Outcome in six children with mucopolysaccharidosis type IH, Hurler syndrome, after haematopoietic stem cell transplantation (HSCT)

Effects of lithium administration on vertebral bone disease in mucopolysaccharidosis I dogs

Mucopolysaccharidosis (MPS) I is a lysosomal storage disease characterized by deficient activity of the enzyme alpha-L-iduronidase, leading to abnormal accumulation of heparan and dermatan sulfate glycosaminoglycans in cells and tissues. Patients commonly exhibit progressive skeletal abnormalities, in part due to failures of endochondral ossification during postnatal growth. Previously, using the naturally-occurring canine model, we showed that bone and cartilage cells in MPS I exhibit elevated lysosomal storage from an early age and that animals subsequently exhibit significantly diminished vertebral trabecular bone formation. Wnts are critical regulators of endochondral ossification that depend on glycosaminoglycans for signaling. The objective of this study was to examine whether lithium, a glycogen synthase kinase-3 inhibitor and stimulator of Wnt/beta-catenin signaling, administered during postnatal growth could attenuate progression of vertebral trabecular bone disease in MPS I. MPS I dogs were treated orally with therapeutic levels of lithium carbonate from 14 days to 6 months-of-age. Untreated heterozygous and MPS I dogs served as controls. Serum was collected at 3 and 6 months for assessment of bone turnover markers. At the study end point, thoracic vertebrae were excised and assessed using microcomputed tomography and histology. Lithium-treated animals exhibited significantly improved trabecular spacing, number and connectivity density, and serum bone-specific alkaline phosphatase levels compared to untreated animals. Growth plates from lithium-treated animals exhibited increased numbers of hypertrophic chondrocytes relative to both untreated MPS I and heterozygous animals. These findings suggest that bone and cartilage cells in MPS I are still capable of responding to exogenous osteogenic signals even in the presence of significant lysosomal storage, and that targeted osteogenic therapies may represent a promising approach for attenuating bone disease progression in MPS I.

Mucopolysaccharidosis Type I: Current Treatments, Limitations, and Prospects for Improvement

Mucopolysaccharidosis type I (MPS I) is a lysosomal disease, caused by a deficiency of the enzyme alpha-L-iduronidase (IDUA). IDUA catalyzes the degradation of the glycosaminoglycans dermatan and heparan sulfate (DS and HS, respectively). Lack of the enzyme leads to pathologic accumulation of undegraded HS and DS with subsequent disease manifestations in multiple organs. The disease can be divided into severe (Hurler syndrome) and attenuated (Hurler-Scheie, Scheie) forms. Currently approved treatments consist of enzyme replacement therapy (ERT) and/or hematopoietic stem cell transplantation (HSCT). Patients with attenuated disease are often treated with ERT alone, while the recommended therapy for patients with Hurler syndrome consists of HSCT. While these treatments significantly improve disease manifestations and prolong life, a considerable burden of disease remains. Notably, treatment can partially prevent, but not significantly improve, clinical manifestations, necessitating early diagnosis of disease and commencement of treatment. This review discusses these standard therapies and their impact on common disease manifestations in patients with MPS I. Where relevant, results of animal models of MPS I will be included. Finally, we highlight alternative and emerging treatments for the most common disease manifestations.

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.

Treatment of thoracolumbar kyphosis in patients with mucopolysaccharidosis type I: results of an international consensus procedure

Background

In all patients with mucopolysaccharidosis type I (MPS I), skeletal disease (dysostosis multiplex) is a prominent, debilitating, condition related complication that may impact strongly on activities of daily living. Unfortunately, it is not alleviated by treatment with hematopoietic cell transplantation (HCT) or enzyme replacement therapy (ERT). Although early kyphosis is one of the key features of dysostosis multiplex, there is no international consensus on the optimal management. Therefore, an international consensus procedure was organized with the aim to develop the first clinical practice guideline for the management of thoracolumbar kyphosis in MPS I patients.

Methods

A literature review was conducted to identify all available information about kyphosis and related surgery in MPS I patients. Subsequently, a modified Delphi procedure was used to develop consensus statements. The expert panel included 10 spinal orthopedic surgeons, 6 pediatricians and 3 physiotherapists, all experienced in MPS I. The procedure consisted of 2 written rounds, a face-to-face meeting and a final written round. The first 2 rounds contained case histories, general questions and draft statements. During the face-to-face meeting consensus statements were developed. In the final round, the panel had the opportunity to anonymously express their opinion about the proposed statements.

Results

Eighteen case series and case reports were retrieved from literature reporting on different surgical approaches and timing of thoracolumbar kyphosis surgery in MPS I. During the face-to-face meeting 16 statements were discussed and revised. Consensus was reached on all statements.

Conclusion

This international consensus procedure resulted in the first clinical practice guideline for the management of thoracolumbar kyphosis in MPS I patients, focusing on the goals and timing of surgery, as well as the optimal surgical approach, the utility of bracing and required additional assessments (e.g. radiographs). Most importantly, it was concluded that the decision for surgery depends not only on the kyphotic angle, but also on additional factors such as the progression of the deformity and its flexibility, the presence of symptoms, growth potential and comorbidities. The eventual goal of treatment is the maintenance or improvement of quality of life. Further international collaborative research related to long-term outcome of kyphosis surgery in MPS I is essential as prognostic information is lacking.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-0997-5) contains supplementary material, which is available to authorized users.

The effect of haemopoietic stem cell transplantation on the ocular phenotype in mucopolysaccharidosis type I (Hurler)

PURPOSE

To determine whether the ocular phenotype in patients with mucopolysaccharidosis type I (MPSI) Hurler is affected by the efficacy of previous haemopoietic stem cell transplantation (HSCT).

DESIGN

A retrospective cohort study of patients with MPSI who had undergone treatment with HSCT.

METHODS

Ocular phenotype was documented for each patient and compared to levels of biomarkers representing efficacy of previous transplantation.

MAIN OUTCOME MEASURES

Assessment of visual acuity (VA), severity of corneal clouding and the presence of optic neuropathy or retinopathy. Biomarker assessment included dermatan sulphate/chondroitin sulphate (DS/CS) ratio and iduronidase enzyme level.

RESULTS

Severe corneal clouding was significantly greater in patients with lower iduronidase levels (p = 0.023) and raised DS/CS ratio (R²  = 0.28 p = 0.043). Better VA was related to a higher iduronidase levels (R²  = 0.15, p = 0.004) and lower DS/CS ratio (R²  = 0.38, p = 0.001).

CONCLUSION

Improved ocular phenotypes in MPSI are associated with markers signifying efficacy of prior transplant. Early and effective HSCT may result in a better visual prognosis and reduction in ocular complications for patients with MPSI.

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.

Chiari I malformation and syringomyelia in mucopolysaccharidosis type I (Hurler syndrome) treated with posterior fossa decompression: Case report and review of the literature

Background:

Hurler Syndrome is the most severe phenotype of mucopolysaccharidosis type I. With bone marrow transplant and enzyme replacement therapy, the life expectancy of a child with Hurler syndrome has been extended, predisposing them to multiple musculoskeletal issues most commonly involving the spine.

Case Description:

This is the case report of a 6-year-old male with Hurler syndrome who was diagnosed with Chiari I malformation and cervicothoracic syringomyelia on a preoperative magnetic resonance imaging (MRI) for his thoracolumbar kyphosis. This report details the successful management of a Chiari I malformation and syringomyelia with posterior fossa decompression in a child with Hurler syndrome.

Conclusion:

Children born with MPS I can have complex spine issues that require surgical management. The most common orthopedic spinal condition for these patients, thoracolumbar kyphosis, requires evaluation with an MRI before performing surgery. This resulted in the diagnosis of a Chiari I malformation and syringomyelia in our patient with Hurler syndrome. This was successfully treated with decompression of the posterior fossa.

Cognitive and adaptive measurement endpoints for clinical trials in mucopolysaccharidoses types I, II, and III: A review of the literature

Sensitive, reliable measurement instruments are critical for the evaluation of disease progression and new treatments that affect the brain in the mucopolysaccharidoses (MPS). MPS I, II, and III have early onset clinical phenotypes that affect the brain during development and result in devastating cognitive decline and ultimately death without treatment. Comparisons of outcomes are hindered by diverse protocols and approaches to assessment including applicability to international trials necessary in rare diseases. We review both cognitive and adaptive measures with the goal of providing evidence to a Delphi panel to come to a consensus about recommendations for clinical trials for various age groups. The results of the consensus panel are reported in an accompanying article. The following data were gathered (from internet resources and from test manuals) for each measure and summarized in the discussion: reliability, validity, date and adequacy of normative data, applicability of the measure's metrics, cross cultural validity including translations and adaptations, feasibility in the MPS population, familiarity to sites, sensitivity to change, and interpretability. If, resulting from this consensus, standard protocols are used for both natural history and treatment studies, patients, their families, and health care providers will benefit from the ability to compare study outcomes.

Cognitive endpoints for therapy development for neuronopathic mucopolysaccharidoses: Results of a consensus procedure

The design and conduct of clinical studies to evaluate the effects of novel therapies on central nervous system manifestations in children with neuronopathic mucopolysaccharidoses is challenging. Owing to the rarity of these disorders, multinational studies are often needed to recruit enough patients to provide meaningful data and statistical power. This can make the consistent collection of reliable data across study sites difficult. To address these challenges, an International MPS Consensus Conference for Cognitive Endpoints was convened to discuss approaches for evaluating cognitive and adaptive function in patients with mucopolysaccharidoses. The goal was to develop a consensus on best practice for the design and conduct of clinical studies investigating novel therapies for these conditions, with particular focus on the most appropriate outcome measures for cognitive function and adaptive behavior. The outcomes from the consensus panel discussion are reported here.

Cognitive outcomes and age of detection of severe mucopolysaccharidosis type 1

The US Secretary of Health and Human Services recommended in February 2016 that mucopolysaccharidosis type 1 (MPS I) be added to the recommended uniform screening panel for state newborn screening programs. One of the key factors in this decision was the evidence suggesting that earlier treatment with hematopoietic cell transplantation (HCT) for the most severe form, Hurler syndrome (MPS IH), would lead to improved cognitive outcomes. Consistent evidence from peer-reviewed studies suggests that transplantation in the first year of life is associated with improved developmental quotient or intelligence quotient and continued cognitive growth, with earlier age of treatment associated with improved outcomes. However, available evidence suggests that cognitive functioning and attention can still lag behind unaffected age-matched children, leading to the need for special education services. Verbal and nonverbal cognitive abilities outcomes may be affected differently by HCT. With the recent addition of MPS I to the recommended uniform screening panel, future work is needed to evaluate the impact of earlier, presymptomatic detection and treatment initiation and other supportive therapies on cognitive outcomes.Genet Med advance online publication 26 January 2017.

Pathogenesis and treatment of spine disease in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a family of lysosomal storage disorders characterized by deficient activity of enzymes that degrade glycosaminoglycans (GAGs). Skeletal disease is common in MPS patients, with the severity varying both within and between subtypes. Within the spectrum of skeletal disease, spinal manifestations are particularly prevalent. Developmental and degenerative abnormalities affecting the substructures of the spine can result in compression of the spinal cord and associated neural elements. Resulting neurological complications, including pain and paralysis, significantly reduce patient quality of life and life expectancy. Systemic therapies for MPS, such as hematopoietic stem cell transplantation and enzyme replacement therapy, have shown limited efficacy for improving spinal manifestations in patients and animal models. Therefore, there is a pressing need for new therapeutic approaches that specifically target this debilitating aspect of the disease. In this review, we examine how pathological abnormalities affecting the key substructures of the spine - the discs, vertebrae, odontoid process and dura - contribute to the progression of spinal deformity and symptomatic compression of neural elements. Specifically, we review current understanding of the underlying pathophysiology of spine disease in MPS, how the tissues of the spine respond to current clinical and experimental treatments, and discuss future strategies for improving the efficacy of these treatments.

Long-Term Cognitive and Functional Outcomes in Children with Mucopolysaccharidosis (MPS)-IH (Hurler Syndrome) Treated with Hematopoietic Cell Transplantation

The long-term cognitive and functional outcomes of children with mucopolysaccharidosis type I (MPS-IH) post-hematopoietic cell transplant (HCT) are not well documented, and the role of genetic and treatment factors in these outcomes has yet to be defined. In this multi-site, international study, we (1) characterize the cognitive and functional status of 47 individuals (ages 2-25, mean of 10.6 years) with MPS-IH who are 1-24 years post HCT (mean = 9 years) and (2) examine contributions of genotype, transplant characteristics, and sociodemographic factors to cognitive ability, adaptive behavior, and quality of life. The overall cognitive ability of our sample was mildly impaired, more than two standard deviations below general population norms. Parent reported adaptive behaviors (i.e., communication, daily living, and motor skills) were similarly impaired with a relative strength in socialization. Quality of life, as reported by parents, fell more than two standard deviations below population norms for physical functioning; however, psychosocial quality of life (emotional well-being) approximated population norms. In linear regression analysis, adjusted for demographic and treatment factors, mutation severity was associated with lower cognitive ability (p = 0.005) and adaptive functioning (p = 0.004), but not parent ratings of children's quality of life. Older age at HCT was associated with poorer physical quality of life (p = 0.002); lower socioeconomic status (p = 0.028) and unrelated bone marrow HCT (p = 0.010) were associated with poorer psychosocial quality of life. Implications for screening and early intervention for children at risk for poorer cognitive and functional outcomes are described.

Characterization of the MPS I-H knock-in mouse reveals increased femoral biomechanical integrity with compromised material strength and altered bone geometry

Mucopolysaccharidosis type I (MPS I), is an autosomal recessive lysosomal storage disorder caused by a deficiency in the α-L-iduronidase enzyme, resulting in decreased enzymatic activity and accumulation of glycosaminoglycans. The disorder phenotypically manifests with increased urine glycosaminoglycan excretion, facial dysmorphology, neuropathology, cardiac manifestations, and bone deformities. While the development of new treatment strategies have shown promise in attenuating many symptoms associated with the disorder, the bone phenotype remains unresponsive. The aim of this study was to investigate and further characterize the skeletal manifestations of the Idua-W392X knock-in mouse model, which carries a nonsense mutation corresponding to the IDUA-W402X mutation found in Hurler syndrome (MPS I-H) patients. μCT analysis of the microarchitecture demonstrated increased cortical thickness, trabecular number, and trabecular connectivity along with decreased trabecular separation in the tibiae of female homozygous Idua-W392X knock-in (IDUA^−/−) mice, and increased cortical thickness in male IDUA^−/− tibiae. Cortical density, as determined by μCT, and bone mineral density distribution, as determined by quantitative backscattered microscopy, were equivalent in IDUA^−/− and wildtype (Wt) bone. However, tibial porosity was increased in IDUA^−/− cortical bone. Raman spectroscopy results indicated that tibiae from female IDUA^−/− had decreased phosphate to matrix ratios and increased carbonate to phosphate ratios compared to Wt female tibiae, whereas these ratios remained equivalent in male IDUA^−/− and Wt tibiae. Femora demonstrated altered geometry and upon torsional loading to failure analysis, female IDUA^−/− mouse femora exhibited increased torsional ultimate strength, with a decrease in material strength relative to Wt littermates. Taken together, these findings suggest that the IDUA^−/− mutation results in increased bone torsional strength by altering the overall bone geometry and the microarchitecture which may be a compensatory response to increased porosity, reduced bone tensile strength and altered physiochemical composition.

Neurocognition across the spectrum of mucopolysaccharidosis type I: Age, severity, and treatment

OBJECTIVES

Precise characterization of cognitive outcomes and factors that contribute to cognitive variability will enable better understanding of disease progression and treatment effects in mucopolysaccharidosis type I (MPS I). We examined the effects on cognition of phenotype, genotype, age at evaluation and first treatment, and somatic disease burden.

METHODS

Sixty patients with severe MPS IH (Hurler syndrome treated with hematopoietic cell transplant and 29 with attenuated MPS I treated with enzyme replacement therapy), were studied with IQ measures, medical history, genotypes. Sixty-seven patients had volumetric MRI. Subjects were grouped by age and phenotype and MRI and compared to 96 normal controls.

RESULTS

Prior to hematopoietic cell transplant, MPS IH patients were all cognitively average, but post-transplant, 59% were below average, but stable. Genotype and age at HCT were associated with cognitive ability. In attenuated MPS I, 40% were below average with genotype and somatic disease burden predicting their cognitive ability. White matter volumes were associated with IQ for controls, but not for MPS I. Gray matter volumes were positively associated with IQ in controls and attenuated MPS I patients, but negatively associated in MPS IH.

CONCLUSIONS

Cognitive impairment, a major difficulty for many MPS I patients, is associated with genotype, age at treatment and somatic disease burden. IQ association with white matter differed from controls. Many attenuated MPS patients have significant physical and/or cognitive problems and receive insufficient support services. Results provide direction for future clinical trials and better disease management.

Delivering drugs to the central nervous system: an overview

Developing therapies for the brain is perhaps the greatest challenge facing modern medicine today. While a great many potential therapies show promise in animal models, precious few make it to approval or are even studied in human patients. The particular challenges to the translation of neurotherapeutics to the clinic are many, but a major barrier is difficulty in delivering therapeutics into the brain. The goal of this workshop was to present ways to deliver therapeutics to the brain, including the limitations of each method, and describe ways to track their delivery, safety, and efficacy. Solving the problem of delivery will aid translation of therapeutics for patients suffering from neurodegeneration and other disorders of the brain.

Long-term functional outcomes of children with hurler syndrome treated with unrelated umbilical cord blood transplantation

OBJECTIVES

Hurler syndrome is characterized by progressive multisystem deterioration leading to early death in childhood. This prospective study evaluated the long-term outcomes of patients with Hurler syndrome who underwent umbilical cord blood transplantation from unrelated donors.

STUDY DESIGN

Only patients with Hurler syndrome who underwent umbilical cord blood transplantation between December 1995 and March 2006 (n = 25) and who were followed for at least 5 years (n = 19) were included in the analysis. The patients were longitudinally evaluated by a multidisciplinary team of specialists following a standardized protocol.

RESULTS

Median age at transplantation was 15.9 months (range 2.1-35), and patients were followed up until a median age of 10.1 years (range 7.2-14.9). Overall survival was 80%. All successfully transplanted patients achieved full donor chimerism and normal enzyme levels, and all children continue to make gains in development. Gross motor function was the most affected area. Vision and hearing were compromised in a minority of the patients, with some requiring corneal transplant or hearing aids. Cardiopulmonary function improved. Some children required orthopedic surgery, but severe complications were prevented in most patients. Although longitudinal growth was lower than that of unaffected children, it was considerably higher than expected from the natural course of the disease. Head circumference normalized. Hydrocephalus was not observed at longer follow-up, and cerebral atrophy decreased over time.

CONCLUSIONS

In this descriptive study of children with Hurler syndrome, unrelated umbilical cord blood transplantation was associated with improved somatic disease and neurodevelopment.

Early treatment is associated with improved cognition in Hurler syndrome

OBJECTIVE

Hurler syndrome is the most clinically severe form of an autosomal recessive lysosomal disorder characterized by the deficiency of α-L-iduronidase. The resulting accumulation of glycosaminoglycans causes progressive multisystem deterioration, resulting in death in childhood. Umbilical cord blood transplantation from unrelated donors has been previously shown to improve neurological outcomes of children <2 years of age and prolong life. The purpose of this article is to determine whether age at transplantation can predict cognitive outcomes.

METHODS

Between June 1997 and February 2013, 31 patients with Hurler syndrome underwent umbilical cord blood transplantation and were evaluated at baseline and every 6 to 12 months thereafter. All 31 patients underwent complete neurodevelopmental evaluation (median follow-up = 7.3 years, range = 2-21.7) and a median of 7.0 evaluations (range = 3-18).

RESULTS

Younger age at transplantation was associated with improved cognitive function (p = 0.001), receptive and expressive language (p = 0.004 and p = 0.01), and adaptive behavior (p = 0.03).

INTERPRETATION

Early age at transplantation is a strong predictor of cognitive, language, and adaptive behavior outcomes. Children younger than 9 months at the time of transplant showed normal cognitive development. Our results demonstrate that early diagnosis is necessary for optimal outcomes and support the need for newborn screening, because most patients are not identified at this young age.

Biomarkers of bone remodeling in children with mucopolysaccharidosis types I, II, and VI

PURPOSE

Skeletal disease causes significant morbidity in mucopolysaccharidoses (MPS), and bone remodeling processes in MPS have not been well characterized. The objective of this study was to determine if biomarkers of bone turnover are abnormal in children with specific MPS disorders (i.e. MSP-I, MPS-II, and MPS-VI) compared to healthy children.

METHODS

A cross-sectional study was performed of serum biomarkers of bone formation (bone-specific alkaline phosphatase [BSAP], osteocalcin) and urine biomarkers of bone resorption (pyridinoline, deoxypyridinoline) in MPS and healthy controls. Measures of physical function and pain were obtained using the Children's Health Questionnaire (CHQ).

RESULTS

The cohort consisted of 39 children with MPS (MPS-I=26; MPS-II=11; MPS-VI=4) and 51 healthy children. Adjusting for sex and Tanner stage group, MPS individuals had statistically significant increases for osteocalcin (p< 0.001), with trends toward higher BSAP (p=0.054) and urinary pyridinoline (p=0.084). These biomarkers were not significantly associated with CHQ bodily pain and physical-function scores.

CONCLUSION

Osteocalcin was increased in children with MPS disorders, with trends for increases in BSAP and urinary pyridinoline, suggesting that bone remodeling is altered in children with MPS. Future studies to assess the ability of these biomarkers to quantify and monitor MPS skeletal disease in response to therapy are needed.

Phase I/II clinical trial of enzyme replacement therapy with idursulfase beta in patients with mucopolysaccharidosis II (Hunter syndrome)

Background

Mucopolysaccharidosis II (MPS II, Hunter syndrome) is a rare X-linked lysosomal storage disorder caused by the deficiency of iduronate-2-sulfatase (IDS). In affected patients, glycosaminoglycan (GAG) accumulates in the lysosomes of many organs and tissues contributing to the pathology associated with MPS II. The objective of this phase I/II clinical study was to evaluate the efficacy and safety of recombinant human iduronate-2-sulfatase (idursulfase beta, Hunterase^®) in the treatment of MPS II.

Methods

Thirty-one MPS II patients between 6 and 35 years of age were enrolled in a randomized, single-blinded, active comparator-controlled phase I/II trial for 24 weeks. Patients were randomized to active comparator infusions (N=11), 0.5 mg/kg idursulfase beta infusions (N=10), or 1.0 mg/kg idursulfase beta infusions (N=10). The primary efficacy variable was the level of urinary GAG excretion. The secondary variables were changes in the distance walked in 6 minutes (6-minute walk test, 6MWT), echocardiographic findings, pulmonary function tests, and joint mobility.

Results

Patients in all three groups exhibited reduction in urine GAG and this reduced GAG level was maintained for 24 weeks. Urine GAG was also significantly reduced in the 0.5 mg/kg and 1.0 mg/kg idursulfase beta groups when compared to the active comparator group (P = 0.043, 0.002, respectively). Changes in 6MWT were significantly greater in the 0.5 mg/kg and 1.0 mg/kg idursulfase groups than in the active comparator group (p= 0.003, 0.015, respectively). Both idursulfase beta infusions were generally safe and well tolerated, and elicited no serious adverse drug reactions. The most frequent adverse events were urticaria and skin rash, which were easily controlled with administration of antihistamines.

Conclusions

This study indicates that idursulfase beta generates clinically significant reduction of urinary GAG, improvements in endurance as measured by 6MWT, and it has an acceptable safety profile for the treatment of MPS II.

Trial registration

ClinicalTrials.gov: NCT01301898

Variable disease progression after successful stem cell transplantation: prospective follow-up investigations in eight patients with Hurler syndrome

We report the results of a prospective, standardized follow-up programme of eight children (median age at SCT 1.2 yr) with mucopolysaccharidosis (MPS1H, M. Hurler) transplanted using a fludarabine-based SCT. SCT resulted in stable engraftment without transplant-related mortality. All patients are alive, engrafted and in ambulatory care. During follow-up (median five yr, 1.9-8 yr), six of eight showed developmental delay (two severe, two mild/no), all eight had spinal deformities and one received hip surgery for acetabular dysplasia. Hand surgery for carpal tunnel release and trigger digits was required in five of the patients. The cranio-cervical junction was narrowed in four patients, one child having already received surgery. CC was present in all patients prior to SCT. It remained unchanged in seven and regressed in one child. Severe cardiac dysfunction was present in two of the eight children before SCT. Cardiac pump function was normal in six patients and ameliorated in two, while valve abnormalities could be detected in six patients. Currently, transplantation seems no longer the major obstacle for MPS1H patients, but the variable musculoskeletal disease progression after successful SCT remains a challenge. Patients with Hurler syndrome need specialized follow-up care because of their manifold health problems. The standardized follow-up presented here is a step to optimize care for MPS children and their families after SCT.

Cardiac disease in patients with mucopolysaccharidosis: presentation, diagnosis and management

The mucopolysaccharidoses (MPSs) are inherited lysosomal storage disorders caused by the absence of functional enzymes that contribute to the degradation of glycosaminoglycans (GAGs). The progressive systemic deposition of GAGs results in multi-organ system dysfunction that varies with the particular GAG deposited and the specific enzyme mutation(s) present. Cardiac involvement has been reported in all MPS syndromes and is a common and early feature, particularly for those with MPS I, II, and VI. Cardiac valve thickening, dysfunction (more severe for left-sided than for right-sided valves), and hypertrophy are commonly present; conduction abnormalities, coronary artery and other vascular involvement may also occur. Cardiac disease emerges silently and contributes significantly to early mortality.The clinical examination of individuals with MPS is often difficult due to physical and, sometimes, intellectual patient limitations. The absence of precordial murmurs does not exclude the presence of cardiac disease. Echocardiography and electrocardiography are key diagnostic techniques for evaluation of valves, ventricular dimensions and function, which are recommended on a regular basis. The optimal technique for evaluation of coronary artery involvement remains unsettled.Standard medical and surgical techniques can be modified for MPS patients, and systemic therapies such as hematopoietic stem cell transplantation and enzyme replacement therapy (ERT) may alter overall disease progression with regression of ventricular hypertrophy and maintenance of ventricular function. Cardiac valve disease is usually unresponsive or, at best, stabilized, although ERT within the first few months of life may prevent valve involvement, a fact that emphasizes the importance of early diagnosis and treatment in MPS.

Orthopaedic management of Hurler's disease after hematopoietic stem cell transplantation: a systematic review

OBJECTIVE

The introduction of hematopoietic stem cell transplantation (HSCT) has significantly improved the life-span of Hurler patients (mucopolysaccharidosis type I-H, MPS I-H). Yet, the musculoskeletal manifestations seem largely unresponsive to HSCT. In order to facilitate evidence based management, the aim of the current study was to give a systematic overview of the orthopaedic complications and motor functioning of Hurler's patients after HSCT.

METHODS

A systematic review was conducted of the medical literature published from January 1981 to June 2010. Two reviewers independently assessed all eligible citations, as identified from the Pubmed and Embase databases. A pre-developed data extraction form was used to systematically collect information on the prevalence of radiological and clinical signs, and on the orthopaedic treatments and outcomes.

RESULTS

A total of 32 studies, including 399 patient reports were identified. The most frequent musculoskeletal abnormalities were odontoid hypoplasia (72%), thoracolumbar kyphosis (81%), genu valgum (70%), hip dysplasia (90%) and carpal tunnel syndrome (63%), which were often treated surgically during the first decade of life. The overall complication rate of surgical interventions was 13.5%. Motor functioning was further hampered due to reduced joint mobility, hand dexterity, motor development and longitudinal growth.

CONCLUSION

Stem cell transplantation does not halt the progression of a large range of disabling musculoskeletal abnormalities in Hurler's disease. Although prospective data on the quantification, progression and treatment of these deformities were very limited, early surgical intervention is often advocated. Prospective data collection will be mandatory to achieve better evidence on the effect of treatment strategies.

The craniocervical junction following successful haematopoietic stem cell transplantation for mucopolysaccharidosis type I H (Hurler syndrome)

Mucopolysaccharidosis I Hurler (MPS IH) is a progressive multisystemic disorder caused by alpha-L-iduronidase deficiency. First choice of treatment in MPS IH children is haematopoietic stem cell transplantation (HSCT). The effect of HSCT has been shown to have limited influence on skeletal manifestations by poor penetration of musculoskeletal tissues by the enzyme derived from donor leucocytes. Aim of this study was to investigate the effect of HSCT on the craniocervical junction (CCJ) in Hurler patients. We analysed retrospectively sequential magnetic resonance imaging (MRI) scans of 30 patients with Hurler disease treated by HSCT since 1982 at the Royal Manchester Children's Hospital, UK, in order to determine whether the patients suffer from dens hypoplasia. Results were compared with biochemical and clinical characteristics: Enzyme activity (EA), chimerism, urinary glycosaminoglycan (GAG) excretion and neurological status. Investigations were part of standard clinical procedures. Results are descriptive in presentation. In 26/30 patients a determination of odontoid hypoplasia was feasible. The majority showed a normal dens length and an increase with age. Only 3/26 revealed a dens hypoplasia. One of them had only partial donor engraftment (DE) with reduced EA, one of them suffered from chronic graft versus host disease (GVHD). One patient with only partial DE and reduced EA presented with initial dens hypoplasia until preadolescence but normalized later on. There may be a trend towards lower EA and the occurrence of DH in transplanted MPS patients - perhaps the dosage of enzyme plays a role in the correction of skeletal complications in this patient group. HSCT patients with incomplete DE and therefore lower EAs may require special attention and care.

Therapeutic liver repopulation for phenylketonuria

Problems with long-term dietary compliance in phenylketonuria (PKU) necessitate the development of alternative treatment approaches. Therapeutic liver repopulation with phenylalanine hydroxylase (PAH)-expressing cells following hepatocyte or haematopoietic stem cell transplantation has been investigated as a possible novel treatment approach for PKU. Successful therapeutic liver repopulation requires both a stimulus for liver regeneration at the time of cell transplantation and a selective growth advantage for the PAH+ donor cells. Unfortunately, wild-type PAH+ hepatocytes do not enjoy any growth advantage over PAH- cells. Successful correction of hyperphenylalaninemia following therapeutic liver repopulation has been accomplished only in an animal model that yields a selective advantage for the donor cells. Haematopoietic stem cell (HSC)-mediated therapeutic liver repopulation has not been reported in any hyperphenylalaninemic system, and the success of HSC-mediated liver repopulation for PKU may be limited by the slow kinetics of this approach. If therapeutic liver repopulation is to be employed successfully in humans with PKU, an effective method of providing a selective growth advantage for the donor cells must be developed. If this can be achieved, liver repopulation with 10-20% wild-type hepatocytes will likely completely normalize Phe clearance in individuals with PKU.

Laronidase for cardiopulmonary disease in Hurler syndrome 12 years after bone marrow transplantation

A patient with severe mucopolysaccharidosis type I (Hurler syndrome) underwent bone marrow transplantation twice (at the ages of 2 and 2.5 years), both times with his HLA-identical heterozygous brother as the donor. Between the ages of 10 and 14 years, despite 92% donor engraftment and 50% normal α-L-iduronidase activity, he developed progressive respiratory failure with severe pulmonary arterial hypertension, upper airway obstruction, and interstitial lung disease. Noninvasive ventilation and weekly laronidase therapy were initiated. Within 24 months, his mean pulmonary artery pressure was within the upper limit of normal and interstitial lung disease and airway obstruction improved markedly. He went from using a wheelchair to having full ambulation, he no longer required daytime ventilation, and his quality-of-life scores (Child Health Assessment Questionnaire) significantly improved.

Therapeutic approaches for neuronopathic lysosomal storage disorders

Therapy of the central nervous system (CNS) manifestations of lysosomal storage diseases (LSDs) has remained a major challenge because of its inability to deliver therapeutic agents efficiently across the intact blood-brain barrier. Non-specific therapies such as hematopoietic stem cell transplantation have been useful in globoid cell leukodystrophy (Krabbe disease) and in some mucopolysaccharidoses. Anti-inflammatory agents also show promise as adjuvant therapy. High doses of replacement therapy with native or modified enzyme show renewed promise for correction of CNS cells. Alternatively, small molecules can enter the brain relatively easily and promote reduction of accumulated substrate or function as pharmacological chaperones to enhance the level of the deficient enzyme. Gene therapy is still being developed and tested in patients. It is therefore likely that, thanks to a better understanding of disease mechanism, a variety of therapeutic approaches, used alone or in combination, will be useful to treat the devastating neurological complications of LSDs.

Therapeutic approaches for lysosomal storage diseases

The lysosomal storage disorders (LSDs) comprise a heterogeneous group of inborn errors of metabolism characterized by tissue substrate deposits, most often caused by a deficiency of the enzyme normally responsible for catabolism of various byproducts of cellular turnover. Individual entities are typified by involvement of multiple body organs, in a pattern reflecting the sites of substrate storage. It is increasingly recognized that one or more processes, such as aberrant inflammation, dysregulation of apoptosis and/or defects of autophagy, may mediate organ dysfunction or failure. Several therapeutic options for various LSDs have been introduced, including hematopoietic stem cell transplantation, enzyme replacement therapy and substrate reduction therapy. Additional strategies are being explored, including the use of pharmacological chaperones and gene therapy. Most LSDs include a variant characterized by primary central nervous system (CNS) involvement. At present, therapy of the CNS manifestations remains a major challenge because of the inability to deliver therapeutic agents across the intact blood-brain barrier. With improved understanding of underlying disease mechanisms, additional therapeutic options may be developed, complemented by various strategies to deliver the therapeutic agent(s) to recalcitrant sites of pathology such as brain, bones and lungs.

Allogeneic hematopoietic SCT in patients with non-malignant diseases, and importance of chimerism

In this retrospective study, we evaluated the chimerism status and outcome in 58 patients (64 transplants) with non-malignant diseases. Reduced intensity conditioning (RIC) was given in half of the transplants. Mixed chimerism (MC) was defined as >1% recipient cells. Two consecutive samples showing >30% recipient cells were defined as high chimerism (high MC). Patients with high MC and the management of these patients were analyzed in greater detail. The overall survival rate was 87%. In total, 23 transplants were donor chimerism (DC) and 41 transplants showed some degree of MC. The incidence of MC was 78 and 50% after RIC and myeloablative conditioning, respectively (P=0.04). Acute GVHD of grades II-III was more common in patients with DC (39%) than in patients with MC (8%) (P=0.002). Owing to high MC, donor lymphocyte infusions were given in 17 cases. The level of MC was reduced in seven cases, unchanged in four cases, increased in one case and there was graft rejection in five cases. A second transplant was carried out in six cases with rejections, five are alive and in remission. We conclude that patients with non-malignant diseases, who develop MC after transplant have less acute GVHD. Despite the high incidence of MC, overall survival is promising.

Musculoskeletal complications encountered in the lysosomal storage disorders

The lysosomal storage disorders are a heterogeneous group of inherited metabolic diseases resulting from defects in the degradation or transport of several distinct by-products of cellular turnover. The various subtypes are characterized by multi-systemic involvement; the wide range in patient ages at symptom onset is only partly explained by the underlying mutation(s). Neurodegenerative features and musculoskeletal complications are often seen in the most severe variants, and are features of the disease that have the most significant impact on patients' physical and functional well-being. Until recently, the care of affected individuals relied mainly on palliative or supportive measures. The introduction of therapies directed at correcting the primary defect (i.e., deficient enzyme activity) in several of these disorders has led to modification of the phenotype and natural history or disease course; however, clinical problems arising from brain and bone involvement remain major sources of morbidity. Factors that might influence therapeutic outcome include pre-existing pathology at the time of treatment initiation, drug access to tissues sites of pathology, and - in the case of enzyme therapy - antibody formation. Increasing understanding of the pathogenesis or relevant mechanism(s) of diseases is providing insights into additional therapeutic targets, enabling the potential for optimized patient outcomes with the use of adjunctive or supplemental agents. Physical and occupational therapy remain critical components of a comprehensive approach to patient care.