Mucopolysaccharidosis type II: European recommendations for the diagnosis and multidisciplinary management of a rare disease

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.

An empowered, clinically viable hematopoietic stem cell gene therapy for the treatment of multisystemic mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II), or Hunter syndrome, is a rare X-linked recessive lysosomal storage disorder due to a mutation in the lysosomal enzyme iduronate-2-sulfatase (IDS) gene. IDS deficiency leads to a progressive, multisystem accumulation of glycosaminoglycans (GAGs) and results in central nervous system (CNS) manifestations in the severe form. We developed up to clinical readiness a new hematopoietic stem cell (HSC) gene therapy approach for MPS II that benefits from a novel highly effective transduction protocol. We first provided proof of concept of efficacy of our approach aimed at enhanced IDS enzyme delivery to the CNS in a murine study of immediate translational value, employing a lentiviral vector (LV) encoding a codon-optimized human IDS cDNA. Then the therapeutic LV was tested for its ability to efficiently and safely transduce bona fide human HSCs in clinically relevant conditions according to a standard vs. a novel protocol that demonstrated superior ability to transduce bona fide long-term repopulating HSCs. Overall, these results provide strong proof of concept for the clinical translation of this approach for the treatment of Hunter syndrome.

Characterization of orthopedic manifestations in patients with mucopolysaccharidosis II using data from 15 years of the Hunter Outcome Survey

Mucopolysaccharidosis II (MPS II) is a rare, life-limiting lysosomal storage disease caused by reduced iduronate-2-sulfatase activity. Patients experience broad ranging signs and symptoms, including bone and joint manifestations. This study reported on orthopedic involvement and management in patients with MPS II using 15 years of data from the Hunter Outcome Survey (HOS). Of the 245 patients in the study population, 90.2% had skeletal deformity (median onset, 2.8 years), 76.7% had upper body stiffness (onset, 4.2 years), and 61.2% had lower body stiffness (onset, 5.3 years); 63.7% of patients had at least three joint manifestations. Orthopedic manifestations were common in adults and children with MPS II, and in patients with and without cognitive impairment. Joint range of motion (JROM) was restricted in all joints assessed (shoulder, elbow, hip, wrist, knee, and ankle). Little correlation was observed between JROM measurements, subjective reports of joint stiffness and limited function, and 6-minute walk test results. Patients with joint stiffness and limited function were generally more likely to have central and peripheral nervous system, pulmonary, and cardiovascular manifestations than those without these symptoms. Carpal tunnel decompression was the most common orthopedic surgery (recorded in 49/245 patients [20.0%]), but orthopedic surgeries were uncommon overall. Our findings highlight the need for routine monitoring of orthopedic manifestations using multiple assessment types in patients with MPS II to help inform clinical decision-making and improve patient quality of life. They also underline the contribution of factors other than orthopedic manifestations to the walking ability of patients with MPS II.

Intracerebroventricular enzyme replacement therapy in patients with neuronopathic mucopolysaccharidosis type II: Final report of 5-year results from a Japanese open-label phase 1/2 study

Intravenous idursulfase is standard treatment for mucopolysaccharidosis II (MPS II) in Japan. In the interim analysis of this open-label, phase 1/2 study (Center for Clinical Trials, Japan Medical Association: JMA-IIA00350), intracerebroventricular (ICV) idursulfase beta was well tolerated, suppressed cerebrospinal fluid (CSF) heparan sulfate (HS) levels, and stabilized developmental decline over 100 weeks in Japanese children with MPS II. Here, we report the final study results, representing 5 years of ICV idursulfase beta treatment. Six male patients with MPS II and developmental delay were enrolled starting in June 2016 and followed until March 2021. Patients received up to 30 mg ICV idursulfase beta every 4 weeks. Outcomes included CSF HS levels, developmental age (DA) (assessed by the Kyoto Scale of Psychological Development), and safety (adverse events). Monitoring by laboratory biochemistry tests, urinary uronic tests, immunogenicity tests, and head computed tomography or magnetic resonance imaging were also conducted regularly. Following ICV idursulfase beta administration, mean CSF HS concentrations decreased from 7.75 μg/mL at baseline to 2.15 μg/mL at final injection (72.3% reduction). Mean DA increased from 23.2 months at screening to 36.0 months at final observation. In five patients with null mutations, mean DA at the final observation was higher than or did not regress compared with that of historical controls receiving intravenous idursulfase only, and the change in DA was greater in patients who started administration aged ≤3 years than in those aged >3 years (+28.7 vs -6.5 months). The difference in DA change versus historical controls in individual patients was +39.5, +40.8, +17.8, +10.5, +7.6 and - 4.5 (mean + 18.6). Common ICV idursulfase beta-related adverse events were vomiting, pyrexia, gastroenteritis, and upper respiratory tract infection (most mild/moderate). These results suggest that long-term ICV idursulfase beta treatment improved neurological symptoms in Japanese children with neuronopathic MPS II.

Neurodevelopmental status and adaptive behavior of pediatric patients with mucopolysaccharidosis II: a longitudinal observational study

BACKGROUND

Mucopolysaccharidosis (MPS) II is a rare, X-linked lysosomal storage disease. Approximately two-thirds of patients have central nervous system involvement with some demonstrating progressive cognitive impairment (neuronopathic disease). The natural history of cognitive and adaptive function in patients with MPS II is not well-defined. This 2-year, prospective, observational study evaluated the neurodevelopmental trajectories of boys with MPS II aged ≥ 2 years and < 18 years.

RESULTS

Overall, 55 patients were enrolled. At baseline, mean (standard deviation [SD]) age was 5.60 (3.32) years; all patients were receiving intravenous idursulfase. Cognitive and adaptive function were assessed using the Differential Ability Scales, Second Edition (DAS-II) General Conceptual Ability (GCA) and the Vineland Adaptive Behavior Scales, Second Edition (VABS-II) Adaptive Behavior Composite (ABC) scores, respectively. Baseline mean (SD) DAS-II GCA and VABS-II ABC scores were 78.4 (19.11) and 83.7 (14.22), respectively, indicating low cognitive function and moderately low adaptive behavior. Over 24 months, modest deteriorations in mean (SD) scores were observed for DAS-II GCA (-3.8 [12.7]) and VABS-II ABC (-2.0 [8.07]). Changes in DAS-II GCA scores varied considerably, and data suggested the existence of four potential patient subgroups: (1) patients with marked early impairment and rapid subsequent decline, (2) patients with marked early impairment then stabilization, (3) patients with mild early impairment then stabilization, and (4) patients without impairment who remained stable. Subgroup analyses revealed numerically greater DAS-II GCA score reductions from baseline in patients aged < 7 years at baseline (vs. those aged ≥ 7 years) and in patients with DAS-II GCA scores ≤ 70 at baseline (vs. those with scores > 70); between-group differences were nonsignificant. No clear subgroups or patterns were identified for individual changes in VABS-II ABC scores. In total, 49 patients (89.1%) reported ≥ 1 adverse event (AE) and nine patients (16.4%) reported serious AEs.

CONCLUSIONS

Some patients with MPS II had rapid declines in cognitive ability, whereas others remained relatively stable after an initial decline. These insights provide a basis for more detailed analyses of different patient subgroups, which may enhance the definition and understanding of factors that influence cognitive and adaptive function in MPS II.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01822184. Registered retrospectively: April 2, 2013.

A post hoc analysis of Projected Retained Ability Scores (PRAS) for the longitudinal assessment of cognitive functioning in patients with neuronopathic mucopolysaccharidosis II receiving intrathecal idursulfase-IT

BACKGROUND

Norm-based scores used to assess cognitive ability have clinical value when describing functioning of patients with neuronopathic disorders compared with unaffected, same-age peers. However, they have limitations when used to assess change in cognitive ability between two timepoints, especially in children with severe cognitive decline. Calculation of Projected Retained Ability Scores (PRAS) is a novel method developed to characterize absolute change in norm-based ability test scores. In this analysis, PRAS were calculated post hoc for children with mucopolysaccharidosis II (MPS II; Hunter syndrome) and early cognitive impairment in a 52-week phase 2/3 randomized controlled trial (RCT) and its extension study of intrathecal idursulfase (idursulfase-IT). Patients completing the first year of the extension after receiving idursulfase-IT in the RCT and extension (n = 32 of 34 enrolled) or the extension only (n = 15 of 15 enrolled) were categorized according to changes in Differential Ability Scales, Second Edition, General Conceptual Ability (DAS-II GCA) scores and PRAS at 1 and 2 years. Analyses were conducted in the overall population and a subpopulation aged < 6 years at baseline (idursulfase-IT in the RCT and extension [n = 27] and extension only [n = 12]).

RESULTS

PRAS methodology differentiated patients with decreases in DAS-II GCA scores into three separate categories reflecting below-average cognitive growth rates, plateauing cognitive development, and deteriorating cognitive functioning. After 1 year in the RCT, 72.4% of patients who initiated idursulfase-IT had above-average or average cognitive growth rates in DAS-II GCA scores compared with 53.3% of those who did not receive idursulfase-IT; 6.9% versus 20.0% experienced deteriorating cognitive functioning. Similar results were seen in children aged < 6 years: 76% (idursulfase-IT group) versus 50% (no idursulfase-IT) had above-average or average cognitive growth rates in DAS-II GCA scores; 4% versus 17% had deteriorating cognitive functioning. The difference in the distributions of cognitive categories at 1 year in children aged < 6 years was significant (p = 0.048). At 2 years, the proportions of patients in different cognitive categories were more similar between treatment groups.

CONCLUSIONS

PRAS methodology may help to differentiate changes in cognitive development in MPS II, and therefore may represent a valuable addition to existing approaches for interpreting changes in cognitive scores over time.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02055118 (registration date: 4 February 2014) and NCT02412787 (registration date: 9 April 2015).

Long-term experience with idursulfase beta (Hunterase) in two adolescent patients with MPS II: A case series

Mucopolysaccharidosis (MPS) type II (Hunter syndrome) is a rare X-linked, recessive, lysosomal storage disorder caused by the deficit of the enzyme iduronate 2-sulfatase (IDS), resulting in accumulation of glycosaminoglycans (GAGs) impairing cellular function in multiple organ systems. Idursulfase (Elaprase, Takeda Pharmaceuticals) and idursulfase beta (Hunterase, GC Biopharma Corp.) are the two currently available enzyme replacement therapies (ERT) for MPS II in Malaysia. ERT in patients with MPS II is associated with improvements in somatic symptoms, pulmonary function, endurance, joint mobility, and quality of life. Though mostly well tolerated, infusion-associated reactions (IARs), such as allergic (IgE-mediated) or nonallergic (non- immunologic) reactions can develop during ERT. In certain cases, when patients develop recurrent IARs despite reduced infusion rate and premedication, either interruption or cessation of ERT might be necessary. However, interruption of ERT is associated with worsening of clinical symptoms such as recurrent respiratory infections, difficulty in standing and walking, and increased joint stiffness, emphasizing the need for continuation of ERT. Here we report successful long-term experience with the use of idursulfase beta in two adolescent Malaysian patients with MPS II, who experienced recurrent infusion-associated reactions warranting discontinuation of ERT with idursulfase.

Alterations of Plasmatic Biomarkers of Neurodegeneration in Mucopolysaccharidosis Type II Patients Under Enzyme Replacement Therapy

Mucopolysaccharidosis type II (MPS II) is a disorder caused by a deficient activity of iduronate-2-sulfatase, a lysosomal enzyme responsible for degrading glycosaminoglycans (GAGs). The abnormal storage of GAGs within lysosomes disrupts cellular homeostasis and leads to a severe symptomatology. Patients present neuropsychiatric impairment characterized by mental retardation and impaired cognition. The aim of this study was to quantify four neurodegeneration biomarkers in plasma: brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF-AA), neural cell adhesion molecule (NCAM) and cathepsin-D, as well as to identify possible correlations with urinary GAGs in seven patients undergoing treatment with ERT (Elaprase® 0.5 mg/kg of body weight). Patients with both severe and attenuated forms of MPS II showed signs of neurodegeneration in neuroimaging exams. Patients have a decrease in BDNF and PDGF-AA concentrations, and an increase in NCAM level compared to controls. No alterations in cathepsin-D concentration were seen. GAGs levels were higher in patients than in controls, but no significant correlations between GAGs and biomarkers were observed. These results evidence that patients have neurodegeneration and that monitoring these biomarkers might be useful for assessing this process. To this date, this is the first work to analyze these plasmatic markers of neurodegeneration in patients.

Diagnosis and Management of Mucopolysaccharidosis Type II (Hunter Syndrome) in Poland

Mucopolysaccharidosis type II (MPS II; also known as Hunter syndrome) is a rare, inherited lysosomal storage disease. The disease is caused by deficiency of the lysosomal enzyme iduronate-2-sulphatase (I2S) due to mutations in the IDS gene, which leads to accumulation of glycosaminoglycans (GAGs). Deficiency of I2S enzyme activity in patients with MPS II leads to progressive lysosomal storage of GAGs in the liver, spleen, heart, bones, joints, and respiratory tract. This process disturbs cellular functioning and leads to multisystemic disease manifestations. Symptoms and their time of onset differ among patients. Diagnosis of MPS II involves assessment of clinical features, biochemical parameters, and molecular characteristics. Life-long enzyme replacement therapy with idursulfase (recombinant human I2S) is the current standard of care. However, an interdisciplinary team of specialists is required to monitor and assess the patient's condition to ensure optimal care. An increasing number of patients with this rare disease reach adulthood and old age. The transition from pediatric care to the adult healthcare system should be planned and carried out according to guidelines to ensure maximum benefit for the patient.

Phenotypic and genetic characteristics of 130 patients with mucopolysaccharidosis type II: A single-center retrospective study in China

Background: Mucopolysaccharidosis Type II (MPS II) is a rare, progressive and ultimately fatal X-linked lysosomal storage disorder caused by mutations in the iduronate-2-sulfatase (IDS) gene. This report conducted a retrospective analysis to investigate the clinical characteristics, genotypes and management strategies in a large cohort of Chinese patients with MPS II. Methods: In this study, we explored 130 Chinese patients with MPS II between September 2008 and April 2022. Clinical manifestations, auxiliary examination, IDS pathogenic gene variants and IDS enzyme activity, surgical history were analysed in the study. Results: A total of 130 patients were enrolled and the mean age at diagnosis was 5 years old. This study found the most common symptoms in our patients were claw-like hands, followed by coarse facial features, birthmarks (Mongolian spot), delayed development, inguinal or umbilical hernia. The most commonly cardiac manifestations were valve abnormalities, which were mitral/tricuspid valve regurgitation (71.9%) and aortic/pulmonary valve regurgitation (36.8%). We had found 43 different IDS pathogenic gene variants in 55 patients, included 16 novel variants. The variants were concentrated in exon 9 (20% = 11/55), exon 3 (20% = 11/55) and exon 8 (15% = 8/55). A total of 50 patients (38.5%) underwent surgical treatment, receiving a total of 63 surgeries. The average age of first surgery was 2.6 years, and the majority of surgery (85.7%, 54/63) was operated before 4 years old. The most common and earliest surgery was hernia repair. Three patients were died of respiratory failure. Conclusion: This study provided additional information on the clinical, cardiac ultrasound and surgical procedure in MPS II patients. Our study expanded the genotype spectrum of MPS II. Based on these data, characterization of MPS II patients group could be used to early diagnosis and treatment of the disease.

Circulatory C-type natriuretic peptide reduces mucopolysaccharidosis-associated craniofacial hypoplasia in vivo

Skeletal alterations in the head and neck region, such as midfacial hypoplasia, foramen magnum stenosis and spinal canal stenosis, are commonly observed in patients with mucopolysaccharidosis (MPS). However, enzyme replacement therapy (ERT), one of the major treatment approaches for MPS, shows limited efficacy for skeletal conditions. In this study, we analysed the craniofacial morphology of mice with MPS type VII, and investigated the underlying mechanisms promoting jaw deformities in these animals. Furthermore, we investigated the effects of C-type natriuretic peptide (CNP), a potent endochondral ossification promoter, on growth impairment of the craniofacial region in MPS VII mice when administered alone or in combination with ERT. MPS VII mice exhibited midfacial hypoplasia caused by impaired endochondral ossification, and histological analysis revealed increased number of swelling cells in the resting zone of the spheno-occipital synchondrosis (SOS), an important growth centre for craniomaxillofacial skeletogenesis. We crossed MPS VII mice with transgenic mice in which CNP was expressed in the liver under the control of the human serum amyloid-P component promoter, resulting in elevated levels of circulatory CNP. The maxillofacial morphological abnormalities associated with MPS VII were ameliorated by CNP expression, and further prevented by a combination of CNP and ERT. Histological analysis showed that ERT decreased the swelling cell number, and CNP treatment increased the width of the proliferative and hypertrophic zones of the SOS. Furthermore, the foramen magnum and spinal stenoses observed in MPS VII mice were significantly alleviated by CNP and ERT combination. These results demonstrate the therapeutic potential of CNP, which can be used to enhance ERT outcome for MPS VII-associated head and neck abnormalities.

Effect of Anti-Iduronate 2-Sulfatase Antibodies in Patients with Mucopolysaccharidosis Type II Treated with Enzyme Replacement Therapy

OBJECTIVE

To assess the relationship between anti-Iduronate 2-sulfatase (IDS) antibodies, IDS genotypes, phenotypes and their impact in patients with enzyme replacement therapy (ERT)-treated Mucopolysaccharidosis type II.

STUDY DESIGN

Dutch patients treated with ERT were analyzed in this observational cohort study. Antibody titers were determined by enzyme-linked immunosorbent assay. Neutralizing effects were measured in fibroblasts. Pharmacokinetic analysis of ERT was combined with immunoprecipitation. Urinary glycosaminoglycans were measured using mass spectrometry and dimethylmethylene blue.

RESULTS

Eight of 17 patients (47%) developed anti-IDS antibodies. Three patients with the severe, neuronopathic phenotype, two of whom did not express IDS protein, showed sustained antibodies for up to 10 years of ERT. Titers of 1:5120 or greater inhibited cellular IDS uptake and/or intracellular activity in vitro. In 1 patient who was neuronopathic with a titer of 1:20 480, pharmacokinetic analysis showed that all plasma recombinant IDS was antibody bound. This finding was not the case in 2 patients who were not neuronopathic with a titer of 1:1280 or less. Patients with sustained antibody titers showed increased urinary glycosaminoglycan levels compared with patients with nonsustained or no-low titers.

CONCLUSIONS

Patients with the neuronopathic form and lack of IDS protein expression were most at risk to develop sustained anti-IDS antibody titers, which inhibited IDS uptake and/or activity in vitro, and the efficacy of ERT in patients by lowering urinary glycosaminoglycan levels.

Intrathecal idursulfase-IT in patients with neuronopathic mucopolysaccharidosis II: Results from a phase 2/3 randomized study

Two-thirds of patients with mucopolysaccharidosis II (MPS II; Hunter syndrome) have cognitive impairment. This phase 2/3, randomized, controlled, open-label, multicenter study (NCT02055118) investigated the effects of intrathecally administered idursulfase-IT on cognitive function in patients with MPS II. Children older than 3 years with MPS II and mild-to-moderate cognitive impairment (assessed by Differential Ability Scales-II [DAS-II], General Conceptual Ability [GCA] score) who had tolerated intravenous idursulfase for at least 4 months were randomly assigned (2:1) to monthly idursulfase-IT 10 mg (n = 34) via an intrathecal drug delivery device (IDDD; or by lumbar puncture) or no idursulfase-IT treatment (n = 15) for 52 weeks. All patients continued to receive weekly intravenous idursulfase 0.5 mg/kg as standard of care. Of 49 randomized patients, 47 completed the study (two patients receiving idursulfase-IT discontinued). The primary endpoint (change from baseline in DAS-II GCA score at week 52 in a linear mixed-effects model for repeated measures analysis) was not met: although there was a smaller decrease in DAS-II GCA scores with idursulfase-IT than with no idursulfase-IT at week 52, this was not significant (least-squares mean treatment difference [95% confidence interval], 3.0 [-7.3, 13.3]; p = 0.5669). Changes from baseline in Vineland Adaptive Behavioral Scales-II Adaptive Behavior Composite scores at week 52 (key secondary endpoint) were similar in the idursulfase-IT (n = 31) and no idursulfase-IT (n = 14) groups. There were trends towards a potential positive effect of idursulfase-IT across DAS-II composite, cluster, and subtest scores, notably in patients younger than 6 years at baseline. In a post hoc analysis, there was a significant (p = 0.0174), clinically meaningful difference in change from baseline in DAS-II GCA scores at week 52 with idursulfase-IT (n = 13) versus no idursulfase-IT (n = 6) among those younger than 6 years with missense iduronate-2-sulfatase gene variants. Overall, idursulfase-IT reduced cerebrospinal glycosaminoglycan levels from baseline by 72.0% at week 52. Idursulfase-IT was generally well tolerated. These data suggest potential benefits of idursulfase-IT in the treatment of cognitive impairment in some patients with neuronopathic MPS II. After many years of extensive review and regulatory discussions, the data were found to be insufficient to meet the evidentiary standard to support regulatory filings.

Assessment, pharmacological therapy and rehabilitation management of musculoskeletal pain in children with mucopolysaccharidoses: a scoping review

Background

Pain of musculoskeletal origin is very common in young patients affected by Mucopolysaccharidoses. This scoping review evaluates the evidence for assessment, pharmacological treatment and rehabilitation management for musculoskeletal pain of the latter.

Methods

A Medline search through PubMed has been performed for studies published in English at least for the past twenty years. Two investigators independently reviewed all search results and extracted those that met the inclusion criteria.

Results

29 studies have been selected and analysed in depth, of which 10 related to pain assessment, 11 concerned pharmacological approach, and 8 reported rehabilitation approaches.

Conclusion

Few data are available in literature concerning the classification and management of pain in children with Mucopolysaccharidoses. Notwithstanding, pain evaluation methods are effectively used to classify pain intensity, according to the age group and communication abilities of young Mucopolysaccharidoses patients. The review emphasizes that drug therapies have a palliative purpose, while rehabilitation reduces musculoskeletal pain and can provide a therapeutic effect on disabilities.

Anaesthesia-Relevant Disease Manifestations and Perianaesthetic Complications in Patients with Mucolipidosis—A Retrospective Analysis of 44 Anaesthetic Cases in 12 Patients

Mucolipidosis (ML) type II, intermediate, and III are lysosomal storage disorders with progressive multiorgan manifestations predisposing patients to a high risk of perioperative morbidity. The aims of the study were to systematically assess disease manifestations relevant to anaesthesia as well as anaesthesia-related complications. This retrospective study includes ML patients who underwent anaesthesia in two centres between 2008 and 2022. We reviewed patients’ demographics, medical history, disease manifestations, as well as procedure- and outcome-related data. A total of 12 patients (7 MLII, 2 ML intermediate, 3 MLIII) underwent 44 anaesthesia procedures (per patient: median 3, range 1–11). The median age was 3.3 years (range 0.1–19.1). At least one complication occurred in 27.3% of the anaesthesia procedures. The vast majority of complications (94%) occurred in children with MLII and ML intermediate. A predicted difficult airway was found in 100% and 80% of the MLII and ML intermediate patients, respectively. Accordingly, most complications (59%) occurred during the induction of anaesthesia. Altogether, respiratory complications were the most frequent (18%), followed by difficult airway management (14%). The risk for anaesthesia-related complications is alarmingly high in patients with ML, particularly in those with MLII and ML intermediate. Multidisciplinary risk–benefit analysis and thoughtful anaesthesia planning are crucial in these patients.

New Indications for Hematopoietic Stem Cell Gene Therapy in Lysosomal Storage Disorders

Lysosomal storage disorders (LSDs) are a heterogenous group of disorders due to genetically determined deficits of lysosomal enzymes. The specific molecular mechanism and disease phenotype depends on the type of storage material. Several disorders affect the brain resulting in severe clinical manifestations that substantially impact the expectancy and quality of life. Current treatment modalities for LSDs include enzyme replacement therapy (ERT) and hematopoietic cell transplantation (HCT) from allogeneic healthy donors, but are available for a limited number of disorders and lack efficacy on several clinical manifestations. Hematopoietic stem cell gene therapy (HSC GT) based on integrating lentiviral vectors resulted in robust clinical benefit when administered to patients affected by Metachromatic Leukodystrophy, for whom it is now available as a registered medicinal product. More recently, HSC GT has also shown promising results in Hurler syndrome patients. Here, we discuss possible novel HSC GT indications that are currently under development. If these novel drugs will prove effective, they might represent a new standard of care for these disorders, but several challenges will need to be addresses, including defining and possibly expanding the patient population for whom HSC GT could be efficacious.

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.

Iduronate-2-sulfatase interactome: Validation by Yeast Two-Hybrid Assay

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is a rare X-linked recessive disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS), which activates intracellular accumulation of nonmetabolized glycosaminoglycans such as heparan sulfate and dermatan sulfate. This accumulation causes severe damage to several tissues, principally the central nervous system. Previously, we identified 187 IDS-protein interactions in the mouse brain. To validate a subset of these interactions, we selected and cloned the coding regions of 10 candidate genes to perform a targeted yeast two-hybrid assay. The results allowed the identification of the physical interaction of IDS with LSAMP and SYT1. Although the physiological relevance of these complexes is unknown, recent advances allow us to point out that these interactions could be involved in vesicular trafficking of IDS through the interaction with SYT1, as well as to the ability to form a transcytosis module between the cellular components of the blood-brain-barrier (BBB) through its interaction with LSAMP. These results may shed light on the role of IDS on cellular homeostasis and may also contribute to the understanding of MPS II physiopathology and the development of novel therapeutic strategies to transport recombinant IDS through the brain endothelial cells toward the brain parenchyma.

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.

Transcatheter aortic valve implantation for severe aortic stenosis in a patient with mucopolysaccharidosis type II (Hunter syndrome) accompanied by severe airway obstruction

Mucopolysaccharidosis type II, known as Hunter syndrome, is a rare inherited metabolic disorder with glycosaminoglycan accumulation leading to progressive multisystem involvement, such as heart, respiratory, and central nervous systems. In particular, concurrence of major heart and respiratory problems in this syndrome often causes difficulty in performing curative and invasive treatments. Transcatheter aortic valve implantation (TAVI) has been an established therapy for severe aortic stenosis (AS). In patients who cannot undergo surgical aortic valve replacement because of high risk for general anesthesia, TAVI with local anesthesia has become an alternative therapy for severe AS. We report herein a case of 50-year-old man with Hunter syndrome accompanied by severe airway obstruction who underwent TAVI with local anesthesia for severe AS. <Learning objective: Mucopolysaccharidosis is characterized by glycosaminoglycan accumulation leading to progressive multisystem involvement. Heart disease and respiratory problems are often concomitant in patients with mucopolysaccharidosis. When surgical treatment is required, consideration about treatment strategy and perioperative management are important because of its high surgical risk or inoperable status. We describe a case with mucopolysaccharidosis accompanied by severe airway obstruction who underwent transcatheter aortic valve implantation with local anesthesia for severe aortic stenosis.>.

Assessment of the function and morphology of the thyroid gland in paediatric patients treated with enzyme replacement therapy due to selected storage diseases - preliminary results of our own research and a review of the literature

INTRODUCTION

Some storage diseases, caused by a deficiency of a specific enzyme, which results in the systemic accumulation of non-metabolized substances, can be treated with enzyme replacement therapy (ERT), which can protect many organs, including the endocrine system.

AIM

The aim of the study was to assess the function and morphology of the thyroid gland in children with storage diseases treated with ERT, and to review the literature.

MATERIAL AND METHODS

Eight patients were included in the study: 3 with Fabry disease (age: 17; 9.9; 10 years), 3 with Hunter's disease (12.3; 4.1; 9,3), and 2 with Pompe disease (6.8; 9,5). Thyroid function and morphology were assessed in each patient during ERT, and 4 of them were reassessed 27 months later.

RESULTS

One patient with Fabry disease had been treated for hypothyroidism due to autoimmune thyroiditis diagnosed before the study. The remaining patients had normal thyroid tests and negative anti-thyroid antibodies at first and second evaluation; however, in all reassessed patients a decrease in TSH value was noted. Among the remaining patients with Fabry disease, one had normal and a second had heterogeneous echogenicity of the thyroid during first assessment. In the second patient, normalisation of echogenicity was observed at reassessment. Both patients with Pompe disease assessed once had slightly heterogeneous thyroid echogenicity. In 3 patients with Hunter's disease in the first ultrasound examination, no abnormalities were found. In re-evaluation, 2 of them showed heterogeneous thyroid echogenicity.

CONCLUSIONS

We conclude that patients with storage diseases should undergo assessment of thyroid function and morphology before and during ERT.

[The combination of recurrent otitis media and adenotomy in early childhood as diagnostic marker of mucopolysaccharidosis type II (Hunter syndrome)]

Mucopolysaccharidoses are a group of rare lysosomal accumulation diseases caused by a deficiency of the lysosomal enzyme and the accumulation of mucopolysaccharides in various organs and tissues. Children with mucopolysaccharidosis type II (Hunter syndrome) develop multisystem dysfunction, including severe airway obstruction. At the same time, 34% of patients already at an early age (2-3 years) undergo surgical manipulations related to ENT organs (tonsillectomy, adenotomy). The article describes a clinical case of diagnosis of type II mucopolysaccharidosis by a pediatric otorhinolaryngologist. The main manifestations of the disease are discussed in detail, including the presence of indications for adenotomy at the age of 2 years, episodes of otitis media, which served as diagnostic markers for suspected orphan disease mucopolysaccharidosis type II. The leading role of the pediatric otorhinolaryngologist in the early diagnosis of the rare disease mucopolysaccharidosis type II is substantiated.

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.

Evaluation of the long-term treatment effects of intravenous idursulfase in patients with mucopolysaccharidosis II (MPS II) using statistical modeling: data from the Hunter Outcome Survey (HOS)

BACKGROUND

Mucopolysaccharidosis II (MPS II; Hunter syndrome) is a rare, life-limiting lysosomal storage disease caused by deficient iduronate-2-sulfatase activity. Enzyme replacement therapy (ERT) with intravenous (IV) idursulfase can stabilize or improve many somatic manifestations, but there remains a need for further analysis of long-term treatment outcomes. Using data from patients with MPS II enrolled in the Hunter Outcome Survey (HOS), mixed modeling was performed to evaluate and predict the effects of IV idursulfase treatment on selected clinical parameters for up to 8 years following treatment start. The modeling population comprised male patients followed prospectively in HOS who had received IV idursulfase for at least 5 years and who had data available for two or more time points (at least one post-ERT). Age at ERT start and time since ERT start were included as covariates.

RESULTS

In total, 481 patients were eligible for inclusion in at least one model. At 8 years post-ERT start, improvement from baseline was predicted for each age group (< 18 months, 18 months to < 5 years and ≥ 5 years at treatment start) in the following parameters: mean urinary glycosaminoglycan levels (percentage changes of > -75% in each group), mean left ventricular mass index (decreases of ~ 1 g/m2) and mean palpable liver size (decreases of > 2 cm). Improvements in mean 6-min walk test distance (increase of > 50 m) and stabilization in percent predicted forced vital capacity and forced expiratory volume in 1 s (decreases of ~ 4 and ~ 9 percentage points, respectively) at 8 years post-ERT start were predicted for patients aged ≥ 5 years at ERT start (these assessments are unsuitable for patients aged < 5 years). Predicted changes over time were similar across the three age groups; however, overall outcomes were most favorable in children aged < 18 months at ERT start.

CONCLUSIONS

These findings suggest that the previously reported positive effects of IV idursulfase on the somatic manifestations of MPS II are predicted to be maintained for at least 8 years following ERT initiation and highlight the value of statistical modeling to predict long-term treatment outcomes in patients with rare diseases.

Functional results after carpal tunnel release in mucopolysaccharidosis

BACKGROUND

Mucopolysaccharidosis consists of a group of diseases caused by the deficiency of lysosomal enzymes, which may lead to the compression of the median nerve in the carpal tunnel due to the accumulation of glycosaminoglycan, resulting in the hand disability. The study purpose is to present functional results of carpal tunnel release in mucopolysaccharidosis patients. Patients were selected from an enzyme replacement group in the Department of Pediatric Neurology. The legal guardians of the patients were informed about the likely functional change of the hands induced by compression of the median nerve. Clinical evaluation was performed in those patients who received their legal guardians' consent to participate and was included inspection, assessment of functional level, wrinkle test and the digital pinch function to manipulate small and large objects. Ultrasound and electromyography were performed to confirm the clinical median nerve compression. Bilateral extended opening technique was performed to access the carpal tunnel and analyze the anatomic findings of the median nerve and the flexed tendons of the fingers. After the surgical release of the carpal tunnel, the clinical evaluation was repeated. Subjective observations of the legal guardians were also considered.

RESULTS

Seven patients underwent bilateral surgical opening of the carpal tunnel; six boys, mean age of 9.5 (5 to 13), five of them presenting Type II mucopolysaccharidosis, 1 Type I and 1 Type VI. The average follow-up was 12 months (10-13 months). The functional results observed included the improvement in the handling of small and large objects in all children who underwent decompression of the median nerve. The comparison between the pre-operative and post-operative functional levels revealed that 2 patients evolved from Level II to IV, 3 from Level III to IV, 1 from Level IV to V and 1 patient remained in Level III. Tenosynovitis around the flexor tendons and severe compression of the median nerve in the fourteen carpal tunnels were observed during the surgical procedure. In 6 wrists, partial tenosynovitis was performed.

CONCLUSIONS

Despite the improvement in the overall function of the children' hands, we cannot conclude that only surgery was responsible for the benefit. Better designed studies are required.

A unique case of skeletal dysplasia in an adult male in Late Iron Age Switzerland

OBJECTIVE

We report a probable case of multiple skeletal dysplasia observed in a Late Iron Age young adult male.

MATERIALS

The individual studied belongs to a Late Iron Age necropolis from Switzerland. The skeletal elements are well preserved METHODS: Macroscopic and radiographic assessment.

RESULTS

The individual shows evidence of both craniofacial and mandibular deformation. Developmental defects are also visible with effects on the general shape and articular surfaces of both humeri, as well as the left femur and tibia.

CONCLUSION

We propose that the lesions observed are manifestations of skeletal dysplasia, such as pseudo-achondroplasia or multiple epiphyseal dysplasia.

SIGNIFICANCE

This is the first recorded case of multiple skeletal dysplasia in an Iron Age necropolis in Switzerland, questioning the integration of physically compromised individuals in La Tène society.

LIMITATIONS

Examination of other skeletal dysplasias from archaeological contexts provides support for this diagnosis.

SUGGESTIONS FOR FUTURE RESEARCH

The integration of individuals with disabilities in La Tène societies is still poorly understood and further research is needed to better characterize these communities.

Gene Therapy for Neuronopathic Mucopolysaccharidoses: State of the Art

The need for long-lasting and transformative therapies for mucopolysaccharidoses (MPS) cannot be understated. Currently, many forms of MPS lack a specific treatment and in other cases available therapies, such as enzyme replacement therapy (ERT), do not reach important areas such as the central nervous system (CNS). The advent of newborn screening procedures represents a major step forward in early identification and treatment of individuals with MPS. However, the treatment of brain disease in neuronopathic MPS has been a major challenge to date, mainly because the blood brain barrier (BBB) prevents penetration of the brain by large molecules, including enzymes. Over the last years several novel experimental therapies for neuronopathic MPS have been investigated. Gene therapy and gene editing constitute potentially curative treatments. However, despite recent progress in the field, several considerations should be taken into account. This review focuses on the state of the art of in vivo and ex vivo gene therapy-based approaches targeting the CNS in neuronopathic MPS, discusses clinical trials conducted to date, and provides a vision for the future implications of these therapies for the medical community. Recent advances in the field, as well as limitations relating to efficacy, potential toxicity, and immunogenicity, are also discussed.

Differences in MPS I and MPS II Disease Manifestations

Mucopolysaccharidosis (MPS) type I and II are two closely related lysosomal storage diseases associated with disrupted glycosaminoglycan catabolism. In MPS II, the first step of degradation of heparan sulfate (HS) and dermatan sulfate (DS) is blocked by a deficiency in the lysosomal enzyme iduronate 2-sulfatase (IDS), while, in MPS I, blockage of the second step is caused by a deficiency in iduronidase (IDUA). The subsequent accumulation of HS and DS causes lysosomal hypertrophy and an increase in the number of lysosomes in cells, and impacts cellular functions, like cell adhesion, endocytosis, intracellular trafficking of different molecules, intracellular ionic balance, and inflammation. Characteristic phenotypical manifestations of both MPS I and II include skeletal disease, reflected in short stature, inguinal and umbilical hernias, hydrocephalus, hearing loss, coarse facial features, protruded abdomen with hepatosplenomegaly, and neurological involvement with varying functional concerns. However, a few manifestations are disease-specific, including corneal clouding in MPS I, epidermal manifestations in MPS II, and differences in the severity and nature of behavioral concerns. These phenotypic differences appear to be related to different ratios between DS and HS, and their sulfation levels. MPS I is characterized by higher DS/HS levels and lower sulfation levels, while HS levels dominate over DS levels in MPS II and sulfation levels are higher. The high presence of DS in the cornea and its involvement in the arrangement of collagen fibrils potentially causes corneal clouding to be prevalent in MPS I, but not in MPS II. The differences in neurological involvement may be due to the increased HS levels in MPS II, because of the involvement of HS in neuronal development. Current treatment options for patients with MPS II are often restricted to enzyme replacement therapy (ERT). While ERT has beneficial effects on respiratory and cardiopulmonary function and extends the lifespan of the patients, it does not significantly affect CNS manifestations, probably because the enzyme cannot pass the blood-brain barrier at sufficient levels. Many experimental therapies, therefore, aim at delivery of IDS to the CNS in an attempt to prevent neurocognitive decline in the patients.

A review of the clinical outcomes in idursulfase-treated and untreated Filipino patients with mucopolysaccharidosis type II: data from the local lysosomal storage disease registry

BACKGROUND

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked multisystem disorder characterized by glycosaminoglycan (GAG) accumulation, caused by a deficiency of iduronate-2-sulfatase (I2S). Enzyme replacement therapy (ERT) with recombinant idursulfase (IDS), the standard of care, was started in the Philippines in 2017. This study reviewed the clinical outcomes in idursulfase-treated and untreated Filipino MPS II patients who were included in the local Lysosomal Storage Disease (LSD) registry of the Institute of Human Genetics-National Institutes of Health (IHG-NIH) from January 1999 to December 2019.

METHODS

A retrospective audit of records of MPS II patients listed in the registry was done. Qualified patients were divided into two cohorts: idursulfase-treated group (patients on enzyme replacement therapy, ERT, for ≥ 6 months) and untreated group. Baseline characteristics, including demographic data, biochemical results, neurocognitive classification, respiratory involvement, mortality, and adverse events, were recorded. Height, weight, cardiac pathology, liver and spleen sizes, six-minute walking test (6MWT), joint mobility, were determined at baseline and at year 1 and 2 of follow up.

RESULTS

Forty male patients were included in this review, with only 8 receiving ERT since 2017. The mean age at diagnosis was 6.99 years (SD 4.15; 0.75-20) and mean age at start of ERT was 14.03 years (SD 7.1; 4-21.5), more delayed than previous reports. Eighty percent have early progressive phenotype which was higher than reported average. The early growth pattern differed in our Filipino cohort, but was followed by the expected slowed growth in later years. Improvements in the following endpoints were observed in the treated cohort: height and weight, cardiac disease, liver and spleen sizes, and joint mobility. There were also positive effects on respiratory involvement and mortality rate. Adverse events were consistent with previous reports.

CONCLUSIONS

ERT is generally well tolerated and effective in reducing GAG storage and improving clinical endpoints among our Filipino MPS II patients. In untreated patients, typical disease progression was observed.

A molecular genetics view on Mucopolysaccharidosis Type II

Mucopolysaccharidosis Type II (MPS II) is an X-linked recessive genetic disorder that primarily affects male patients. With an incidence of 1 in 100,000 male live births, the disease is one of the orphan diseases. MPS II symptoms are caused by mutations in the lysosomal iduronate-2-sulfatase (IDS) gene. The mutations cause a loss of enzymatic performance and result in the accumulation of glycosaminoglycans (GAGs), heparan sulfate and dermatan sulfate, which are no longer degradable. This inadvertent accumulation causes damage in multiple organs and leads either to a severe neurological course or to an attenuated course of the disease, although the exact relationship between mutation, extent of GAG accumulation and disease progression is not yet fully understood. This review is intended to present current diagnostic procedures and therapeutic interventions. In times when the genetic profile of patients plays an increasingly important role in the assessment of therapeutic success and future drug design, we chose to further elucidate the impact of genetic diversity within the IDS gene on disease phenotype and potential implications in current diagnosis, prognosis and therapy. We report recent advances in the structural biological elucidation of I2S enzyme that that promises to improve our future understanding of the molecular damage of the hundreds of IDS gene variants and will aid damage prediction of novel mutations in the future.

Therapy-type related long-term outcomes in mucopolysaccaridosis type II (Hunter syndrome) - Case series

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare, X-linked recessive multisystem lysosomal storage disease due to iduronate-2-sulfatase enzyme deficiency. We presented three unrelated Slovenian patients with the severe form of MPS II that received three different management approaches: natural course of the disease without received specific treatment, enzyme replacement therapy (ERT), and hematopoietic stem cell transplantation (HSCT). The decision on the management depended on disease severity, degree of cognitive impairment, and parent's informed decision. The current benefits of MPS II treatments are limited. The lifelong costly intravenous ERT brings significant benefits but the patients with severe phenotypes and neurological involvement progress to cognitive decline and disability regardless of ERT, as demonstrated in published reviews and our case series. The patient after HSCT was the only one of the three cases reported to show a slowly progressing cognitive development. The type of information from the case series is insufficient for generalized conclusions, but with advanced myeloablative conditioning, HSCT may be a preferred treatment option in early diagnosed MPS II patients with the severe form of the disease and low disease burden at the time of presentation.

The Impact of Excluding Nonrandomized Studies From Systematic Reviews in Rare Diseases: "The Example of Meta-Analyses Evaluating the Efficacy and Safety of Enzyme Replacement Therapy in Patients With Mucopolysaccharidosis"

Nonrandomized studies are usually excluded from systematic reviews. This could lead to loss of a considerable amount of information on rare diseases. In this article, we explore the impact of excluding nonrandomized studies on the generalizability of meta-analyses results on mucopolysaccharidosis (MPS) disease. A comprehensive search of systematic reviews on MPS patients up to May 2020 was carried out (CRD42020191217). The primary endpoint was the rate of patients excluded from systematic reviews if only randomized studies were considered. Secondary outcomes included the differences in patient and study characteristics between randomized and nonrandomized studies, the methods used to combine data from studies with different designs, and the number of patients excluded from systematic reviews if case reports were not considered. More than 50% of the patients analyzed have been recruited in nonrandomized studies. Patient characteristics, duration of follow-up, and the clinical outcomes evaluated differ between the randomized and nonrandomized studies. There are feasible strategies to combine the data from different randomized and nonrandomized designs. The analyses suggest the relevance of including case reports in the systematic reviews, since the smaller the number of patients in the reference population, the larger the selection bias associated to excluding case reports. Our results recommend including nonrandomized studies in the systematic reviews of MPS to increase the representativeness of the results and to avoid a selection bias. The recommendations obtained from this study should be considered when conducting systematic reviews on rare diseases.

Clinical assessment of upper airway and its complications in Hunter syndrome

BACKGROUND

Hunter syndrome (HS) is an X-linked, recessive, lysosomal storage disease caused by a deficiency of the lysosomal enzyme, iduronate sulfatase (IDS). It is characterized by multisystem accumulations of glycosaminoglycans and upper airway obstruction is one of the major causes of death. While the current disease severity classifications for HS are mainly based on the degree of neurocognitive impairment, its association with the level of upper airway obstruction has not been assessed.

METHODS

A retrospective chart review of HS patients who were followed at the Jikei University School of Medicine was performed. Association between the degree of airway obstruction and the currently used disease severity scores was evaluated.

RESULTS

We identified eight HS patients and they were enrolled in the study. The Modified Mallampati classification (MMC) score, used to predict difficulties for oropharyngeal procedures, was significantly correlated with the HS severity. It was also correlated with the Apnea-Hypopnea Index (AHI). No significant correlation between IDS enzymatic activity and the severity of HS disease was identified.

CONCLUSIONS

Variable clinical expressivities exist in HS, but the risk of respiratory complications is likely to be associated with disease severity, assessed by the previously recognized neurocognitive function-based severity scoring systems. MMC can be a simple supplementary tool to evaluate disease severity as well as predict difficulties for oropharyngeal procedures and respiratory function complications in HS, such as sleep apnea.

Dosage Compensation in Females with X-Linked Metabolic Disorders

Through the use of new genomic and metabolomic technologies, our comprehension of the molecular and biochemical etiologies of genetic disorders is rapidly expanding, and so are insights into their varying phenotypes. Dosage compensation (lyonization) is an epigenetic mechanism that balances the expression of genes on heteromorphic sex chromosomes. Many studies in the literature have suggested a profound influence of this phenomenon on the manifestation of X-linked disorders in females. In this review, we summarize the clinical and genetic findings in female heterozygotic carriers of a pathogenic variant in one of ten selected X-linked genes whose defects result in metabolic disorders.

Impact of intracerebroventricular enzyme replacement therapy in patients with neuronopathic mucopolysaccharidosis type II

This open-label, phase 1/2 study (JMACCT CTR JMA-IIA00350) evaluated the efficacy and safety of intracerebroventricular idursulfase beta in patients with mucopolysaccharidosis II (MPS II). Herein, we report the 100-week results. Six patients with severe MPS II aged 23-65 months were enrolled. Idursulfase beta (increasing from 1 to 30 mg between weeks 0 and 24, followed by a 30-mg final dose) was administered intracerebroventricularly once every 4 weeks using an implanted cerebrospinal fluid (CSF) reservoir; intravenous administration of idursulfase was also continued throughout the study. Efficacy endpoints included developmental age by the Kyoto Scale of Psychological Development 2001 and heparan sulfate (HS) concentration in CSF (primary outcome). In all six patients, HS concentrations decreased (40%-80%) from baseline to week 100. For overall developmental age, the difference in change from baseline to week 100 in each patient compared with patients treated by intravenous idursulfase administration (n = 13) was +8.0, +14.5, +4.5, +3.7, +8.2, and -8.3 months (mean, +5.1 months). Idursulfase beta was well tolerated. The most common adverse events were pyrexia, upper respiratory tract infection, and vomiting. The results suggest that intracerebroventricular idursulfase beta is well tolerated and can be effective at preventing and stabilizing developmental decline in patients with neuronopathic MPS II.

Natural progression of cardiac features and long-term effects of enzyme replacement therapy in Taiwanese patients with mucopolysaccharidosis II

Background

Cardiac abnormalities have been observed in patients with mucopolysaccharidosis type II (MPS II). The aim of this study was to investigate the cardiac features and natural progression of Taiwanese patients with MPS II, and evaluate the impact of enzyme replacement therapy (ERT) on cardiac structure and function.

Methods

The medical records and echocardiograms of 48 Taiwanese patients with MPS II (median age, 6.9 years; age range, 0.1–27.9 years) were reviewed. The relationships between age and each echocardiographic parameter were analyzed.

Results

The mean z-scores of left ventricular mass index (LVMI), interventricular septum diameter in diastole (IVSd), left ventricular posterior wall diameter in diastole (LVPWd), and aortic diameter were 1.10, 2.70, 0.95 and 1.91, respectively. Z scores > 2 were identified in 33%, 54%, 13%, and 46% for LVMI, IVSd, LVPWd, and aortic diameter, respectively. The most prevalent cardiac valve abnormality was mitral regurgitation (MR) (56%), followed by aortic regurgitation (AR) (33%). The severity of mitral stenosis (MS), MR, aortic stenosis (AS), AR, and the existence of valvular heart disease were all positively correlated with increasing age (p < 0.01). We also compared the echocardiographic parameters between two groups: (1) 12 patients who had up to 17 years of follow-up echocardiographic data without ERT, and (2) nine patients who had up to 12 years of follow-up data with ERT. The results showed that z-score changes of LVMI significantly improved in the patients who received ERT compared to those who did not receive ERT (0.05 versus 1.52, p < 0.05). However, the severity score changes of MS, MR, AS, and AR all showed gradual progression in both groups (p > 0.05).

Conclusions

High prevalence rates of valvular heart disease and cardiac hypertrophy were observed in the MPS II patients in this study. The existence and severity of cardiac hypertrophy and valvular heart disease in these patients worsened with increasing age, reinforcing the concept of the progressive nature of this disease. ERT for MPS II appeared to be effective in stabilizing or reducing the progression of cardiac hypertrophy, but it only had a limited effect on valvulopathy.

IMPACT study: measuring the impact of caregiving on families and healthcare professionals of children and adults living with mucopolysaccharidoses in Ireland

Introduction

Disease trajectories are often uncertain among individuals living with mucopolysaccharidoses (MPS) due to the progressive nature of the illness and the goal of care. This study investigated the impact on caregivers and care providers of children and adults living with MPS.

Methods

The study used a cross-sectional design and a convenience sampling strategy which involved two sequential study components. The stage 1 quantitative component included three validated scales: the abbreviated World Health Organization Quality of Life (WHOQOL-BREF), the Paediatric Inventory for Parents (PIP) and the 14-item Resilience Scale (RS-14). The stage 2 qualitative component consisted of two focus groups with healthcare professionals (HCPs) (n = 9) working with children and adults living with MPS across three clinical sites in Ireland. Data were collected between November 2017 and July 2019.

Results

A total of 31 parents identified as caregivers participated in this study. The mean quality of life (QoL) score was 93.81, indicating a significantly high QoL. The PIP frequency total mean was 102.74 and difficulty mean 104.94. The mean score for the RS-14 was notably high, 81.42 out of a maximum of 98. The majority of the results showed high levels of concern for the future, with just under 50% finding themselves very often feeling scared that their child's condition will deteriorate or that their child will die and finding these thoughts very difficult. The healthcare professionals' (HCPs) perceptions were focused on the complexity of MPS, coping strategies, managing expectations and support services.

Conclusion

The overall findings of the study reinforced the need for sustained and enhanced psychological support to ensure both families of children and adults living with MPS and the HCPs are supported in the continued delivery of quality patient care and outcomes. Subjective and objective measures from family caregivers and HCPs yield results that can decrease stress and improve psychological support.

Plain language summary

Impact of caregiving on families and healthcare professionals of children and adults living with mucopolysaccharidoses in Ireland Mucopolysaccharidoses (MPS) is a group of one of the many rare inherited metabolic disorders that come under category three of life-limiting conditions. Children born with this genetic condition show no change at birth, but effects start to show in subsequent years as it is a progressive disease. The severity of the condition varies according to the specific type, ranging from very mild symptoms to, in most cases, multisystemic, restricted growth or mental and physical disabilities. Recent developments in treatments for some forms of MPS have dramatically changed the quality of life (QoL) for patients. Other forms of treatment are currently under investigation and development. This study aimed to provide a detailed and reliable evidence base on the impact of caregiving for patients living with MPS on family caregivers and healthcare providers. Paper questionnaires were completed by the family caregivers of children and adults living with MPS. These three questionnaires focused on measuring QoL, parental stress and anxiety, and resilience among these families. Two focus group interviews were carried out with healthcare professionals working with children and adults living with MPS across three clinical sites in Ireland.A total of 31 parents completed the questionnaires in this study, indicating a significantly high QoL and notably high resilience. The majority of the parental stress results were related to concern for the future, with just half of the families finding themselves very often scared that their child's condition will deteriorate or that their child will die and find these thoughts very difficult. The healthcare providers also spoke about the complexity of MPS, coping strategies, managing expectations and support services for the families of children and adults living with MPS. This study provided evidence for clinicians and policymakers to improve the availability of appropriate healthcare provisions for people living with MPS and their families.

Mucopolysaccharidosis Type II: A Kenyan Case Series

Hunter syndrome, or mucopolysaccharidosis type 2 (MPS2), is a lysosomal storage disorder associated with the involvement of multiple organs such as the central nervous system, hepatomegaly, musculoskeletal, respiratory, cardiac, and hearing. This is due to the accumulation of glycosaminoglycans in body tissues leading to organ failure. Since the laboratories in Kenya do not screen for metabolic diseases, there is the likelihood of assumption that these patients do not exist. These first cases were referred from the eastern part of Kenya where the majority of inhabitants are from the same ethnic community. It was noted that there was increased mortality among boys below the age of 20 years, and hence, the families sought for help in the national referral and teaching hospital. The case series is meant to show that these cases exist and the majority of the patients may be dying before the diagnosis is made. There are no data on MPS2 from Kenya, and the prevalence and incidence are unknown. In this retrospective study, we present a case series of 6 Kenyan boys with MPS2 from a national referral hospital. They were part of 17 patients who had had their blood analyzed for metabolic diseases. All of them were symptomatic with varying degrees of central nervous system involvement. They had undetectable levels of iduronate-2-sulfatase (I2S) enzyme, and three genetic mutations were detected in the IDS gene.

Occurrence of Inborn Errors of Metabolism in Newborns, Diagnosis and Prophylaxis

Inborn errors of metabolism (IEM) are a heterogeneous group of rare genetic disorders that are generally transmitted as autosomal or X-linked recessive disorders. These defects arise due to mutations associated with specific gene(s), especially the ones associated with key metabolic enzymes. These enzymes or their product(s) are involved in various metabolic pathways, leading to the accumulation of intermediary metabolite(s), reflecting their toxic effects upon mutations. The diagnosis of these metabolic disorders is based on the biochemical analysis of the clinical manifestations produced and their molecular mechanism. Therefore, it is imperative to devise diagnostic tests with high sensitivity and specificity for early detection of IEM. Recent advances in biochemical and polymerase chain reaction-based genetic analysis along with pedigree and prenatal diagnosis can be life-saving in nature. The latest development in exome sequencing for rapid diagnosis and enzyme replacement therapy would facilitate the successful treatment of these metabolic disorders in the future. However, the longterm clinical implications of these genetic manipulations is still a matter of debate among intellectuals and requires further research.

Mucopolysaccharidoses I and II: Brief Review of Therapeutic Options and Supportive/Palliative Therapies

Purpose. Mucopolysaccharidoses (MPS) are group of inherited lysosomal storage diseases caused by mutations of enzymes involved in catalyzing different glycosaminoglycans (GAGs). MPS I and MPS II exhibit both somatic and neurological symptoms with a relatively high disease incidence. Hematopoietic stem cell therapy (HSCT) and intravenous enzyme replacement therapy (ERT) have had a significant impact on the treatment and comprehension of disease. This review is aimed at providing a comprehensive evaluation of the pros and cons of HSCT and ERT, as well as an up-to-date knowledge of new drugs under development. In addition, multiple disease management strategies for the uncontrollable manifestations of MPS I and MPS II to improve patients' quality of life are presented. Findings. Natural history of MPS I and MPS II shows that somatic and neurological symptoms occur earlier in severe forms of MPS I than in MPS II. ERT increases life expectancy and alleviates some of the somatic symptoms, but musculoskeletal, ophthalmological, and central nervous system (CNS) manifestations are not controlled. Additionally, life-long treatment burdens and immunogenicity restriction are unintended consequences of ERT application. HSCT, another treatment method, is effective in controlling the CNS symptoms and hence has been adopted as the standard treatment for severe types of MPS I. However, it is ineffective in MPS II, which can be explained by the relatively late diagnosis. In addition, several factors such as transplant age limits or graft-versus-host disease in HSCT have limited its application for patients. Novel therapies, including BBB-penetrable-ERT, gene therapy, and substrate reduction therapy, are under development to control currently unmanageable manifestations. BBB-penetrable-ERT is being studied comprehensively in the hopes of being used in the near future as a method to effectively control CNS symptoms. Gene therapy has the potential to “cure” the disease with a one-time treatment rather than just alleviate symptoms, which makes it an attractive treatment strategy. Several clinical studies on gene therapy reveal that delivering genes directly into the brain achieves better results than intravenous administration in patients with neurological symptoms. Considering new drugs are still in clinical stage, disease management with close monitoring and supportive/palliative therapy is of great importance for the time being. Proper rehabilitation therapy, including physical and occupational therapy, surgical intervention, or medications, can benefit patients with uncontrolled musculoskeletal, respiratory, ophthalmological, and neurological manifestations.

CNS-Targeting Therapies for Lysosomal Storage Diseases: Current Advances and Challenges

During the past decades, several therapeutic approaches have been developed and made rapidly available for many patients afflicted with lysosomal storage disorders (LSDs), inborn organelle disorders with broad clinical manifestations secondary to the progressive accumulation of undegraded macromolecules within lysosomes. These conditions are individually rare, but, collectively, their incidence ranges from 1 in 2,315 to 7,700 live-births. Most LSDs are manifested by neurological symptoms or signs, including developmental delay, seizures, acroparesthesia, motor weakness, and extrapyramidal signs. The chronic and later-onset clinical forms are at one end of the continuum spectrum and are characterized by a subtle and slow progression of neurological symptoms. Due to its inherent physiological properties, unfortunately, the blood-brain barrier (BBB) constitutes a significant obstacle for current and upcoming therapies to achieve the central nervous system (CNS) and treat neurological problems so prevalent in these conditions. To circumvent this limitation, several strategies have been developed to make the therapeutic agent achieve the CNS. This narrative will provide an overview of current therapeutic strategies under development to permeate the BBB, and address and unmet need for treatment of the progressive neurological manifestations, which are so prevalent in these inherited lysosomal disorders.

Allogeneic hematopoietic stem cell transplant in rare hematologic disorders: a single center experience from Pakistan

Management of rare hematological disorders pose unique diagnostic and therapeutic challenges due to unusual occurrence and limited treatment options. We retrospectively identified 45 patients receiving matched related donor transplant for rare hematological disorders from 2006 to 2019. Patients were divided into two groups (1) malignant and (2) non malignant. The malignant disorder group included four patients while the nonmalignant group included 41 patients divided into immune dysregulation (n = 23), bone marrow failure (n = 10), metabolic (n = 5), and bleeding diathesis (n = 3). Twenty-six (57.8%) patients received myeloablative conditioning (MAC) and 16 (35.6%) received reduced intensity conditioning (RIC), while 3 (6.6%) patients with severe combined immunodeficiency received stem cell infusion alone without conditioning. The cumulative incidence (CI) of grade II-IV acute GVHD (aGVHD) was 39.1% (n = 18) and chronic GVHD (cGVHD) 15.2% (n = 7). There was no primary graft failure while CI of secondary graft failure was 9%. Overall survival (OS) and disease-free survival (DFS) was 82.2% and 77.8% respectively. Group wise OS was 75% in the malignant group, 82.6% in the immune dysregulation group, 80% in patients with metabolic disorders and bone marrow failure, while 100% in patients with bleeding diathesis. This retrospective analysis shows that hematopoietic stem cell transplant can be a feasible treatment option for rare hematological disorders.

Therapeutic Options for Mucopolysaccharidosis II (Hunter Disease)

BACKGROUND

Mucopolysaccharidosis type II (Hunter syndrome, or MPS II) is an X-linked lysosomal disorder caused by the deficiency of iduronate-2-sulfatase, which leads to the accumulation of glycosaminoglycans (GAGs) in a variety of tissues, resulting in a multisystemic disease that can also impair the central nervous system (CNS).

OBJECTIVE

This review focuses on providing the latest information and expert opinion about the therapies available and under development for MPS II.

METHODS

We have comprehensively revised the latest studies about hematopoietic stem cell transplantation (HSCT), enzyme replacement therapy (ERT - intravenous, intrathecal, intracerebroventricular, and intravenous with fusion proteins), small molecules, gene therapy/genome editing, and supportive management.

RESULTS AND DISCUSSION

Intravenous ERT is a well-established specific therapy, which ameliorates the somatic features but not the CNS manifestations. Intrathecal or intracerebroventricular ERT and intravenous ERT with fusion proteins, presently under development, seem to be able to reduce the levels of GAGs in the CNS and have the potential of reducing the impact of the neurological burden of the disease. Gene therapy and/or genome editing have shown promising results in preclinical studies, bringing hope for a "one-time therapy" soon. Results with HSCT in MPS II are controversial, and small molecules could potentially address some disease manifestations. In addition to the specific therapeutic options, supportive care plays a major role in the management of these patients.

CONCLUSION

At this time, the treatment of individuals with MPS II is mainly based on intravenous ERT, whereas HSCT can be a potential alternative in specific cases. In the coming years, several new therapy options that target the neurological phenotype of MPS II should be available.

[Clinical experience with orphan drugs for rare metabolic diseases]

INTRODUCTION

Inborn errors of metabolism are a highly heterogeneous group of orphan diseases. Diet therapy and enzyme and coenzyme replacement are the most frequently used treatment. There are few patients and published studies about inborn errors of metabolism. The main objective of this study was to describe the effectiveness of orphan drugs in inborn errors of metabolism in paediatric patients.

MATERIAL AND METHODS

Retrospective descriptive study of 24 months on patients diagnosed with inborn errors of metabolism during childhood and who attended the pharmacy clinic or Day-Care Unit of a 630-bed general hospital.

RESULTS

The study included 15 patients with a median age of 17.8 years and were treated with nine different drugs: sapropterin, sodium phenylbutyrate, miglustat, velaglucerase, sebelipase, idursulfase, 5-hydroxytryptophan, succinate, and riboflavin. Nine different inborn errors of metabolism were observed: phenylketonuria, defects of the urea cycle, Gaucher, Nieman-Pick, Hunter's disease, along with acid lipase deficiency, and mitochondrial diseases. Orphan drugs used for the treatment of inborn errors of metabolism accounted for 1.3% of hospital drug costs. Some orphan drugs achieved asymptomatic patients, but others just produced a modest symptomatic improvement. Most patients showed good tolerance to the treatment.

CONCLUSIONS

Orphan drugs used in inborn errors of metabolism had an easy to manage toxicity profile, with many disparities in effectiveness. These drugs have a high economic impact. The cost-effectiveness ratio for orphan drugs is a controversial issue due to their high cost and the inconclusive clinical evidence.

The Value of Case Reports in Systematic Reviews from Rare Diseases. The Example of Enzyme Replacement Therapy (ERT) in Patients with Mucopolysaccharidosis Type II (MPS-II)

BACKGROUND

Case reports are usually excluded from systematic reviews. Patients with rare diseases are more dependent on novel individualized strategies than patients with common diseases. We reviewed and summarized the novelties reported by case reports in mucopolysaccharidosis type II (MPS-II) patients treated with enzyme replacement therapy (ERT).

METHODS

We selected the case reports included in a previous meta-analysis of patients with MPS-II treated with ERT. Later clinical studies evaluating the same topic of those case reports were reported. Our primary aim was to summarize novelties reported in previous case reports. Secondary objectives analyzed the number of novelties evaluated in subsequent clinical studies and the time elapsed between the publication of the case report to the publication of the clinical study.

RESULTS

We identified 11 innovative proposals in case reports that had not been previously considered in clinical studies. Only two (18.2%) were analyzed in subsequent nonrandomized cohort studies. The other nine novelties (81.8%) were analyzed in later case reports (five) or were not included in ulterior studies (four) after more than five years from their first publication.

CONCLUSIONS

Case reports should be included in systematic reviews of rare disease to obtain a comprehensive summary of the state of research and offer valuable information for healthcare practitioners.

Current Practices for U.S. Newborn Screening of Pompe Disease and MPSI

Two lysosomal storage disorders (LSDs), Pompe disease and Mucopolysaccharidosis type I (MPSI) were added to the Recommended Uniform Screening Panel (RUSP) for newborn screening (NBS) in 2015 and 2016, respectively. These conditions are being screened with variable practice in terms of primary and reflex analytes (either biochemical or molecular testing) as well as collection of short- and long-term follow-up elements. The goal of this study is to evaluate practices of state health departments in regards to screening methods and follow-up data collected. We conducted online surveys and phone questionnaires to determine each U.S. state's practices for screening and follow-up of positive newborn screens. We report the first snapshot of practices for NBS for the LSDs included on the RUSP. All 50 U.S. states responded to our survey. The majority of U.S. states are not currently screening for Pompe disease and MPSI as of March 2020, but this number will increase to 38 states in the coming 1-3 years based on survey results. Our survey identifies data elements used by state health departments for short-and long-term follow-up that could serve as the basis of common elements for larger, public health-based analyses of the benefits and efficacy of screening for Pompe disease and MPSI.

Case report of endoprosthesis -Y implantation in severe respiratory failure in the MPSII patient; comparison with literature data

Background

The tracheobronchomalacia is a life-threatening complication of mucopolysaccharidosis (MPS) without known effective, optimal treatment. The severe expiratory collapse of the trachea and bronchi is one of causes of the high rate of deaths in the course of airway impairment in MPSII patients.

Case presentation

Due to the adynamic tracheobronchomalacia despite of enzymatic treatment (ERT) in our MPSII patient, a life-saving tracheal bifurcated type-Y endoprosthesis (a self-expanding, metal stent for the prosthesis of tracheal and bronchial stenosis) was implanted. In the followed months, the breathing efficiency improved, but then gradual worsening, progression of bronchi occlusion at the stent border resulted in patient’s death.

Conclusion

The Y-stent implantation appears to be a short-term, life-saving solution without satisfactory long-term effects due to the progress of peripheral bronchomalacia and increased tissue proliferation and granulation, that arises during the illness’ course.