Effects of enzyme replacement therapy on growth in patients with mucopolysaccharidosis type II

Intravenous Idursulfase for the Treatment of Mucopolysaccharidosis Type II: A Systematic Literature Review

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is a rare, X-linked disorder caused by deficient activity of the enzyme iduronate-2-sulfatase. Signs and symptoms typically emerge at 1.5-4 years of age and may include cognitive impairment, depending on whether patients have the neuronopathic or non-neuronopathic form of the disease. Treatment is available in the form of enzyme replacement therapy (ERT) with recombinant iduronate-2-sulfatase (idursulfase). A systematic literature review was conducted to assess the evidence regarding efficacy, effectiveness, and safety of ERT with intravenous idursulfase for MPS II. Electronic databases were searched in January 2023, and 33 eligible articles were found. These were analyzed to evaluate the effects of intravenous idursulfase and the overall benefits and disadvantages in patient subgroups. Studies showed that intravenous idursulfase treatment resulted in improved short- and long-term clinical and patient-centered outcomes, accompanied by a favorable safety profile. Patients with non-neuronopathic MPS II had more pronounced improvements in clinical outcomes than those with neuronopathic MPS II. In addition, the review identified that improvements in clinical outcomes are particularly apparent if intravenous idursulfase is started early in life, strengthening previous recommendations for early ERT initiation to maximally benefit patients. This review provides a comprehensive summary of our current knowledge on the efficacy of ERT in different populations of patients with MPS II and will help to inform the overall management of the disease in an evolving treatment landscape.

Capsular and retinaculum thickening in type II mucopolysaccharidosis: a novel MRI finding

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage diseases caused by a deficiency of glycosaminoglycan (GAG) catalytic enzymes, resulting in an accumulation of unprocessed or partly degraded GAGs in different tissues, including bones and joints. Notably, skeletal and joint abnormalities may be the first complaint that prompts patients to seek medical attention, especially in the milder forms of the disease. To our knowledge, there are no prior imaging reports that have documented capsuloligamentous thickening in patients with MPS on MRI. In this study, we present four cases of patients with clinically and genetically confirmed diagnosis of type II MPS, encompassing seven MRI examination of different joints, including cervical spine, hip, wrist, knee, and shoulder. All of the patients were male, aged between 14 and 35 years, and exhibited varying degrees of joint stiffness in the clinical examination and carpal tunnel syndrome in cases of the wrist joint was affected. None of the patients had a history of surgical procedures on the affected joint, other metabolic or deposit diseases, or sports activity practice. The MRI revealed significant capsuloligamentous and retinaculum thickening, up to eight times greater than the normal capsular thickness reported in the literature.

Mucopolysaccharidosis: What Pediatric Rheumatologists and Orthopedics Need to Know

Mucopolysaccharidosis (MPS) is a group of disorders caused by the reduced or absent activity of enzymes involved in the glycosaminoglycans (GAGs) degradation; the consequence is the progressive accumulation of the substrate (dermatan, heparan, keratan or chondroitin sulfate) in the lysosomes of cells belonging to several tissues. The rarity, the broad spectrum of manifestations, the lack of strict genotype-phenotype association, and the progressive nature of MPS make diagnosing this group of conditions challenging. Musculoskeletal involvement represents a common and prominent feature of MPS. Joint and bone abnormalities might be the main clue for diagnosing MPS, especially in attenuated phenotypes; therefore, it is essential to increase the awareness of these conditions among the pediatric rheumatology and orthopedic communities since early diagnosis and treatment are crucial to reduce the disease burden of these patients. Nowadays, enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are available for some MPS types. We describe the musculoskeletal characteristics of MPS patients through a literature review of MPS cases misdiagnosed as having rheumatologic or orthopedic conditions.

Growth in individuals with attenuated mucopolysaccharidosis type I during untreated and treated periods: Data from the MPS I registry

Mucopolysaccharidosis Type I (MPS I) is caused by deficiency of α-L-iduronidase. Short stature and growth deceleration are common in individuals with the attenuated MPS I phenotype. Study objectives were to assess growth in individuals with attenuated MPS I enrolled in The MPS I Registry while untreated and after initiation of enzyme replacement therapy (ERT) with laronidase (recombinant human iduronidase). Individuals in the MPS I Registry with at least one observation for height and assigned attenuated MPS I phenotype as of September 2020 were included. The cohort included 142 males and 153 females 2-18 years of age. Age and sex adjusted standardized height-for-age z-scores during the natural history and ERT-treatment periods were assessed using linear mixed model repeated measures analyses. Growth curves were estimated during both periods and compared to standard growth charts from the Center for Disease Control (CDC). There was a significantly slower decline in height z-scores with age during the ERT-treated period compared to the natural history period. Estimated average height z-scores in the ERT-treatment versus the natural history period at age 10 were -2.4 versus -3.3 in females and -1.4 versus -2.9 in males (females first treated 3 year; males <4.1 year). While median height remained below CDC standards during both the natural history and ERT-treated periods for individuals with attenuated MPS I, laronidase ERT was associated with slower declines in height z-scores.

Spinal cord compression in patients with mucopolysaccharidosis

PURPOSE

Spinal abnormalities frequently occur in patients with mucopolysaccharidosis (MPS) types I, II, IV, and VI. The symptoms are manifold, which sometimes prolongs the diagnostic process and delays therapy. Spinal stenosis (SS) with spinal cord compression due to bone malformations and an accumulation of storage material in soft tissue are serious complications of MPS disease. Data on optimal perioperative therapeutic care of SS is limited.

METHODS

A retrospective chart analysis of patients with MPS and SS for the time period 01/1998 to 03/2021 was performed. Demographics, clinical data, neurological status, diagnostic evaluations (radiography, MRI, electrophysiology), and treatment modalities were documented. The extent of the SS and spinal canal diameter were analyzed. A Cox regression analysis was performed to identify prognostic factors for neurological outcomes.

RESULTS

Out of 209 MPS patients, 15 were included in this study. The most dominant type of MPS was I (-H) (n = 7; 46.7%). Preoperative neurological deterioration was the most frequent indication for further diagnostics (n = 12; 80%). The surgical procedure of choice was dorsal instrumentation with microsurgical decompression (n = 14; 93.3%). A univariate Cox regression analysis showed MPS type I (-H) to be associated with favorable neurological outcomes.

CONCLUSION

Early detection of spinal stenosis is highly relevant in patients with MPS. Detailed neurological assessment during follow-up is crucial for timeous detection of patients at risk. The surgical intervention of choice is dorsal instrumentation with microsurgical decompression and resection of thickened intraspinal tissue. Patients with MPS type I (-H) demonstrated the best neurological course.

Evaluation of the long-term treatment effects of intravenous idursulfase in patients with mucopolysaccharidosis II (MPS II) using statistical modeling: data from the Hunter Outcome Survey (HOS)

BACKGROUND

Mucopolysaccharidosis II (MPS II; Hunter syndrome) is a rare, life-limiting lysosomal storage disease caused by deficient iduronate-2-sulfatase activity. Enzyme replacement therapy (ERT) with intravenous (IV) idursulfase can stabilize or improve many somatic manifestations, but there remains a need for further analysis of long-term treatment outcomes. Using data from patients with MPS II enrolled in the Hunter Outcome Survey (HOS), mixed modeling was performed to evaluate and predict the effects of IV idursulfase treatment on selected clinical parameters for up to 8 years following treatment start. The modeling population comprised male patients followed prospectively in HOS who had received IV idursulfase for at least 5 years and who had data available for two or more time points (at least one post-ERT). Age at ERT start and time since ERT start were included as covariates.

RESULTS

In total, 481 patients were eligible for inclusion in at least one model. At 8 years post-ERT start, improvement from baseline was predicted for each age group (< 18 months, 18 months to < 5 years and ≥ 5 years at treatment start) in the following parameters: mean urinary glycosaminoglycan levels (percentage changes of > -75% in each group), mean left ventricular mass index (decreases of ~ 1 g/m2) and mean palpable liver size (decreases of > 2 cm). Improvements in mean 6-min walk test distance (increase of > 50 m) and stabilization in percent predicted forced vital capacity and forced expiratory volume in 1 s (decreases of ~ 4 and ~ 9 percentage points, respectively) at 8 years post-ERT start were predicted for patients aged ≥ 5 years at ERT start (these assessments are unsuitable for patients aged < 5 years). Predicted changes over time were similar across the three age groups; however, overall outcomes were most favorable in children aged < 18 months at ERT start.

CONCLUSIONS

These findings suggest that the previously reported positive effects of IV idursulfase on the somatic manifestations of MPS II are predicted to be maintained for at least 8 years following ERT initiation and highlight the value of statistical modeling to predict long-term treatment outcomes in patients with rare diseases.

"Growth patterns in children with mucopolysaccharidosis type I-Hurler after hematopoietic stem cell transplantation: Comparison with untreated patients"

The impact of hematopoietic stem cell transplantation (HSCT) on growth in patients diagnosed with mucopolysaccharidosis I Hurler (MPS-IH) has been historically regarded as unsatisfactory. Nevertheless, the growth patterns recorded in transplanted patients have always been compared to those of healthy children.

The objective of this study was to verify the impact of HSCT on MPS-IH long term growth achievements. The auxological data of 15 patients were assessed longitudinally and compared both to the WHO growth centiles for healthy individuals and to recently published curves of untreated MPS-IH children. Despite a progressive decrease after HSCT when estimated with reference to the WHO growth charts, median height SDS showed a progressive and statistically significant increase when comparing the stature recorded at each timepoint in our population to the curves of untreated MPS-IH individuals (from ‐0.39 SDS at t₀ to +1.35 SDS 5 years after HSCT, p value < 0.001 and to +3.67 SDS at the age of 9 years, p value < 0.0001).

In conclusion, though not efficient enough to restore a normal growth pattern in MPS-IH patients, we hereby demonstrate that HSCT positively affects growth and provides transplanted patients with a remarkable height gain compared to untreated gender- and age- matched individuals.

Acute Arterial Ischemic Stroke in a Treated Child with Hunter's Syndrome: A Case Report and Review of the Literature

Enzyme replacement therapy (ERT) has limited therapeutic effects on neurologic, skeletal, and cardiovascular pathophysiology. We report an acute right-sided flaccid hemiparesis in an 11-year-old boy with the severe neuronopathic phenotype of Hunter's syndrome who was receiving weekly idursulfase ERT. Due to his psychomotor regression and epilepsy, his presentation to the hospital was delayed. Computed tomography scan of brain showed no acute changes or hemorrhage. Stroke code was not called as patient was already outside of the time window for tissue plasminogen activator (tPA) therapy. Brain magnetic resonance imaging (MRI) showed diffuse cortical and deep atrophy consistent with his baseline neurological status and restricted diffusion in the territory of the left-middle cerebral artery (MCA) consistent with recent infarction. T1-weighted MRI revealed low signal intensity of the left insular cortex, as well as volume loss, consistent with previous undiagnosed stroke in the same vascular territory. In addition, MR angiogram (MRA) demonstrated left terminal M1 segment MCA occlusion. Echocardiogram showed aortic root dilation and moderate aortic valve insufficiency. Patient was also noted to have bacteremia related to port infection. ERT is limited by blood–brain barrier and the underlying glycosaminoglycans (GAGs) extracellular tissue accumulation which produces a proinflammatory state. GAG and bacterial lipopolysaccharide (LPS) are known to activate toll-like receptor 4 (TLR-4). GAGs released in the extracellular space of intracranial vessels induce inflammation by activating the TLR-4 pathway which is exacerbated by bacterial LPS contributing to focal arteritis. Our case suggests the importance of GAGs in the activation of the TLR-4 pathway as a cause of stroke in Hunter's syndrome.

Failures of Endochondral Ossification in the Mucopolysaccharidoses

PURPOSE OF REVIEW

The mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders characterized by abnormal accumulation of glycosaminoglycans (GAGs) in cells and tissues. MPS patients frequently exhibit failures of endochondral ossification during postnatal growth leading to skeletal deformity and short stature. In this review, we outline the current understanding of the cellular and molecular mechanisms underlying failures of endochondral ossification in MPS and discuss associated treatment challenges and opportunities.

RECENT FINDINGS

Studies in MPS patients and animal models have demonstrated that skeletal cells and tissues exhibit significantly elevated GAG storage from early in postnatal life and that this is associated with impaired cartilage-to-bone conversion in primary and secondary ossification centers, and growth plate dysfunction. Recent studies have begun to elucidate the underlying cellular and molecular mechanisms, including impaired chondrocyte proliferation and hypertrophy, diminished growth factor signaling, disrupted cell cycle progression, impaired autophagy, and increased cell stress and apoptosis. Current treatments such as hematopoietic stem cell transplantation and enzyme replacement therapy fail to normalize endochondral ossification in MPS. Emerging treatments including gene therapy and small molecule-based approaches hold significant promise in this regard. Failures of endochondral ossification contribute to skeletal deformity and short stature in MPS patients, increasing mortality and reducing quality of life. Early intervention is crucial for effective treatment, and there is a critical need for new approaches that normalize endochondral ossification by directly targeting affected cells and signaling pathways.

Mucopolysaccharidosis Type I in Children, a Forgotten Diagnosis Responsible for Undiagnosed Musculoskeletal Complaints: Report of Two Cases

Mucopolysaccharidoses (MPS) are a subgroup of lysosomal storage disorders. The underlying mechanism of MPS disorders are deficiency in specific enzymes which leads to accumulation of partially degraded glycosaminoglycans (GAGs) in various tissues. A wide variety of manifestations are reported but musculoskeletal complaints are common among them. In milder forms of MPS, musculoskeletal complaints are presenting symptoms. Delays in diagnosis due to unspecific and mild symptoms is common. Misdiagnosis of MPS as juvenile idiopathic arthritis and other inflammatory arthritis disorders is frequent. Early diagnosis and treatment prevents irreversible cellular damages and is a key factor in efficacy of enzyme replacement therapy. In this study we described two MPS patients with musculoskeletal complaints who were not diagnosed for a period of time. Although musculoskeletal manifestation are common in a variety of clinical conditions, their presence at low ages or co-occurrence of other manifestations (such as cardiac, respiratory, neurologic, etc.) in multiple systems should prompt evaluation of patients for MPS and other metabolic disorders. The rheumatologists' awareness on MPS should be promoted to achieve timely diagnosis and subsequent early treatment.

Enzyme replacement therapy for mucopolysaccharidoses; past, present, and future

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders, which lack an enzyme corresponding to the specific type of MPS. Enzyme replacement therapy (ERT) has been the standard therapeutic option for some types of MPS because of the ability to start immediate treatment with feasibility and safety and to improve prognosis. There are several disadvantages for current ERT, such as limited impact to the brain and avascular cartilage, weekly or biweekly infusions lasting 4-5 h, the immune response against the infused enzyme, a short half-life, and the high cost. Clinical studies of ERT have shown limited efficacy in preventing or resolving progression in neurological, cardiovascular, and skeletal diseases. One focus is to penetrate the avascular cartilage area to at least stabilize, if not reverse, musculoskeletal diseases. Although early intervention in some types of MPS has shown improvements in the severity of skeletal dysplasia and stunted growth, this limits the desired effect of ameliorating musculoskeletal disease progression to young MPS patients. Novel ERT strategies are under development to reach the brain: (1) utilizing a fusion protein with monoclonal antibody to target a receptor on the BBB, (2) using a protein complex from plant lectin, glycan, or insulin-like growth factor 2, and (3) direct infusion across the BBB. As for MPS IVA and VI, bone-targeting ERT will be an alternative to improve therapeutic efficacy in bone and cartilage. This review summarizes the effect and limitations on current ERT for MPS and describes the new technology to overcome the obstacles of conventional ERT.

Hunter Syndrome: Is It Time to Make It Part of Newborn Screening?

BACKGROUND

Hunter syndrome, or mucopolysaccharidosis type II (MPS II), is a lysosomal storage disease that affects the breakdown of sugar in the body. Research has made it possible to reveal the cause of the disease, thus helping diagnose and treating this rare disorder. Enzyme replacement therapy will help children live longer and healthier lives.

PURPOSE

The purpose of this literature review is to explore the existing knowledge on MPS II and to inform the nursing community about the prevalence of MPS II and examine why it is important to offer screening to parents of a newborn or child.

SEARCH STRATEGY

CINAHL, PubMed, Cochrane, and Google Scholar were searched using the key words to find publications in English on MPS II during 2009 to 2018.

FINDINGS

Early detection is key for successful management of MPS II. Early initiation of enzyme replacement therapy will enhance the health of children. Support groups advocate for services for the children and their families.

IMPLICATIONS FOR PRACTICE

Earlier initiation of treatment leads to better outcomes, and healthcare providers should advocate for including MPS II in newborn screening. Families should be offered genetic counseling and support services.

IMPLICATIONS FOR RESEARCH

More research is essential to identify the long-term effects on families and the effect of enzyme replacement therapy on children with MPS II.

CONCLUSION

The birth of a child with the rare disorder such as MPS II will change the lives of families forever. Early identification and treatment can slow down decline in health and improve quality of life of children and their families.

Intrafamilial variability in the clinical manifestations of mucopolysaccharidosis type II: Data from the Hunter Outcome Survey (HOS)

Several cases of phenotypic variability among family members with mucopolysaccharidosis type II (MPS II) have been reported, but the data are limited. Data from patients enrolled in the Hunter Outcome Survey (HOS) were used to investigate intrafamilial variability in male siblings with MPS II. As of July 2015, data were available for 78 patients aged ≥5 years at last visit who had at least one affected sibling (39 sibling pairs). These patients were followed prospectively (i.e., they were alive at enrollment in HOS). The median age at the onset of signs and symptoms was the same for the elder and younger brothers (2.0 years); however, the younger brothers were typically diagnosed at a younger age than the elder brothers (median age, 2.5 and 5.1 years, respectively). Of the 39 pairs, eight pairs were classified as being discordant (the status of four or more signs and symptoms differed between the siblings); 21 pairs had one, two, or three signs and symptoms that differed between the siblings, and 10 pairs had none. Regression status of the majority of the developmental milestones studied was generally concordant among siblings. Functional classification, a measure of central nervous system involvement, was the same in 24/28 pairs, although four pairs were considered discordant as functional classification differed between the siblings. Overall, this analysis revealed similarity in the clinical manifestations of MPS II among siblings. This information should help to improve our understanding of the clinical presentation of the disease, including phenotype prediction in affected family members.

Treatment of mucopolysaccharidosis type II (Hunter syndrome): results from a systematic evidence review

PurposeA pilot systematic evidence review to establish methodology utility in rare genetic diseases, support clinical recommendations, and identify important knowledge gaps.MethodsBroad-based published/gray-literature searches through December 2015 for studies of males with confirmed mucopolysaccharidosis type II (any age, phenotype, genotype, family history) treated with enzyme replacement therapy or hematopoietic stem cell transplantation. Preset inclusion criteria employed for abstract and full document selection, and standardized methods for data extraction and assessment of quality and strength of evidence.ResultsTwelve outcomes reported included benefits of urinary glycosaminoglycan and liver/spleen volume reductions and harms of immunoglobulin G/neutralizing antibody development (moderate strength of evidence). Less clear were benefits of improved 6-minute walk tests, height, early treatment, and harms of other adverse reactions (low strength of evidence). Benefits and harms of other outcomes were unclear (insufficient strength of evidence). Current benefits and harms of hematopoietic stem cell transplantation are unclear, based on dated, low-quality studies. A critical knowledge gap is long-term outcomes. Consensus on selection of critical outcomes and measures is needed to definitively evaluate treatment safety and effectiveness.ConclusionMinor methodology modifications and a focus on critical evidence can reduce review time and resources. Summarized evidence was sufficient to support guidance development and highlight important knowledge gaps.

Newborn screening for mucopolysaccharidoses: a pilot study of measurement of glycosaminoglycans by tandem mass spectrometry

BACKGROUND

Mucopolysaccharidoses (MPS) are a group of inborn errors of metabolism that are progressive and usually result in irreversible skeletal, visceral, and/or brain damage, highlighting a need for early diagnosis.

METHODS

This pilot study analyzed 2862 dried blood spots (DBS) from newborns and 14 DBS from newborn patients with MPS (MPS I, n = 7; MPS II, n = 2; MPS III, n = 5). Disaccharides were produced from polymer GAGs by digestion with chondroitinase B, heparitinase, and keratanase II. Heparan sulfate (0S, NS), dermatan sulfate (DS) and mono- and di-sulfated KS were measured by liquid chromatography tandem mass spectrometry (LC-MS/MS). Median absolute deviation (MAD) was used to determine cutoffs to distinguish patients from controls. Cutoffs were defined as median + 7× MAD from general newborns.

RESULTS

The cutoffs were as follows: HS-0S > 90 ng/mL; HS-NS > 23 ng/mL, DS > 88 ng/mL; mono-sulfated KS > 445 ng/mL; di-sulfated KS > 89 ng/mL and ratio di-KS in total KS > 32 %. All MPS I and II samples were above the cutoffs for HS-0S, HS-NS, and DS, and all MPS III samples were above cutoffs for HS-0S and HS-NS. The rate of false positives for MPS I and II was 0.03 % based on a combination of HS-0S, HS-NS, and DS, and for MPS III was 0.9 % based upon a combination of HS-0S and HS-NS.

CONCLUSIONS

Combination of levels of two or more different GAGs improves separation of MPS patients from unaffected controls, indicating that GAG measurements are potentially valuable biomarkers for newborn screening for MPS.

Parents' experiences of living with, and caring for children, adolescents and young adults with Mucopolysaccharidosis (MPS)

BACKGROUND

Many rare diseases of childhood are life-threatening and chronically debilitating, so living with a rare disease is an on-going challenge for patients and their families. MPS is one of a range of rare inherited metabolic disorders (IMDs) that come under category 3 of life-limiting conditions, where there is no curative treatment available at present. Although the study of rare diseases is increasingly novel, and of clinical importance to the population, the lack of empirical data in the field to support policy and strategy development is a compelling argument for further research to be sought.

METHODS

This qualitative hermeneutic phenomenological study explored and interpreted Irish parents' experiences of living with and caring for children, adolescents and young adults with MPS and the impact of these diseases on their day to day life. A purposively selected sample of parents' attending the Irish National Centre for Inherited Metabolic Disorders was invited to participate in serial in-depth interviews.

RESULTS

A total of eight parents' (n = 8) of children with a range of MPS disorders aged from 6 months to 22 years (MPS I Hurler syndrome, Scheie syndrome), MPS II (Hunter syndrome), MPS III (Sanfilipo syndrome) and MPS VI (Maroteaux-Lamy syndrome) were interviewed at three time points over a 17 month period. The main themes identified during data analysis were described as living with MPS, living with a genetic rare disease, the stigma of a rare condition, MPS as encompassing multiple diseases, Unknown future, hospital vs. home, experience of waiting, a tough road ahead, and things in their day-to-day life with MPS. They spoke of their child's Quality of Life (QoL), their healthy children's wellbeing, and for some, the impact on their own physical and psychological wellbeing. They also reflected on issues of stigmatisation and isolation in their experience of living with a child with a rare disorder.

CONCLUSION

This study's findings reflect the wider literature on the impact of rare diseases, which have also indicated how caring for someone with MPS, a condition that is chronic, progressive and degenerative can impact on all dimensions of the family's life. Analysis of the findings using a hemenutic pheomenology perspecitve suggest that parents of children with MPS experience multiple cyclical movements across all five human lived existential experience, and they gradually develop ways to incorporate MPS in their day to day life. It was also evident that all the carers in this study experienced a range of uncertainties, with parents using terms such as 'no man's land' and 'future is unknown' to describe their world.

A longitudinal study of emotional adjustment, quality of life and adaptive function in attenuated MPS II

OBJECTIVES

The behavioral, adaptive and quality of life characteristics of attenuated mucopolysaccharidosis type II (MPS II) have not been well studied. Understanding changes over time in the attenuated phenotype may assist in helping achieve better outcomes in long-term function. This longitudinal study investigates these outcomes in relation to age, somatic disease burden, and IQ. Specifically, somatic disease burden is a major challenge for these patients, even with treatment with enzyme replacement therapy.

METHODS

15 patients, 10 between ages 6 and < 12 and 5 between ages ≥ 12 and 18, were selected who had at least 2 yearly visits. The occurrence of physical signs, the Physical Symptom Score, and IQ in these two groups was studied as well as the longitudinal association of age with standardized measures of quality of life, adaptive function, and behavioral symptoms as rated by parents and the child's self-report. Slopes by age across and within patients were calculated for these measures.

RESULTS

All but one child had hearing loss, most had joint contractures and short stature. Somatic disease burden increased with age. IQ, although normal for most, also improved with age in those under 12 years of age. Physical quality of life decreased while psychosocial quality of life increased with age. Although other adaptive skills were in the broad average range, daily living skills were low at baseline relative to normative data and decreased over time. Behavior ratings indicated improvement in attention and hyperactivity over time. No patient had severe psychopathology, but older children reported an increasing sense of inadequacy and low self-esteem on self-report, presumably due to increasing awareness of differences from peers over time.

CONCLUSIONS

Attenuated MPS II patients have increasing somatic disease burden and poor physical quality of life as they develop as well as decreasing self-esteem and sense of adequacy. Psychosocial quality of life, adaptive skills, and attention improve. Recognition of and intervention around these issues will be beneficial to MPS II attenuated patients who have the resources to use such assistance to improve their long-term outcomes.

The natural history of growth in patients with Hunter syndrome: Data from the Hunter Outcome Survey (HOS)

Hunter syndrome (mucopolysaccharidosis type II) affects growth but the overall impact is poorly understood. This study investigated the natural history of growth and related parameters and their relationship with disease severity (as indicated by cognitive impairment). Natural history data from males followed prospectively in the Hunter Outcome Survey registry and not receiving growth hormone or enzyme replacement therapy, or before treatment start, were analysed (N=676; January 2014). Analysis of first-reported measurements showed short stature by 8years of age; median age-corrected standardized height score (z-score) in patients aged 8-12years was -3.1 (1st, 3rd quartile: -4.3, -1.7; n=68). Analysis of growth velocity using consecutive values found no pubertal growth spurt. Patients had large head circumference at all ages, and above average body weight and body mass index (BMI) during early childhood (median z-score in patients aged 2-4years, weight [n=271]: 1.7 [0.9, 2.4]; BMI [n=249]: 2.0 [1.1, 2.7]). Analysis of repeated measurements over time found greater BMI in those with cognitive impairment than those without, but no difference in height, weight or head circumference. Logistic regression modelling (data from all time points) found that increased BMI was associated with the presence of cognitive impairment (odds ratio [95% CI], 3.329 [2.313-4.791]), as were increased weight (2.365 [1.630-3.433]) and head circumference (1.749 [1.195-2.562]), but not reduced height. Unlike some other MPS disorders, there is no evidence at present for predicting disease severity in patients with Hunter syndrome based on changes in growth characteristics.

Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome)

BACKGROUND

Mucopolysaccharidosis II, also known as Hunter syndrome, is a rare, X-linked disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyses a step in the catabolism of glycosaminoglycans. The glycosaminoglycans accumulate within tissues affecting multiple organs and physiologic systems. The clinical manifestations include neurologic involvement, severe airways obstruction, skeletal deformities and cardiomyopathy. The disease has a variable age of onset and variable rate of progression. In those with severe disease, death usually occurs in the second decade of life, whereas those individuals with less severe disease may survive into adulthood. Enzyme replacement therapy with intravenous infusions of idursulfase has emerged as a new treatment for mucopolysaccharidosis type II. This is an update of a previously published version of this review.

OBJECTIVES

To evaluate the effectiveness and safety of enzyme replacement therapy with idursulfase compared to other interventions, placebo or no intervention, for treating mucopolysaccharidosis type II.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register (date of last search 23 November 2015).We also searched Embase, PubMed and the Literature Latino-Americana e do Caribe em Ciências da Saúde (LILACS) (date of last search 28 November 2015).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of enzyme replacement therapy with idursulfase compared to no intervention, placebo or other options (e.g. behavioral strategies, transplantation).

DATA COLLECTION AND ANALYSIS

Two authors independently screened the trials identified, appraised quality of papers and extracted data.

MAIN RESULTS

One study (96 male participants) met the inclusion criteria, although the primary outcome of this review - z score for height and weight, was not assessed in the study. This trial was considered to be of overall good quality. Following 53 weeks of treatment, participants in the weekly idursulfase 0.5 mg/kg group demonstrated a significant improvement rate compared with placebo for the primary outcome: distance walked in six minutes on the basis of the sum of ranks of change from baseline, mean difference 37.00 (95% confidence interval 6.52 to 67.48). The every-other-week idursulfase 0.5 mg/kg group also showed an improvement, which was not significant compared with placebo, mean difference 23.00 (95% confidence interval -4.49 to 50.49). After 53 weeks, there was no statistical significance difference in per cent predicted forced vital capacity between the three groups and absolute forced vital capacity was significantly increased from baseline in the weekly dosing group compared to placebo, mean difference 0.16 (95% confidence interval CI 0.05 to 0.27). No difference was observed between the every-other-week idursulfase 0.5 mg/kg group and placebo.In addition, liver and spleen volumes and urine glycosaminoglycan excretion were significantly reduced from baseline by both idursulfase dosing regimens. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 31.7% of participants at the end of the study and they were related to a smaller reduction in urine glycosaminoglycan levels.

AUTHORS' CONCLUSIONS

The current evidence is limited. While the randomised clinical trial identified was considered to be of good quality, it failed to describe important outcomes. It has been demonstrated that enzyme replacement therapy with idursulfase is effective in relation to functional capacity (distance walked in six minutes and forced vital capacity), liver and spleen volumes and urine glycosaminoglycan excretion in people with mucopolysaccharidosis type II compared with placebo. There is no available evidence in the included study and in the literature on outcomes such as improvement in growth, sleep apnoea, cardiac function, quality of life and mortality. More studies are needed to obtain more information on the long-term effectiveness and safety of enzyme replacement therapy.

Growth patterns in children with mucopolysaccharidosis I and II

BACKGROUND

Mucopolysaccharidosis (MPS) diseases lead to a profound disruption in normal mechanisms of growth and development. This study was undertaken to determine the general growth of children with MPS I and II.

METHODS

The anthropometric data of patients with MPS I and II (n=76) were retrospectively analyzed. The growth patterns of these patients were analyzed and then plotted onto Polish reference charts. Longitudinal analyses were performed to estimate age-related changes.

RESULTS

At the time of birth, the body length was greater than reference charts for all MPS groups (Hurler syndrome, P=0.006; attenuated MPS II, P=0.011; severe MPS II, P<0.001). The mean z-score values for every MPS group showed that until the 30th month of life, the growth patterns for all patients were similar. Afterwards, these growth patterns start to differ for individual groups. The body height below the 3rd percentile was achieved around the 30th month for boys with Hurler syndrome, between the 4th and 5th year for patients with severe MPS II and between the 7th and 8th year for patients with attenuated MPS II.

CONCLUSIONS

The growth pattern differs between patients with MPS I and II. It reflects the clinical severity of MPS and may assist in the evaluation of clinical efficacy of available therapies.

Enzymatic replacement therapy for Hunter disease: Up to 9 years experience with 17 patients

Hunter disease is an X-linked lysosomal storage disorder characterized by progressive storage of glycosaminoglycans (GAGs) and multi-organ impairment. The central nervous system (CNS) is involved in at least 50% of cases. Since 2006, the enzymatic replacement therapy (ERT) is available but with no effect on the cognitive impairment, as the present formulation does not cross the blood-brain barrier. Here we report the outcome of 17 Hunter patients treated in a single center. Most of them (11) started ERT in 2006, 3 had started it earlier in 2004, enrolled in the phase III trial, and 3 after 2006, as soon as the diagnosis was made. The liver and spleen sizes and urinary GAGs significantly decreased and normalized throughout the treatment. Heart parameters improved, in particular the left ventricular mass index/m(2) decreased significantly. Amelioration of hearing was seen in many patients. Joint range of motion improved in all patients. However, no improvement on respiratory function, eye, skeletal and CNS disease was found. The developmental quotient of patients with a CNS involvement showed a fast decline. These patients were no more testable after 6 years of age and, albeit the benefits drawn from ERT, their quality of life worsened throughout the years. The whole group of patients showed a consistent residual disease burden mainly represented by persistent skeletal disease and frequent need of surgery. This study suggests that early diagnosis and treatment and other different therapies which are able to cross the blood-brain barrier, might in the future improve the MPS II outcome.

Safety and efficacy of enzyme replacement therapy with idursulfase beta in children aged younger than 6 years with Hunter syndrome

Idursulfase beta (Hunterase®) has been used for enzyme replacement therapy (ERT) of patients with mucopolysaccharidosis II (MPS II, Hunter syndrome) aged 6 years or older since 2012 in Korea. The objective of this study was to evaluate the safety and efficacy of ERT with idursulfase beta in Hunter syndrome children younger than 6 years. This study was a 52-week, single center, single arm, open-label clinical trial (NCT01645189). Idursulfase beta (0.5mg/kg/week) was administered intravenously for 52 weeks. The primary endpoint was safety assessed by adverse events (AEs). Secondary endpoints included vital signs, physical examination, ECG, laboratory tests, anti-idursulfase antibodies, and efficacy represented by changes in urinary glycosaminoglycan (GAG) at week 53 from baseline. In addition, growth indices and developmental milestones (Denver II test) were evaluated as exploratory variables. All six patients experienced at least one AE. A total of 109 AEs were reported. One patient experienced a serious AE (hospitalization due to gastroenteritis) that was considered not to be treatment related. One patient (16.7%) experienced infusion-related adverse drug reactions (ADRs), developing urticaria six times and a cough five times. There were no serious ADRs and no clinically significant changes in vital signs, physical exam, laboratory parameters, or ECG. Of the six patients, four (66.7%) showed anti-idursulfase antibodies and neutralizing antibodies on at least one occasion during the study. At week 53, urinary GAG was significantly reduced by -35.1±30.6mgGAG/g creatine from baseline (P=0.038). This study indicates that the safety and efficacy of idursulfase beta are similar to those reported in Hunter syndrome patients aged 6 years or older.

Disease stage determines the efficacy of treatment of a paediatric neurodegenerative disease

Lysosomal storage disorders are a large group of inherited metabolic conditions resulting from the deficiency of proteins involved in lysosomal catabolism, with resulting accumulation of substrates inside the cell. Two-thirds of these disorders are associated with a neurodegenerative phenotype and, although few therapeutic options are available to patients at present, clinical trials of several treatments including lysosomal enzyme replacement are underway. Although animal studies indicate the efficacy of presymptomatic treatment, it is largely unknown whether symptomatic disease-related pathology and functional deficits are reversible. To begin to address this, we used a naturally-occurring mouse model with Sanfilippo syndrome (mucopolysaccharidosis type IIIA) to examine the effectiveness of intracisternal cerebrospinal fluid enzyme replacement in early, mid- and symptomatic disease stage mice. We observed a disease-stage-dependent treatment effect, with the most significant reductions in primary and secondary substrate accumulation, astrogliosis and protein aggregate accumulation seen in mucopolysaccharidosis type IIIA mice treated very early in the disease course. Affected mice treated at a symptomatic age exhibited little change in these neuropathological markers in the time-frame of the study. Microgliosis was refractory to treatment regardless of the age at which treatment was instigated. Although longer-term studies are warranted, these findings indicate the importance of early intervention in this condition.

An overview of Korean patients with mucopolysaccharidosis and collaboration through the Asia Pacific MPS Network

Mucopolysaccharidosis (MPS) is a constellation of disorders characterized by the accumulation of mucopolysaccharides in tissues and organs. This accumulation results in the deterioration and degeneration of multiple organs. This paper describes the general distribution of types of MPS in patients, their clinical characteristics and genotypes, the development of animal studies and preclinical studies, enzyme replacement therapy in South Korea, and the development of idursulfase beta and clinical trials on idursulfase beta in South Korea. In addition, this paper discusses academic collaboration among specialists in MPS care in the Asia-Pacific region, which includes Japan, Taiwan, Malaysia, and South Korea, through an organization called the Asia-Pacific MPS Network (APMN). The Asia-Pacific MPS Registry, an electronic remote data entry system, has been developed by key doctors in the APMN. Rare diseases require international cooperation and collaboration to elucidate their mechanisms and carry out clinical trials; therefore, an organization such as the APMN is required. Furthermore, international collaboration among Asian countries and countries around the world will be of utmost importance in the future.

Mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) are a group of rare genetic disorders of glycosaminoglycan catabolism, caused by a deficiency of lysosomal enzymes required for GAG degradation. Incomplete breakdown of glycosaminoglycans leads to progressive accumulation of these substances in many tissues throughout the body. Different residual enzymatic activity can result in different phenotypes of the same MPS disorder, from severe to attenuated. Musculoskeletal manifestations are common across all forms of MPS. Skeletal and joint abnormalities are prominent features of many MPS disorders, particularly attenuated phenotypes. However, diagnostic delays occur frequently for patients with an MPS, especially those with more attenuated forms of disease. In the absence of appropriate treatment, these conditions are chronic, progressive and often debilitating, but treatment for many types of MPS is now available. Therefore, increasing awareness of MPS among rheumatologists is extremely important.

Guidelines for diagnosis and treatment of Hunter Syndrome for clinicians in Latin America

This review aims to provide clinicians in Latin America with the most current information on the clinical aspects, diagnosis, and management of Hunter syndrome, a serious and progressive disease for which specific treatment is available. Hunter syndrome is a genetic disorder where iduronate-2-sulfatase (I2S), an enzyme that degrades glycosaminoglycans, is absent or deficient. Clinical manifestations vary widely in severity and involve multiple organs and tissues. An attenuated and a severe phenotype are recognized depending on the degree of cognitive impairment. Early diagnosis is vital for disease management. Clinical signs common to children with Hunter syndrome include inguinal hernia, frequent ear and respiratory infections, facial dysmorphisms, macrocephaly, bone dysplasia, short stature, sleep apnea, and behavior problems. Diagnosis is based on screening urinary glycosaminoglycans and confirmation by measuring I2S activity and analyzing I2S gene mutations. Idursulfase (recombinant I2S) (Elaprase^®, Shire) enzyme replacement therapy (ERT), designed to address the underlying enzyme deficiency, is approved treatment and improves walking capacity and respiratory function, and reduces spleen and liver size and urinary glycosaminoglycan levels. Additional measures, responding to the multi-organ manifestations, such as abdominal/inguinal hernia repair, carpal tunnel surgery, and cardiac valve replacement, should also be considered. Investigational treatment options such as intrathecal ERT are active areas of research, and bone marrow transplantation is in clinical practice. Communication among care providers, social workers, patients and families is essential to inform and guide their decisions, establish realistic expectations, and assess patients’ responses.

Enzyme Replacement Therapy in Mucopolysaccharidosis II Patients Under 1 Year of Age

Mucopolysaccharidosis (MPS) II, or Hunter syndrome, is a lysosomal storage disease characterized by multi-systemic involvement and a progressive clinical course. Enzyme replacement therapy with idursulfase has been approved in more than 50 countries worldwide; however, safety and efficacy data from clinical studies are currently only available for patients 1.4 years of age and older. Sibling case studies of infants with MPS I, II, and VI who initiated ERT in the first weeks or months of life have reported no new safety concerns and a more favorable clinical course for the sibling treated in infancy than for the later-treated sibling. Here we describe our experiences with a case series of eight MPS II patients for whom idursulfase treatment was initiated at under 1 year of age. The majority of the patients were diagnosed because of a family history of disease. All of the infants displayed abnormalities consistent with MPS II at diagnosis. The youngest age at treatment start was 10 days and the oldest was 6.5 months, with duration of treatment varying between 6 weeks and 5.5 years. No new safety concerns were observed, and none of the patients experienced an infusion-related reaction. All of the patients treated for more than 6 weeks showed improvements and/or stabilization of some somatic manifestations while on treatment. In some cases, caregivers made comparisons with other affected family members and reported that the early-treated patients experienced a less severe clinical course, although a lack of medical records for many family members precluded a rigorous comparison.

Impact of enzyme replacement therapy on linear growth in Korean patients with mucopolysaccharidosis type II (Hunter syndrome)

Hunter syndrome (or mucopolysaccharidosis type II [MPS II]) arises because of a deficiency in the lysosomal enzyme iduronate-2-sulfatase. Short stature is a prominent and consistent feature in MPS II. Enzyme replacement therapy (ERT) with idursulfase (Elaprase®) or idursulfase beta (Hunterase®) have been developed for these patients. The effect of ERT on the growth of Korean patients with Hunter syndrome was evaluated at a single center. This study comprised 32 patients, who had received ERT for at least 2 yr; they were divided into three groups according to their ages at the start of ERT: group 1 (<6 yr, n=14), group 2 (6-10 yr, n=11), and group 3 (10-20 yr, n=7). The patients showed marked growth retardation as they got older. ERT may have less effect on the growth of patients with the severe form of Hunter syndrome. The height z-scores in groups 2 and 3 revealed a significant change (the estimated slopes before and after the treatment were -0.047 and -0.007, respectively: difference in the slope, 0.04; P<0.001). Growth in response to ERT could be an important treatment outcome or an endpoint for future studies.

The effect of recombinant human iduronate-2-sulfatase (Idursulfase) on growth in young patients with mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked, recessive, lysosomal storage disorder caused by deficiency of iduronate-2-sulfatase. Early bone involvement leads to decreased growth velocity and short stature in nearly all patients. Our analysis aimed to investigate the effects of enzyme replacement therapy (ERT) with idursulfase (Elaprase) on growth in young patients with mucopolysaccharidosis type II. Analysis of longitudinal anthropometric data of MPS II patients (group 1, n = 13) who started ERT before 6 years of age (range from 3 months to 6 years, mean 3.6 years, median 4 years) was performed and then compared with retrospective analysis of data for MPS II patients naïve to ERT (group 2, n = 50). Patients in group 1 received intravenous idursulfase at a standard dose of 0.58 mg/kg weekly for 52–288 weeks. The course of average growth curve for group 1 was very similar to growth pattern in group 2. The average value of body height in subsequent years in group 1 was a little greater than in group 2, however, the difference was not statistically significant. In studied patients with MPS II, idursulfase did not appear to alter the growth patterns.

Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome)

BACKGROUND

Mucopolysaccharidosis II, also known as Hunter syndrome, is a rare, X-linked disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyses a step in the catabolism of glycosaminoglycans. The glycosaminoglycans accumulate within tissues affecting multiple organs and physiologic systems. The clinical manifestations include neurologic involvement, severe airways obstruction, skeletal deformities and cardiomyopathy. The disease has a variable age of onset and variable rate of progression. In those with severe disease, death usually occurs in the second decade of life, whereas those patients with less severe disease may survive into adulthood. Enzyme replacement therapy with intravenous infusions of idursulfase has emerged as a new treatment for mucopolysaccharidosis type II.

OBJECTIVES

To evaluate the effectiveness and safety of enzyme replacement therapy with idursulfase compared to other interventions, placebo or no intervention, for treating mucopolysaccharidosis type II.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register (date of last search 22 July 2013).We also searched EMBASE, PubMed and the Literature Latino-Americana e do Caribe em Ciências da Saúde (LILACS) (date of last search 09 July 2013).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of enzyme replacement therapy with idursulfase compared to no intervention, placebo or other options (e.g. behavioral strategies, transplantation).

DATA COLLECTION AND ANALYSIS

Two authors independently screened the trials identified, appraised quality of papers and extracted data.

MAIN RESULTS

One study (96 patients) met the inclusion criteria, although the primary outcome of this review - z score for height and weight, was not assessed in the study. This trial was considered to be of overall good quality. Following 53 weeks of treatment, patients in the weekly idursulfase 0.5 mg/kg group demonstrated a significant improvement rate compared with placebo for the primary outcome: distance walked in six minutes on the basis of the sum of ranks of change from baseline, mean difference 37.00 (95% confidence interval 6.52 to 67.48). The every-other-week idursulfase 0.5 mg/kg group also showed an improvement, which was not significant compared with placebo, mean difference 23.00 (95% confidence interval -4.49 to 50.49). After 53 weeks, there was no statistical significance difference in per cent predicted forced vital capacity between the three groups and absolute forced vital capacity was significantly increased from baseline in the weekly dosing group compared to placebo, mean difference 0.16 (95% confidence interval CI 0.05 to 0.27). No difference was observed between the every-other-week idursulfase 0.5 mg/kg group and placebo.In addition, liver and spleen volumes and urine glycosaminoglycan excretion were significantly reduced from baseline by both idursulfase dosing regimens. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 31.7% of patients at the end of the study and they were related to a smaller reduction in urine glycosaminoglycan levels.

AUTHORS' CONCLUSIONS

The current evidence is limited. While the randomised clinical trial identified was considered to be of good quality, it failed to describe important outcomes. It has been demonstrated that enzyme replacement therapy with idursulfase is effective in relation to functional capacity (distance walked in six minutes and forced vital capacity), liver and spleen volumes and urine glycosaminoglycan excretion in patients with mucopolysaccharidosis type II compared with placebo. There is no available evidence in the included study and in the literature on outcomes such as improvement in growth, sleep apnoea, cardiac function, quality of life and mortality. More studies are needed to obtain more information on the long-term effectiveness and safety of enzyme replacement therapy.

Impact of Enzyme Replacement Therapy and Hematopoietic Stem Cell Therapy on Growth in Patients with Hunter Syndrome

Patients with Hunter syndrome (mucopolysaccharidosis II) present with skeletal dysplasia including short stature as well as CNS and visceral organ involvement. A previous study on Hunter syndrome indicated an impact on brain and heart involvement after hematopoietic stem cell therapy (HSCT) at an early stage but little impact after enzyme replacement therapy (ERT) (Tanaka et al 2012). Meanwhile, impact on growth in patients with Hunter syndrome treated with ERT and HSCT has not been compared until now. We recently developed baseline growth charts for untreated patients with Hunter syndrome to evaluate the natural history of growth of these patients compared to unaffected controls (Patel et al, 2014). To assess impact of ERT and HSCT on growth, clinical data were obtained from 44 Japanese male patients with MPS II; 26 patients had been treated with ERT, 12 patients had been treated with HSCT, and 6 had been treated with both ERT and HSCT. Height and weight were compared to untreated patients and unaffected controls from the previous study. We demonstrated 1) that MPS II patients, who had been treated with either ERT or HSCT, had increased height and weight when compared to untreated patients, and 2) that HSCT and ERT were equally effective in restoring growth of MPS II patients. In conclusion, HSCT should be considered as one of the primary therapeutic options for early stage treatment of MPS II, as HSCT has also been reported to have a positive effect on brain and heart valve development (Tanaka et al 2012).

Mucopolysaccharidoses and other lysosomal storage diseases

Mucopolysaccharidosis and other lysosomal storage diseases are rare, chronic, and progressive inherited diseases caused by a deficit of lysosomal enzymes. Patients are affected by a wide variety of symptoms. For some lysosomal storage diseases, effective treatments to arrest disease progression, or slow the pathologic process, and increase patient life expectancy are available or being developed. Timely diagnosis is crucial. Rheumatologists, orthopedics, and neurologists are commonly consulted due to unspecific musculoskeletal signs and symptoms. Pain, stiffness, contractures of joints in absence of clinical signs of inflammation, bone pain or abnormalities, osteopenia, osteonecrosis, secondary osteoarthritis or hip dysplasia are the alerting symptoms that should induce suspicion of a lysosomal storage disease.

IgE-mediated anaphylaxis and allergic reactions to idursulfase in patients with Hunter syndrome

BACKGROUND

Enzyme replacement therapy (ERT) with recombinant human idursulfase is effective for the treatment of Hunter syndrome, mucopolysaccharidosis (MPS) type II. However, various adverse events can occur by the infusion of idursulfase. The purpose was to evaluate the occurrence of infusion-related allergic reactions, including anaphylaxis, to idursulfase in patients with MPS II receiving ERT and to elucidate its possible mechanism.

METHODS

A total of 34 patients with MPS II were enrolled to receive ERT with Elaprase(®) at a dose of 0.5 mg/kg intravenously once a week. Information regarding the symptoms, frequency, and timing of anaphylaxis during treatment was analyzed. Presence of anti-idursulfase IgE antibody was assessed by skin prick test (SPT) and enzyme-linked immunosorbent assay (ELISA). Western blotting was performed to confirm the reaction between idursulfase and specific IgE.

RESULTS

Three patients (8.8%) showed anaphylaxis by infusion of idursulfase. No deaths occurred during the study. Anti-idursulfase IgE antibody was detected by SPT and ELISA. Immunoblotting with patients' sera and Elaprase(®) showed a single band of specific IgE binding to the protein around 70 kD, and idursulfase did not display amino acid sequence homology to known allergens. SPT with idursulfase demonstrated positive results in all patients with anaphylaxis. However, we failed to reveal any risk factors for the development of infusion-related immediate-type allergic reactions.

CONCLUSIONS

Anaphylaxis related to infusion of idursulfase is mediated by anti-idursulfase IgE antibody, which might be produced by de novo synthesis. SPT is useful in predicting the occurrence of anti-idursulfase IgE-mediated anaphylaxis during infusion.

The effect of idursulfase on growth in patients with Hunter syndrome: data from the Hunter Outcome Survey (HOS)

Hunter syndrome (mucopolysaccharidosis type II) is a rare and life-limiting multisystemic disorder with an X-linked recessive pattern of inheritance. Short stature is a prominent feature of this condition. This analysis aimed to investigate the effects of enzyme replacement therapy with idursulfase on growth in patients enrolled in HOS - the Hunter Outcome Survey which is a multinational observational database. As of Jan 2012, height data before treatment were available for 567 of 740 males followed prospectively after HOS entry. Cross-sectional analysis showed that short stature became apparent after approximately 8 years of age; before this, height remained within the normal range. Age-corrected standardized height scores (z-scores) before and after treatment were assessed using piecewise regression model analysis in 133 patients (8-15 years of age at treatment start; data available on ≥ 1 occasion within +/-24 months of treatment start; growth hormone-treated patients excluded). Results showed that the slope after treatment (slope=-0.005) was significantly improved compared with before treatment (slope=-0.043) (difference=0.038, p=0.004). Analysis of covariates (age at treatment start, cognitive involvement, presence of puberty at the start of ERT, mutation type, functional classification), showed a significant influence on growth of mutation type (height deficit in terms of z-scores most pronounced in patients with deletions/large rearrangements/nonsense mutations, p<0.0001) and age (most pronounced in the 12-15-year group, p<0.0001). Cognitive involvement, pubertal status at the start of ERT and functional classification were not related to the growth deficit or response to treatment. In conclusion, the data showed an improvement in growth rate in patients with Hunter syndrome following idursulfase treatment.

Receiving enzyme replacement therapy for a lysosomal storage disorder: a preliminary exploration of the experiences of young patients and their families

Medical intervention for lysosomal storage disorders becomes part of life, shaping the reality of the condition for affected individuals and families. Enzyme replacement therapy (ERT) is available to treat some lysosomal storage disorders. ERT is costly and time consuming, requiring frequent hospital visits to receive intravenous infusions. This qualitative study sought to explore the impact of receiving ERT for a lysosomal storage disorder on the health related quality of life (HRQoL) of young patients and their families. Fifteen semi-structured interviews were conducted with young people and parents and siblings of young people accessing ERT for Pompe disease, Gaucher disease or mucopolysaccharidosis types I or II living in Victoria, Australia. Interviews were transcribed then analyzed thematically. The biopsychosocial model assisted in interpreting themes. Findings revealed positive attitudes towards ERT, with noticed improvements in physical and psychosocial well-being. Participants prioritised intervention over other activities and provided suggestions for improving current service delivery. Communication with family members and professionals was deemed important, especially in respect to information provision. Participants described challenges associated with living with a lysosomal storage disorder and receiving ERT and coping strategies, such as positive thinking and ways to manage uncertainty. These findings provide valuable insights into the impact of living with a chronic genetic condition and receiving intensive treatment on HRQoL.

Botulinum toxin type A for the treatment of equinus deformity in patients with mucopolysaccharidosis type II

Mucopolysaccharidoses are lysosomal storage disorders that are caused by a deficiency in the enzymes that degrade glycosaminoglycans. The accumulation of glycosaminoglycans affects multiple systems, resulting in coarse facial features, short stature, organomegaly, and variable neurological changes from normal intelligence to severe mental retardation and spasticity. Effects on the musculoskeletal system include dysostosis multiplex, joint stiffness, and muscle shortening. This article reports 2 patients with mucopolysaccharidosis type II (Hunter syndrome) who showed progressive equinus deformity of the feet. Both patients were treated with intramuscular botulinum toxin type A injections in the gastrocnemius and the soleus muscles, followed by serial casting. In both patients, passive range of motion, muscle tone, and gait performance were significantly improved. Botulinum toxin type A injections followed by serial casting are a therapeutic option for contractures in patients with mucopolysaccharidosis. However, the long-term effects and the effect of application in other muscles remain unknown.

Biomarkers for the mucopolysaccharidoses: discovery and clinical utility

The mucopolysaccharidoses (MPSs), a group of inherited lysosomal storage diseases, are complex, progressive, multisystem disorders with extreme clinical heterogeneity. The introduction of therapies that target the underlying enzyme deficiency in a number of the MPSs has brought to light the need for biomarkers that would aid in the evaluation of disease burden and as a means to objectively measure therapeutic response in individual patients. It is increasingly recognized that due to the extraordinarily complex pathogenesis of the MPSs, achieving these goals with a single analyte, such as urinary glycosaminoglycans, is unlikely. This recognition has created an impetus for the search for clinically useful biomarkers that reflect the disease pathogenesis and that are stage- or organ-specific. In this review, the current state of MPS biomarker research is discussed, with a focus on clinical utility in the MPSs.

Overview of the mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) are a group of rare, inherited lysosomal storage disorders that are clinically characterized by abnormalities in multiple organ systems and reduced life expectancy. The MPSs are heterogeneous, progressive disorders. Patients typically appear normal at birth, but during early childhood they experience the onset of clinical disease, including skeletal, joint, airway and cardiac involvement, hearing and vision impairment, and mental retardation in the severe forms of MPS I, MPS II and MPS VII and all subtypes of MPS III. There are two treatment options for patients with MPS that are directed at the underlying pathophysiology: haematopoietic stem cell transplantation, which is useful for selected patients, and recombinant i.v. enzyme replacement therapy, which is available for MPS I, II and VI. Early diagnosis and treatment can improve patient outcomes and may reduce the disease burden on patients and caregivers. As skeletal and joint abnormalities are characteristic of many patients with MPS, rheumatologists are positioned to recognize the features of the disease and to facilitate early diagnosis and referral. In this overview, the clinical features of the MPS disorders and a brief review of treatment options will be presented in order to aid the rheumatologist in recognizing the features of these rare genetic disorders.

Diagnosing Hunter syndrome in pediatric practice: practical considerations and common pitfalls

Mucopolysaccharidosis II (MPS II), or Hunter syndrome, is an X-linked lysosomal storage disorder caused by a deficiency in the enzyme iduronate-2-sulfatase. Affected patients suffer progressive damage to multiple organ systems and early mortality. Two thirds of patients also manifest cognitive impairment and developmental delays. MPS II can be extremely difficult to diagnose before irreversible organ and tissue damage has occurred because of an insidious onset and the overlap in signs and symptoms with common childhood complaints. This is particularly true of patients without cognitive impairment (attenuated phenotype). Although not curative, early treatment with enzyme replacement therapy before irreversible organ damage has occurred may result in the greatest clinical benefit. Here, the signs, symptoms, and surgical history that should trigger suspicion of MPS II are described, and the diagnostic process is reviewed with a focus on practical considerations and the avoidance of common diagnostic pitfalls. Once a diagnosis is made, multidisciplinary management with an extended team of pediatric specialists is essential and should involve the pediatrician or family practice physician as facilitator and medical home for the patient and family.

CONCLUSION

Because routine newborn screening is not yet available for MPS II, the involvement and awareness of pediatricians, family practice physicians, and pediatric specialists is critical for early identification, diagnosis, and referral in order to help optimize patient outcomes.

Enzyme replacement therapy for mucopolysaccharidosis II from 3 months of age: a 3-year follow-up

AIM

We present a 3-year follow-up of a boy with mucopolysaccharidosis type II (MPS II) who had idursulfase therapy initiated at the age of 3 months and compare his clinical course to his healthy twin brother.

METHODS

Detailed anthropometric features, ultrasound studies of liver and spleen volumes, echocardiography and audiological examinations, psychological tests, joint range of motion (ROM) and skeletal radiographs were monitored.

RESULTS

After 3 years of treatment, the patient has not developed any clinical manifestations of MPS II. He did not develop coarse facial features, joint disease, or organomegaly, and his cardiac function remained normal. There were no pronounced signs of dysostosis multiplex on radiographs. The only difference when compared with his healthy twin brother was lower IQ (Termann-Merrill 98 vs. 118) and mild deformity of one vertebrae.

CONCLUSION

Our study suggests that early initiation of enzyme replacement therapy may significantly slow or prevent the development of irreversible disease manifestations and therefore modify the natural history of MPS II.

Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome)

BACKGROUND

Mucopolysaccharidosis II, also known as Hunter syndrome, is a rare, X-linked disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyses a step in the catabolism of glycosaminoglycans. The glycosaminoglycans accumulate within tissues affecting multiple organs and physiologic systems. The clinical manifestations include neurologic involvement, severe airways obstruction, skeletal deformities and cardiomyopathy. The disease has a variable age of onset and variable rate of progression. In those with severe disease, death usually occurs in the second decade of life, whereas those patients with less severe disease may survive into adulthood. Enzyme replacement therapy with intravenous infusions of idursulfase has emerged as a new treatment for mucopolysaccharidosis type II.

OBJECTIVES

To evaluate the effectiveness and safety of enzyme replacement therapy with idursulfase compared to other interventions, placebo or no intervention, for treating mucopolysaccharidosis type II.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register (date of last search 01 September 2011).We also searched EMBASE, PubMed and the Literature Latino-Americana e do Caribe em Ciências da Saúde (LILACS) (date of last search October 2009).

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of enzyme replacement therapy with idursulfase compared to no intervention, placebo or other options (e.g. behavioral strategies, transplantation).

DATA COLLECTION AND ANALYSIS

Two authors independently screened the trials identified, appraised quality of papers and extracted data.

MAIN RESULTS

One study (96 patients) met the inclusion criteria, although the primary outcome of this review - z score for height and weight, was not assessed in the study. Following 53 weeks of treatment, patients in the weekly idursulfase 0.5 mg/kg group demonstrated a significant improvement rate compared with placebo for the primary outcome: distance walked in six minutes on the basis of the sum of ranks of change from baseline, mean difference 37.00 (95% confidence interval 6.52 to 67.48). The every-other-week idursulfase 0.5 mg/kg group also showed an improvement, which was not significant compared with placebo, mean difference 23.00 (95% confidence interval -4.49 to 50.49). After 53 weeks, there was no statistical significance difference in per cent predicted forced vital capacity between the three groups and absolute forced vital capacity was significantly increased from baseline in the weekly dosing group compared to placebo, mean difference 0.16 (95% confidence interval CI 0.05 to 0.27). No difference was observed between the every-other-week idursulfase 0.5 mg/kg group and placebo.In addition, liver and spleen volumes and urine glycosaminoglycan excretion were significantly reduced from baseline by both idursulfase dosing regimens. Idursulfase was generally well tolerated, but infusion reactions did occur. Idursulfase antibodies were detected in 31.7% of patients at the end of the study and they were related to a smaller reduction in urine glycosaminoglycan levels.

AUTHORS' CONCLUSIONS

The current evidence is limited. While the randomised clinical trial identified was considered to be of good quality, it failed to describe important outcomes. It has been demonstrated that enzyme replacement therapy with idursulfase is effective in relation to functional capacity (distance walked in six minutes and forced vital capacity), liver and spleen volumes and urine glycosaminoglycan excretion in patients with mucopolysaccharidosis type II compared with placebo. There is no available evidence in the included study and in the literature on outcomes such as improvement in growth, sleep apnoea, cardiac function, quality of life and mortality. More studies are needed to obtain more information on the long-term effectiveness and safety of enzyme replacement therapy.

Mucopolysaccharidosis type II: European recommendations for the diagnosis and multidisciplinary management of a rare disease

Mucopolysaccharidosis type II (MPS II) is a rare, life-limiting, X-linked recessive disease characterised by deficiency of the lysosomal enzyme iduronate-2-sulfatase. Consequent accumulation of glycosaminoglycans leads to pathological changes in multiple body systems. Age at onset, signs and symptoms, and disease progression are heterogeneous, and patients may present with many different manifestations to a wide range of specialists. Expertise in diagnosing and managing MPS II varies widely between countries, and substantial delays between disease onset and diagnosis can occur. In recent years, disease-specific treatments such as enzyme replacement therapy and stem cell transplantation have helped to address the underlying enzyme deficiency in patients with MPS II. However, the multisystem nature of this disorder and the irreversibility of some manifestations mean that most patients require substantial medical support from many different specialists, even if they are receiving treatment. This article presents an overview of how to recognise, diagnose, and care for patients with MPS II. Particular focus is given to the multidisciplinary nature of patient management, which requires input from paediatricians, specialist nurses, otorhinolaryngologists, orthopaedic surgeons, ophthalmologists, cardiologists, pneumologists, anaesthesiologists, neurologists, physiotherapists, occupational therapists, speech therapists, psychologists, social workers, homecare companies and patient societies.

Take-home message

Expertise in recognising and treating patients with MPS II varies widely between countries. This article presents pan-European recommendations for the diagnosis and management of this life-limiting disease.