GAG ratios in complement to quantitative GAG values obtained by LC-MS enhance discrimination of MPS types. Exclusion of patients with UTI improve diagnostic accuracy in MPS IV but not in other types.

Use of Marsupialization as a Definitive Treatment for Large-sized Dentigerous Cysts in a Patient with Mucopolysaccharidosis Type I

The correct diagnosis is fundamental for the appropriate treatment to be employed in a particular pathology. The best treatment is not the one that solves only local problems, fragmenting the patient, and therefore, it is necessary to integrate the entire systemic condition of the individual before initiating any local treatment. This context inevitably requires dentistry to participate in a multidisciplinary approach, where the role of the dentist is expanded in concepts that encompass ethics, human dignity, and professional valorization. This article describes a clinical case of a patient with mucopolysaccharidosis type I, whose treatment of cystic lesions present in the mandible was exclusively performed through marsupialisation. The objective of this study is to demonstrate, within the complexity of this rare syndrome, the difficulties of diagnosis and the need for evaluation of the patient beyond the limits of the oral cavity, as well as to report two cases of large dentigerous cysts, surgically treated conservatively through marsupialisation, without the need for re-approach for enucleation and without recurrences over a 20-year period.

Post-tonsillectomy outcomes in children with mucopolysaccharidosis and obstructive sleep apnea

OBJECTIVE

To describe the incidence of respiratory complications, postoperative hemorrhage, length of stay, and cost of care in children with mucopolysaccharidosis (MPS) undergoing adenotonsillectomy (AT).

METHODS

Analysis of the 2009, 2012, and 2016 editions of the Healthcare Cost and Utilization Project Kids' Inpatient Database (HCUP KID) identified 24,700 children who underwent AT (40 children with MPS). Demographics, respiratory complications, postoperative hemorrhage, length of stay, and total cost were compared across children with and without MPS.

RESULTS

Children with MPS had a higher likelihood of being male (P < 0.017). There was a higher rate of respiratory complications in children with MPS compared with children without MPS [6/40 (15%) vs. 586/24,660 (2.4%), P < 0.001], which remained significant after adjusting for sex [adjusted odds ratio 6.88 (95% CI 2.87-16.46)]. There was also a higher risk of postoperative hemorrhage [4/40 (10%) vs. 444/24,660 (1.8%), P < 0.001), with sex-adjusted odds ratio of 5.97 (95% CI 2.12-16.86). Median (IQR) length of stay was increased in children with MPS (3 days, 1-4) compared with children without MPS (1 day, 1-2, P < 0.001). There was an increase in median (IQR) charges for hospital stay in children with MPS compared with their peers [$33,016 ($23,208.50-$72,280.50 vs. $15,383 ($9937-$24,462), P < 0.001].

CONCLUSIONS

Children with MPS undergoing AT had an increased risk of respiratory complications, postoperative hemorrhage, longer length of stay, and a higher cost of treatment when compared with children without MPS. This information may help inform interventional, perioperative, and postoperative decision making.

Child Neurology: Mucopolysaccharidosis IIID: Evidence From Ultrastructural and Genomic Study

Mucopolysaccharidosis IIID (MPS IIID/Sanfilippo syndrome D, OMIM # 252940) is an autosomal recessive lysosomal storage disorder (LSD) and the rarest form of the mucopolysaccharidosis (MPS) III subtypes. It is caused by sequence variations in the gene encoding lysosomal enzyme N-acetyl glucosamine-6-sulphatase (GNS). Deficiency of GNS impairs catabolism of glycosaminoglycans causing accumulation of heparan sulphate within lysosomes of various tissues, which is visualized as membranous cytoplasmic bodies (MCBs) on electron microscopy. The recognition of this ultrastructural feature in a muscle biopsy instigated genetic evaluation for LSD in our case resulting in the detection of a novel pathogenic GNS gene variant. The patient also exhibited intellectual disability since childhood, reduced vision due to pigmentary retinopathy, and behavioral abnormalities without other systemic features of MPS. In this study, we report a patient of Indian origin with MPS IIID based on a novel pathogenic variant c.1078 G>T (p.G360C) in the GNS and the presence of MCBs in muscle biopsy, characterized by several novel findings including the occurrence of pigmentary retinopathy, which extends the clinical spectrum of MPS IIID.

Therapeutic potential of lithium chloride and valproic acid against neuronopathic types of mucopolysaccharidoses through induction of the autophagy process

Mucopolysaccharidoses (MPS) are a group of inherited disorders, caused by mutations in the genes coding for proteins involved (directly or indirectly) in glycosaminoglycan (GAG) degradation. A lack or drastically decreased residual activity of a GAG-degrading enzyme leads to the storage of these compounds, thus damaging proper functions of different cells, including neurons. The disease leads to serious psycho-motor dysfunctions and death before reaching the adulthood. Until now, induction of the autophagy process was considered as one of the therapeutic strategies for treatment of diseases caused by protein aggregation (Alzheimer's, Parkinson's, and Huntington's diseases). However, this strategy has only been recently suggested as a potential therapy for MPS. In this work, we show that the pharmacological stimulation of autophagy, by using valproic acid and lithium chloride, led to accelerated degradation of accumulated GAGs. Cytotoxicity tests indicated the safety of the use of the investigated compounds. We observed an increased number of lysosomes and enhanced degradation of heparan sulfate (one of GAGs). Induction of the autophagy process was confirmed by measuring abundance of the marker proteins, including LC3-II. Moreover, inhibition of this process resulted in abolition of the valproic acid- and LiCl-mediated reduction in GAG levels. This is the first report on the possibility of using valproic acid and lithium chloride for reducing levels of GAGs in neuronopathic forms of MPS.

Enhanced Efficiency of the Basal and Induced Apoptosis Process in Mucopolysaccharidosis IVA and IVB Human Fibroblasts

Morquio disease, also called mucopolysaccharidosis IV (MPS IV), belongs to the group of lysosomal storage diseases (LSD). Due to deficiencies in the activities of galactose-6-sulfate sulfatase (in type A) or β-galactosidase (in type B), arising from mutations in GALNS or GLB1, respectively, keratan sulfate (one of glycosaminoglycans, GAGs) cannot be degraded efficiently and accumulates in lysosomes. This primary defect leads to many cellular dysfunctions which then cause specific disease symptoms. Recent works have indicated that different secondary effects of GAG accumulation might significantly contribute to the pathomechanisms of MPS. Apoptosis is among the cellular processes that were discovered to be affected in MPS cells on the basis of transcriptomic studies and some cell biology experiments. However, Morquio disease is the MPS type which is the least studied in light of apoptosis dysregulation, while RNA-seq analyses suggested considerable changes in the expression of genes involved in apoptosis in MPS IVA and IVB fibroblasts. Here we demonstrate that cytochrome c release from mitochondria is more efficient in MPS IVA and IVB fibroblasts relative to control cells, both under the standard cultivation conditions and after treatment with staurosporine, an apoptosis inducer. This indication of apoptosis stimulation was corroborated by measurements of the levels of caspases 9, 3, 6, and 7, as well as PARP, cleaved at specific sites, in Morquio disease and control fibroblasts. The more detailed analyses of the transcriptomic data revealed which genes related to apoptosis are down- and up-regulated in MPS IVA and IVB fibroblasts. We conclude that apoptosis is stimulated in Morquio disease under both standard cell culture conditions and after induction with staurosporine which may contribute to the pathomechanism of this disorder. Dysregulation of apoptosis in other MPS types is discussed.

Dysregulation of genes coding for proteins involved in metabolic processes in mucopolysaccharidoses, evidenced by a transcriptomic approach

Mucopolysaccharidoses (MPS) are a group of lysosomal storage diseases (LSD) caused by mutations in genes coding for enzymes responsible for degradation of glycosaminoglycans (GAGs). Most types of these severe disorders are characterized by neuronopathic phenotypes. Although lysosomal accumulation of GAGs is the primary metabolic defect in MPS, secondary alterations in biochemical processes are considerable and influence the course of the disease. Early hypothesis suggested that these secondary changes might be due to lysosomal storage-mediated impairment of activities of other enzymes, and subsequent accumulation of various compounds in cells. However, recent studies indicated that expression of hundreds of genes is changed in MPS cells. Therefore, we asked whether metabolic effects observed in MPS are caused primarily by GAG-mediated inhibition of specific biochemical reactions or appear as results of dysregulation of expression of genes coding for proteins involved in metabolic processes. Transcriptomic analyses of 11 types of MPS (using RNA isolated from patient-derived fibroblasts), performed in this study, showed that a battery of the above mentioned genes is dysregulated in MPS cells. Some biochemical pathways might be especially affected by changes in expression of many genes, including GAG metabolism and sphingolipid metabolism which is especially interesting as secondary accumulation of various sphingolipids is one of the best known additional (while significantly enhancing neuropathological effects) metabolic defects in MPS. We conclude that severe metabolic disturbances, observed in MPS cells, can partially arise from changes in the expression of many genes coding for proteins involved in metabolic processes.

Actin Cytoskeleton Polymerization and Focal Adhesion as Important Factors in the Pathomechanism and Potential Targets of Mucopolysaccharidosis Treatment

The main approach used in the current therapy of mucopolysaccharidosis (MPS) is to reduce the levels of glycosaminoglycans (GAGs) in cells, the deposits considered to be the main cause of the disease. Previous studies have revealed significant differences in the expression of genes encoding proteins involved in many processes, like those related to actin filaments, in MPS cells. Since the regulation of actin filaments is essential for the intracellular transport of specific molecules, the process which may affect the course of MPSs, the aim of this study was to evaluate the changes that occur in the actin cytoskeleton and focal adhesion in cells derived from patients with this disease, as well as in the MPS I mouse model, and to assess whether they could be potential therapeutic targets for different MPS types. Western-blotting, flow cytometry and transcriptomic analyses were employed to address these issues. The levels of the key proteins involved in the studied processes, before and after specific treatment, were assessed. We have also analyzed transcripts whose levels were significantly altered in MPS cells. We identified genes whose expressions were changed in the majority of MPS types and those with particularly highly altered expression. For the first time, significant changes in the expression of genes involved in the actin cytoskeleton structure/functions were revealed which may be considered as an additional element in the pathogenesis of MPSs. Our results suggest the possibility of using the actin cytoskeleton as a potential target in therapeutic approaches for this disease.

Posterior Atlantoaxial Fusion With C1-2 Pedicle Screw Fixation for Atlantoaxial Dislocation in Pediatric Patients With Mucopolysaccharidosis IVA (Morquio a Syndrome): A Case Series

OBJECTIVE

To investigate the efficacy and safety of posterior atlantoaxial fusion (AAF) with C1-2 pedicle screw fixation for atlantoaxial dislocation (AAD) in pediatric patients with mucopolysaccharidosis IVA (MPS IVA).

METHODS

This study included 21 pediatric patients with MPS IVA who underwent posterior AAF with C1-2 pedicle screw fixation. Anatomical parameters of the C1 and C2 pedicle were measured on preoperative computed tomography (CT). The American Spinal Injury Association (ASIA) scale was used to evaluate the neurological status. The fusion and accuracy of pedicle screw was assessed on postoperative CT. Demographic, radiation dose, bone density, surgical, and clinical data were recorded.

RESULTS

Patients reviewed included 21 patients younger than 16 years with an average age of 7.4 ± 4.2 years and an average of 20.9 ± 7.7 months follow-up. Fixation of 83 C1 and C2 pedicle screws was performed successfully and 96.3% of them were identified as being safe. One patient developed postoperative transient disturbance of consciousness and one developed fetal airway obstruction and died about 1 month after the surgery. Out of the remaining20 patients, fusion was achieved, symptoms were improved, and no other serious surgical complications were observed at the latest follow-up.

CONCLUSIONS

Posterior AAF with C1-2 pedicle screw fixation is effective and safe for AAD in pediatric patients with MPS IVA. However, the procedure is technically demanding and should be performed by experienced surgeons with strict multidisciplinary consultations.

Bone Growth Induction in Mucopolysaccharidosis IVA Mouse

Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is caused by a deficiency of the N-acetylgalactosamine-6-sulfate-sulfatase (GALNS) enzyme, leading to the accumulation of glycosaminoglycans (GAG), keratan sulfate (KS) and chondroitin-6-sulfate (C6S), mainly in cartilage and bone. This lysosomal storage disorder (LSD) is characterized by severe systemic skeletal dysplasia. To this date, none of the treatment options for the MPS IVA patients correct bone pathology. Enzyme replacement therapy with elosulfase alpha provides a limited impact on bone growth and skeletal lesions in MPS IVA patients. To improve bone pathology, we propose a novel gene therapy with a small peptide as a growth-promoting agent for MPS IVA. A small molecule in this peptide family has been found to exert biological actions over the cardiovascular system. This work shows that an AAV vector expressing a C-type natriuretic (CNP) peptide induces bone growth in the MPS IVA mouse model. Histopathological analysis showed the induction of chondrocyte proliferation. CNP peptide also changed the pattern of GAG levels in bone and liver. These results suggest the potential for CNP peptide to be used as a treatment in MPS IVA patients.

The Interplay of Glycosaminoglycans and Cysteine Cathepsins in Mucopolysaccharidosis

Mucopolysaccharidosis (MPS) consists of a group of inherited lysosomal storage disorders that are caused by a defect of certain enzymes that participate in the metabolism of glycosaminoglycans (GAGs). The abnormal accumulation of GAGs leads to progressive dysfunctions in various tissues and organs during childhood, contributing to premature death. As the current therapies are limited and inefficient, exploring the molecular mechanisms of the pathology is thus required to address the unmet needs of MPS patients to improve their quality of life. Lysosomal cysteine cathepsins are a family of proteases that play key roles in numerous physiological processes. Dysregulation of cysteine cathepsins expression and activity can be frequently observed in many human diseases, including MPS. This review summarizes the basic knowledge on MPS disorders and their current management and focuses on GAGs and cysteine cathepsins expression in MPS, as well their interplay, which may lead to the development of MPS-associated disorders.

Decreased Levels of Chaperones in Mucopolysaccharidoses and Their Elevation as a Putative Auxiliary Therapeutic Approach

Mucopolysaccharidoses (MPS) are rare genetic disorders belonging to the lysosomal storage diseases. They are caused by mutations in genes encoding lysosomal enzymes responsible for degrading glycosaminoglycans (GAGs). As a result, GAGs accumulate in lysosomes, leading to impairment of cells, organs and, consequently, the entire body. Many of the therapies proposed thus far require the participation of chaperone proteins, regardless of whether they are therapies in common use (enzyme replacement therapy) or remain in the experimental phase (gene therapy, STOP-codon-readthrough therapy). Chaperones, which include heat shock proteins, are responsible for the correct folding of other proteins to the most energetically favorable conformation. Without their appropriate levels and activities, the correct folding of the lysosomal enzyme, whether supplied from outside or synthesized in the cell, would be impossible. However, the baseline level of nonspecific chaperone proteins in MPS has never been studied. Therefore, the purpose of this work was to determine the basal levels of nonspecific chaperone proteins of the Hsp family in MPS cells and to study the effect of normalizing GAG concentrations on these levels. Results of experiments with fibroblasts taken from patients with MPS types I, II, IIIA, IIIB, IIIC, IID, IVA, IVB, VI, VII, and IX, as well as from the brains of MPS I mice (Idua^-/-), indicated significantly reduced levels of the two chaperones, Hsp70 and Hsp40. Interestingly, the reduction in GAG levels in the aforementioned cells did not lead to normalization of the levels of these chaperones but caused only a slight increase in the levels of Hsp40. An additional transcriptomic analysis of MPS cells indicated that the expression of other genes involved in protein folding processes and the cell response to endoplasmic reticulum stress, resulting from the appearance of abnormally folded proteins, was also modulated. To summarize, reduced levels of chaperones may be an additional cause of the low activity or inactivity of lysosomal enzymes in MPS. Moreover, this may point to causes of treatment failure where the correct structure of the enzyme supplied or synthesized in the cell is crucial to lower GAG levels.

Cervical spine involvement in pediatric mucopolysaccharidosis patients: Clinical features, early diagnosis, and surgical management

Mucopolysaccharidosis (MPS) is a progressive genetic disease that causes a deficiency in lysosomal enzymes, which play an important role in the degradation pathway of glycosaminoglycans. As a result of enzyme defects, mucopolysaccharides cannot be metabolized and thus accumulate. The cervical spine is one of the most commonly involved sites; thus, prompt surgical management before the onset of severe neurological deterioration is critical. However, because of the rarity of the disease, there is no standard treatment. In this review, we characterize the cervical spinal involvement in pediatric patients with MPS, describe the useful imaging technologies for diagnosis, and provide screening procedure for children with MPS. Surgical managements, including indications, surgical methods, possible difficulties, and solutions, are reviewed in detail.

Gene editing strategies to treat lysosomal disorders: The example of mucopolysaccharidoses

Lysosomal storage disorders are a group of progressive multisystemic hereditary diseases with a combined incidence of 1:4,800. Here we review the clinical and molecular characteristics of these diseases, with a special focus on Mucopolysaccharidoses, caused primarily by the lysosomal storage of glycosaminoglycans. Different gene editing techniques can be used to ameliorate their symptoms, using both viral and nonviral delivery methods. Whereas these are still being tested in animal models, early results of phase I/II clinical trials of gene therapy show how this technology may impact the future treatment of these diseases. Hurdles related to specific hard-to-reach organs, such as the central nervous system, heart, joints, and the eye must be tackled. Finally, the regulatory framework necessary to advance into clinical practice is also discussed.

Radiographic Findings of Mucopolysaccharidosis and Comparison with Bone Mineral Density: A Study from Southeastern Turkey

INTRODUCTION

The first aim of this study is to define the severity of radiologic features according to mucopolysaccharidosis (MPS) type. The second aim is to compare spine radiographs with dual-energy X-ray absorptiometry (DXA) scores.

METHODOLOGY

A total of 64 MPS children were enrolled between January 2017 and March 2021. Patients with a history of surgery, fracture or improper radiographs were excluded. Finally, 48 cases (20 MPS VI, 12 MPS IVA, 7 MPS IIIA, 4 MPS IIIB, 3 MPS II, 2 MPS I) were yielded. Among them, 38 had DXA performed in the same week with radiographs. Demographic and radiographic features and the hip acetabular index were noted. T12-L5 vertebral body heights were measured from lateral spine radiographs and divided by patient height. DXA measurements, bone mineral density and Z-scores were also recorded.

RESULTS

Spine and hip findings were most frequently seen in MPS VI and IVA. Oar-shaped ribs were more common in MPS VI, whereas anteromedial beaking of vertebra was predominantly seen in MPS IVA. Femoral head dysplasia is most common in MPS IVA, VI and I. The highest mean acetabular was observed in MPS I. The mean Z-score of L1-L4 vertebrae was low for MPS I (-3.8), IVA (-3.79) and VI (-3.73), but normal for MPS II (0.6) and IIIA (0.23). Correlation between the Z-score and vertebral index was highest in the L1 vertebral body.

CONCLUSION

Interpreting the characteristic radiographic features of different MPS types is important. In addition to dysostosis multiplex, quantitative measurements from radiographs may be beneficial in evaluating disease progression.

A Novel Mutation in the NAGLU (N-Acetyl-Alpha-Glucosaminidase) Gene Associated With Mucopolysaccharidosis Type III-B in a Saudi Girl

Mucopolysaccharidosis type III-B (MPS III), also known as Sanfilippo syndrome, is a rare autosomal recessive lysosomal storage disease that primarily affects the brain and spinal cord. In this report, we describe the case of an eight-year-old female child who presented to the emergency room with an asthma exacerbation. She had coarse facial features, thick eyebrows, deep-seated eyes, thinning coarse hair, and macrocephaly. Moreover, she suffered from hepatosplenomegaly, generalized muscular atrophy, global developmental delay, and scoliosis. Urinary glycosaminoglycans (GAGs) were within normal limits. Full genetic testing confirmed the diagnosis of Sanfilippo syndrome type B with a deficiency of alpha-N-acetylglucosaminidase caused by a homozygous mutation c.889C>T, p.(Arg297*) in the NAGLU (N-acetyl-alpha-glucosaminidase) gene. Chromosomal microarray analysis (CMA) showed a copy number variant (CNV) within the 1q24 region. Thus far, CNVs similar in size and position have not been reported in the literature, making this a novel mutation.

Sanfilippo Syndrome: Optimizing Care with a Multidisciplinary Approach

Sanfilippo syndrome, or mucopolysaccharidosis type III (MPS III), is a disease grouping five genetic disorders, four of them occurring in humans and one known to date only in a mouse model. In every subtype of MPS III (designed A, B, C, D or E), a lack or drastically decreased activity of an enzyme involved in the degradation of heparan sulfate (HS) (a compound from the group of glycosaminoglycans (GAGs)) arises from a genetic defect. This leads to primary accumulation of HS, and secondary storage of other compounds, combined with changes in expressions of hundreds of genes and many defects in organelles and various biochemical processes in the cell. As a result, dysfunctions of tissues and organs occur, leading to severe symptoms in patients. Although changes in somatic organs are considerable, the central nervous system is especially severely affected, and neurological, cognitive and behavioral disorders are the most significant changes, making the disease enormously burdensome for patients and their families. In the light of the current lack of any registered therapy for Sanfilippo syndrome (despite various attempts of many research groups to develop effective treatment, still no specific drug or procedure is available for MPS III), optimizing care with a multidisciplinary approach is crucial for managing this disease and making quality of patients’ life passable. This includes efforts to make/organize (i) accurate diagnosis as early as possible (which is not easy due to various possible misdiagnosis events caused by similarity of MPS III symptoms to those of other diseases and variability of patients), (ii) optimized symptomatic treatment (which is challenging because of complexity of symptoms and often untypical responses of MPS III patients to various drugs), and (iii) psychological care (for both patients and family members and/or caregivers). In this review article, we focus on these approaches, summarizing and discussing them.

Cell cycle disturbances in mucopolysaccharidoses: Transcriptomic and experimental studies on cellular models

Mucopolysaccharidoses (MPS) are a group of lysosomal storage diseases caused by defects in genes coding for proteins involved in degradation of glycosaminoglycans (GAGs). These complex carbohydrates accumulate in cells causing their serious dysfunctions. Apart from the physical GAG storage, secondary and tertiary changes may contribute significantly to the pathomechanism of the disease. Among processes which were not systematically investigated in MPS cells to date there is the cell cycle. Here, we studied perturbances in this crucial cellular process in majority of MPS types. Transcriptomic analyses indicated that expression of many genes coding for proteins involved in the cell cycle is dysregulated in all tested MPS cells. Importantly, levels of transcripts of particular genes were changed in the same manner (i.e. either up- or down-regulated) in most or all types of the disease, indicating a common mechanism of the dysregulation. Flow cytometric studies demonstrated that the cell cycle is disturbed in all MPS types, with increased fractions of cells in the G₀/G₁ phase in most types and decreased fractions of cells in the G₂/M phase in all types. We found that increased levels of cyclin D1 and disturbed timing of its appearance during the cell cycle may contribute to the mechanism of dysregulation of this process in MPS. Reduction of GAG levels by either a specific enzyme or genistein-mediated inhibition of synthesis of these compounds improved, but not fully corrected, the cell cycle in MPS fibroblasts. Therefore, it is suggested that combination of the therapeutic approaches devoted to reduction of GAG levels with cyclin D1 inhibitors might be considered in further works on developing effective treatment procedures for MPS.

Limited diagnostic facilities impeding the therapeutic approach of Mucopolysaccharidosis in Bangladesh: a case report

In resource-constrained settings, mucopolysaccharidosis (MPS) is a rare hereditary metabolic illness that frequently remains undiagnosed. We present a scenario that illustrates the challenges in diagnosing and managing MPS because of test inaccessibility, and we propose potential approaches to minimize the hurdles. We recommend that physicians anticipate a rare genetic disease, such as MPS, based on the clinical history findings from routine radiological investigations. Additionally, stakeholders should perform risk stratification and implement screening tests as soon as possible to ensure that patients are effectively enrolled in treatment programs.

Rare Metabolic and Endocrine Diseases with Cardiovascular Involvement: Insights from Cardiovascular Magnetic Resonance - A Review

The identification of rare diseases with cardiovascular involvement poses significant diagnostic challenges due to the rarity of the diseases, but also due to the lack of knowledge and expertise. Most of them remain underrecognized and undiagnosed, leading to clinical mismanagement and affecting the patients' prognosis, as these diseases are per definition life-threatening or chronic debilitating. This article reviews the cardiovascular involvement of the most well-known rare metabolic and endocrine diseases and their diagnostic approach through the lens of cardiovascular magnetic resonance (CMR) imaging and its prognostic role, highlighting its fundamental value compared to other imaging modalities.

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.

The Inflammation in the Cytopathology of Patients With Mucopolysaccharidoses- Immunomodulatory Drugs as an Approach to Therapy

Mucopolysaccharidoses (MPS) are a group of lysosomal storage diseases (LSDs), characterized by the accumulation of glycosaminoglycans (GAGs). GAG storage-induced inflammatory processes are a driver of cytopathology in MPS and pharmacological immunomodulation can bring improvements in brain, cartilage and bone pathology in rodent models. This manuscript reviews current knowledge with regard to inflammation in MPS patients and provides hypotheses for the therapeutic use of immunomodulators in MPS. Thus, we aim to set the foundation for a rational repurposing of the discussed molecules to minimize the clinical unmet needs still remaining despite enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT).

Splicing Modulation as a Promising Therapeutic Strategy for Lysosomal Storage Disorders: The Mucopolysaccharidoses Example

Over recent decades, the many functions of RNA have become more evident. This molecule has been recognized not only as a carrier of genetic information, but also as a specific and essential regulator of gene expression. Different RNA species have been identified and novel and exciting roles have been unveiled. Quite remarkably, this explosion of novel RNA classes has increased the possibility for new therapeutic strategies that tap into RNA biology. Most of these drugs use nucleic acid analogues and take advantage of complementary base pairing to either mimic or antagonize the function of RNAs. Among the most successful RNA-based drugs are those that act at the pre-mRNA level to modulate or correct aberrant splicing patterns, which are caused by specific pathogenic variants. This approach is particularly tempting for monogenic disorders with associated splicing defects, especially when they are highly frequent among affected patients worldwide or within a specific population. With more than 600 mutations that cause disease affecting the pre-mRNA splicing process, we consider lysosomal storage diseases (LSDs) to be perfect candidates for this type of approach. Here, we introduce the overall rationale and general mechanisms of splicing modulation approaches and highlight the currently marketed formulations, which have been developed for non-lysosomal genetic disorders. We also extensively reviewed the existing preclinical studies on the potential of this sort of therapeutic strategy to recover aberrant splicing and increase enzyme activity in our diseases of interest: the LSDs. Special attention was paid to a particular subgroup of LSDs: the mucopolysaccharidoses (MPSs). By doing this, we hoped to unveil the unique therapeutic potential of the use of this sort of approach for LSDs as a whole.

Complex Changes in the Efficiency of the Expression of Many Genes in Monogenic Diseases, Mucopolysaccharidoses, May Arise from Significant Disturbances in the Levels of Factors Involved in the Gene Expression Regulation Processes

Monogenic diseases are primarily caused by mutations in a single gene; thus, they are commonly recognized as genetic disorders with the simplest mechanisms. However, recent studies have indicated that the molecular mechanisms of monogenic diseases can be unexpectedly complicated, and their understanding requires complex studies at the molecular level. Previously, we have demonstrated that in mucopolysaccharidoses (MPS), a group of monogenic lysosomal storage diseases, several hundreds of genes reveal significant changes in the expression of various genes. Although the secondary effects of the primary biochemical defect and the inefficient degradation of glycosaminoglycans (GAGs) might be considered, the scale of the changes in the expression of a large fraction of genes cannot be explained by a block in one biochemical pathway. Here, we demonstrate that in cellular models of 11 types of MPS, the expression of genes coding for proteins involved in the regulation of the expression of many other genes at various stages (such as signal transduction, transcription, splicing, RNA degradation, translation, and others) is significantly disturbed relative to the control cells. This conclusion was based on transcriptomic studies, supported by biochemical analyses of levels of selected proteins encoded by genes revealing an especially high level of dysregulation in MPS (EXOSC9, SRSF10, RPL23, and NOTCH3 proteins were investigated). Interestingly, the reduction in GAGs levels, through the inhibition of their synthesis normalized the amounts of EXOSC9, RPL23, and NOTCH3 in some (but not all) MPS types, while the levels of SRSF10 could not be corrected in this way. These results indicate that different mechanisms are involved in the dysregulation of the expression of various genes in MPS, pointing to a potential explanation for the inability of some therapies (such as enzyme replacement therapy or substrate reduction therapy) to fully correct the physiology of MPS patients. We suggest that the disturbed expression of some genes, which appears as secondary or tertiary effects of GAG storage, might not be reversible, even after a reduction in the amounts of the storage material.

The landscape of Mucopolysaccharidosis in Southern and Eastern European countries: a survey from 19 specialistic centers

Background

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by defects in genes coding for different lysosomal enzymes which degrade glycosaminoglycans. Impaired lysosomal degradation causes cell dysfunction leading to progressive multiorgan involvement, disabling consequences and poor life expectancy. Enzyme replacement therapy (ERT) is now available for most MPS types, offering beneficial effects on disease progression and improving quality of life of patients. The landscape of MPS in Europe is not completely described and studies on availability of treatment show that ERT is not adequately implemented, particularly in Southern and Eastern Europe. In this study we performed a survey analysis in main specialist centers in Southern and Eastern European countries, to outline the picture of disease management in the region and understand ERT implementation. Since the considerable number of MPS IVA patients in the region, particularly adults, the study mainly focused on MPS IVA management and treatment.

Results

19 experts from 14 Southern and Eastern European countries in total responded to the survey. Results outlined a picture of MPS management in the region, with a high number of MPS patients managed in the centers and a high level of care. MPS II was the most prevalent followed by MPS IVA, with a particular high number of adult patients. The study particularly focused on management and treatment of MPS IVA patients. Adherence to current European Guidelines for follow-up of MPS IVA patients is generally adequate, although some important assessments are reported as difficult due to the lack of MPS skilled specialists. Availability of ERT in Southern and Eastern European countries is generally in line with other European regions, even though regulatory, organizational and reimbursement constrains are demanding.

Conclusions

The landscape of MPS in Southern and Eastern European countries is generally comparable to that of other European regions, regarding epidemiology, treatment accessibility and follow up difficulties. However, issues limiting ERT availability and reimbursement should be simplified, to start treatment as early as possible and make it available for more patients. Besides, educational programs dedicated to specialists should be implemented, particularly for pediatricians, clinical geneticists, surgeons, anesthesiologists and neurologists.

Molecular environment and atypical function: What do we know about enzymes associated with Mucopolysaccharidoses?

Mucopolysaccharidoses are a group of lysosomal storage disorders caused by deficiency of enzymes involved in glycosaminoglycans degradation. Relationship between mucopolysaccharidoses and related enzymes has been clarified clearly. Based on such relationship, lots of therapies have been commercialized or are in the process of research and development. However, many potential treatments failed, because those treatments did not demonstrate expected efficacy or safety data. Molecular environment of enzyme, which is essential for their expression and activity, is fundamental for efficacy of therapy. In addition to enzyme activities, mucopolysaccharidoses-related enzymes have other atypical functions, such as regulation, which may cause side effects. This review tried to discuss molecular environment and atypical function of enzymes that are associated with mucopolysaccharidoses, which is very important for the efficacy and safety of potential therapies.

Hunter Syndrome: The Phenotype of a Rare Storage Disease

Hunter syndrome is a rare lysosomal storage disorder with systemic involvement that occurs over time. Affected patients have coarse facial features, growth retardation with short stature, and skeletal deformities called dysostosis multiplex; joint stiffness, progressive mental retardation, and organomegaly are some of the clinical signs. It ranges from mild to severe manifestations and the distinction between them is related to neurological involvement. Cardiac and respiratory failure is commonly the cause of early death (before adulthood) for severe forms, but those with attenuated forms who have normal cognitive development can survive until late adulthood. Treatment with enzyme replacement therapy is available and can improve the prognosis of this disease. The authors present a case of a 36-year-old male with Hunter syndrome to show not only the clinical features typical of this multisystemic disease that should alert to a prompt investigation but also to remind that treatment must start as early as possible to reach the best outcome. Management of this disease is typically challenging and requires a multidisciplinary approach.

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.

Mucopolysaccharidosis patients have reduced functional capacity

INTRODUCTION

Mucopolysaccharidoses (MPSs) are a group of rare diseases caused by an intralysosomal accumulation of glycosaminoglycans, resulting in a multisystemic clinical condition characterized by variable degrees of physical-functional impairment.

OBJECTIVE

To evaluate the functional capacity (FC) of MPS patients and compare with a healthy control group.

METHODS

This is a cross-sectional study of 6- to 39-year-old patients followed at a medical reference center and compared with their control peers, matched by age and sex. FC was assessed using the Sit-to-Stand Test (SST) and Incremental Shuttle Walk Test (ISWT). Heart rate (HR) and Borg rating of perceived exertion were measured before and after ISWT. HR recovery (HRR) was defined as the HR at the end of the test minus the HR in the second minute after ISWT.

RESULTS

Nineteen (19) MPS patients, 69% with type II MPS and mean age 17 ± 11 years were evaluated. Every patient was under enzyme replacement therapy. The time to perform the SST was longer in the MPS group (10.6 ± 2.5 s vs. 6.7 ± 1.2 s; p < .01). The MPS group achieved lower values of distance covered on the ISWT (407.6 ± 329.8 m vs. 1131.9 ± 183.3 m; p < .01), with a significantly higher Borg (6 [5-8] vs. 2 [1-4]; p = .02). The MPS group's HRR was slower than the controls (32.9 ± 20.2 beats per minute [bpm] vs. 69.1 ± 25.9 bpm; p < .001).

DISCUSSION

We observed a pronounced reduction in the MPS group's FC compared to their healthy peers and a worse HRR after completing the test.

Case Report: Mucopolysaccharidosis Type I Treatment With α-L-Iduronidase Replacement Therapy

Mucopolysaccharidosis is a rare disease and can be divided into seven different subtypes, according to the affected enzyme. Mucopolysaccharidosis type I, the first subtype discovered and reported, mainly affects the in vivo storage of degraded sugar. The current treatment methods are symptomatic therapy, enzyme replacement therapy, and allogeneic hematopoietic stem cell transplantation. In China, the enzyme for the treatment of mucopolysaccharidosis type I was approved in June 2020. We report a case of an 18-month-old Chinese boy with mucopolysaccharidosis type I who received enzyme replacement therapy with concentrated laronidase solution. This is the second case of the disease in China, and the first case of a child under 2 years of age. Following the therapy, urine mucopolysaccharide particle levels were significantly lower, and the patient's symptoms improved. The medical records of Chinese patients who have been treated with enzyme replacement therapy for mucopolysaccharidosis type I also showed similar results. This case demonstrated that enzyme replacement therapy is a safe and effective treatment for patients with mucopolysaccharidosis type I.

Evaluation of Patients Referred to Children's Medical Center Laboratory for Diagnosis of Mucopolysaccharidoses: Eight Years' Experience from Iran

Mucopolysaccharidoses (MPSs) are rare lysosomal storage diseases, resulting from deficiencies of enzymes responsible for Glycosaminoglycans (GAGs) degradation. This leads to accumulation of GAGs in tissues and their excretion in urine, with a wide variety of manifestations. Early diagnosis of MPSs is strictly recommended due to available therapy that can slow down disease progression during the early ages. This study aimed to evaluate patients with suspected MPS referred to Children's Medical Center laboratory over eight years. We also evaluated the usefulness of urine GAG as a screening test for identification of such patients. A total of 1414 patients (40% female, 60% male, with mean age 3.1 ± 4.1years) have participated in this study. The urinary GAG analysis (uGAG) was performed by 1, 9-dimethyl-methylene blue (DMMB) and Berry spot test (BST). All patients with positive and mild positive results or with disease-related symptoms were evaluated in terms of definitive diagnosis, received treatments, morbidity, and mortality rate. In 407 (36.5%) patients uGAG were positive or mild positive, of which 26.3% suffered from one of the types of MPSs, 28.5% suffered from other diseases, 32.9% were undiagnosed, 12.3% were apparently healthy, and 19 died. The negative predictive value of uGAG test in our study was 100%. About 21% of MPSs patients received enzyme replacement therapy, while four patients underwent stem cell transplants. The rest received supportive care. We concluded that a combination of DMMB and BST methods has acceptable sensitivity for screening suspicious MPS patients.

Targeting neurological abnormalities in lysosomal storage diseases

Central nervous system (CNS) abnormalities and corresponding neurological and psychiatric symptoms are frequently observed in lysosomal storage disorders (LSDs). The genetic background of individual LSDs is indeed unique to each illness. However, resulting defective lysosomal function within the CNS can transition normal cellular processes (i.e., autophagy) into aberrant mechanisms, facilitating overlapping downstream consequences including neurocircuitry dysfunction, neurodegeneration as well as sensory, motor, cognitive, and psychological symptoms. Here, the neurological and biobehavioral phenotypes of major classes of LSDs are discussed alongside therapeutic strategies in development that aim to tackle neuropathology among other disease elements. Finally, focused ultrasound blood-brain barrier opening is proposed to enhance therapeutic delivery thereby overcoming the key hurdle of central distribution of disease modifying therapies in LSDs.

Establishing a core outcome set for mucopolysaccharidoses (MPS) in children: study protocol for a rapid literature review, candidate outcomes survey, and Delphi surveys

Background

Mucopolysaccharidoses (MPS) are a group of inherited metabolic diseases characterized by chronic, progressive multi-system manifestations with varying degrees of severity. Disease-modifying therapies exist to treat some types of MPS; however, they are not curative, underscoring the need to identify and evaluate co-interventions that optimize functioning, participation in preferred activities, and quality of life. A Canadian pediatric MPS registry is under development and may serve as a platform to launch randomized controlled trials to evaluate such interventions. To promote the standardized collection of patient/family-reported and clinical outcomes considered important to patients/families, health care providers (HCPs), and policymakers, the choice of outcomes to include in the registry will be informed by a core outcome set (COS). We aim to establish a patient-oriented COS for pediatric MPS using a multi-stakeholder approach.

Methods

In step 1 of the six-step process to develop the COS, we will identify relevant outcomes through a rapid literature review and candidate outcomes survey. A two-phase screening approach will be implemented to identify eligible publications, followed by extraction of outcomes and other pre-specified data elements. Simultaneously, we will conduct a candidate outcomes survey with children with MPS and their families to identify outcomes most important to them. In step 2, HCPs experienced in treating patients with MPS will be invited to review the list of outcomes generated in step 1 and identify additional clinically relevant outcomes. We will then ask patients/families, HCPs, and policymakers to rate the outcomes in a set of Delphi Surveys (step 3), and to participate in a subsequent consensus meeting to finalize the COS (step 4). Step 5 involves establishing a set of outcome measurement instruments for the COS. Finally, we will disseminate the COS to knowledge users (step 6).

Discussion

The proposed COS will inform the choice of outcomes to include in the MPS registry and, more broadly, promote the standardized collection of patient-oriented outcomes for pediatric MPS research. By involving patients/families from the earliest stage of the research, we will ensure that the COS will be relevant to those who will ultimately benefit from the research.

Trial registration

PROSPERO CRD42021267531, COMET

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05791-8.

ADHD symptoms in neurometabolic diseases: Underlying mechanisms and clinical implications

Neurometabolic diseases (NMDs) are typically caused by genetic abnormalities affecting enzyme functions, which in turn interfere with normal development and activity of the nervous system. Although the individual disorders are rare, NMDs are collectively relatively common and often lead to lifelong difficulties and high societal costs. Neuropsychiatric manifestations, including ADHD symptoms, are prominent in many NMDs, also when the primary biochemical defect originates in cells and tissues outside the nervous system. ADHD symptoms have been described in phenylketonuria, tyrosinemias, alkaptonuria, succinic semialdehyde dehydrogenase deficiency, X-linked ichthyosis, maple syrup urine disease, and several mitochondrial disorders, but are probably present in many other NMDs and may pose diagnostic and therapeutic challenges. Here we review current literature linking NMDs with ADHD symptoms. We cite emerging evidence that many NMDs converge on common neurochemical mechanisms that interfere with monoamine neurotransmitter synthesis, transport, metabolism, or receptor functions, mechanisms that are also considered central in ADHD pathophysiology and treatment. Finally, we discuss the therapeutic implications of these findings and propose a path forward to increase our understanding of these relationships.

Identification and structure characterization of novel IDS variants causing mucopolysaccharidosis type II: A retrospective analysis of 30 Chinese children

BACKGROUND

Mucopolysaccharidosis type II (MPS II) or Hunter syndrome is a rare X-linked recessive genetic disease resulting from deficient activity of the iduronate-2-sulfatase(IDS) enzyme and the accumulation of glycosaminoglycans in almost all cells, tissues and organs, which makes viscera function impaired.This study retrospectively analyzed the clinical characteristics, leukocyte IDS activity and mutations in the IDS gene of 30 Chinese children with MPS II.

METHODS

Whole-exome sequencing (WES) was performed on samples of the 30 patients.

RESULTS

A total of 25 mutations were identified in the IDS genes including 16 previously reported and 9 novel mutations (6 frameshift: c.815-818dupAACG, c.1453dupA, c.1270-1271delGT, c.1484-1485insTA, c.854delA, c.12_13delCC;3missense: c.325 T > G, c.140 T > C, c.248 T > G).The computer simulations of the protein structure analysis of the novel missense mutations showed these amino acid replacements (W109G tryptophan replaced by the glycine, L47P leucine replaced by the proline, V83G valine replaced by glycine) near the active site of IDS protein sulfatase domain and would cause a severe impairment of protein structure and function.

CONCLUSIONS

Our study expands the spectrum of MPS II genotype, provides new insights into the molecular mechanisms of MPS II, and contributes to future studies of genotype-phenotypic associations to estimate prognosis and develop new treatment regimens.