Correlation of automated volumetric analysis of brain MR imaging with cognitive impairment in a natural history study of mucopolysaccharidosis II

BACKGROUND AND PURPOSE

Reliable markers for predicting neurologic outcome in patients with MPS II are lacking. The purpose of this study is to explore whether quantitative volumetric measurements of brain MR imaging can be used to differentiate between MPS II patients with and without cognitive impairment. This MR imaging study is the first in MPS II patients to use automated/semi-automated methods to quantify brain volumes in a longitudinal design.

MATERIALS AND METHODS

Sixteen male patients with MPS II in a natural history study had annual brain MR imaging and detailed neurodevelopmental assessment over 2 years. Automated and semi-automated methods were used to determine brain volumes. Linear mixed regression models adjusting for age were used to assess the correlation between the volumetric parameters and cognition.

RESULTS

Among the 16 MPS II patients, 10 (22 MR imaging studies) had cognitive impairment whereas the other 6 (11 MR imaging studies) had normal cognition. A decreased brain tissue/ICV ratio (-5%; P < .001) and an increased lateral ventricle/ICV ratio (+4%; P = .029) were found in patients with cognitive impairment compared with patients with normal cognition. These changes were apparent in patients as young as 7 years of age in addition to older patients.

CONCLUSIONS

Quantitative volumetric measurements of brain MR imaging in MPS II patients can be obtained by using automated and semi-automated segmentation methods. MPS II patients with cognitive impairment have decreased brain tissue volumes, but longer studies with more subjects are required to confirm these results.

Evaluation of disease severity in mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders characterized by a wide variation in symptoms and progression rates. Each of the MPS types is caused by a deficiency in one of the enzymes involved in the catabolic pathway of glycosaminoglycans. MPS are usually suspected on the basis of the concomitant presence of several typical features of the disease, such as short stature, coarse facial features, loss of hearing, bone deformities, joint stiffness, organomegaly, respiratory and cardiovascular complications, and, in some cases, developmental delay. Very reduced or absent enzyme activity is required to confirm an MPS diagnosis. In the past, treatment of MPS was limited to the management of individual symptoms of the diseases. Currently, specific therapies such as hematopoietic stem cell transplantation and enzyme replacement therapy have improved the outlook for many MPS patients. To monitor disease progression and the impact of therapy in these patients, there is need for a validated scoring system for evaluating disease severity in MPS. A scoring system should take into account all aspects of MPS, particularly quality of life and functioning of arms, hands and legs and related mobility, endurance, self care and social functioning. This paper discusses several of the available scoring systems for bone/skeletal disorders and their potential usefulness in patients with MPS.

Multidisciplinary management of Hunter syndrome

Hunter syndrome is a rare, X-linked disorder caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase. In the absence of sufficient enzyme activity, glycosaminoglycans accumulate in the lysosomes of many tissues and organs and contribute to the multisystem, progressive pathologies seen in Hunter syndrome. The nervous, cardiovascular, respiratory, and musculoskeletal systems can be involved in individuals with Hunter syndrome. Although the management of some clinical problems associated with the disease may seem routine, the management is typically complex and requires the physician to be aware of the special issues surrounding the patient with Hunter syndrome, and a multidisciplinary approach should be taken. Subspecialties such as otorhinolaryngology, neurosurgery, orthopedics, cardiology, anesthesiology, pulmonology, and neurodevelopment will all have a role in management, as will specialty areas such as physiotherapy, audiology, and others. The important management topics are discussed in this review, and the use of enzyme-replacement therapy with recombinant human iduronate-2-sulfatase as a specific treatment for Hunter syndrome is presented.

Long-term efficacy and safety of laronidase in the treatment of mucopolysaccharidosis I

OBJECTIVE

Our goal was to evaluate the long-term safety and efficacy of recombinant human alpha-l-iduronidase (laronidase) in patients with mucopolysaccharidosis I.

PATIENTS AND METHODS

All 45 patients who completed a 26-week, double-blind, placebo-controlled trial of laronidase were enrolled in a 3.5-year open-label extension study. Mean patient age at baseline was 16 (range: 6-43) years. All patients had attenuated disease (84% Hurler-Scheie, 16% Scheie phenotypes). Clinical, biochemical, and health outcomes measures were evaluated through the extension phase. Changes are presented as the mean +/- SEM.

RESULTS

All 40 patients (89%) who completed the trial received at least 80% of scheduled infusions. As shown in earlier trials, urinary glycosaminoglycan levels decreased within the first 12 weeks and liver volume decreased within the first year. Percent predicted forced vital capacity remained stable, with a linear slope of -0.78 percentage points per year. The 6-minute walk distance increased 31.7 +/- 10.2 m in the first 2 years, with a final gain of 17.1 +/- 16.8 m. Improvements in the apnea/hypopnea index (decrease of 7.6 +/- 4.5 events per hour among the patients with significant baseline sleep apnea) and shoulder flexion (increase of 17.4 degrees +/- 3.6 degrees) were most rapid during the first 2 years. Improvements in the Child Health Assessment Questionnaire/Health Assessment Questionnaire disability index (decrease of 0.31 +/- 0.11, signifying a clinically meaningful improvement in activities of daily living) were gradual and sustained over the treatment period. Laronidase infusions were generally well tolerated except in 1 patient who experienced an anaphylactic reaction. Infusion-associated reactions, which occurred in 53% of the patients, were mostly mild, easily managed, and decreased markedly after 6 months. One patient died as a result of an upper respiratory infection unrelated to treatment. Antibodies to laronidase developed in 93% of the patients; 29% of the patients were seronegative at their last assessment.

CONCLUSIONS

This trial demonstrates the long-term clinical benefit and safety of laronidase in attenuated patients with mucopolysaccharidosis I and highlights the magnitude and chronology of treatment effects. Prompt diagnosis and early treatment will maximize treatment outcomes.

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.

Recognition and diagnosis of mucopolysaccharidosis II (Hunter syndrome)

Mucopolysaccharidosis II, also known as Hunter syndrome, is a rare, X-linked disorder caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyzes a step in the catabolism of glycosaminoglycans. In patients with mucopolysaccharidosis II, glycosaminoglycans accumulate within tissues and organs, contributing to the signs and symptoms of the disease. Mucopolysaccharidosis II affects multiple organs and physiologic systems and has a variable age of onset and variable rate of progression. Common presenting features include excess urinary glycosaminoglycan excretion, facial dysmorphism, organomegaly, joint stiffness and contractures, pulmonary dysfunction, myocardial enlargement and valvular dysfunction, and neurologic involvement. In patients with neurologic involvement, intelligence is impaired, and death usually occurs in the second decade of life, whereas those patients with minimal or no neurologic involvement may survive into adulthood with normal intellectual development. Enzyme replacement therapy has emerged as a new treatment for mucopolysaccharidosis disorders, including Hunter syndrome. The purpose of this report is to provide a concise review of mucopolysaccharidosis II for practitioners with the hope that such information will help identify affected boys earlier in the course of their disease.

The characterization of a murine model of mucopolysaccharidosis II (Hunter syndrome)

Mucopolysaccharidosis II (MPS II, Hunter syndrome in humans) is an X-linked inherited lysosomal storage disease caused by a deficiency in the lysosomal enzyme iduronate-2-sulfatase (I2S). I2S catalyses a step in the catabolism of glycosaminoglycans (GAGs) dermatan sulfate and heparan sulfate, and when it is deficient or absent GAGs accumulate in tissues and organs. Male knockout mice (IdS-KO), which lack the gene coding for I2S, exhibit many of the characteristics seen in the human disease. Compared to wild-type control mice, urine GAG excretion was elevated at 4 weeks of age and remained high throughout the lifespan, and tissue GAG levels were elevated as early as 7 weeks of age. Liver, spleen and other organs were significantly larger in the IdS-KO mice than in the wild-type. Radiographic examination revealed sclerosis and enlargement of the skull at 4 weeks of age and appendicular bone enlargement at 10-13 weeks of age. Micro CT scans showed severe periosteal bone formation at the lateral aspect of the distal tibia and calcification of the calcaneus tendon. This model was used in the development of idursulfase for treatment of MPS II and may continue to be useful in the evaluation of treatment strategies of this chronic and progressive disorder.

Preclinical dose ranging studies for enzyme replacement therapy with idursulfase in a knock-out mouse model of MPS II

Mucopolysaccharidosis II (MPS II; Hunter syndrome) is an X-linked metabolic disorder caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase (I2S), which catalyzes the catabolism of glycosaminoglycans (GAG) by cleaving the O-linked sulfate from dermatan sulfate and heparan sulfate. Recently, enzyme replacement therapy (ERT) with recombinant human I2S (Elaprase (idursulfase), Shire Human Genetic Therapies, Inc.), has been approved in the US and European Union for the treatment and management of MPS II. The purpose of the studies presented here was to describe some of the preclinical development of idursulfase using the I2S knock-out mouse model of MPS II designed to study the effect of dose and various dosing regimens of idursulfase on urine and tissue GAG levels. Urine and tissue samples were collected prior to idursulfase treatment and periodically throughout each study and analyzed for GAGs. The presence of anti-idursulfase antibodies in the mice serum after idursulfase use was also determined. Results showed that idursulfase, at several doses and at several dosing frequencies, caused a reduction in tissue and urine GAG levels in a dose-dependent manner. These studies also demonstrated that after IV administration, idursulfase is biologically active in the IdS-KO mouse model and is transported to key target tissues, reaching the lysosomes in an active form, and degrading the accumulated GAG. In conclusion, these results indicated that ERT with idursulfase produced in a human cell line could be useful in the treatment and management of MPS II, and were used in the design of clinical studies to evaluate the efficacy of idursulfase in MPS II patients.

The MPS I registry: design, methodology, and early findings of a global disease registry for monitoring patients with Mucopolysaccharidosis Type I

A global, observational disease registry has been established to characterize the course of disease and track clinical outcomes in patients with Mucopolysaccharidosis Type I (MPS I), a rare and treatable lysosomal storage disorder. This report outlines procedures for data collection and presents the recommended minimum schedule of assessments that comprise the disease-specific clinical and laboratory parameters that are tracked in the database. Aggregate data are summarized for the first 302 patients enrolled, representing entries from 24 countries. The median current age of the patients is 9.0 years (range: 0.4-64.8). Syndrome diagnoses include 47% Hurler (severe form), 25% Hurler-Scheie (attenuated form with an intermediate phenotype), 13% Scheie (most attenuated form), and 15% unknown. Younger ages at symptom onset and disease diagnosis are associated with the severe Hurler syndrome, but there is overlap among syndromes. Diagnosis was delayed by years to decades in several patients with Hurler-Scheie and Scheie syndromes. Patients with symptom onset before age 5 are more likely to have a gibbus, cognitive impairment, and pneumonia, whereas patients with symptom onset above age 5 are more likely to have carpal tunnel syndrome, myelopathy, and glaucoma. Cardiac valve abnormalities, joint contractures, corneal clouding, and hernia are reported by over 70% of patients regardless of the age of symptom onset. Approximately 80% of the patients have received enzyme replacement therapy, hematopoietic stem cell transplantation, or both. Overall, the MPS I Registry database contains a broad sample of the global patient population, providing a potentially useful tool for expanding knowledge of MPS I and facilitating evidence-based decisions about the optimal means of monitoring and treating affected individuals.

Significantly increased lifespan and improved behavioral performances by rAAV gene delivery in adult mucopolysaccharidosis IIIB mice

Mucopolysaccharidosis (MPS) IIIB is an inherited lysosomal storage disease, caused by the deficiency of alpha-N-acetylglucosaminidase (NaGlu), resulting in severe global neurological involvement with high mortality. One major hurdle in therapeutic development for MPS IIIB is the presence of the blood-brain barrier, which impedes the global central nervous system (CNS) delivery of therapeutic materials. In this study, we used a minimal invasive strategy, combining an intravenous (i.v.) and an intracisternal (i.c.) injection, following an i.v. infusion of mannitol, to complement the CNS delivery of adeno-associated viral (AAV) vector for treating MPS IIIB in young adult mice. This treatment resulted in a significantly prolonged lifespan of MPS IIIB mice (11.1-19.5 months), compared with that without treatment (7.9-11.3), and correlated with significantly improved behavioral performances, the restoration of functional NaGlu, and variable correction of lysosomal storage pathology in the CNS, as well as in different somatic tissues. This study demonstrated the great potential of combining i.v. and i.c. administration for improving rAAV CNS gene delivery and developing rAAV gene therapy for treating MPS IIIB in patients.

Longitudinal neurocognitive outcome in an adolescent with Hurler-Scheie syndrome

An adolescent with Hurler-Scheie syndrome is reported. This now 15 year-old-young woman was initially diagnosed at age 4. She was assessed for neurocognitive functioning at ages 5, 13, and 15 years. Results show a significant decline in intellectual functioning from the superior range to the average range from age 5 to age 13, and then no change from age 13 to age 15. The relationship between Hurler-Scheie syndrome, premorbid intellectual functioning, and cognitive-behavioral interventions are discussed in light of the longitudinal neurocognitive effects of this disease.

A phase II/III clinical study of enzyme replacement therapy with idursulfase in mucopolysaccharidosis II (Hunter syndrome)

PURPOSE

To evaluate the safety and efficacy of recombinant human iduronate-2-sulfatase (idursulfase) in the treatment of mucopolysaccharidosis II.

METHODS

Ninety-six mucopolysaccharidosis II patients between 5 and 31 years of age were enrolled in a double-blind, placebo-controlled trial. Patients were randomized to placebo infusions, weekly idursulfase (0.5 mg/kg) infusions or every-other-week infusions of idursulfase (0.5 mg/kg). Efficacy was evaluated using a composite endpoint consisting of distance walked in 6 minutes and the percentage of predicted forced vital capacity based on the sum of the ranks of change from baseline.

RESULTS

Patients in the weekly and every-other-week idursulfase groups exhibited significant improvement in the composite endpoint compared to placebo (P = 0.0049 for weekly and P = 0.0416 for every-other-week) after one year. The weekly dosing group experienced a 37-m increase in the 6-minute-walk distance (P = 0.013), a 2.7% increase in percentage of predicted forced vital capacity (P = 0.065), and a 160 mL increase in absolute forced vital capacity (P = 0.001) compared to placebo group at 53 weeks. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 46.9% of patients during the study.

CONCLUSION

This study supports the use of weekly infusions of idursulfase in the treatment of mucopolysaccharidosis II.

Glutaric acidemia type 1 in patients of Lumbee heritage from North Carolina

Glutaric acidemia type I (GA-I) is an autosomal recessive disorder of the catabolism of lysine, hydroxylysine, and tryptophan caused by deficiency of glutaryl-CoA dehydrogenase (GCD). Among our patients with GA-I, we noted a prevalence of Lumbee individuals. The Lumbee are a close-knit Native American tribe of eastern North Carolina. Five Lumbee individuals with GA-I had homozygous 1240G>A mutations in GCD. This is a rare, known mutation that was likely introduced by a Lumbee founder.

Reduction of GAG storage in MPS II mouse model following implantation of encapsulated recombinant myoblasts

BACKGROUND

Hunter syndrome, mucopolysaccharidosis type II (MPS II), is a X-linked inherited disorder caused by the deficiency of the enzyme iduronate-2-sulfatase (IDS), involved in the lysosomal catabolism of the glycosaminoglycans (GAG) dermatan and heparan sulfate. Such a deficiency leads to the intracellular accumulation of undegraded GAG and eventually to a progressive severe clinical pattern. Many attempts have been made in the last two to three decades to identify possible therapeutic strategies for the disorder, including gene therapy and somatic cell therapy.

METHODS

In this study we evaluated the intraperitoneal implantation of allogeneic myoblasts over-expressing IDS, enclosed in alginate microcapsules, in the MPS II mouse model. Animals were monitored for 8 weeks post-implantation, during which plasma and tissue IDS levels, as well as tissue and urinary GAG contents, were measured.

RESULTS AND CONCLUSIONS

Induced enzyme activity occurred both in the plasma and in the different tissues analyzed. A significant decrease in urinary undegraded GAG between the fourth and the sixth week of treatment was observed. Moreover, a biochemical reduction of GAG deposits was measured 8 weeks after treatment in the liver and kidney, on average 30 and 38%, respectively, while in the spleen GAG levels were almost normalized. Finally, the therapeutic effect was confirmed by histolochemical examination of the same tissues. Such effects were obtained following implantation of about 1.5 x 10(6) recombinant cells/animal. Taken together, these results represent a clear evidence of the therapeutic efficacy of this strategy in the MPS II mouse model, and encourage further evaluation of this approach for potential treatment of human beings.

The tandem mass spectrometry newborn screening experience in North Carolina: 1997-2005

North Carolina (NC) was the first US state to initiate universal tandem mass spectrometry (MS/MS) newborn screening. This began as a statewide pilot project in 1997 to determine the incidence and feasibility of screening for fatty acid oxidation, organic acid and selected amino acid disorders. The MS/MS analyses were done by a commercial laboratory and all follow-up and confirmatory testing was performed through the NC Newborn Screening (NBS) Program. In April 1999, the NC NBS Laboratory began the MS/MS analyses in-house. Between 28 July 1997 and 28 July 2005, 944,078 infants were screened and 219 diagnoses were confirmed on newborns with elevated screening results, for an overall incidence of 1:4,300. Ninety-nine infants were identified with fatty acid oxidation disorders, 58 with organic acidaemias and 62 with aminoacidopathies. Medium-chain acyl-CoA dehydrogenase deficiency, 3-methylcrotonyl-CoA carboxylase deficiency and disorders of phenylalanine metabolism were the most common disorders detected. Identification of affected infants has allowed retrospective testing of other family members, resulting in an additional 16 diagnoses. Seven neonates died from complications of their metabolic disorders/prematurity despite timely MS/MS screening. In addition, there were six infants who were not identified by elevated NBS results but who presented with symptoms later in infancy. The NC MS/MS NBS Program uses a two-tier system, categorizing results as either 'borderline' or 'diagnostic' elevated, for both the cutoffs and follow-up protocol. Infants with an initial borderline result had only a repeat screen. Infants with a diagnostic or two borderline results were referred for confirmatory testing. The positive predictive value of the NC MS/MS NBS for those infants requiring confirmatory testing was 53% for 2003 and 2004. The success of the NC MS/MS NBS Program in identifying infants with metabolic disorders was dependent on a comprehensive follow-up protocol integrating the public health laboratory and the academic metabolic centres.

Self-complementary adeno-associated virus serotype 2 vector: global distribution and broad dispersion of AAV-mediated transgene expression in mouse brain

The blood-brain barrier is the main obstacle to efficient delivery of therapeutic reagents, including viral vectors, into the central nervous system (CNS) for treating global CNS diseases. In this study, the effects of mannitol infusions on global brain gene expression of a novel AAV vector were examined after intravenous (i.v.) or intracisternal injection. Initially, a self-complementary adeno-associated virus serotype 2 vector (scAAV) was compared to traditional single-stranded AAV2 vector for reporter gene expression in the brain of adult mice with or without pretreatment of an i.v. mannitol infusion. One to two months postinjection, analysis of vector-transduced green fluorescent protein (GFP) expression in the brain revealed that vector delivery to the CNS via i.v. injection required pretreatment with mannitol. This expression was observed only when scAAV vectors were used. Using these conditions, transgene expression was observed in various neurons and glial cells throughout the brain. The peripherally administered scAAV vectors also transduced the cells in multiple somatic tissues with efficient expression in liver (20-30% of hepatocytes), but was less efficient in other somatic tissues. Intracisternal injection of scAAV vector produced a broad and intense transgene expression in both neurons and glial cells in the CNS of injected mice ranging from the olfactory area to the brain stem and spinal cord. More than 50% of the Purkinje cells in the cerebellum expressed GFP. Intravenous infusion of mannitol before intracisternal injection of the scAAV vector enhanced the dispersion of the vector in the CNS. Further optimization of these steps combining peripheral and intracisternal scAAV gene delivery should facilitate the development of treatments for global CNS diseases, especially diseases involving both the somatic system and the CNS, such as lysosomal storage disorders.

Brain MRI findings in patients with mucopolysaccharidosis types I and II and mild clinical presentation

Our objective was to determine the brain magnetic resonance imaging (MRI) abnormalities in a selected group of patients with mucopolysaccharidosis (MPS) types I and II who had only mild clinical manifestations. We retrospectively assessed MRI brain studies in 18 patients with MPS (type I: 6 and type II: 12). We evaluated abnormal signal intensity in the white matter, widening of the cortical sulci, size of the supratentorial ventricles, dilatation of the perivascular spaces (PVS) and enlargement of the subarachnoid spaces. We observed a broad spectrum of findings, and despite severely abnormal MRI studies, no patients had mental retardation. We also observed that dilated PVS, previously believed to be caused by macroscopic deposition of the mucopolysaccharides, had an appearance similar to cerebrospinal fluid (CSF) in all MRI sequences performed, even in FLAIR and trace diffusion weighted images. Based on our results, we believe that with the exception of white matter abnormalities and brain atrophy, all other findings may be related to abnormal resorption of CSF, and there is no relationship between the imaging and clinical manifestations of the disease.