Correction of odontoid dysplasia following bone-marrow transplantation and engraftment (in Hurler syndrome MPS 1H)

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.

Mucopolysaccharidosis Type I: A Review of the Natural History and Molecular Pathology

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive inherited disease, caused by deficiency of the enzyme α-L-iduronidase, resulting in accumulation of the glycosaminoglycans (GAGs) dermatan and heparan sulfate in organs and tissues. If untreated, patients with the severe phenotype die within the first decade of life. Early diagnosis is crucial to prevent the development of fatal disease manifestations, prominently cardiac and respiratory disease, as well as cognitive impairment. However, the initial symptoms are nonspecific and impede early diagnosis. This review discusses common phenotypic manifestations in the order in which they develop. Similarities and differences in the three animal models for MPS I are highlighted. Earliest symptoms, which present during the first 6 months of life, include hernias, coarse facial features, recurrent rhinitis and/or upper airway obstructions in the absence of infection, and thoracolumbar kyphosis. During the next 6 months, loss of hearing, corneal clouding, and further musculoskeletal dysplasias develop. Finally, late manifestations including lower airway obstructions and cognitive decline emerge. Cardiac symptoms are common in MPS I and can develop in infancy. The underlying pathogenesis is in the intra- and extracellular accumulation of partially degraded GAGs and infiltration of cells with enlarged lysosomes causing tissue expansion and bone deformities. These interfere with the proper arrangement of collagen fibrils, disrupt nerve fibers, and cause devastating secondary pathophysiological cascades including inflammation, oxidative stress, and other disruptions to intracellular and extracellular homeostasis. A greater understanding of the natural history of MPS I will allow early diagnosis and timely management of the disease facilitating better treatment outcomes.

An Evidence-based Approach to the Management of Children With Morquio A Syndrome Presenting With Craniocervical Pathology

STUDY DESIGN

Retrospective case series OBJECTIVE.: The aim of this study was to review clinical and radiological outcomes of craniovertebral surgery in children with Morquio A syndrome (Mucopolysaccharidosis type IVA) and develop an evidence-based management algorithm.

SUMMARY OF BACKGROUND DATA

Myelopathy secondary to craniovertebral pathology is a common cause of neurological disability in Morquio A syndrome. Previously unresolved surgical controversies include the value of surveillance, surgical indications, and operative technique.

METHODS

A retrospective case-based review of children with Morquio A syndrome and craniovertebral pathology seen in a tertiary referral pediatric center from 1992 to 2016 was performed. Patients treated nonoperatively and operatively were included. Medical records and imaging were reviewed to determine clinical and radiological findings at initial assessment, before cervical spine surgery, early postoperative period, and final follow-up. The clinical outcomes of interest were neurological status and mobility at follow-up, complications, and need for further surgery.

RESULTS

Twenty-seven patients were included. Surgical indications were radiological evidence of cervicomedullary compression alone (six cases) or with clinical evidence of myelopathy (12 cases). Eighteen patients (median age 6.2 years, range 3.5-15.9 years) underwent surgery, with median follow-up of 8.5 years. Occiput to upper cervical spine fusion with C1 decompression was performed in all cases with the addition of autologous calvarial graft in young patients (12 cases) and occipital-cervical plate fixation in older children (six cases). Neurological improvement occurred in 38% of cases but by one functional level only. Six of nine conservatively treated patients remained independent walkers.

CONCLUSION

Surgery for craniovertebral pathology is required in the majority of children with Morquio A syndrome. Close clinical and radiological surveillance is essential for timely intervention. Occiput to cervical fusion is safe and feasible even in young patients and improves clinical and radiological parameters.

LEVEL OF EVIDENCE

4.

Mucopolysaccharidoses: overview of neuroimaging manifestations

The mucopolysaccharidoses are a heterogeneous group of inherited lysosomal storage disorders, characterized by the accumulation of undegraded glycosaminoglycans in various organs, leading to tissue damage. Mucopolysaccharidoses include eight individual disorders (IS [Scheie syndrome], IH [Hurler syndrome], II, III, IV, VI, VII and IX). They have autosomal-recessive transmission with the exception of mucopolysaccharidosis II, which is X-linked. Each individual disorder has a wide spectrum of phenotypic variation, depending on the specific mutation, from very mild to very severe. The skeletal and central nervous systems are particularly affected. The typical clinical presentation includes organomegaly, dysostosis multiplex with short trunk dwarfism, mental retardation and developmental delay. In this article, we review the neuroimaging manifestations of the different types of mucopolysaccharidoses including the dysostosis multiplex of the skull and spine as well as the various central nervous system complications. These include white matter injury, enlargement of the perivascular spaces, hydrocephalus, brain atrophy, characteristic enlargement of the subarachnoid spaces as well as compressive myelopathy. The correlation between several of the neuroimaging features and disease severity remains controversial, without well-established imaging biomarkers at this time. Imaging has, however, a crucial role in monitoring disease progression, in particular craniocervical junction stenosis, cord compression and hydrocephalus, because this allows for timely intervention before permanent damage occurs.

The mucopolysaccharidoses: advances in medical care lead to challenges in orthopaedic surgical care

The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders with clinical manifestations relevant to the orthopaedic surgeon. Our aim was to review the recent advances in their management and the implications for surgical practice. The current literature about MPSs is summarised, emphasising orthopaedic complications and their management. Recent advances in the diagnosis and management of MPSs include the recognition of slowly progressive, late presenting subtypes, developments in life-prolonging systemic treatment and potentially new indications for surgical treatment. The outcomes of surgery in these patients are not yet validated and some procedures have a high rate of complications which differ from those in patients who do not have a MPS. The diagnosis of a MPS should be considered in adolescents or young adults with a previously unrecognised dysplasia of the hip. Surgeons treating patients with a MPS should report their experience and studies should include the assessment of function and quality of life to guide treatment. Cite this article: Bone Joint J 2017;99-B:1132-9.

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.

Musculoskeletal manifestations in mucopolysaccharidosis type I (Hurler syndrome) following hematopoietic stem cell transplantation

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is the treatment of choice for young Hurler patients. Despite halting of neurocognitive decline and improvement of life expectancy, the beneficial effect on the skeletal system is limited. As orthopedic complications are one of the most disabling factors following HSCT, this points to the need for new treatment strategies. The study summarizes musculoskeletal manifestations in 19 transplanted Hurler patients.

METHODS

Data were obtained retrospectively. Patients' charts for physical examinations of the joint range of motion (JROM) of shoulders, elbows, hips and knees were reviewed. Radiographic evaluations of thorax, spine, pelvis and hands were performed. MRI scans of the craniocervical junction were analyzed to determine odontoid hypoplasia and the prevalence of craniocervical stenosis.

RESULTS

Nineteen Hurler patients (10 females, 9 males) with an average age of 8.1 years (range 2.5-23.8) at the latest follow-up, who underwent allogenic HSCT between 1991 and 2012, were assessed after an average follow-up period of 6.4 years (range 0.7-22.5). Seventeen patients achieved long-term engraftment, two developed graft failures. The majority of patients showed a steady state or improvements in the mobility of knees (31 %/63 %), hips (47 %/40 %) and elbows (56 %/38 %). However, shoulder abduction was impaired in ¾ of patients and showed the highest rate of progression (31 %). In patients with graft failure, progressive restrictions in JROM were noted. Assessments of the craniocervical junction by MRI showed stable or improved diameters in 67 % of patients. Correction or stabilization of odontoid hypoplasia was found in 64 %. However thoracolumbar kyphosis, scoliosis, hip dysplasia and genua valga were progressive despite HSCT. At the last follow up, 47 % of patients were partially wheelchair dependent, 10 % wheelchair bound and 25 % regularly experienced pain in the spine, hips and lower extremities due to orthopedic problems.

CONCLUSION

Joint mobility, odontoid hypoplasia and craniocervical stenosis might stabilize or even improve in Hurler patients following HSCT. However, despite the beneficial effects on some musculoskeletal manifestations, skeletal complications are frequently observed and the overall burden of orthopedic disease is significant. Frequent multi-disciplinary follow-up in a specialized center are essential. Novel therapeutic approaches (e.g. anti-inflammatory drugs) are needed to improve musculoskeletal outcomes.

Characterization of Hip Morphology in Children With Mucopolysaccharidosis Types I and II

BACKGROUND

The purpose of this study is to describe the natural history of hip morphology in patients with mucopolysaccharidoses (MPS) I and MPS II.

METHODOLOGY

This is a retrospective radiographic analysis of 88 hips in 44 children with MPS I and II. Radiographs were examined to determine hip migration, femoral head sphericity, and acetabular dysplasia at different ages throughout childhood. In individual hips, change in morphology and rate of change were analyzed.

RESULTS

There was a high rate of hip migration and femoral head dysplasia in both MPS I and MPS II. Progressive migration was seen in three quarters of hips and progressive femoral head deformity in over half of hips. Acetabular dysplasia was variable, ranging from normal to severely dysplastic, but did not change with time. Overall, hips were more dysplastic in MPS I than MPS II.

CONCLUSIONS

Hip morphology is variable in MPS I and MPS II ranging from almost normal to severely dysplastic. Some hips do not deteriorate with time and thus surgical intervention may not be necessary in all cases. Deterioration is slow allowing time to plan a holistic approach to treatment.

LEVEL OF EVIDENCE

Level IV-case series.

The eye and the skin in nonendocrine metabolic disorders

As metabolism is controlled by the input of genes and the environment, metabolic disorders result from some disturbance in the interaction between genes and environmental factors. Many metabolic disorders consist in congenital enzyme deficiencies, also known as "inborn errors of metabolism," that may be disabling or cause severe illness and death and are predominantly inherited in an autosomal recessive fashion. The deposit in cells and tissues of storage substances from errors in metabolic processes may produce a wide variety of disorders affecting different organs and functions, with different degrees of severity, and often present around the time of birth or early childhood. Distinctive ocular and skin manifestations accompany many metabolic diseases and may provide clues for their diagnosis and evolution.

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.

Characterization of knee alignment in children with mucopolysaccharidosis types I and II and outcome of treatment with guided growth

PURPOSE

To describe knee alignment in children of different ages with severe mucopolysaccharidosis (MPS) I and II and the outcome of treatment with guided growth in a patient subgroup.

METHODS

This is a retrospective observational study of 58 knees in 29 children with severe MPS I and II. Long-leg standing radiographs were evaluated to determine mechanical axis deviation, mechanical lateral distal femoral angle and medial proximal tibial angle at different ages throughout childhood. The change in deformity in individual children over time is reported. 20 knees in 10 patients were treated with guided growth using eight-plates. Radiographic measurements were recorded at the time of plate insertion, at plate removal and at 1 year following removal.

RESULTS

At 8 years of age, all MPS I children and three-quarters of MPS II children had valgus knee alignment. There was deformity progression in two-thirds of MPS I knees and half of MPS II knees. Guided growth corrected the deformities. There was recurrence in most cases 1 year after plate removal.

CONCLUSIONS

Knee deformity is common in children with severe MPS I and II. Guided growth can be considered where there is significant and/or or progressive deformity with the aim of halting progression and correcting existing deformity and thus minimizing the risk of gross deformity. Patients should be aware of the high rate of recurrence and the need for repeat surgery.

Effects of neonatal enzyme replacement therapy and simvastatin treatment on cervical spine disease in mucopolysaccharidosis I dogs

Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease characterized by deficient α-L-iduronidase activity, leading to the accumulation of poorly degraded glycosaminoglycans (GAGs). Children with MPS I exhibit high incidence of spine disease, including accelerated disc degeneration and vertebral dysplasia, which in turn lead to spinal cord compression and kyphoscoliosis. In this study we investigated the efficacy of neonatal enzyme replacement therapy (ERT), alone or in combination with oral simvastatin (ERT + SIM) for attenuating cervical spine disease progression in MPS I, using a canine model. Four groups were studied: normal controls; MPS I untreated; MPS I ERT-treated; and MPS I ERT + SIM-treated. Animals were euthanized at age 1 year. Intervertebral disc condition and spinal cord compression were evaluated from magnetic resonance imaging (MRI) images and plain radiographs, vertebral bone condition and odontoid hypoplasia were evaluated using micro-computed tomography (µCT), and epiphyseal cartilage to bone conversion was evaluated histologically. Untreated MPS I animals exhibited more advanced disc degeneration and more severe spinal cord compression than normal animals. Both treatment groups resulted in partial preservation of disc condition and cord compression, with ERT + SIM not significantly better than ERT alone. Untreated MPS I animals had significantly lower vertebral trabecular bone volume and mineral density, whereas ERT treatment resulted in partial preservation of these properties. ERT + SIM treatment demonstrated similar, but not greater, efficacy. Both treatment groups partially normalized endochondral ossification in the vertebral epiphyses (as indicated by absence of persistent growth plate cartilage), and odontoid process size and morphology. These results indicate that ERT begun from a very early age attenuates the severity of cervical spine disease in MPS I, particularly for the vertebral bone and odontoid process, and that additional treatment with simvastatin does not provide a significant additional benefit over ERT alone.

Odontoid infiltration and spinal compression in Farber Disease: reversal by haematopoietic stem cell transplantation

Farber disease (FD) is a lysosomal storage disorder caused by accumulation of ceramide in various organs and tissues, most notably the central nervous system, subcutaneous tissues and respiratory tract. We report a girl who developed major destructive bone involvement, which affected the odontoid process and produced spinal compression at 9 years of age. Bone involvement was proven histologically but resolved, as assessed by serial MRI scanning, following matched unrelated donor haematopoietic stem cell transplantation. This transplant resulted in only partial donor chimerism (less than 10 % donor cells in peripheral blood), yet this was sufficient to almost normalize acid ceramidase levels in leukocytes and to produce dramatic improvements in subcutaneous nodules and joint mobility as well as the beneficial effect on the involved bone. Unfortunately, the transplant was rejected after 2 years but the patient was rescued from an aplastic state by successful haploidentical peripheral blood stem cell transplantation and remained a full donor chimera without recurrence of the bone involvement and with steadily improving mobility at the age of 17 years. We describe an FD patient who presented with severe destruction of the odontoid by inflammatory tissue which was reversed after long-term control achieved by allogeneic hematopoietic stem cell transplantation. After extensive literature search, we believe that this is the first report of bony involvement in Farber disease.

Imaging of the craniovertebral junction anomalies in children

The craniovertebral junction (CVJ) is interposed between the unsegmented skull and the segmented spine; it is functionally unique as it allows the complex motion of the head. Because of its unique anatomy, numerous craniometric indices have been devised. Because of its complex embryology, different from that of the adjacent skull and spine, it is commonly the seat of malformations. Because of the mobility of the head, and its relative weight, the craniovertebral junction is vulnerable to trauma. Like the rest of the axial skeleton, it may be affected by many varieties of dysplasia. In addition, the bony craniovertebral junction contains the neural craniovertebral junction and its surrounding CSF: any bony instability or loss of the normal anatomic relationships may therefore compromise the neural axis. In addition, the obstruction of the meningeal spaces at this level can compromise the normal dynamics of the CSF and result in hydrocephalus and/or syringohydromyelia. To image the CVJ, plain X-rays are essentially useless. MR is optimal in depicting the soft tissues (including the neural axis) and the joints, as well as the bone itself. CT still may be important to better demonstrate the bony abnormalities.

Craniovertebral junction pathological features and their management in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are multisystemic inherited metabolic diseases caused by the deficiency of the enzymes involved in the degradation of glycosaminoglycans (GAGs), which variably involve the central nervous system, heart, lungs, and bones.Undegraded or only partly degraded GAGs accumulate in the extracellular matrix, joint fluid, and connective tissue leading to widespread tissue and organ dysfunction.The introduction of hematopoietic stem cell transplantation (HSCT) and enzyme replacement therapy (ERT) has positively affected the natural history of MPS patients and their life expectancy. However, the presence of spinal abnormalities and deposition of GAGs in soft tissues remains nearly unaltered.Abnormalities of the craniovertebral junction (CVJ) and GAG deposits can result in spinal cord compression with slowly progressive myelopathy or acute posttraumatic tetraplegia.The current paper discusses neuroimaging findings in a consecutive series of 42 MPS patients followed at our Center for Metabolic Diseases and their neurosurgical issues.Current recommendations for decompression and fusion will be discussed according to our experience and review of the literature.

Postnatal progression of bone disease in the cervical spines of mucopolysaccharidosis I dogs

INTRODUCTION

Mucopolysaccharidosis I (MPS I) is a lysosomal storage disorder characterized by deficient α-l-iduronidase activity leading to accumulation of poorly degraded dermatan and heparan sulfate glycosaminoglycans (GAGs). MPS I is associated with significant cervical spine disease, including vertebral dysplasia, odontoid hypoplasia, and accelerated disk degeneration, leading to spinal cord compression and kypho-scoliosis. The objective of this study was to establish the nature and rate of progression of cervical vertebral bone disease in MPS I using a canine model.

METHODS

C2 vertebrae were obtained post-mortem from normal and MPS I dogs at 3, 6 and 12 months-of-age. Morphometric parameters and mineral density for the vertebral trabecular bone and odontoid process were determined using micro-computed tomography. Vertebrae were then processed for paraffin histology, and cartilage area in both the vertebral epiphyses and odontoid process were quantified.

RESULTS

Vertebral bodies of MPS I dogs had lower trabecular bone volume/total volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and bone mineral density (BMD) than normals at all ages. For MPS I dogs, BV/TV, Tb.Th and BMD plateaued after 6 months-of-age. The odontoid process appeared morphologically abnormal for MPS I dogs at 6 and 12 months-of-age, although BV/TV and BMD were not significantly different from normals. MPS I dogs had significantly more cartilage in the vertebral epiphyses at both 3 and 6 months-of-age. At 12 months-of-age, epiphyseal growth plates in normal dogs were absent, but in MPS I dogs they persisted.

CONCLUSIONS

In this study we report reduced trabecular bone content and mineralization, and delayed cartilage to bone conversion in MPS I dogs from 3 months-of-age, which may increase vertebral fracture risk and contribute to progressive deformity. The abnormalities of the odontoid process we describe likely contribute to increased incidence of atlanto-axial subluxation observed clinically. Therapeutic strategies that enhance bone formation may decrease incidence of spine disease in MPS I patients.

Prevalence and development of orthopaedic symptoms in the dutch hurler patient population after haematopoietic stem cell transplantation

Hurler syndrome (MPS-IH) is a rare autosomal recessive lysosomal storage disease. Besides a variety of other features, Hurler syndrome is characterized by a range of skeletal abnormalities known as dysostosis multiplex. Despite the successful effect of haematopoietic stem cell transplantation on the other features, dysostosis remains a disabling symptom of the disease. This study analyzed the status and development of the orthopaedic manifestations of 14 Dutch Hurler patients after stem cell transplantation.Data were obtained retrospectively by reviewing patients' charts, radiographs and MRIs. Existing methods to measure the deficiencies were modified to optimally address the dysostosis. These measurements were done by two of the authors independently. The odontoïd/body ratio, kyphotic angle, scoliotic angle and parameters for hip dysplasia and genu valgum were measured and plotted against age. The degree of progression was determined. The intraclass correlation coefficient (ICC) was calculated to determine the reliability of the measurements.All patients showed hypoplasia of the odontoïd, which significantly improved during growth. Kyphosis in the thoracolumbar area was present in 13 patients and proved to be progressive. Scoliosis was observed in eight patients. Hip dysplasia was present in all patients and showed no tendency of improvement. In all but one patient, knee valgus remained more than two standard deviations above normal.Dysostosis remains a major problem after haematopoietic stem cell transplantation in Hurler patients. Moreover, except for dens hypoplasia, it appears to be progressive and therefore surgical interventions may be necessary in the majority of these patients.

Brain and spinal MR imaging findings in mucopolysaccharidoses: a review

MPS represents a group of rare hereditary disorders characterized by multisystem involvement due to intralysosomal GAG accumulation. Among various tissues, both the central and peripheral nervous system are affected in almost all types of the disease. Thus, brain and spinal MR imaging are valuable tools for the assessment of neurologic involvement, and there is evidence that they might be reliable markers demonstrating disease severity and efficacy of treatment options currently used in patients with MPS. We aimed to review the most prominent MR imaging features of patients with MPS, paying attention to the physiopathologic mechanisms responsible for these alterations. Along with the description of neuroimaging findings, existing data in relation to their correlation with the severity of neurologic involvement is discussed, while another topic of great importance is the effect of various therapeutic regimens in the progression of brain and spinal MR imaging alterations. Finally, recent data concerning MR spectroscopy studies in MPS are also critically discussed.

Orthopaedic aspects of mucopolysaccharidoses

Skeletal abnormalities are an early and prominent feature of most mucopolysaccharide (MPS) disorders, with the degree of skeletal involvement varying between and within MPS subtypes. Most patients exhibit a constellation of radiographic abnormalities known as dysostosis multiplex, consisting of abnormally shaped vertebrae and ribs, enlarged skull, spatulate ribs, hypoplastic epiphyses, thickened diaphyses and bullet-shaped metacarpals. Thoracolumbar kyphosis or the gibbus deformity is often a key diagnostic clue. Also common are hip dysplasia, genu valgum and, later in the course of the disease, spinal cord compression, which can be life-threatening. Short stature is ubiquitous. Treatment of skeletal manifestations usually involves surgical intervention. All patients with MPS should be considered at high risk for surgical intervention requiring anaesthesia because of airway and cardiac disease manifestations. Regular imaging of the cervical, thoracic and lumbar spine, the hips and the lower extremities is recommended for patients with 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.

Brain and spine MRI features of Hunter disease: frequency, natural evolution and response to therapy

BACKGROUND

Hunter disease is a rare X-linked mucopolysaccharidosis. Despite frequent neurological involvement, characterizing the severe phenotype, neuroimaging studies are scarce.

OBJECTIVES

To determine frequency and severity of neuroradiological mucopolysaccharidosis-related features; to correlate them with clinical phenotype; to evaluate their natural evolution and the impact of intravenous enzymatic replacement therapy (ERT).

METHODS

Sixty nine brain MRI examinations of 36 Italian patients (mean-age 10.4 years; age-range 2.2-30.8; severe phenotype in 22 patients) were evaluated. Twenty patients had multiple MRIs (median follow-up 3.1 years, range 1-16.9): among them 15 had MRIs before and after ERT, six had repeated MRIs without being on ERT and five while on ERT. Perivascular, subarachnoid and ventricle space enlargement, white matter abnormality (WMA) burden, pituitary sella/skull/posterior fossa abnormalities, periodontoid thickening, spinal stenosis, dens hypoplasia, myelopathy, vertebral and intervertebral disc abnormalities were graded by means of dedicated scales.

RESULTS

Perivascular spaces enlargement (89%), WMAs (97%), subarachnoid space enlargement (83%), IIIrd-ventricle dilatation (100%), pituitary sella abnormalities (80%), cranial hyperostosis (19%), craniosynostosis (19%), enlarged cisterna magna (39%), dens hypoplasia (66%), periodontoid thickening (94%), spinal stenosis (46%), platyspondylia (84%) and disc abnormalities (79%) were frequently detected. WMAs, IIIrd-ventricle dilatation and hyperostosis correlated with the severe phenotype (p < 0.05). Subarachnoid spaces and ventricle enlargement, WMAs and spinal stenosis progressed despite ERT, while other MR features showed minimal or no changes.

CONCLUSIONS

The spectrum of brain and spine MRI abnormalities in Hunter disease is extremely wide and requires a thorough evaluation. WMAs, atrophy/communicating hydrocephalus and spinal stenosis progress over time and might represent possible disease severity markers for new treatment efficacy assessment.

Mucopolysaccharidosis I, II, and VI: Brief review and guidelines for treatment

Mucopolysaccharidoses (MPS) are rare genetic diseases caused by the deficiency of one of the lysosomal enzymes involved in the glycosaminoglycan (GAG) breakdown pathway. This metabolic block leads to the accumulation of GAG in various organs and tissues of the affected patients, resulting in a multisystemic clinical picture, sometimes including cognitive impairment. Until the beginning of the XXI century, treatment was mainly supportive. Bone marrow transplantation improved the natural course of the disease in some types of MPS, but the morbidity and mortality restricted its use to selected cases. The identification of the genes involved, the new molecular biology tools and the availability of animal models made it possible to develop specific enzyme replacement therapies (ERT) for these diseases. At present, a great number of Brazilian medical centers from all regions of the country have experience with ERT for MPS I, II, and VI, acquired not only through patient treatment but also in clinical trials. Taking the three types of MPS together, over 200 patients have been treated with ERT in our country. This document summarizes the experience of the professionals involved, along with the data available in the international literature, bringing together and harmonizing the information available on the management of these severe and progressive diseases, thus disclosing new prospects for Brazilian patients affected by these conditions.

Transplant outcomes in mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) are inherited metabolic disorders (IMDs) caused by single-gene defects leading to progressive cellular accumulation of glycosaminoglycans (GAGs) and damage to multiple organs, including the central nervous, musculoskeletal, cardiorespiratory, and other systems. Hurler syndrome (MPS IH), the most severe form, is the prototypical model. Enzyme replacement therapy (ERT), available for MPS I, II, and VI, is beneficial in some patients. However, ERT does not improve neurocognitive function because of its inability to cross the blood-brain barrier. In contrast, allogeneic hematopoietic stem cell transplantation (HSCT) allows donor-derived, enzyme-producing cells to migrate to the brain and other organs to provide permanent enzyme therapy and thus help somatic organs, improve neurocognitive function and quality of life, and prolong survival, particularly when performed early in the course of the disease. Bone marrow has been the graft source in the past. However, in the last 5 years many patients have been treated with unrelated donor (URD) umbilical cord blood transplant (UCBT), allowing rapid and increased access to transplantation with favorable outcomes. This review describes published and our institutional clinical experiences, discusses the current status of the field, and provides therapy guidelines for patients with MPS.

Cord blood and bone marrow transplantation in inherited metabolic diseases: scientific basis, current status and future directions

Progressive degeneration of the central nervous system leading to the loss of neuromotor, neurophysiological and cognitive abilities is the fundamental clinical problem in patients with many inherited metabolic diseases (IMD). Worldwide experience shows that morbidity, quality of life, and survival in these patients can be improved by allogeneic haematopoietic stem cell transplantation (HSCT), particularly when performed early in the course of the disease. At present, while available for some conditions, exogenous enzyme replacement therapy is unable to correct cognitive and central nervous system disease because of its inability to cross the blood-brain barrier. In contrast, HSCT allows donor-derived, enzyme-producing cells to migrate to the brain and other organs providing a permanent enzyme replacement therapy. HSCT may also mediate non-hematopoietic cell regeneration or repair. Traditionally, bone marrow has been the graft source for IMD patients. However, in the last 5 years many studies utilizing unrelated donor umbilical cord blood (UCB) as a graft source have demonstrated that UCB provides rapid and increased access to transplantation with favourable outcomes. This review describes preclinical studies and past and present clinical treatment approaches and discusses current controversies and future directions of this promising field.

Mucopolysaccharidosis I: management and treatment guidelines

OBJECTIVE

Disease management for mucopolysaccharidosis type I has been inconsistent because of disease rarity (approximately 1 case per 100,000 live births), phenotypic heterogeneity, and limited therapeutic options. The availability of hematopoietic stem cell transplantation and the recent introduction of enzyme replacement therapy for mucopolysaccharidosis I necessitate the establishment of system-specific management guidelines for this condition.

METHODS

Twelve international experts on mucopolysaccharidosis I met in January 2003 to draft management and treatment guidelines for mucopolysaccharidosis I. Initial guidelines were revised and updated in 2008, on the basis of additional clinical data and therapeutic advances. Recommendations are based on our extensive clinical experience and a review of the literature.

RESULTS

All patients with mucopolysaccharidosis I should receive a comprehensive baseline evaluation, including neurologic, ophthalmologic, auditory, cardiac, respiratory, gastrointestinal, and musculoskeletal assessments, and should be monitored every 6 to 12 months with individualized specialty assessments, to monitor disease progression and effects of intervention. Patients are best treated by a multidisciplinary team. Treatments consist of palliative/supportive care, hematopoietic stem cell transplantation, and enzyme replacement therapy. The patient's age (>2 years or < or =2 years), predicted phenotype, and developmental quotient help define the risk/benefit profile for hematopoietic stem cell transplantation (higher risk but can preserve central nervous system function) versus enzyme replacement therapy (low risk but cannot cross the blood-brain barrier).

CONCLUSION

We anticipate that provision of a standard of care for the treatment of patients with mucopolysaccharidosis I will optimize clinical outcomes and patients' quality of life.

Imaging the craniocervical junction

INTRODUCTION

The craniovertebral junction (CVJ) comprises the occiput, atlas, and axis. Radiographic evaluation of this region involves knowledge of only a few anatomical landmarks, as well as basic normal measurements and relationships to perform CVJ craniometry. Occipital bone anomalies and atlanto-occipital non-segmentation typically produce basilar invagination. Atlas anomalies predominantly involve the posterior arch, while the os odontoideum accounts for the majority of axis anomalies.

RESULTS AND DISCUSSION

A number of syndromes are associated with CVJ pathology, the most notable being Klippel-Feil and Down syndromes, achondroplasia, the mucopolysaccharidoses, and osteogenesis imperfecta. Skull-base softening associated with some of these syndromes results in acquired basilar invagination or basilar impression. In this article, we present a detailed review of essential anatomy and craniometry needed for radiographic assessment of the CVJ and illustrate various congenital anomalies of the occiput, atlas, and axis. The common syndromes affecting this region are also discussed and illustrated.

Mobility in Hurler syndrome

Hurler syndrome is an autosomal recessive metabolic storage disease. Hematopoietic stem cell transplant increases life expectancy, but the effects on associated musculoskeletal abnormalities remains unclear, and long-term data are limited. We detail the follow-up of 23 patients at a mean of 8.5 years after successful hematopoietic stem cell transplant. All patients underwent clinical examination at an annual multidisciplinary clinic. Serial radiological studies were reviewed to assess development and management of hip dysplasia and genu valgum. All patients demonstrated characteristic acetabular dysplasia and failure of ossification of the superolateral femoral head. Eight patients underwent bilateral pelvic and femoral derotation (mean age at surgery, 4.4 years); 4 patients had pelvic osteotomy only. Mean preoperative acetabular angle was 34 degrees. Genu valgum of variable severity due to failure of ossification of the lateral aspect of the proximal tibial metaphysis was observed early, and 6 patients underwent medial epiphyseal stapling, decreasing tibiofemoral angle by a mean of 8 degrees. Clinically, all patients were independently mobile, with restriction of internal hip rotation being the most significant clinical finding. Valgus knees and pronated feet were a typical finding. This cohort represents one of the largest available for study, and ongoing review will clarify the progression of musculoskeletal problems and determine the effectiveness of orthopaedic intervention.

Emerging trends in transplantation of inherited metabolic diseases

Allogeneic hematopoietic stem cell transplantation (HSCT) can prolong life and improve its quality in patients with inherited metabolic diseases. HSCT offers a permanent source of enzyme replacement therapy and also might mediate nonhematopoietic cell regeneration or repair. Unrelated cord blood is an exciting newer graft source for treatment of patients with these fatal disorders, providing increased access to donors and significant clinical efficacy, particularly when transplantation is performed in early stages. Pre-transplant performance status is highly predictive of overall survival.

Allogeneic stem cell transplantation for the treatment of lysosomal and peroxisomal metabolic diseases

This is a review of the clinical responses and prospectus of new therapies following use of allogeneic hematopoietic stem cell transplantation for the treatment of the following disorders: Hurlers syndrome (MPS 1-H), globoid cell leukodystrophy (GLD; Krabbes disease), adrenoleukodystrophy, metachromatic leukodystrophy, Wolmans disease, I-cell disease (mucolipidosis II; MLS-II), alpha-mannosidosis, fucosidosis, Niemann-Pick B/A disease, Slys disease (MPS VII), Gauchers disease (Gaucher-II-III), Battens disease, Farbers disease, Sanfilippo syndrome (MPS-III), Hunters disease (MPS-II), Maroteaux-Lamy syndrome (MPS-VI), and aspartylglucosaminuria (AGU). Over 500 patients with lysosomal and peroxisomal metabolic storage diseases due to deficiency of primary enzymes have been treated with hematopoietic stem cell transplantation since the initial patient was treated a quarter of century ago. Normal enzymatic activity has been robust and continuous over these years without the need for any medication. Proof of principle has been reported for multiple positive effects including that of the reconstruction of the central nervous system. Furthermore, the excellent engraftment rate along with significantly diminished graft-vs-host-disease needs to be emphasized. The genetic diseases enumerated above have remarkable differences from those discussed elsewhere in this issue of Seminars in Immunopathology. Each has a greater genetic heterogeneity. Misdiagnosis resulting in delay of treatment and further decline of function and ultimate quality of life occurs almost all the time. Neonatal screening of these diseases will be mandatory to vastly improve outcomes. Plans are being implemented to use dried blood spots on filter paper, as is commonly done for many other genetic diseases. Many new therapies are being adopted which should enhance positivity and acceptance of treatment by hematopoietic stem cell transplantation.

Cord-blood transplants from unrelated donors in patients with Hurler's syndrome

BACKGROUND

Hurler's syndrome (the most severe form of mucopolysaccharidosis type I) causes progressive deterioration of the central nervous system and death in childhood. Allogeneic bone marrow transplantation before the age of two years halts disease progression and prolongs life, but many children lack a bone marrow donor. We investigated the feasibility of using cord-blood transplants from unrelated donors and a myeloablative preparative regimen that did not involve total-body irradiation in young children with Hurler's syndrome.

METHODS

Between December 1995 and October 2002, 20 consecutive children with Hurler's syndrome received busulfan, cyclophosphamide, and antithymocyte globulin before receiving cord-blood transplants from unrelated donors. The children were subsequently evaluated for engraftment, adverse effects, and effects on disease symptoms.

RESULTS

Cord-blood donors had normal alpha-L-iduronidase activity (mean number of cells, 10.53x10(7) per kilogram of body weight) and were discordant for up to three of six HLA markers. Neutrophil engraftment occurred a median of 24 days after transplantation. Five patients had grade II or grade III acute graft-versus-host disease; none had extensive chronic graft-versus-host disease. Seventeen of the 20 children were alive a median of 905 days after transplantation, with complete donor chimerism and normal peripheral-blood alpha-L-iduronidase activity (event-free survival rate, 85 percent). Transplantation improved neurocognitive performance and decreased somatic features of Hurler's syndrome.

CONCLUSIONS

Cord blood from unrelated donors appears to be an excellent source of stem cells for transplantation in patients with Hurler's syndrome. Sustained engraftment can be achieved without total-body irradiation. Cord-blood transplantation favorably altered the natural history of Hurler's syndrome and thus may be important to consider in young children with this form of the disease.

Musculoskeletal manifestations of Hurler syndrome: long-term follow-up after bone marrow transplantation

Bone marrow transplantation (BMT) is effective in ameliorating many of the clinical manifestations of Hurler syndrome. However, long-term data on the natural history of the musculoskeletal disorders of Hurler syndrome after BMT are limited. The authors report the orthopaedic outcomes in seven patients with Hurler syndrome who were successfully engrafted between 1990 and 1999, and have been followed for a mean of 7.6 years since transplantation. Medical records, clinical examinations, and imaging studies were reviewed to assess the development and management of hip dysplasia, genu valgum, spine abnormalities, hand abnormalities, and joint range of motion. BMT does not appear to alter the natural history of the musculoskeletal disorders in Hurler syndrome, although there may be a beneficial effect on upper extremity joint mobility.