The Neurobehavioral Phenotype in Mucopolysaccharidosis Type IIIB: an Exploratory Study

The 100 Most Cited Kluver-Bucy Research Articles: A Bibliometric Analysis

Kluver-Bucy Syndrome (KBS) is a rare neuropsychiatric disorder characterized by hyperorality, hypersexuality, bulimia, visual agnosia, and amnesia due to lesions affecting bilateral temporal lobes. It is attributed to a multitude of causes, including stroke, herpes simplex encephalitis, Alzheimer's disease, and head trauma. Current treatments for KBS include symptomatic management with antipsychotics, mood stabilizers, carbamazepine, and selective serotonin reuptake inhibitors. The bibliometric analysis was done to reflect the relevance and understanding of KBS in recent literature. The SCOPUS database was utilized to conduct a search for all articles with the terms "Kluver-Bucy" and "Kluver Bucy" from January 1, 1955 (the first available articles from the search) to February 1, 2023. The parameters included in this analysis were article title, citation numbers, citations per year, authors, institutions, publishing journals, country of origin, Source Normalized Impact per Paper, and Scopus CiteScore. Since 1937, when Kluver-Bucy Syndrome was first defined, the publications on KBS have steadily increased, with up to six publications a year in 2002. The most common institutions were SUNY Upstate Medical University, VA Medical Center, and the State University of New York (SUNY) System. Seven of these papers were published in Neurology. Almost 75% of the articles were published in journals of medicine and neuroscience. This is the first bibliometric analysis to evaluate the most influential publications about Kluver-Bucy Syndrome. A majority of the research is case-based and there is a dearth of clinical trials to identify the exact pathophysiology and physiotherapy management, possibly owing to the rarity of the disease. Our research suggests that there may be a significant overlap between Sanfilippo syndrome and KBS, suggesting that refined guidelines for establishing diagnosis may be required for children. Our study could bring a renewed interest in this field and lead to additional research focused on understanding the pathophysiology of KBS in order to promote the development of novel diagnostics and treatment.

Safety, pharmacokinetics and CNS distribution of tralesinidase alfa administered via intracerebroventricular infusion to juvenile cynomolgus monkeys

Mucopolysaccharidosis Type IIIB (MPS IIIB) is an ultrarare, fatal pediatric disease with no approved therapy. It is caused by mutations in the gene encoding for lysosomal enzyme alpha-N-acetylglucosaminidase (NAGLU). Tralesinidase alfa (TA) is a fusion protein comprised of recombinant NAGLU and a modified human insulin-like growth factor 2 that is being developed as an enzyme replacement therapy for MPS IIIB. Since MPS IIIB is a pediatric disease the safety/toxicity, pharmacokinetics and biodistribution of TA were evaluated in juvenile non-human primates that were administered up to 5 weekly intracerebroventricular (ICV) or single intravenous (IV) infusions of TA. TA administered by ICV slow-, ICV isovolumetric bolus- or IV-infusion was well-tolerated, and no effects were observed on clinical observations, electrocardiographic or ophthalmologic parameters, or respiratory rates. The drug-related changes observed were limited to increased cell infiltrates in the CSF and along the ICV catheter track after ICV administration. These findings were not associated with functional changes and are associated with the use of ICV catheters. The CSF PK profiles were consistent across all conditions tested and TA distributed widely in the CNS after ICV administration. Anti-drug antibodies were observed but did not appear to significantly affect the exposure to TA. Correlations between TA concentrations in plasma and brain regions in direct contact with the cisterna magna suggest glymphatic drainage may be responsible for clearance of TA from the CNS. The data support the administration of TA by isovolumetric bolus ICV infusion to pediatric patients with MPS IIIB.

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.

Tralesinidase alfa enzyme replacement therapy prevents disease manifestations in a canine model of mucopolysaccharidosis type IIIB

Mucopolysaccharidosis type IIIB (MPS IIIB; Sanfilippo syndrome B; OMIM #252920) is a lethal, pediatric, neuropathic, autosomal recessive, and lysosomal storage disease with no approved therapy. Patients are deficient in the activity of N-acetyl-alpha-glucosaminidase (NAGLU; EC 3.2.150), necessary for normal lysosomal degradation of the glycosaminoglycan heparan sulfate (HS). Tralesinidase alfa (TA), a fusion protein comprised of recombinant human NAGLU and a modified human insulin-like growth factor 2, is in development as an enzyme replacement therapy that is administered via intracerebroventricular (ICV) infusion, thus circumventing the blood brain barrier. Previous studies have confirmed ICV infusion results in widespread distribution of TA throughout the brains of mice and nonhuman primates. We assessed the long-term tolerability, pharmacology, and clinical efficacy of TA in a canine model of MPS IIIB over a 20-month study. Long-term administration of TA was well tolerated as compared with administration of vehicle. TA was widely distributed across brain regions, which was confirmed in a follow-up 8-week pharmacokinetic/pharmacodynamic study. MPS IIIB dogs treated for up to 20 months had near-normal levels of HS and nonreducing ends of HS in cerebrospinal fluid and central nervous system (CNS) tissues. TA-treated MPS IIIB dogs performed better on cognitive tests and had improved CNS pathology and decreased cerebellar volume loss relative to vehicle-treated MPS IIIB dogs. These findings demonstrate the ability of TA to prevent or limit the biochemical, pathologic, and cognitive manifestations of canine MPS IIIB disease, thus providing support of its potential long-term tolerability and efficacy in MPS IIIB subjects.

Natural History and Molecular Characteristics of Korean Patients with Mucopolysaccharidosis Type III

Background: Mucopolysaccharidosis type III (MPS III) is an autosomal recessive lysosomal storage disorder characterised by progressive neurocognitive deterioration. MPS III subtypes are clinically indistinguishable, with a wide range of symptoms and variable severity. The natural history of this disorder within an Asian population has not yet been extensively studied. This study investigated the natural history of Korean patients with MPS III. Methods: Thirty-four patients from 31 families diagnosed with MPS III from January 1997 to May 2020 in Samsung Medical Centre were enrolled. Clinical, molecular, and biochemical characteristics were retrospectively collected from the patients’ medical records and via interviews. Results: 18 patients had MPS IIIA, 14 had IIIB, and two had IIIC. Twenty (58.9%) patients were male. Mean age at symptom onset was 2.8 ± 0.8 years and at diagnosis was 6.3 ± 2.2 years. All patients with MPS IIIA and IIIB were classified into the rapidly progressing (RP) phenotype. The most common symptom at diagnosis was language retardation (88.2%), followed by motor retardation (76.5%), general retardation (64.7%), and hyperactivity (41.2%). Language retardation was more predominant in IIIA, and motor retardation was more predominant in IIIB. The mean age of the 13 deceased patients at the time of the study was 14.4 ± 4.1 years. The age at diagnosis and lag time were significantly older and longer in the non-survivor group compared with the survivor group (p = 0.029 and 0.045, respectively). Genetic analysis was performed in 24 patients with MPS III and identified seven novel variants and three hot spots. Conclusion: This study is the first to analyse the genetic and clinical characteristics of MPS III patients in Korea. Better understanding of the natural history of MPS III might allow early diagnosis and timely management of the disease and evaluation of treatment outcomes in future clinical trials for MPS III.

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.

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.

Delivering gene therapy for mucopolysaccharide diseases

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

Intracerebral Gene Therapy in Four Children with Sanfilippo B Syndrome: 5.5-Year Follow-Up Results

We report the safety (primary endpoint) and efficacy (secondary endpoint) of a novel intracerebral gene therapy at 5.5 years of follow-up in children with Sanfilippo B. An uncontrolled, phase 1/2 clinical trial was performed in four patients aged 20, 26, 30, and 53 months. Treatment consisted of 16 intracerebral and cerebellar deposits of a recombinant adeno-associated viral vector encoding human α-N-acetylglucosaminidase (rAAV2/5-hNAGLU) plus immunosuppression. An intermediate report at 30 months was previously published. Thirty treatment-emergent adverse events were reported between 30 and 66 months after surgery, including three classified as severe with no serious drug reactions. At 5.5 years, NAGLU activity was persistently detected in the lumbar cerebrospinal fluid (18% of unaffected control level). Circulating T cells reacting against NAGLU peptides were present, indicating a lack of acquired tolerance. Patients 2, 3, and 4 showed progressive brain atrophy and neurocognitive evolution that did not differ from untreated Sanfilippo A/B children. Patient 1, enrolled at 20 months of age, had a milder disease with normal brain imaging and a significantly better cognitive outcome than the three other patients and untreated patients, although not equivalent to normal children. After 5.5 years, the primary endpoint of this study was achieved with a good safety profile of the proposed treatment. We have also observed sustained enzyme production in the brain and absence of immunological tolerance. Cognitive benefit was not confirmed in the three oldest patients. Milder disease in the youngest patient supports further investigations of adeno-associated vector-mediated intracerebral gene therapy in Sanfilippo B.

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.

Challenging behavior in mucopolysaccharidoses types I-III and day-to-day coping strategies: a cross sectional explorative study

Background

Challenging behavior represents a core symptom in neuropathological mucopolysaccharidoses (MPS) and puts major strain on affected families. Although multimodal approaches including behavioral strategies to treatment could be valuable, there is lack of research to the effectiveness of specific measures. This explorative, cross-sectional study is aimed at the collection of parental experiences regarding effective day-to-day measures against challenging behavior in MPS and focuses on 4 major research questions: First: What is challenging behavior in MPS? Second: Which strategies are helpful in the day-to-day coping with challenging behavior? Third: How strong is parental acceptance of illness and the disorder’s impact on family relationships? Fourth: What are beneficial personal and interfamilial strategies for generally coping with the disorder?

Methods

A semi structured questionnaire was designed de novo in cooperation with affected families. 37/268 questionnaires were returned (rate: 13.8%), of which 34 (MPS I: n = 8, MPS II: n = 8; MPS III: n = 18) could be included in data analysis in accordance with inclusion criteria. Assessment of challenging symptoms was based on perceived frequency, parent- and child stress. Exploration of possible coping strategies for challenging behavior and general illness-related strain included the evaluation of perceived effectiveness. Questionnaires were completed by patient’s relatives and analyzed for strategies to cope with challenging behavior and the disorder’s impact. STROBE criteria were respected.

Results

MPS I was reported to show lower frequency and better perceived manageability of challenging behavior than MPS II and -III. Sleep disturbance, hyperactivity, agitation, aggression and orality seemed relevant symptoms regarding frequency and/or parent stress. Reported measures were manifold, worthwhile approaches against challenging behavior appeared to be aiming at distraction, relief and environmental changes. Medication and non-medication approaches were rated similarly effective. Social exchange, private space and networking with other affected families seemed highly important for personal and interfamilial well-being.

Conclusions

Multimodal mentoring for affected families could be based on the following equivalent pillars: (1) Medication therapy for challenging behavior including evaluation of cost and benefit (2) Guided implementation and re-evaluation of specific behavioral measures against challenging behavior. (3) Psychosocial support of MPS-families, including options for strengthening parental well-being and family functioning.

Trial registration This study was registered at clinicaltrials.gov prior to study start (NCT-Number: NCT03161171, Date: 2017/05/19).

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-020-01548-9) contains supplementary material, which is available to authorized users.

Cerebellar tumour-like aggregate of glycosaminoglycans in a MPS IIIB patient: a case report

INTRODUCTION

Mucopolysaccharidosis (MPS) IIIB is a lysosomal disorder in which a deficiency in α-N-acetylglucosaminidase impairs the degradation of heparan sulphate, which accumulates in tissues causing multiple organs dysfunction. This disease is associated with significant central nervous system (CNS) abnormalities, but a presentation with a tumour-like lesion has never been reported so far.

CLINICAL PRESENTATION

The present report describes the case of a 5-year-old girl suffering from MPS IIIB who developed a cerebellar lesion with evident mass effect. She underwent surgery with a subsequent notable improvement of her clinical picture. Surprisingly, the pathological analysis revealed the lesion to have the typical MPS features.

CONCLUSION

This case would describe a neglected possible presentation of MPS IIIB with a lesion mimicking a neoplasm, which could even be successfully treated with surgery.

Therapy development for the mucopolysaccharidoses: Updated consensus recommendations for neuropsychological endpoints

Neurological dysfunction represents a significant clinical component of many of the mucopolysaccharidoses (also known as MPS disorders). The accurate and consistent assessment of neuropsychological function is essential to gain a greater understanding of the precise natural history of these conditions and to design effective clinical trials to evaluate the impact of therapies on the brain. In 2017, an International MPS Consensus Panel published recommendations for best practice in the design and conduct of clinical studies investigating the effects of therapies on cognitive function and adaptive behavior in patients with neuronopathic mucopolysaccharidoses. Based on an International MPS Consensus Conference held in February 2020, this article provides updated consensus recommendations and expands the objectives to include approaches for assessing behavioral and social-emotional state, caregiver burden and quality of life in patients with all mucopolysaccharidoses.

Haematopoietic stem cell gene therapy with IL-1Ra rescues cognitive loss in mucopolysaccharidosis IIIA

Mucopolysaccharidosis IIIA is a neuronopathic lysosomal storage disease, characterised by heparan sulphate and other substrates accumulating in the brain. Patients develop behavioural disturbances and cognitive decline, a possible consequence of neuroinflammation and abnormal substrate accumulation. Interleukin (IL)‐1β and interleukin‐1 receptor antagonist (IL‐1Ra) expression were significantly increased in both murine models and human MPSIII patients. We identified pathogenic mechanisms of inflammasome activation, including that disease‐specific 2‐O‐sulphated heparan sulphate was essential for priming an IL‐1β response via the Toll‐like receptor 4 complex. However, mucopolysaccharidosis IIIA primary and secondary storage substrates, such as amyloid beta, were both required to activate the NLRP3 inflammasome and initiate IL‐1β secretion. IL‐1 blockade in mucopolysaccharidosis IIIA mice using IL‐1 receptor type 1 knockout or haematopoietic stem cell gene therapy over‐expressing IL‐1Ra reduced gliosis and completely prevented behavioural phenotypes. In conclusion, we demonstrate that IL‐1 drives neuroinflammation, behavioural abnormality and cognitive decline in mucopolysaccharidosis IIIA, highlighting haematopoietic stem cell gene therapy treatment with IL‐1Ra as a potential neuronopathic lysosomal disease treatment.

Molecular Bases of Neurodegeneration and Cognitive Decline, the Major Burden of Sanfilippo Disease

The mucopolysaccharidoses (MPS) are a group of diseases caused by the lysosomal accumulation of glycosaminoglycans, due to genetic deficiencies of enzymes involved in their degradation. MPS III or Sanfilippo disease, in particular, is characterized by early-onset severe, progressive neurodegeneration but mild somatic involvement, with patients losing milestones and previously acquired skills as the disease progresses. Despite being the focus of extensive research over the past years, the links between accumulation of the primary molecule, the glycosaminoglycan heparan sulfate, and the neurodegeneration seen in patients have yet to be fully elucidated. This review summarizes the current knowledge on the molecular bases of neurological decline in Sanfilippo disease. It emerges that this deterioration results from the dysregulation of multiple cellular pathways, leading to neuroinflammation, oxidative stress, impaired autophagy and defects in cellular signaling. However, many important questions about the neuropathological mechanisms of the disease remain unanswered, highlighting the need for further research in this area.

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.

Neurobehavioral phenotypes of neuronopathic mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of lysosomal multisystemic, chronic, and progressive diseases characterized by the storage of glycosaminoglycans (GAGs) that may affect the central nervous system. Neuronopathic MPS such as MPS IH, MPS II, MPS IIIA–D, and MPS VII are characterized by neurocognitive regression. In severe MPS I (MPS IH, or Hurler syndrome) initial developmental trajectory is usually unremarkable but cognitive development shows a plateau by 2 to 4 years of age and then progressively regresses with aging. Patients with neuronopathic MPS II have a plateau of cognitive and adaptive development on average by 4 to 4.5 years of age, although there is significant variability, followed by progressive neurocognitive decline. In patients with classic MPS III, developmental trajectory reaches a plateau around 3 years of age, followed by regression. Sleep disturbances and behavioral problems occur early in MPS II and III with features of externalizing disorders. Acquired autism-like behavior is often observed in children with MPS III after 4–6 years of age. Impaired social and communication abilities do occur, but MPS III children do not have restricted and repetitive interests such as in autism spectrum disorder. MPS type VII is an ultra-rare neuronopathic MPS with a wide clinical spectrum from very severe with early mortality to milder phenotypes with longer survival into adolescence and adulthood. Most patients with MPS VII have intellectual disability and severely delayed speech development, usually associated with hearing impairment. Cognitive regression in neuronopathic MPS runs parallel to a significant decrease in brain tissue volume. Assessment of the developmental profile is challenging because of low cognitive abilities, physical impairment, and behavioral disturbances. Early diagnosis is crucial as different promising treatment approaches have been extensively studied in animal MPS models and are currently being applied in clinical trials.

MPS-IIIA mice acquire autistic behaviours with age

Mucopolysaccharidosis (MPS) type IIIA is an inherited, neurodegenerative lysosomal storage disorder resulting from mutations in the SGSH gene. Consequently, N-sulphoglucosamine sulphohydrolase enzyme activity is reduced resulting in impaired catabolism of heparan sulphate. After an asymptomatic period, patients typically show a progressive loss of cognitive and motor skills, with death often during the second decade of life. The diagnostic criteria of autism spectrum disorders (ASD) include impaired communication and social interactions, as well as displays of repetitive behaviours and fixed interests. Children with MPS-IIIA have been shown to exhibit decreased social communicative behaviours from approximately 3-4 years of age but behavioural stereotypies are mostly absent. In this study, we investigated whether a mouse model of MPS-IIIA exhibited ASD-like symptoms. The BTBR T⁺Itpr3^tf/J inbred mouse model of autism was used as a positive control. Male MPS-IIIA and BTBR mice were less sociable compared with unaffected C57BL/6 male mice in the reciprocal social approach test administered at 20 weeks of age. Alternations in the frequency of social interactions was not evident at earlier stages of the disease course, suggesting an acquisition of ASD-like social behaviours. Stereotypical behaviours were not evident in male MPS-IIIA mice in the marble-burying test nor was the quality of nest constructed by mice affected. Collectively, these data suggest that MPS-IIIA mice acquire autistic social behaviours similar to the human condition, and thus they may be useful for elucidating symptom generating mechanisms and novel treatments for ASD.

Observational Prospective Natural History of Patients with Sanfilippo Syndrome Type B

OBJECTIVE

To evaluate the natural course of disease progression in patients with Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB), identify potential end points for future therapy trials, and characterize biomarkers related to the disease.

STUDY DESIGN

A prospective, multicenter study was conducted. Baseline, 6-month, and 12-month assessments included neurodevelopmental status (Bayley Scales of Infant Development, Third edition), adaptive status (Vineland Adaptive Behavior Scales, Second Edition), volumetric brain magnetic resonance imaging, cerebrospinal fluid heparan sulfate, and urine glycosaminoglycan (GAG) measurements.

RESULTS

Nineteen patients aged 1.6-31.7 years were enrolled. Over 12 months, cognition, adaptive behavior, and cortical gray matter volume (GMV) declined in most patients. For patients diagnosed at <6 years, although there was no overall mean change over 12 months, there were 10%-48%, 3%-66%, and 1%-14% decreases in cognitive development quotient score, Vineland Adaptive Behavior Scales, Second Edition development quotient score, and cortical GMV in 8/12, 9/11, and 10/11 patients, respectively. Mean urine GAG and cerebrospinal fluid heparan sulfate levels were stable, but patients diagnosed at <6 years (n = 14) had higher levels than those ≥6 years at diagnosis (n = 4), which was likely associated with age as they also were generally younger.

CONCLUSIONS

Cognition, adaptive behavior, and cortical GMV measures sensitively tracked deterioration in patients with mucopolysaccharidosis type IIIB aged ≤8.6 years. Biomarkers may have prognostic value, but their sensitivity to disease progression requires further investigation. These findings should help evaluate enzyme replacement and gene therapy agents for this rare, devastating, neurodegenerative disease.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01509768.

Developmental and behavioral aspects of mucopolysaccharidoses with brain manifestations - Neurological signs and symptoms

The mucopolysaccharidoses (MPS) are a group of rare, inherited lysosomal storage disorders, caused by mutations in lysosomal enzymes involved in the degradation of glycosaminoglycans (GAGs). The resulting accumulation of GAGs in the body leads to widespread tissue and organ dysfunction. The spectrum, severity, and progression rate of clinical manifestations varies widely between and within the different MPS types. In addition to somatic signs and symptoms, which vary between the different MPS disorders, patients with MPS I, II, III, and VII present with significant neurological signs and symptoms, including impaired cognitive abilities, difficulties in language and speech, and/or behavioral and sleep problems. To effectively manage and develop therapies that target these neurological manifestations, it is of utmost importance to have a profound knowledge of their natural history and pathophysiology. This review describes the appearance and progression of neurological signs and symptoms in patients with MPS I, II, and III, based on presentations and discussions among an international group of experts during a meeting on the brain in MPS on April 28-30, 2016, and additional literature searches on this subject.

Assessments of neurocognitive and behavioral function in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a group of rare, inherited lysosomal storage disorders in which accumulation of glycosaminoglycans (GAGs) leads to progressive tissue and organ dysfunction. In addition to a variety of somatic signs and symptoms, patients with rapidly progressing MPS I (Hurler), II, III, and VII can present with significant neurological manifestations, including impaired cognitive abilities, difficulties in language and speech, behavioral abnormalities, sleep problems, and/or seizures. Neurological symptoms have a substantial impact on the quality of life of MPS patients and their families. Due to the progressive nature of cognitive impairment in these MPS patients, neurocognitive function is a sensitive indicator of disease progression, and a relevant outcome when testing efficacy of therapies for these disorders. In order to effectively manage and develop therapies that address neurological manifestations of MPS, it is important to use appropriate neurocognitive assessment tools that are sensitive to changes in neurocognitive function in MPS patients. This review discusses expert opinions on key issues and considerations for effective neurocognitive testing in MPS patients. In addition, it describes the neurocognitive assessment tools that have been used in clinical practice for these patients. The content of this review is based on existing literature and information from a meeting of international experts with extensive experience in managing and treating MPS disorders.

Practical management of behavioral problems in mucopolysaccharidoses disorders

The mucopolysaccharidosis (MPS) disorders are caused by deficiencies of specific lysosomal enzymes, resulting in progressive glycosaminoglycan (GAG) accumulation in cells and tissues throughout the body. Excessive GAG storage can lead to a variety of somatic manifestations as well as primary and secondary neurological symptoms. Behavioral problems (like hyperactivity, attention difficulties, and severe frustration) and sleeping problems are typical primary neurological symptoms of MPS caused by GAG accumulation in neurons, and are frequently observed in patients with MPS I, II, III, and VII. As these problems often place a significant burden on the family, proper management is important. This review summarizes current insights into behavioral and sleeping problems in MPS disorders and the most optimal management approaches, as presented and discussed during a meeting of an international group of experts with extensive experience in managing and treating MPS.

Symptoms of Autism Spectrum Disorder (ASD) in Individuals with Mucopolysaccharide Disease Type III (Sanfilippo Syndrome): A Systematic Review

The prevalence of autism spectrum disorder (ASD) in many genetic disorders is well documented but not as yet in Mucopolysaccharidosis type III (MPS III). MPS III is a recessively inherited metabolic disorder and evidence suggests that symptoms of ASD present in MPS III. This systematic review examined the extant literature on the symptoms of ASD in MPS III and quality assessed a total of 16 studies. Results indicated that difficulties within speech, language and communication consistent with ASD were present in MPS III, whilst repetitive and restricted behaviours and interests were less widely reported. The presence of ASD-like symptoms can result in late diagnosis or misdiagnosis of MPS III and prevent opportunities for genetic counselling and the provision of treatments.

Intracerebral gene therapy in children with mucopolysaccharidosis type IIIB syndrome: an uncontrolled phase 1/2 clinical trial

BACKGROUND

Mucopolysaccharidosis type IIIB syndrome (also known as Sanfilippo type B syndrome) is a lysosomal storage disease resulting in progressive deterioration of cognitive acquisition after age 2-4 years. No treatment is available for the neurological manifestations of the disease. We sought to assess the safety and efficacy of a novel intracerebral gene therapy.

METHODS

Local regulatory authorities in France allowed inclusion of up to four children in this phase 1/2 study. Treatment was 16 intraparenchymal deposits (four in the cerebellum) of a recombinant adenoassociated viral vector serotype 2/5 (rAAV2/5) encoding human α-N-acetylglucosaminidase (NAGLU) plus immunosuppressive therapy. We assessed tolerance, neurocognitive progression, brain growth, NAGLU enzymatic activity in CSF, and specific anti-NAGLU immune response for 30 months after surgery. This trial is registered with EudraCT, number 2012-000856-33, and the International Standard Clinical Trial Registry, number ISRCTN19853672.

FINDINGS

Of seven eligible children, the four youngest, from France (n=2), Italy (n=1), and Greece (n=1), aged 20, 26, 30, and 53 months, were included between February, 2012, and February, 2014. 125 adverse events were recorded, of which 117 were treatment emergent and included six classified as severe, but no suspected unexpected serious adverse drug reactions were seen. Vector genomes were detected in blood for 2 days after surgery. Compared with the natural history of mucopolysaccharidosis type III syndromes, neurocognitive progression was improved in all patients, with the youngest patient having function close to that in healthy children. Decrease in developmental quotient was -11·0 points in patient one, -23·0 in patient two, -29·0 in patient three, and -17·0 in patient four, compared with -37·7 in the natural history of the disease. NAGLU activity was detected in lumbar CSF and was 15-20% of that in unaffected children. Circulating T lymphocytes that proliferated and produced tumour necrosis factor α upon ex-vivo exposure to NAGLU antigens were detectable at 1-12 months and 3-12 months, respectively, but not at 30 months in three of four patients.

INTERPRETATION

Intracerebral rAVV2/5 was well tolerated and induced sustained enzyme production in the brain. The initial specific anti-NAGLU immune response that later subsided suggested acquired immunological tolerance. The best results being obtained in the youngest patient implies a potential window of opportunity. Longer follow-up is needed to further assess safety outcomes and persistence of improved cognitive development.

FUNDING

Association Française Contre les Myopathies, Vaincre les Maladies Lysosomales, Institut Pasteur, and UniQure.

Recommendations on clinical trial design for treatment of Mucopolysaccharidosis Type III

Background

Mucopolysaccharidosis type III is a progressive, neurodegenerative lysosomal storage disorder for which there is currently no effective therapy. Though numerous potential therapies are in development, there are several challenges to conducting clinical research in this area. We seek to make recommendations on the approach to clinical research in MPS III, including the selection of outcome measures and trial endpoints, in order to improve the quality and impact of research in this area.

Results

An international workshop involving academic researchers, clinical experts and industry groups was held in June 2015, with presentations and discussions on disease pathophysiology, biomarkers, potential therapies and clinical outcome measures. A set of recommendations was subsequently prepared by a working group and reviewed by all delegates. We present a series of 11 recommendations regarding the conduct of clinical research, outcome measures and management of natural history data in Mucopolysaccharidosis type III.

Conclusions

Improving the quality of clinical research in Mucopolysaccharidosis type III will require an open, collaborative and systematic approach between academic researchers, clinicians and industry. Natural history data should be published as soon as possible and ideally collated in a central repository. There should be agreement on outcome measures and instruments for evaluation of clinical outcomes to maximise the effectiveness of current and future clinical research.

Role of Genetics in the Etiology of Autistic Spectrum Disorder: Towards a Hierarchical Diagnostic Strategy

Progress in epidemiological, molecular and clinical genetics with the development of new techniques has improved knowledge on genetic syndromes associated with autism spectrum disorder (ASD). The objective of this article is to show the diversity of genetic disorders associated with ASD (based on an extensive review of single-gene disorders, copy number variants, and other chromosomal disorders), and consequently to propose a hierarchical diagnostic strategy with a stepwise evaluation, helping general practitioners/pediatricians and child psychiatrists to collaborate with geneticists and neuropediatricians, in order to search for genetic disorders associated with ASD. The first step is a clinical investigation involving: (i) a child psychiatric and psychological evaluation confirming autism diagnosis from different observational sources and assessing autism severity; (ii) a neuropediatric evaluation examining neurological symptoms and developmental milestones; and (iii) a genetic evaluation searching for dysmorphic features and malformations. The second step involves laboratory and if necessary neuroimaging and EEG studies oriented by clinical results based on clinical genetic and neuropediatric examinations. The identification of genetic disorders associated with ASD has practical implications for diagnostic strategies, early detection or prevention of co-morbidity, specific treatment and follow up, and genetic counseling.

Klüver-Bucy syndrome associated with a recessive variant in HGSNAT in two siblings with Mucopolysaccharidosis type IIIC (Sanfilippo C)

Klüver-Bucy syndrome (KBS) comprises a set of neurobehavioral symptoms with psychic blindness, hypersexuality, disinhibition, hyperorality, and hypermetamorphosis that were originally observed after bilateral lobectomy in Rhesus monkeys. We investigated two siblings with KBS from a consanguineous family by whole-exome sequencing and autozygosity mapping. We detected a homozygous variant in the heparan-α-glucosaminidase-N-acetyltransferase gene (HGSNAT; c.518G>A, p.(G173D), NCBI ClinVar RCV000239404.1), which segregated with the phenotype. Disease-causing variants in this gene are known to be associated with autosomal recessive Mucopolysaccharidosis type IIIC (MPSIIIC, Sanfilippo C). This lysosomal storage disease is due to deficiency of the acetyl-CoA:α-glucosaminidase-N-acetyltransferase, which was shown to be reduced in patient fibroblasts. Our report extends the phenotype associated with MPSIIIC. Besides MPSIIIA and MPSIIIB, due to variants in SGSH and NAGLU, this is the third subtype of Sanfilippo disease to be associated with KBS. MPSIII should be included in the differential diagnosis of young patients with KBS.

Behavioral deficits and cholinergic pathway abnormalities in male Sanfilippo B mice

Sanfilippo B syndrome is a progressive neurological disorder caused by inability to catabolize heparan sulfate glycosaminoglycans. We studied neurobehavior in male Sanfilippo B mice and heterozygous littermate controls from 16 to 20 weeks of age. Affected mice showed reduced anxiety, with a decrease in the number of stretch-attend postures during the elevated plus maze (p=0.001) and an increased tendency to linger in the center of an open field (p=0.032). Water maze testing showed impaired spatial learning, with reduced preference for the target quadrant (p=0.01). In radial arm maze testing, affected mice failed to achieve above-chance performance in a win-shift working memory task (t-test relative to 50% chance: p=0.289), relative to controls (p=0.037). We found a 12.4% reduction in mean acetylcholinesterase activity (p<0.001) and no difference in choline acetyltransferase activity or acetylcholine in whole brain of affected male animals compared to controls. Cholinergic pathways are affected in adult-onset dementias, including Alzheimer disease. Our results suggest that male Sanfilippo B mice display neurobehavioral deficits at a relatively early age, and that as in adult dementias, they may display deficits in cholinergic pathways.