Mortality in patients with Sanfilippo syndrome

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

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

The Role of the Gut Microbiota in Sanfilippo Syndrome's Physiopathology: An Approach in Two Affected Siblings

Sanfilippo syndrome, or mucopolysaccharidosis type III (MPS III), is a rare lysosomal disease caused by congenital enzymatic deficiencies in heparan sulfate (HS) degradation, leading to organ dysfunction. The most severe hallmark of MPS III comprises neurological alterations, although gastrointestinal symptoms (GISs) have also been shown to be relevant in many patients. Here, we explored the contribution of the gut microbiota to MPS III GISs. We analyzed the composition and functionality of the gut microbiota in two MPS III siblings with the same mutation (c.544C > T, c.1080delC, in the SGSH gene) and the same diet, but with differences in their GISs, including recurrent diarrhea in one of them. Using 16S sequencing, we observed that the MPS III patients exhibited decreased alpha diversity and a lower abundance of Lachnospiraceae and Bifidobacteriaceae accompanied by a higher abundance of the Ruminococcaceae and Rikenellaceae families than the healthy control subjects. Comparing siblings, we found an increased abundance of Bacteroidaceae and a lower abundance of Ruminococcaceae and Akkermansiaceae in the GIS-free patient. This patient also had a higher relative abundance of Sus genes (SusA, SusB, SusE, and SusG) involved in glycosaminoglycan metabolism. We found higher HS levels in the stool of the two MPS III patients than in healthy volunteers, particularly in the patient with GISs. Functionally, whole fecal metabolites from the patient with GISs induced oxidative stress in vitro in healthy monocytes. Finally, the Bacteroides thetaiotaomicron strain isolated from MPS III stool samples exhibited HS degradation ability. Overall, our results reveal different microbiota compositions and functionalities in MPS III siblings, who exhibited differential gastrointestinal symptomatology. Our study may serve as a gateway to explore the impact of the gut microbiota and its potential to enhance the quality of life in Sanfilippo syndrome patients.

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.

AAV gene replacement therapy for treating MPS IIIC: Facilitating bystander effects via EV-mRNA cargo

MPS IIIC is a lysosomal storage disease caused by mutations in heparan-α-glucosaminide N-acetyltransferase (HGSNAT), for which no treatment is available. Because HGSNAT is a trans-lysosomal-membrane protein, gene therapy for MPS IIIC needs to transduce as many cells as possible for maximal benefits. All cells continuously release extracellular vesicles (EVs) and communicate by exchanging biomolecules via EV trafficking. To address the unmet need, we developed a rAAV-hHGSNATEV vector with an EV-mRNA-packaging signal in the 3'UTR to facilitate bystander effects, and tested it in an in vitro MPS IIIC model. In human MPS IIIC cells, rAAV-hHGSNATEV enhanced HGSNAT mRNA and protein expression, EV-hHGSNAT-mRNA packaging, and cleared GAG storage. Importantly, incubation with EVs led to hHGSNAT protein expression and GAG contents clearance in recipient MPS IIIC cells. Further, rAAV-hHGSNATEV transduction led to the reduction of pathological EVs in MPS IIIC cells to normal levels, suggesting broader therapeutic benefits. These data demonstrate that incorporating the EV-mRNA-packaging signal into a rAAV-hHGSNAT vector enhances EV packaging of hHGSNAT-mRNA, which can be transported to non-transduced cells and translated into functional rHGSNAT protein, facilitating cross-correction of disease pathology. This study supports the therapeutic potential of rAAVEV for MPS IIIC, and broad diseases, without having to transduce every cell.

Mucopolysaccharidosis (MPS IIIA) mice have increased lung compliance and airway resistance, decreased diaphragm strength, and no change in alveolar structure

Mucopolysaccharidosis type IIIA (MPS IIIA) is characterized by neurological and skeletal pathologies caused by reduced activity of the lysosomal hydrolase, sulfamidase, and the subsequent primary accumulation of undegraded heparan sulfate (HS). Respiratory pathology is considered secondary in MPS IIIA and the mechanisms are not well understood. Changes in the amount, metabolism, and function of pulmonary surfactant, the substance that regulates alveolar interfacial surface tension and modulates lung compliance and elastance, have been reported in MPS IIIA mice. Here we investigated changes in lung function in 20-wk-old control and MPS IIIA mice with a closed and open thoracic cage, diaphragm contractile properties, and potential parenchymal remodeling. MPS IIIA mice had increased compliance and airway resistance and reduced tissue damping and elastance compared with control mice. The chest wall impacted lung function as observed by an increase in airway resistance and a decrease in peripheral energy dissipation in the open compared with the closed thoracic cage state in MPS IIIA mice. Diaphragm contractile forces showed a decrease in peak twitch force, maximum specific force, and the force-frequency relationship but no change in muscle fiber cross-sectional area in MPS IIIA mice compared with control mice. Design-based stereology did not reveal any parenchymal remodeling or destruction of alveolar septa in the MPS IIIA mouse lung. In conclusion, the increased storage of HS which leads to biochemical and biophysical changes in pulmonary surfactant also affects lung and diaphragm function, but has no impact on lung or diaphragm structure at this stage of the disease.NEW & NOTEWORTHY Heparan sulfate storage in the lungs of mucopolysaccharidosis type IIIA (MPS IIIA) mice leads to changes in lung function consistent with those of an obstructive lung disease and includes an increase in lung compliance and airway resistance and a decrease in tissue elastance. In addition, diaphragm muscle contractile strength is reduced, potentially further contributing to lung function impairment. However, no changes in parenchymal lung structure were observed in mice at 20 wk of age.

Expanding the phenotypic and genotypic spectrum of patients with HGSNAT-related retinopathy

BACKGROUND

Variants in HGSNAT have historically been associated with syndromic mucopolysaccharidosis type IIIC (MPSIIIC) but more recent studies demonstrate cases of HGSNAT-related non-syndromic retinitis pigmentosa. We describe and expand the genotypic and phenotypic spectrum of this disease.

MATERIALS AND METHODS

This is a retrospective, observational, case series of 11 patients with pericentral retinitis pigmentosa due to variants in HGSNAT gene without a syndromic diagnosis of MPSIIIC. We reviewed ophthalmologic data extracted from medical records, genetic testing, color fundus photos, fundus autofluorescence (FAF), and optical coherence tomography (OCT).

RESULTS

Of the 11 patients, the mean age was 52 years (range: 26-78). The mean age of ophthalmologic symptoms onset was 45 years (range: 15-72). The visual acuity varied from 20/20 to 20/80 (mean 20/30 median 20/20). We described five novel variants in HGSNAT: c.715del (p.Arg239Alafs *37), c.118 G>A (p.Asp40Asn), c.1218_1220delinsTAT, c.1297A>G (p.Asn433Asp), and c.1726 G>T (p.Gly576*).

CONCLUSIONS

HGSNAT has high phenotypic heterogeneity. Data from our cohort showed that all patients who had at least one variant of c.1843 G>A (p.Ala615Thr) presented with the onset of ocular symptoms after the fourth decade of life. The two patients with onset of ocular symptoms before the fourth decade did not carry this variant. This may suggest that c.1843 G>A variant is associated with a later onset of retinopathy.

Successful use of an eye gaze AAC communication board by a young adult with advanced Sanfilippo Syndrome (MPS IIIA): Case report

Sanfilippo syndrome (Mucopolysaccharidosis Type III or MPS III) is a family of rare, lysosomal disorders characterized by progressive cognitive and motor deterioration. Even though individuals with MPS III present with complex communication needs, research regarding augmentative and alternative communication (AAC) in this population is scarce. While life expectancy for individuals with MPS IIIA typically does not exceed 20 years of age, this case report involves a 22-year-old adult with postregression MPS IIIA. Prior to this study, the participant could not communicate using speech and only responded to yes/no questions using eye blink responses. The participant was given a low-tech AAC system utilizing eye gaze so that she could respond to a variety of caregiver questions and take conversational turns. The following communication outcomes were measured during each session in which caregivers used the AAC system: number of eye gaze responses, total number of responses (using any means), the percent of responses to questions asked, and the total count of expressive vocabulary words available to the participant with the AAC system. Increases were observed in the number of eye gaze responses per session and in the expressive vocabulary accessible via the eye gaze board. A higher percentage of responses given caregiver questions was noted for the intervention sessions (71%) compared to the baseline sessions (55%). There were also qualitative changes characterized by the types of questions the participant could respond to during conversational exchanges. Despite the progression of MPS IIIA, the results suggest that use of the eye gaze board resulted in quantitative and qualitative changes in functional communication. This case report provides preliminary evidence that AAC can improve communication in a young adult with postregression MPS IIIA.

Ultra-rare ultra-care: Assessing the impact of caring for children with ultra rare diseases

BACKGROUND

We sought to assesses the impact of caring for children with ultra rare diseases (URDs) on family carers and to analyse the way these experiences differ among the caregivers of children diagnosed through prenatal or newborn screening, and those with symptom-based diagnosis.

METHODS

A total of 200 caregivers of 219 URDs children completed an on-line survey regarding the challenges and experiences of caregivers of URDs children.

RESULTS

The majority of URD caregivers felt burdened by their children's health problems, emotional and behavioural changes. 46.5% reported feelings of care overload, 43% coped poorly with the stress, and many experienced a variety of feelings of distress towards the role of caregiver. While most caregivers struggled with the diagnostic odyssey and were dissatisfied with the healthcare services for URD children, caregivers of children diagnosed through prenatal or newborn screening were significantly less burdened than the parents of children with symptom-based diagnoses.

CONCLUSION

Although caregivers of URDs children experience physical and emotional strain, they are often neglected by the healthcare system. A bio-psychosocial approach to URDs should therefore also include family caregivers' physical and psychosocial needs. Apart from financial and emotional support, enhancing access to genetic testing and newborn screening should be prioritised.

Economic Burden of Sanfilippo Syndrome in the United States

Introduction

Sanfilippo syndrome is a rare disease and fatal genetic disorder with no FDA-approved treatment in the United States (US), and no comprehensive assessment of economic disease burden is available.

Objectives

To develop a model to estimate the economic burden associated with Sanfilippo syndrome in the US using direct costs, indirect costs and valued intangibles (disability-adjusted life years, or DALYs) from 2023 onward.

Design and Setting

A multistage comorbidity model was generated based on Sanfilippo syndrome symptoms, and disability weights from the 2010 Global Burden of Disease Study. Attributable increase in caregiver mental health burden were estimated using data from the CDC National Comorbidity Survey and retrospective studies on caregiver burden. Direct costs were approximated from the 2019 EveryLife Foundation survey, and indirect costs were estimated from Federal income data. Monetary valuations were adjusted to USD 2023 and given a 3% discount rate from 2023 onward.

Main Outcome Measures

Incidence of Sanfilippo syndrome was calculated for each year, and year-over-year DALYs due to patient years lived with disability (YLDs) and years life lost (YLLs) were calculated by comparing to the health-adjusted life expectancy (HALE) in the US. Direct and indirect costs were calculated for each simulated patient from onset of symptoms to death.

Results

From 2023-2043, overall economic burden in the US attributable to Sanfilippo syndrome was estimated to be $2.04 billion USD present value (2023) with current standard of care. The burden to individual families exceeded $8 million present value from time of birth per child born with Sanfilippo syndrome.

Conclusion

Sanfilippo syndrome is a rare lysosomal storage disease, however the severe burden associated with the disease for individual families demonstrates a considerable cumulative impact. Our model represents the first disease burden value estimate associated with Sanfilippo syndrome, and underscores the substantial morbidity and mortality burden of Sanfilippo syndrome.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Disease correction in mucopolysaccharidosis type IIIB mice by intraparenchymal or cisternal delivery of a capsid modified AAV8 codon-optimized NAGLU vector

Mucopolysaccharidosis type IIIB (MPS IIIB) is an autosomal recessive lysosomal storage disease caused by mutations in the gene that encodes the protein N-acetyl-glucosaminidase (NAGLU). Defective NAGLU activity results in aberrant retention of heparan sulfate within lysosomes leading to progressive central nervous system (CNS) degeneration. Intravenous treatment options are limited by the need to overcome the blood-brain barrier and gain successful entry into the CNS. Additionally, we have demonstrated that AAV8 provides a broader transduction area in the MPS IIIB mouse brain compared with AAV5, 9 or rh10. A triple-capsid mutant (tcm) modification of AAV8 further enhanced GFP reporter expression and distribution. Using the MPS IIIB mouse model, we performed a study using either intracranial six site or intracisterna magna injection of AAVtcm8-codon-optimized (co)-NAGLU using untreated MPS IIIB mice as controls to assess disease correction. Disease correction was evaluated based on enzyme activity, heparan sulfate storage levels, CNS lysosomal signal intensity, coordination, activity level, hearing and survival. Both histologic and enzymatic assessments show that each injection method results in supranormal levels of NAGLU expression in the brain. In this study, we have shown correction of lifespan and auditory deficits, increased CNS NAGLU activity and reduced lysosomal storage levels of heparan sulfate following AAVtcm8-coNAGLU administration and partial correction of NAGLU activity in several peripheral organs in the murine model of MPS IIIB.

Neurological, neurobehavioral, and radiological alterations in patients with mucopolysaccharidosis III (Sanfilippo's syndrome) in Brazil

Mucopolysaccharidosis type III (MPS III) or Sanfilippo syndrome is the most common form of MPS, in which neurological involvement in all stages of the disease is prominent. The current study aimed to comprehensively describe the neurological profile of children and adolescents with MPS III who visited the largest pediatric hospital in South America. A prospective/retrospective cohort analysis was performed on 10 patients with MPS III from eight unrelated families. Most patients <12 months of age had achieved development milestones within the expected range for their age, with delay in walking independently and first single word acquisition. Behavioral symptoms were reported in seven patients. Eight patients (80%) developed profound intellectual disabilities. Six patients (60%) had epilepsy, among whom 75% had their first seizure between 2 and 4 years of age; the frequency of which increased with age. Monotherapy was effective in 60% of patients. Two patients, both aged <8 years, had normal baseline electroencephalographic activity. Epileptiform activity was observed in three patients. Cortical atrophy was visualized using magnetic resonance imaging in 71% patients; all but one of these patients were aged >6 years. Neurological abnormalities increased in prevalence and severity with age. Anti-seizure drug resistance was uncommon. Dysmorphological and systemic manifestations were uncommon and mild and did not correlate with neurological involvement. Despite high allelic heterogeneity, neurodegeneration was similar among all patients. Overall, these data contribute to the scarce literature from developing countries.

Sanfilippo syndrome: consensus guidelines for clinical care

Sanfilippo syndrome is a group of rare, complex, and progressive neurodegenerative lysosomal storage disorders that is characterized by childhood dementia. The clinical management of patients with progressive neurological decline and multisystem involvement requires a multidisciplinary team with experience in the management of neurodegenerative disorders. Best practice guidelines for the clinical management of patients with these types of rare disorders are critical to ensure prompt diagnosis and initiation of appropriate care. However, there are no published standard global clinical care guidelines for patients with Sanfilippo syndrome. To address this, a literature review was conducted to evaluate the current evidence base and to identify evidence gaps. The findings were reviewed by an international steering committee composed of clinical experts with extensive experience in managing patients with Sanfilippo syndrome. The goal was to create a consensus set of basic clinical guidelines that will be accessible to and informed by clinicians globally, as well as providing a practical resource for families to share with their local care team who may not have experience with this rare disease. This review distills 178 guideline statements into an easily digestible document that provides evidence-based, expert-led recommendations for how to approach common management challenges and appropriate monitoring schedules in the care of patients with Sanfilippo syndrome.

Longitudinal Natural History of Pediatric Subjects Affected with Mucopolysaccharidosis IIIB

OBJECTIVE

To characterize the longitudinal natural history of disease progression in pediatric subjects affected with mucopolysaccharidosis (MPS) IIIB.

STUDY DESIGN

Sixty-five children with a confirmed diagnosis of MPS IIIB were enrolled into 1 of 2 natural history studies and followed for up to 4 years. Cognitive and adaptive behavior functions were analyzed in all subjects, and volumetric magnetic resonance imaging analysis of liver, spleen, and brain, as well as levels of heparan sulfate (HS) and heparan sulfate nonreducing ends (HS-NRE), were measured in a subset of subjects.

RESULTS

The majority of subjects with MPS IIIB achieved an apex on both cognition and adaptive behavior age equivalent scales between age 3 and 6 years. Development quotients for both cognition and adaptive behavior follow a linear trajectory by which subjects reach a nadir with a score <25 for an age equivalent of 24 months by age 8 years on average and by 13.5 years at the latest. All tested subjects (n = 22) had HS and HS-NRE levels above the normal range in cerebrospinal fluid and plasma, along with signs of hepatomegaly. Subjects lost an average of 26 mL of brain volume (-2.7%) over 48 weeks, owing entirely to a loss of cortical gray matter (32 mL; -6.5%).

CONCLUSIONS

MPS IIIB exists along a continuum based on cognitive decline and cortical gray matter atrophy. Although a few individuals with MPS IIIB have an attenuated phenotype, the majority follow predicted trajectories for both cognition and adaptive behavior.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers NCT02493998, NCT03227042, and NCT02754076.

Chemically modified recombinant human sulfamidase (SOBI003) in mucopolysaccharidosis IIIA patients: Results from an open, non-controlled, multicenter study

PURPOSE

Mucopolysaccharidosis IIIA (MPS IIIA) is an inherited lysosomal storage disorder caused by mutations in the N-sulfoglucosamine sulfohydrolase gene that result in deficient enzymatic degradation of heparan sulfate (HS), resulting in progressive neurodegeneration in early childhood and premature death. A chemically modified variant of recombinant human sulfamidase, SOBI003, has shown to cross the blood-brain barrier (BBB) in mice and achieve pharmacologically relevant levels in cerebrospinal fluid (CSF). We report on a phase 1/2, open-label, first-in-human (FIH) study (NCT03423186) and its extension study (NCT03811028) to evaluate the long-term safety, tolerability, pharmacokinetics/pharmacodynamics (PK/PD) and clinical efficacy of SOBI003 in patients with MPS IIIA for up to 104 weeks.

METHODS

Six patients aged 1-6 years with confirmed MPS IIIA with developmental age ≥ 12 months received weekly intravenous injections of SOBI003 at 3 mg/kg (Cohort 1, n = 3) or 10 mg/kg (Cohort 2, n = 3). During the extension study, the individual dose of SOBI003 could be adjusted up to 20 mg/kg at the discretion of the investigator.

RESULTS

SOBI003 was generally well tolerated. Serum concentrations of SOBI003 increased in proportion to dose, and presence in CSF confirmed that SOBI003 crosses the BBB. Anti-drug antibodies (ADA) were detected in serum and CSF in all patients, with subsequent reductions in serum SOBI003 exposure at high ADA titers. SOBI003 exerted a clear PD effect: a mean reduction in HS levels in CSF of 79% was recorded at the last assessment, together with reductions in HS levels in serum and urine. Neurocognitive development age-equivalent scores showed a stabilization of cognition for all patients, whereas no clear overall clinical effect was observed on adaptive behavior, sleep pattern or quality of life.

CONCLUSION

SOBI003 was well tolerated when administered as weekly intravenous infusions at doses of up to 20 mg/kg for up to 104 weeks. ADA development was common and likely affected both PK and PD parameters. SOBI003 crossed the BBB and showed pharmacological activity on HS in CSF.

Mortality in patients with alpha-mannosidosis: a review of patients' data and the literature

BACKGROUND

Alpha-mannosidosis is a rare autosomal recessive lysosomal storage disorder (LSD) caused by reduced activity of alpha-mannosidase. Clinical manifestations include skeletal dysmorphism, mental impairment, hearing loss and recurrent infections. The severe type of the disease leads to early childhood death, while patients with milder forms can live into adulthood. There are no mortality studies to date. This study aimed to investigate the age at death and the causes of death of patients with alpha-mannosidosis who had not received disease-modifying treatment.

METHODS

Clinicians and LSD patient organisations (POs) from 33 countries were invited to complete a questionnaire between April-May 2021. Cause of death and age at death was available for 15 patients. A literature review identified seven deceased patients that met the inclusion criteria.

RESULTS

Median age at death for patients reported by clinicians/POs was 45 years (mean 40.3 ± 13.2, range 18-56, n = 15); 53% were female. One death occurred during the patient's second decade of life, and 14 out of 15 deaths (93.3%) during or after the patients' third decade, including four (26.7%) during their sixth decade. Median age at death for patients identified from the literature was 4.3 years (mean 15.7 ± 17.0, range 2.2-41, n = 7); two were female. Four of the seven patients (57.1%) died within the first decade of life. Seven of 15 deaths (46.7%) reported by clinicians/POs were recorded as pneumonia and three (20.0%) as cancer. Other causes of death included acute renal failure due to sepsis after intestinal perforation, decrease of red blood cells of unknown origin, kidney failure with systemic lupus erythematosus, aortic valve insufficiency leading to heart failure, and dehydration due to catatonia. Three out of seven causes of death (42.9%) reported in the literature were associated with septicaemia, two (28.6%) with respiratory failure and one to pneumonia following aspiration.

CONCLUSIONS

This study suggests that pneumonia has been the primary cause of death during recent decades in untreated patients with alpha-mannosidosis, followed by cancer. Determining the causes of mortality and life expectancy in these patients is crucial to further improve our understanding of the natural history of alpha-mannosidosis.

Understanding disease symptoms and impacts and producing qualitatively-derived severity stages for MPS IIIA: a mixed methods approach

Background

MPS IIIA is a rare, degenerative pediatric genetic disease characterized by symptoms impacting cognition, mobility and behavior; the mean age of death is around 15 years of age. Currently, there are no approved therapies for MPS IIIA.

Methods

A two-year, multi-center, prospective, descriptive cohort study was conducted to document the natural history course of MPS IIIA. In the context of this study, semi-structured interviews were performed with parents of children at study entry and one year later. Interview transcripts were analyzed using thematic analysis methods to identity concepts of interest to children and parents, identify what factors impacted parents’ burden the most, and develop qualitatively-derived disease severity stages. Children were sorted into these stages according to the symptoms their parents described at the entry interview. This sorting was compared quantitatively to the sorting of children at baseline according to the child’s calendar age and their BSID development quotient (DQ).

Results

22 parents in France, Germany, the Netherlands and the UK were interviewed. Children ranged in age from 28 to 105 months (mean 61.4 months). The conceptual models for children’s symptoms and impacts and parents’ impacts provided a detailed and comprehensive picture of what it is like for children of various ages and their parents to live with MPS IIIA. Four factors were identified as mediating the burden perceived by parents: state support, family support, time since diagnosis, and parent coping strategy. Four disease stages were developed, accounting for both the presence and the severity of MPS IIIA symptoms. The comparison of children’s sorting into these stages with the BSID DQ and the child’s calendar age showed strong statistical associations.

Conclusions

The findings of this qualitative research embedded in a natural history study add to the current understanding of MPS IIIA as a complex disease that impacts every aspect of the lives of children and their families. This study demonstrates the unique potential of mixed methods research in rare diseases to address some of the current limitations of more traditional quantitative approaches by providing an individualized, detailed understanding of the patient experience.

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.

Recommended respiratory tests are not routinely performed for mucopolysaccharidosis patients

Mucopolysaccharidoses (MPS) are a group of rare genetic lysosomal storage disorders. The seven types of MPS exhibit a wide spectrum of clinical severity, including cognitive impairment, skeletal and joint abnormalities, short stature, coarsened facial features, vision loss, and cardiovascular and respiratory impairment, which are the leading causes of morbidity and mortality among MPS patients [1–3]. Ear, nose and throat (ENT) and upper airway manifestations are initially more pronounced, and may lead to the initial diagnosis. Lower airway disease becomes more frequent with increasing age. Symptoms can be tracheomalacia, stenosis and bronchomalacia. Bronchitis and pneumonia can appear, and are due to increased secretions and poor airway clearance. Restrictive lung disease predominates among patients with significant skeletal involvement, namely MPS-IV and MPS-VI. Sleep disturbances and obstructive sleep apnoea secondary to airway obstruction are common [4]. Specific therapy, such as enzyme replacement therapy (ERT), is available for most types of MPS.

Recommended respiratory tests used as major outcomes in clinical trials for MPS treatment cannot be routinely performed in everyday practice because neurocognitive impairment and motor skill difficulties affect compliance for most MPS patientshttps://bit.ly/3G4qp8U

The significance of triple-capsid-mutant AAV8 for treatment of Sanfilippo Syndrome Type B

Sanfilippo Syndrome Type-B remains an untreatable childhood neurodegenerative disease with great burden for both patient and caregiver. Very few clinical trials have been undertaken to treat the disease, and none of these have yet yielded clinically obtainable products for patients. Caused by a simple enzyme function deficiency, Sanfilippo Syndrome Type-B has been considered a great prospect for gene-therapy interventions. Adeno-associated virus (AAV) remains a major choice for therapeutic gene delivery due to its relatively low-immunogenicity, versatility and tissue tropism. However, many clinical trials with AAV continue to use wild-type capsids, which in many cases are not able to reach stable transgene expression for long enough to be clinically effective in most cases. Previous research in AAV gene-therapy has created a litany of novel AAV capsids that can improve overall transduction efficiency far above that of wild-type AAV capsids. One such example is the triple-capsid mutant AAV8 (TCM8), which has been shown to exhibit transgene expression far superior to other capsids in Sanfilippo mouse models, specifically. Originally designed to bypass capsid ubiquitination intracellularly, mouse studies suggest this TCM8 vector outperforms both AAV5 and AAV9 when delivered to the central nervous system. This implies it as an ideal contender for an effective gene-therapy clinical trial candidate and has the potential to advance the progress of Sanfilippo Syndrome treatment. Here we provide commentary on the TCM8 vector and its context in the field of Sanfilippo Syndrome Type-B research.

Long-term safety and clinical outcomes of intrathecal heparan-N-sulfatase in patients with Sanfilippo syndrome type A

INTRODUCTION

Currently, there is no effective therapy for mucopolysaccharidosis IIIA (MPS IIIA). Intravenously-administered enzyme replacement therapies, while effective in other forms of MPS without neurological involvement, have not been successful in patients with MPS IIIA, as they are unable to cross the blood-brain barrier to improve neurological symptoms. We evaluated the long-term safety, tolerability, and clinical outcomes of recombinant human heparan-N-sulfatase (rhHNS) administered intrathecally (IT) in children with MPS IIIA in a phase 1/2 extension study.

METHODS

Patients aged ≥3 years with MPS IIIA who had previously completed a phase 1/2 study and received ≥5 of the 6 planned rhHNS infusions via IT administration, were eligible for inclusion. Patients who received 10 mg in the phase 1/2 study had their dose increased to 45 mg. Patients who were treated with 45 mg or 90 mg rhHNS IT in the phase 1/2 study remained on this monthly dose in the extension study. rhHNS was administered via an intrathecal drug delivery device (IDDD). Primary endpoints included the type and severity of adverse events, presence of anti-rhHNS antibodies in the CSF and serum, and changes in laboratory values. Secondary endpoints included standardized neurocognitive assessments and brain magnetic resonance imaging.

RESULTS

In the extension study, 12 patients with a mean (SD) age of 9.6 (7.3) years continued treatment with rhHNS IT for a median of 264.4 weeks. Ten of 12 patients completed the extension study. rhHNS IT was generally well-tolerated. All patients experienced at least one treatment-emergent adverse event (TEAE), most being mild or moderate in severity. No serious adverse events (SAEs) were considered related to the study drug, and no deaths occurred. Most SAEs were related to malfunctions of the IDDD. Declines from baseline in Bayley Scales of Infant Development, Third Edition or Kaufman Assessment Battery for Children, Second Edition, Nonverbal Index developmental quotient scores were evident at all rhHNS dosing groups: -17.97%, -18.99%, and -12.12% in the 10/45, 45, and 90 mg groups, respectively, at Month 54.

CONCLUSIONS

Overall, rhHNS IT was well tolerated in the extension study. However, rhHNS IT was unable to slow the neurocognitive decline of patients with MPS IIIA. This study was subsequently terminated early because pre-specified efficacy criteria were not met, and the study did not yield clinical proof of concept. (Clinicaltrials.gov Identifier NCT01299727).

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

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

Music therapy and Sanfilippo syndrome: an analysis of psychological and physiological variables of three case studies

Introduction

Mucopolysaccharidosis type III (MPS III) or Sanfilippo syndrome is a neurodegenerative disease caused by the accumulation of mucopolysaccharides in the body. As the symptoms are wide ranging, it is a challenge to provide a diagnosis and psychological treatment for affected children.

Method

The main objective of this study was to describe a form of music therapy treatment applied to three children diagnosed with MPS III. The psychological variables were evaluated by an ad hoc observation recording template, and the physiological variables were measured with a digital meter before and after each session. The perception of the parents was also considered through a semi-structured interview.

Results

An improvement in the psychological variables was shown in all cases. Changes in the physiological variables were also noted, although they varied according to each child. The parents report some benefit of music therapy and they share difficulty in assessing the extent of benefits of the music therapy.

Discussion

Findings indicate that music therapy can be a useful form of treatment with multiple benefits for children with conditions such as MPS III or similar conditions. However, further research is needed in this area and in the development of specific ways of evaluating music therapy.

Global epidemiology of mucopolysaccharidosis type III (Sanfilippo syndrome): an updated systematic review and meta-analysis

OBJECTIVES

Mucopolysaccharidosis III, an autosomal recessive lysosomal storage disorder, is characterized by progressive mental retardation and behavioral problems. Meta-analysis of global mucopolysaccharidosis III epidemiology, which serves as a fundamental reference for public health decision-making, was not available prior to this study. To provide a systematic review and meta-analysis of birth prevalence of mucopolysaccharidosis III in multiple countries.

METHODS

MEDLINE and EMBASE databases were searched for original research articles on the epidemiology of mucopolysaccharidosis III from inception until 1st July, 2020. A checklist adapted from STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) was used to assess the quality of all studies involved. Meta-analysis, adopting a random effects logistic model, was performed to estimate pooled birth prevalence of mucopolysaccharidosis III and its subtypes.

RESULTS

Twenty-five studies screened out of 1,826 records were included for data extraction. The pooled global mucopolysaccharidosis III birth prevalence was 0.76 cases (95% CI: 0.57-0.96) per 100,000 live births. The pooled global birth prevalence of mucopolysaccharidosis III subtypes (A, B, and C) was 0.52 cases (95% CI: 0.33-0.72), 0.21 cases (95% CI: 0.12-0.30) and 0.01 cases (95% CI: 0.005-0.02) per 100,000 live births, respectively.

CONCLUSIONS

Based on the global population size (7.8 billion) and the life span of patients, there would be 12-19 thousand mucopolysaccharidosis III patients worldwide. To our knowledge, this is the first comprehensive systematic review that presented quantitative data fundamental for evidence-based public health decision-making by evaluating global epidemiology of mucopolysaccharidosis III.

Schizophreniform presentation and abrupt neurologic decline in a patient with late-onset mucopolysaccharidosis type IIIB

Due to their low frequency and some atypical presentations, inborn errors of metabolism are frequently misdiagnosed or underdiagnosed, which hinders the correct management of these patients. To illustrate that, here we present a patient that, at early school age, had learning disabilities compared to her classmates, especially for writing. She completed basic education in a regular school and was transferred to a secondary school for students with special needs. At 18 years of age, she presented a first psychiatric abrupt outbreak: she spent a month screaming and without sleeping. Behavioral problems then became apparent, especially hyperactivity, destructive and chaotic behavior, anxiety, and auto-aggressivity and hetero-aggressivity. A diagnosis of schizophreniform disorder was established. Clinical genetic evaluation revealed coarse face, macroglossia, coarse thick hair, and mild hepatomegaly, and the hypothesis of mucopolysaccharidosis-III was raised. Laboratory tests indicated high levels of urinary glycosaminoglycans and almost undetectable NAGLU activity, confirming the diagnosis. Sequencing of the NAGLU gene revealed the c.1318G>C (p.Gly440Arg) and c.1834A>G (p.Ser612Gly) mutations.

Gastrointestinal Manifestations in Mucopolysaccharidosis Type III: Review of Death Certificates and the Literature

BACKGROUND

Mucopolysaccharidosis type III (MPS III, Sanfilippo disease) is a life-limiting recessive lysosomal storage disorder caused by a deficiency in the enzymes involved in degrading glycosaminoglycan heparan sulfate. MPS III is characterized by progressive deterioration of the central nervous system. Respiratory tract infections have been reported as frequent and as the most common cause of death, but gastrointestinal (GI) manifestations have not been acknowledged as a cause of concern. The aim of this study was to determine the incidence of GI problems as a primary cause of death and to review GI symptoms reported in published studies.

METHODS

Causes of death from 221 UK death certificates (1957-2020) were reviewed and the literature was searched to ascertain reported GI symptoms.

RESULTS

GI manifestations were listed in 5.9% (n = 13) of death certificates. Median (IQR) age at death was 16.7 (5.3) years. Causes of death included GI failure, GI bleed, haemorrhagic pancreatitis, perforation due to gastrostomies, paralytic ileus and emaciation. Twenty-one GI conditions were reported in 30 studies, mostly related to functional GI disorders, including diarrhoea, dysphagia, constipation, faecal incontinence, abdominal pain/distension and cachexia.

CONCLUSIONS

GI manifestations may be an under-recognized but important clinical feature of MPS III. Early recognition of GI symptoms and timely interventions is an important part of the management of MPS III patients.

An Engineered sgsh Mutant Zebrafish Recapitulates Molecular and Behavioural Pathobiology of Sanfilippo Syndrome A/MPS IIIA

Mucopolysaccharidosis IIIA (MPS IIIA, Sanfilippo syndrome type A), a paediatric neurological lysosomal storage disease, is caused by impaired function of the enzyme N-sulfoglucosamine sulfohydrolase (SGSH) resulting in impaired catabolism of heparan sulfate glycosaminoglycan (HS GAG) and its accumulation in tissues. MPS IIIA represents a significant proportion of childhood dementias. This condition generally leads to patient death in the teenage years, yet no effective therapy exists for MPS IIIA and a complete understanding of the mechanisms of MPS IIIA pathogenesis is lacking. Here, we employ targeted CRISPR/Cas9 mutagenesis to generate a model of MPS IIIA in the zebrafish, a model organism with strong genetic tractability and amenity for high-throughput screening. The sgsh^Δex5-6 zebrafish mutant exhibits a complete absence of Sgsh enzymatic activity, leading to progressive accumulation of HS degradation products with age. sgsh^Δex5-6 zebrafish faithfully recapitulate diverse CNS-specific features of MPS IIIA, including neuronal lysosomal overabundance, complex behavioural phenotypes, and profound, lifelong neuroinflammation. We further demonstrate that neuroinflammation in sgsh^Δex5-6 zebrafish is largely dependent on interleukin-1β and can be attenuated via the pharmacological inhibition of Caspase-1, which partially rescues behavioural abnormalities in sgsh^Δex5-6 mutant larvae in a context-dependent manner. We expect the sgsh^Δex5-6 zebrafish mutant to be a valuable resource in gaining a better understanding of MPS IIIA pathobiology towards the development of timely and effective therapeutic interventions.

Increased Alveolar Heparan Sulphate and Reduced Pulmonary Surfactant Amount and Function in the Mucopolysaccharidosis IIIA Mouse

Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurological and skeletal pathologies. Respiratory dysfunction is a secondary pathology contributing to mortality in MPS IIIA patients. Pulmonary surfactant is crucial to optimal lung function and has not been investigated in MPS IIIA. We measured heparan sulphate (HS), lipids and surfactant proteins (SP) in pulmonary tissue and bronchoalveolar lavage fluid (BALF), and surfactant activity in healthy and diseased mice (20 weeks of age). Heparan sulphate, ganglioside GM3 and bis(monoacylglycero)phosphate (BMP) were increased in MPS IIIA lung tissue. There was an increase in HS and a decrease in BMP and cholesteryl esters (CE) in MPS IIIA BALF. Phospholipid composition remained unchanged, but BALF total phospholipids were reduced (49.70%) in MPS IIIA. There was a reduction in SP-A, -C and -D mRNA, SP-D protein in tissue and SP-A, -C and -D protein in BALF of MPS IIIA mice. Captive bubble surfactometry showed an increase in minimum and maximum surface tension and percent surface area compression, as well as a higher compressibility and hysteresis in MPS IIIA surfactant upon dynamic cycling. Collectively these biochemical and biophysical changes in alveolar surfactant are likely to be detrimental to lung function in MPS IIIA.

Resilience in Familial Caregivers of Children with Developmental Disabilities: A Meta-analysis

The aim of this meta-analysis was to investigate factors associated with resilience in familial caregivers of children with developmental disabilities. The protocol was registered in the PROSPERO database, with the registration number CRD42018105180. Several electronic databases were searched for studies. A random-effects meta-analysis was performed on 26 selected studies that associated resilience to an array of other variables (i.e., psychological distress, social support, coping, perceived health, life satisfaction). Overall, the significant pooled effect sizes were small to medium, ranging from r = 0.291 for coping to r = 0.442 for social support. Although the literature on the topic has improved, there is a lot of study heterogeneity and the need for focusing on male caregivers becomes evident.

Novel therapies for mucopolysaccharidosis type III

Mucopolysaccharidosis type III (MPS III) or Sanfilippo disease is an orphan inherited lysosomal storage disease and one of the most common MPS subtypes. The classical presentation is an infantile-onset neurodegenerative disease characterised by intellectual regression, behavioural and sleep disturbances, loss of ambulation, and early death. Unlike other MPS, no disease-modifying therapy has yet been approved. Here, we review the numerous approaches of curative therapy developed for MPS III from historical ineffective haematopoietic stem cell transplantation and substrate reduction therapy to the promising ongoing clinical trials based on enzyme replacement therapy or adeno-associated or lentiviral vectors mediated gene therapy. Preclinical studies are presented alongside the most recent translational first-in-man trials. In addition, we present experimental research with preclinical mRNA and gene editing strategies. Lessons from animal studies and clinical trials have highlighted the importance of an early therapy before extensive neuronal loss. A disease-modifying therapy for MPS III will undoubtedly mandate development of new strategies for early diagnosis.

Survival and diagnostic age of 175 Taiwanese patients with mucopolysaccharidoses (1985-2019)

Background

Mucopolysaccharidoses (MPSs) are a group of inherited metabolic diseases, which are characterized by the accumulation of glycosaminoglycans, and eventually lead to the progressive damage of various tissues and organs.

Methods

An epidemiological study of MPS in Taiwan was performed using multiple sources. The survival and diagnostic age for different types of MPS between 1985 and 2019 were evaluated.

Results

Between 1985 and 2019, there were 175 patients diagnosed with MPS disorders in the Taiwanese population, with a median diagnostic age of 3.9 years. There were 21 (12%), 78 (45%), 33 (19%), 32 (18%) and 11 (6%) patients diagnosed with MPS I, II, III, IV and VI, respectively, with median diagnostic ages of 1.5, 3.8, 4.7, 4.5 and 3.7 years, respectively. Diagnosis of MPS patients was significantly earlier in recent decades (p < 0.01). Pilot newborn screening programs for MPS I, II, VI, IVA, and IIIB were progressively introduced in Taiwan from 2016, and 48% (16/33) of MPS patients diagnosed between 2016 and 2019 were diagnosed by one of these screening programs, with a median diagnostic age at 0.2 years. For patients born between 2016 and 2019, up to 94% (16/17) were diagnosed with MPS via the newborn screening programs. At the time of this study, 81 patients had passed away with a median age at death of 15.6 years. Age at diagnosis was positively correlated with life expectancy (p < 0.01). Life expectancy also significantly increased between 1985 and 2019, however this increase was gradual (p < 0.01).

Conclusions

The life expectancy of Taiwanese patients with MPS has improved in recent decades and patients are being diagnosed earlier. Because of the progressive nature of the disease, early diagnosis by newborn screening programs and timely implementation of early therapeutic interventions may lead to better clinical outcomes.

MUCOPOLYSACARIDOSIS TYPE IIIB MISDIAGNOSED AS AN AUTISTIC SPECTRUM DISORDER: A CASE REPORT AND LITERATURE REVIEW

Objective:

To report a rare case of mucopolysaccharidosis IIIB in a pediatric patient, with emphasis on the description of the clinical manifestations and the early diagnosis.

Case description:

A 14-year-old male patient, who presented regression of neuropsychomotor development since his three years and six months old, with speech loss and frequent falls, evolving with behavioral changes, with agitation and aggressiveness. Although being diagnosed with autism, there was no response to the established treatment; he was subsequently submitted to metabolic investigation, which lead to the diagnosis of Mucopolysaccharidosis IIIB.

Comments:

Identifying a metabolic disorder requires connecting multiple signs and symptoms, as well as eliminating other apparent causes. MPS IIIB is a diagnostic challenge, particularly in the early stages and in the absence of a family history of the disease.

Evading the AAV Immune Response in Mucopolysaccharidoses

The humoral immune response elicited by adeno-associated virus (AAV)-mediated gene therapy for the treatment of mucopolysaccharidoses (MPS) poses a significant challenge to achieving therapeutic levels of transgene expression. Antibodies targeting the AAV capsid as well as the transgene product diminish the production of glycosaminoglycan (GAG)-degrading enzymes essential for the treatment of MPS. Patients who have antibodies against AAV capsid increase in number with age, serotype, and racial background and are excluded from the clinical trials at present. In addition, patients who have undergone AAV gene therapy are often excluded from the additional AAV gene therapy with the same serotype, since their acquired immune response (antibody) against AAV will limit further efficacy of treatment. Several methods are being developed to overcome this immune response, such as novel serotype design, antibody reduction by plasmapheresis and immunosuppression, and antibody evasion using empty capsids and enveloped AAV vectors. In this review, we examine the mechanisms of the anti-AAV humoral immune response and evaluate the strengths and weaknesses of current evasion strategies in order to provide an evidence-based recommendation on evading the immune response for future AAV-mediated gene therapies for MPS.

Improved Pharmacokinetics and Tissue Uptake of Complexed Daidzein in Rats

The pharmacokinetic profile and tissue uptake of daidzein (DAI) was determined in rat serum and tissues (lungs, eyes, brain, heart, spleen, fat, liver, kidney, and testes) after intravenous and intraperitoneal administration of DAI in suspension or complexed with ethylenediamine-modified γ-cyclodextrin (GCD-EDA/DAI). The absolute and relative bioavailability of DAI suspended (20 mg/kg i.v. vs. 50 mg/kg i.p.) and complexed (0.54 mg/kg i.v. vs. 1.35 mg/kg i.p.) was determined. After i.p. administration, absorption of DAI complexed with GCD-EDA was more rapid (t_max = 15 min) than that of DAI in suspension (t_max = 45 min) with a ca. 3.6 times higher maximum concentration (C_max = 615 vs. 173 ng/mL). The i.v. half-life of DAI was longer in GCD-EDA/DAI complex compared with DAI in suspension (t_0.5 = 380 min vs. 230 min). The volume of distribution of DAI given i.v. in GCD-EDA/DAI complex was ca. 6 times larger than DAI in suspension (38.6 L/kg vs. 6.2 L/kg). Our data support the concept that the pharmacokinetics of DAI suspended in high doses are nonlinear. Increasing the intravenous dose 34 times resulted in a 5-fold increase in AUC. In turn, increasing the intraperitoneal dose 37 times resulted in a ca. 2-fold increase in AUC. The results of this study suggested that GCD-EDA complex may improve DAI bioavailability after i.p. administration. The absolute bioavailability of DAI in GCD-EDA inclusion complex was ca. 3 times greater (F = 82.4% vs. 28.2%), and the relative bioavailability was ca. 21 times higher than that of DAI in suspension, indicating the need to study DAI bioavailability after administration by routes other than intraperitoneal, e.g., orally, subcutaneously, or intramuscularly. The concentration of DAI released from GCD-EDA/DAI inclusion complex to all the rat tissues studied was higher than after administration of DAI in suspension. The concentration of DAI in brain and lungs was found to be almost 90 and 45 times higher, respectively, when administered in complex compared to the suspended DAI. Given the nonlinear relationship between DAI bioavailability and the dose released from the GCD-EDA complex, complexation of DAI may thus offer an effective approach to improve DAI delivery for treatment purposes, for example in mucopolysaccharidosis (MPS), allowing the reduction of ingested DAI doses.

The attenuated end of the phenotypic spectrum in MPS III: from late-onset stable cognitive impairment to a non-neuronopathic phenotype

BACKGROUND

The phenotypic spectrum of many rare disorders is much wider than previously considered. Mucopolysaccharidosis type III (Sanfilippo syndrome, MPS III), is a lysosomal storage disorder traditionally considered to be characterized by childhood onset, progressive neurocognitive deterioration with a rapidly or slowly progressing phenotype. The presented MPS III case series demonstrates adult onset phenotypes with mild cognitive impairment or non-neuronopathic phenotypes.

METHODS

In this case series all adult MPS III patients with a mild- or non-neuronopathic phenotype, who attend the outpatient clinic of 3 expert centers for lysosomal storage disorders were included. A mild- or non-neuronopathic phenotype was defined as having completed regular secondary education and attaining a level of independency during adulthood, involving either independent living or a paid job.

RESULTS

Twelve patients from six families, with a median age at diagnosis of 43 years (range 3-68) were included (11 MPS IIIA, 1 MPS IIIB). In the four index patients symptoms which led to diagnostic studies (whole exome sequencing and metabolomics) resulting in the diagnosis of MPS III; two patients presented with retinal dystrophy, one with hypertrophic cardiomyopathy and one with neurocognitive decline. The other eight patients were diagnosed by family screening. At a median age of 47 years (range 19-74) 9 out of the 12 patients had normal cognitive functions. Nine patients had retinal dystrophy and 8 patients hypertrophic cardiomyopathy.

CONCLUSION

We show the very mild end of the phenotypic spectrum of MPS III, ranging from late-onset stable neurocognitive impairment to a fully non-neuronopathic phenotype. Awareness of this phenotype could lead to timely diagnosis and genetic counseling.

Analysis of the caregiver burden associated with Sanfilippo syndrome type B: panel recommendations based on qualitative and quantitative data

BACKGROUND

Sanfilippo syndrome type B (Sanfilippo B) belongs to a group of rare lysosomal storage diseases characterized by progressive cognitive decline from an early age, acute hyperactivity, and concomitant somatic symptoms. Caregivers face a unique set of challenges related to the complex nature of Sanfilippo B, but the burden and impact on quality of life (QoL) of caregivers is poorly defined and best practice guidance for clinicians is lacking.

METHODS

An international clinical advisors meeting was convened to discuss key aspects of caregiver burden associated with Sanfilippo B based on findings from qualitative and quantitative research undertaken to identify and quantify the nature and impact of the disease on patients and caregivers.

RESULTS

Providing care for patients with Sanfilippo B impinges on all aspects of family life, evolving as the patient ages and the disease progresses. Important factors contributing toward caregiver burden include sleep disturbances, impulsive and hyperactive behavior, and communication difficulties. Caregiver burden remained high throughout the life of the patient and, coupled with the physical burden of daily care, had a cumulative impact that generated significant psychological stress.

CONCLUSION

A Sanfilippo-specific QoL questionnaire is needed that is directed at caregiver needs and burden and best practice management of these domains.

Cardiac disease in mucopolysaccharidosis type III

Mucopolysaccharidosis type III (MPS III; Sanfilippo disease) is primarily characterized by neurocognitive decline with limited somatic disease. Only few reports addressed cardiac disease (CD) in MPS III. We investigated the prevalence of CD in a relatively large cohort of patients. In this cross-sectional study, extensive echocardiographic studies were performed in 30 MPS III patients (16 patients <18 years), all without clinical symptoms of CD. Results were compared to data from matched controls. The mean global longitudinal strain on speckle-tracking echocardiography (STE) was impaired in both pediatric and adult patients vs controls (resp. -18.4% vs -20.7%; mean difference 2.25, 95% CI 0.61-3.89, P = 0.009 and -16.9% vs -19.5%; mean difference 2.64, 95% CI 0.78-4.49, P = 0.007), indicating early systolic dysfunction. Left ventricle ejection fraction (LVEF) was normal in pediatric patients and (slightly) impaired in adult patients vs controls (48.7% vs 55.8%, P = 0.002). Tissue Doppler imaging (TDI) showed significantly slower early diastolic velocities (e') compared to controls indicative for diastolic dysfunction. Furthermore, mitral and aortic valve abnormalities were prevalent (43% and 33% of patients, respectively). Finally, 15.6% of the patients had a first-degree atrioventricular block on electrocardiography (ECG). The impaired STE reveals early, subclinical LV dysfunction which is supported by results of TDI. In addition, mild valvular disease and ECG abnormalities are prevalent. The lowered LVEF in adult patients suggests that the LV dysfunction is progressive, and may ultimately lead to clinical myocardial disease when patients live longer due to an effective disease-modifying treatment of which a number of options are now in clinical trials.

A novel mutation of SGSH and clinical features analysis of mucopolysaccharidosis type IIIA

RATIONALE

The aim of this study was to analyze the clinical and imaging features of a pediatric patient with mucopolysaccharidosis type IIIA (MPS IIIA) and a novel mutation of the N-sulfoglucosamine sulfohydrolase (SGSH) in 1 pedigree.

PATIENT CONCERNS

An 8-year-old female patient presented with developmental regression, seizures, cerebral atrophy, thickened calvarial diploe, apathy, esotropia, slender build, thick hair, prominent eyebrows, hepatomegaly, ankle clonus, muscle and joint contractures, and funnel chest.

DIAGNOSES

The patient was diagnosed as autosomal recessive (AR) MPS IIIA with a novel mutation in the SGSH gene.

INTERVENTIONS

Genomic DNA was extracted from the peripheral blood and next-generation sequencing (NGS) technology was used to detect pathogenic genes, and the Sanger method was applied to perform pedigree verification for the detected suspicious pathogenic mutations.

OUTCOMES

The NGS done for the girl and her family showed 2 variations that were both missense mutations in SGSH. The c.1298G > A (p.Arg433Gln) was a known mutation, and the c.630 G > T (p.Trp210Cys) was a novel variation.

LESSONS

The common clinical manifestations of MPS IIIA were rapid developmental regression, seizures, cerebral atrophy, and thickened calvarial diploe. The results showed that the c.630 G > T was likely pathogenic according to bioinformatics analysis, which probably was a novel mutation. This study reports 1 case of MPS IIIA with some clinical features as determined via clinical and genetic analysis, and found a new mutation in the SGSH gene.

Mucopolysaccharidosis III in Taiwan: Natural history, clinical and molecular characteristics of 28 patients diagnosed during a 21-year period

Mucopolysaccharidosis type III (MPS III, Sanfilippo syndrome) has a variable age of onset and variable rate of progression. However, information regarding the natural history of this disorder in Asian populations is limited. A retrospective analysis was carried out for 28 patients with MPS III (types IIIA [n = 3], IIIB [n = 23], and IIIC [n = 2]; 15 males and 13 females; median age, 8.2 years; age range, 2.7-26.5 years) seen in six medical centers in Taiwan from January 1996 through October 2017. The median age at confirmed diagnosis was 4.6 years. The most common initial symptom was speech delay (75%), followed by hirsutism (64%) and hyperactivity (54%). Both z scores for height and weight were negatively correlated with age (r = -.693 and -0.718, respectively; p < .01). The most prevalent clinical manifestations were speech delay (100%) and intellectual disability (100%), followed by hirsutism (93%), hyperactivity (79%), coarse facial features (68%), sleep disorders (61%), and hepatosplenomegaly (61%). Ten patients (36%) had epilepsy, and the median age at the first seizure was 11 years. Thirteen patients (46%) experienced at least one surgical procedure. At the time of the present study, 7 of the 28 patients had passed away at the median age of 13.0 years. Molecular studies showed an allelic heterogeneity without clear genotype and phenotype correlations. MPS IIIB is the most frequent subtype among MPS III in the Taiwanese population. An understanding of the natural history of MPS III may allow early diagnosis and timely management of the disease facilitating better treatment outcomes.