Spinal involvement in mucopolysaccharidoses: a review

Clinical Characteristics of a Patient with Mucopolysaccharidosis Type IVA (Morquio Syndrome)

Mucopolysaccharidosis (MPS) type IVA (Morquio syndrome) is a hereditary lysosomal storage disease caused by deficiency of N-acetylglucosamine-6-sulfate sulfatase. This enzyme deficiency leads to specific glycosaminoglycans (keratan sulfate and chondroitin-6-sulfate) accumulation mainly in the bone and cartilage tissues, as well as in the cardiovascular, respiratory systems, and visual systems. Patients with MPS IVA look healthy at birth, however, they develop typical spine deformities (kyphoscoliosis), pectus carinatum, wrists hypermobility with decreased muscle strength and loss of fine motor skills, valgus deformation of lower limbs during the first years of life. Pathological changes in cardiovascular and respiratory systems, visual and acoustic analyzers can be revealed. Early diagnosis of the disease is crucial for timely initiation of enzyme replacement therapy. Thus, low incidence of the disease and its heterogeneous clinical picture complicates diagnosis. Consequently, patients with MAS IVA often become severely disabled as early as adolescence. Patients with severe form and without treatment die before the age of 30 due to complications of respiratory system diseases, valvular heart apparatus involvement, and cervical myelopathy.

Cranio-cervical decompression associated with non-instrumented occipito-C2 fusion in children with mucopolysaccharidoses: Report of twenty-one cases

BACKGROUND

Mucopolysaccharidosis (MPS) is a multisystemic storage disorder of glycosaminoglycan deposits. Infiltration of the dura mater and supporting ligaments caused spinal cord compression and consecutive myelopathy, especially at the cranio-cervical junction (CCJ). Craniocervical instability and posterior decompression often raise the problem of fixation in children. The main purpose of this paper was to report the result of an original technique of occipito-cervical arthrodesis using a cranial halo-cast system in pediatric population.

METHODS

We recorded 21 patients with cervical myelopathy. All of them had spinal cord decompression by enlargement of the foramen magnum, C1 laminectomy, and occipito-C2 fusion using corticocancellous bone graft. Only one child has an extended laminectomy from C1 to C3. The occiput-C2 arthrodesis was stabilized by the cranial halo-cast system. This immobilization was performed preoperatively and kept for three months then switched to rigid cervical collar. Clinical assessment, including the Goel grade and mJOA, radiographs and magnetic resonance imaging were performed before surgery. The occipito-cervical arthrodesis was controlled by standard X-rays and CT scan.

RESULTS

According to the type of mucopolysaccharidosis, the patients were divided into MPS type I: n= 3, II: n=7, IV: n=11. The mean age of patients at surgery was 6.76 years. All mucopolysaccharidoses cases required a foramen magnum decompression by craniectomy, C1 laminectomy and occipito-C2 arthrodesis. As major complications, a child had immediate post-operative paraplegia due to spinal cord ischemia. The postoperative follow-up ranged from 1.5 to 4 years, with an average of 3.3 years. The average preoperative mJOA score was 8.9, and it improved to 14 points at the last follow-up.

CONCLUSIONS

Satisfactory fusion and good clinical results were obtained with the 2-stage approach to CCJ anomalies.

Adjunct diagnostic value of radiological findings in mucopolysaccharidosis type IVa-related thoracic spinal abnormalities: a pilot study

Background

In patients with mucopolysaccharidosis (MPS), systematic assessment and management of cervical instability, cervicomedullary and thoracolumbar junction spinal stenosis and spinal cord compression averts or arrests irreversible neurological damage, improving outcomes. However, few studies have assessed thoracic spinal involvement in MPS IVa patients. We aimed to evaluate thoracic spinal abnormalities in MPS IVa patients and identify associated image manifestations by CT and MRI study.

Results

Data of patients diagnosed and/or treated for MPS IVa at MacKay Memorial Hospital from January 2010 to December 2020 were extracted from medical records and evaluated retrospectively. Computed tomography (CT), plain radiography and magnetic resonance imaging (MRI) findings of MPS IVa-related spinal abnormalities were reviewed. Spine CT and plain radiography findings of 12 patients (6 males and 6 females with median age 7.5 years, range 1–28 years) revealed two subtypes of spinal abnormalities: thoracic kyphosis apex around T2 (subtype 1, n = 8) and thoracic kyphosis apex around T5 (subtype 2, n = 4). Spine CT and plain radiography clearly identified various degrees of thoracic kyphosis with apex around T2 or T5 in MPS IVa patients. Square-shaped to mild central beaking in middle thoracic vertebral bodies was observed in subtype 1 patients, while greater degrees of central beaking in middle thoracic vertebral bodies was observed in subtype 2 patients.

Conclusions

Spine CT findings clearly identify new radiological findings of thoracic kyphosis apex around T2 or T5 in MPS IVa patients. The degrees of central beaking at middle thoracic vertebral bodies may be a critical factor associated with different image presentations of thoracic kyphosis.

Addressing the need for patient-friendly medical communications: adaptation of the 2019 recommendations for the management of MPS VI and MPS IVA

BACKGROUND

Patients are the most important stakeholders in the care of any disease and have an educational need to learn about their condition and the treatment they should receive. Considering this need for patient-focused materials, we present a directed approach for mucopolysaccharidosis (MPS) VI and MPS IVA, a pair of rare, inherited diseases that affects multiple organs and parts of the body. Independent guidelines on the treatment of these diseases were recently published, providing evidence- and expertise-driven recommendations to optimize patient management. However, while healthcare providers may have the training and knowledge to understand these guidelines, patients and their caregivers can find the technical content challenging. Hence, we aimed to develop plain language summaries (PLS) of the MPS VI and MPS IVA guidelines with patients as the primary audience.

RESULTS

A review of the guidelines by an expert team identified six domains of information relevant to patients: The multidisciplinary team, regular tests and check-ups, disease-modifying and supportive treatments, general anesthetics, ear-nose-throat/respiratory care, and surgeries. This information was adapted into a series of infographics specific to either MPS VI or MPS IVA, designed to appeal to patients and clearly present information in a concise manner.

CONCLUSIONS

The use of patient-friendly materials, like the infographics we have developed, has the potential to better inform patients and engage them in their care. We issue a "call to arms" to the medical community for the development of similar PLS materials in rare diseases intended to inform and empower patients.

Clinical outcomes of laminoplasty for patients with lysosomal storage disease including mucopolysaccharidosis and mucolipidoses: a retrospective cohort study

Background

Although the clinical efficacy of laminoplasty in adult cervical spondylotic myelopathy or ossification of posterior longitudinal ligament has been frequently reported, there are only few reports of laminoplasty for patients with lysosome storage diseases (LSDs). Therefore, this study aimed to report the midterm clinical and radiological outcomes of patients with LSDs after cervical laminoplasty.

Methods

Six patients with LSD who underwent laminoplasty with/without C1 laminectomy for cervical myelopathy were enrolled. Clinical evaluations, including the cervical Japanese Orthopedic Association (cJOA) score and visual analog scale (VAS) scores for upper extremity numbness, and radiographic parameters, including C2–C7 lordotic angle, atlanto-dens interval (ADI), and ⊿ADI, were evaluated preoperatively, at 2 years postoperatively, and at the final follow-up.

Results

Five patients had mucopolysaccharidoses (type I: n = 1, II: n = 3, VII: n = 1) and one patient had mucolipidoses type III. The mean age of patients at surgery was 27.5 years, and the mean postoperative follow-up period was 61 months. All mucopolysaccharidoses cases required C1 posterior arch resection with C2–C7 laminoplasty. No critical complications were observed postoperatively. There were no significant differences in C2–C7 angle (p = 0.724) and ⊿ADI (p = 0.592) between the preoperative and final follow-ups. The cJOA score and VAS for numbness significantly improved at the final follow-up (p = 0.004 and p = 0.007, respectively).

Conclusions

The cervical myelopathy in patients with LSD could be safely and effectively treated with laminoplasty with/without C1 posterior arch resection after excluding patients with atlantoaxial instability. Atlantoaxial stability and symptom improvement could be maintained at an average of 5 years postoperatively.

Mucolipidosis Ⅱ and III with neurological symptoms due to spinal cord compression

In mucopolysaccharidoses (MPS), spinal cord compression (SCC) resulting from glycosaminoglycan (GAG) accumulation is a critical complication that can cause significant neurological and respiratory morbidities. However, clinically similar disorders such as mucolipidosis types II and III (ML) with SCC have been scarcely reported. Herein, we report four patients with ML who had SCC. Brain MRI revealed progressive spinal canal stenosis and SCC. In addition, T2-weighted high signal changes in the cervical cord were detected in two cases. Severe cases of SCC were detected as early as 1 year of age. All cases had respiratory problems. One case showed severe hypoxia and another, severe sleep apnea. In two cases, respiratory insufficiency and tetraplegia rapidly progressed as SCC progressed. Then, the patients became bedridden and needed artificial ventilation. In addition, two of the four patients died of respiratory failure. The autopsy of one patient revealed a compressed cervical cord and marked dura mater thickening due to GAG accumulation. These findings suggest that the accumulation of substrates in the dura mater caused SCC in the patients with ML. Our cases indicate that SCC is expected to be a common and critical complication of ML and MPS. MRI evaluation of cervical involvements and careful clinical observation are required in patients with ML.

Enzyme replacement combinational therapy: effective treatments for mucopolysaccharidoses

INTRODUCTION

Mucopolysaccharidoses (MPS), as a group of inherited lysosomal storage disorders (LSDs), are clinically heterogeneous and characterized by multi-systemic manifestations, such as skeletal abnormalities and neurological dysfunctions. The currently used enzyme replacement therapy (ERT) might be associated with several limitations including the low biodistribution of the enzymes into the main targets, immunological responses against foreign enzymes, and the high cost of the treatment procedure. Therefore, a suitable combination approach can be considered for the successful treatment of each type of MPS.

AREAS COVERED

In this review, we provide comprehensive insights into the ERT-based combination therapies of MPS by reviewing the published literature on PubMed and Scopus. We also discuss the recent advancements in the treatment of MPS and bring up the hopes and hurdles in the futuristic treatment strategies.

EXPERT OPINION

Given the complex pathophysiology of MPS and its involvement in different tissues, the ERT of MPS in combination with stem cell therapy or gene therapy is deemed to provide a personalized precision treatment modality with the highest therapeutic responses and minimal side effects. By the same token, new combinational approaches need to be evaluated by using drugs that target alternative and secondary pathological pathways.

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

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

Treatment of Severe Kyphoscoliosis in Children with Mucopolysaccharidosis Type I (Pfaundler-Hurler Syndrome) Using the Growing Rod Technique: A Case Series with Mid-Term Results

BACKGROUND

Patients with mucopolysaccharidosis type I (MPS I) have a good life expectancy due to early therapeutic options, such as stem cell therapy. Stem cell therapy can prevent the progression of some skeletal malformations. In contrast, the progression of thoracolumbar kyphoscoliosis, genua vara, and hip dysplasia cannot be influenced. We present 3 cases of children with MPS I with thoracolumbar kyphosis/kyphoscoliosis treated with a growing rod system.

CASE DESCRIPTION

The medical records and radiologic imaging of 3 children with a diagnosis of MPS I and kyphosis/kyphoscoliosis of the lumbar spine treated between 2007 and 2019 were retrospectively analyzed. Two children presented with a kyphoscoliosis, and 1 child had a combination of severe anterolisthesis and kyphoscoliosis. Surgery to correct the kyphosis and dorsal stabilization was performed in all patients after exhausted conservative treatment. There were no neurologic complications. Postoperative treatment and aftercare included a corset for 4 months and physical therapy. In all 3 patients, distraction surgery of the lumbar stabilization was done twice at a mean interval of 1 year.

CONCLUSIONS

If conservative treatment fails and surgery is necessary, an individual approach is needed. Dorsal stabilization with pedicle screws using a growing rod technique is an option for the correction of thoracolumbar/lumbar kyphosis in children with MPS I. However, fusion should be prevented initially or should be kept as short as possible. We achieved acceptable correction of the spinal deformity using the growing rod technique. Finally, surgery with correction and fusion is necessary after exhausted correction potential.

Recommendations for the management of MPS IVA: systematic evidence- and consensus-based guidance

INTRODUCTION

Mucopolysaccharidosis (MPS) IVA or Morquio A syndrome is an autosomal recessive lysosomal storage disorder (LSD) caused by deficiency of the N-acetylgalactosamine-6-sulfatase (GALNS) enzyme, which impairs lysosomal degradation of keratan sulphate and chondroitin-6-sulphate. The multiple clinical manifestations of MPS IVA present numerous challenges for management and necessitate the need for individualised treatment. Although treatment guidelines are available, the methodology used to develop this guidance has come under increased scrutiny. This programme was conducted to provide evidence-based, expert-agreed recommendations to optimise management of MPS IVA.

METHODS

Twenty six international healthcare professionals across multiple disciplines, with expertise in managing MPS IVA, and three patient advocates formed the Steering Committee (SC) and contributed to the development of this guidance. Representatives from six Patient Advocacy Groups (PAGs) were interviewed to gain insights on patient perspectives. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with experience managing patients with MPS IVA and the manuscript was evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers.

RESULTS

A total of 87 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) disease-modifying interventions (enzyme replacement therapy [ERT] and haematopoietic stem cell transplantation [HSCT]); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions (including spinal, limb, ophthalmic, cardio-thoracic and ear-nose-throat [ENT] surgeries). Consensus was reached on all statements after two rounds of voting. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance).

CONCLUSION

This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS IVA and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Recommendations for the management of MPS VI: systematic evidence- and consensus-based guidance

Introduction

Mucopolysaccharidosis (MPS) VI or Maroteaux-Lamy syndrome (253200) is an autosomal recessive lysosomal storage disorder caused by deficiency in N-acetylgalactosamine-4-sulfatase (arylsulfatase B). The heterogeneity and progressive nature of MPS VI necessitates a multidisciplinary team approach and there is a need for robust guidance to achieve optimal management. This programme was convened to develop evidence-based, expert-agreed recommendations for the general principles of management, routine monitoring requirements and the use of medical and surgical interventions in patients with MPS VI.

Methods

26 international healthcare professionals from various disciplines, all with expertise in managing MPS VI, and three patient advocates formed the Steering Committee group (SC) and contributed to the development of this guidance. Members from six Patient Advocacy Groups (PAGs) acted as advisors and attended interviews to ensure representation of the patient perspective. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with expertise and experience managing patients with MPS VI and the manuscript has been evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers.

Results

A total of 93 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions. Consensus was reached on all statements after two rounds of voting. The greatest challenges faced by patients as relayed by consultation with PAGs were deficits in endurance, dexterity, hearing, vision and respiratory function. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance).

Conclusion

This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS VI and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1080-y) contains supplementary material, which is available to authorized users.

The role of imaging in the skeletal involvement of mucopolysaccharidoses

This article discusses the role of imaging modalities including radiography, multi-detector computed tomography, magnetic resonance imaging, and ultrasound in diagnosing and monitoring skeletal abnormalities in mucopolysaccharidoses (MPS). The advantages and disadvantages of these different imaging tools will be discussed, along with their feasibility in this class of patients. As the musculoskeletal involvement is common to all MPS and is one of the main reasons for seeking medical attention, an increased awareness among paediatricians, rheumatologists, orthopaedists, radiologists, and other musculoskeletal specialists on the possible spectrum of abnormalities observed could facilitate a timely diagnosis, an appropriate severity evaluation, and better management.

Spine challenges in mucopolysaccharidosis

PURPOSE

Mucopolysaccharidosis (MPS) are rare inherited metabolic diseases, causing lysosomal storage of mucopolysaccharides; clinical presentation involves skeletal system and particularly the spine. Anomalies include developing kyphosis at thoracolumbar junction, that can causes nervous symptoms, and dens hypoplasia with associated atlantoaxial subluxation that can cause myelopathy. We present our experience in the treatment of spine pathology in MPS.

METHODS

Medical treatments of MPS seem to have little impact on spine disease: treatment of cervical instability often includes surgical decompression and stabilization, as in patient MPS1 that we present, while thoracic lumbar kyphosis is treated by bracing and, in severe cases, with surgery. Bracing is more effective in kyphosis under 40° Cobb. Our surgical cases with thoracic lumbar kyphosis over 40° Cobb, treatment include the first one ever described by only posterior approach with vertebrectomy in MPS and a case of lateral costo-transverse approach instrumented correction.

RESULTS

Surgical patients had no major complications after surgery and CT scan at follow-up showed complete fusion without loss of correction, even if in a cervical case we used an adult rigid instrumentation in a four year-and-six month-old girl (11 years follow-up) and in thoracic lumbar kyphosis case treated by vertebrectomy due to diminutive anatomy we positioned interbody cage in suboptimal position.

CONCLUSIONS

Bracing is a viable treatment strategy in thoracic lumbar kyphosis and can obtain good clinical results at medium terms follow-up even if kyphosis deformity remains in radiographs. Surgical treatment is effective in severe evolving cases both at cervical and thoracic lumbar level, main difficulties arose from unavailability of dedicated instrumentation in very young patient, as even smallest devices available are often too big.

Spinal cord issues in adult patients with MPS: transition of care survey

PURPOSE

This study aims to raise awareness of the need for research and appropriate guidelines for managing spinal cord issues in adult patients with mucopolysaccharidosis (MPS) and transition of these patients from pediatric to adult care.

METHODS

Pediatric/adult neurosurgeons, orthopedic spine surgeons, and treating physicians with expertise in metabolic disorders and spinal cord issues were invited to complete a survey to assess their experience with spinal cord problems in MPS and their opinion on transitioning routes from pediatric to adult care.

RESULTS

Twenty specialists completed the survey; 16 had treated spinal cord issues in patients with MPS. Foramen magnum and cervical stenosis (87%), atlanto-axial instability (67%), and lumbar spine instability (33%) were the main spinal cord issues encountered; 28% had treated adult patients for one or more spinal cord issues. In 40% of cases, this concerned an intervention or procedures performed during childhood. The main specialist responsible for the care of adult patients with MPS differed considerably between institutions and included both pediatric and adult specialists (30% pediatric neurosurgeons, 10% pediatric spine orthopedic surgeons, 30% adult spine neurosurgeons, 20% general adult surgeons). The preferred option (> 50%) for the transition of care was an interdisciplinary team of pediatric and adult specialists.

CONCLUSIONS

Further work needs to be done to address problems of managing spinal cord issues in adult patients with MPS. Currently, the responsibility for the care of patients with MPS with spinal cord issues is inconsistent. The best strategy for transitioning these patients from pediatric to adult care is likely an interdisciplinary approach.

Stand-alone craniocervical decompression is feasible in children with mucopolysaccharidosis type I, IVA, and VI

BACKGROUND CONTEXT

In patients with mucopolysaccharidosis (MPS), glycosaminoglycan deposits in the dura mater and supporting ligaments cause spinal cord compression and consecutive myelopathy, predominantly at the craniocervical junction. Disease characteristics of craniocervical stenosis (CCS) in patients with MPS differ profoundly from other hereditary and degenerative forms. Because of high periprocedural morbidity and mortality, patients with MPS pose a substantial challenge to the inexperienced medical care provider. As literature remains scarce, we present our experience with a large cohort of patients with MPS treated for CCS without atlanto-occipital instrumentation.

PURPOSE

The present study aimed to describe a safe and least traumatic approach for treating CCS in children with MPS, avoiding primary instrumentation.

STUDY DESIGN

This is a prospective follow-up (cohort) study.

PATIENT SAMPLES

We report 15 consecutive patients with CCS related to MPS, who were treated with stand-alone cervical decompression.

OUTCOME MEASURES

Myelopathy was assessed using magnetic resonance imaging (MRI), somatosensory evoked potentials, and clinical evaluation. Cervical instability was evaluated using plain x-ray and MRI. The disability status is quantified using either the Karnofsky or Lansky Performance Score.

METHODS

We describe 15 consecutive patients treated with craniocervical decompression. Data were collected prospectively. The mean follow-up is 6 years (5 standard deviation). The technique and treatment principles are described.

RESULTS

The overall clinical outcome in this patient cohort is good (mean Karnofsky Performance Score of 80). No patient developed signs of C0-C1-C2 instability or progressive myelopathy. Restenosis occurred in seven patients, requiring a total of eight reoperations.

CONCLUSIONS

Surgery in patients with MPS is associated with high morbidity and mortality of up to 4.2%. Because of the unique nature of the disease, recurring stenosis is inevitable. To shorten the procedure time and simplify the anticipated reoperation, we provide data that craniocervical decompression is feasible without the necessity of primary osteosynthesis. In the absence of craniocervical instability, decompression surgery without occipitocervical stabilization yields good postoperative results and challenges the long-standing paradigm of prophylactic craniocervical fixation.

Neurological manifestations of lysosomal disorders and emerging therapies targeting the CNS

Lysosomal disorders have been an area of interest since intravenous enzyme replacement therapy was successfully introduced for the treatment of Gaucher's disease in the early 1990s. This treatment approach has also been developed for several other lysosomal disorders, including Fabry's disease, Pompe's disease, lysosomal acid lipase deficiency, and five types of mucopolysaccharidosis. Despite the benefits of enzyme replacement therapy, it has limitations-most importantly, its ineffectiveness in treating the neurological components of lysosomal disorders, as only a small proportion of recombinant enzymes can cross the blood-brain barrier. Development of strategies to improve drug delivery to the CNS is now the primary focus in lysosomal disorder research. This Review discusses the neurological manifestations and emerging therapies for the CNS component of these diseases. The therapies in development (which are now in phase 1 or phase 2 clinical trials) might be for specific lysosomal disorders (enzyme replacement therapy via intrathecal or intracerebroventricular routes or with fusion proteins, or gene therapy) or applicable to more than one lysosomal disorder (haemopoietic stem cell transplantation, pharmacological chaperones, substrate reduction therapy, or stop codon readthrough). The combination of early diagnosis with effective therapies should change the outlook for patients with lysosomal disorders with neurological involvement in the next 5-10 years.