Musculoskeletal complications associated with lysosomal storage disorders: Gaucher disease and Hurler-Scheie syndrome (mucopolysaccharidosis type I)

Wnt signaling pathway inhibitors, sclerostin and DKK-1, correlate with pain and bone pathology in patients with Gaucher disease

Patients with Gaucher disease (GD) have progressive bone involvement that clinically presents with debilitating bone pain, structural bone changes, bone marrow infiltration (BMI), Erlenmeyer (EM) flask deformity, and osteoporosis. Pain is referred by the majority of GD patients and continues to persist despite the type of therapy. The pain in GD is described as chronic deep penetrating pain; however, sometimes, patients experience severe acute pain. The source of bone pain is mainly debated as nociceptive pain secondary to bone pathology or neuropathic or inflammatory origins. Osteocytes constitute a significant source of secreted molecules that coordinate bone remodeling. Osteocyte markers, sclerostin (SOST) and Dickkopf-1 (DKK-1), inactivate the canonical Wnt signaling pathway and lead to the inhibition of bone formation. Thus, circulated sclerostin and DKK-1 are potential biomarkers of skeletal abnormalities. This study aimed to assess the circulating levels of sclerostin and DKK-1 in patients with GD and their correlation with clinical bone pathology parameters: pain, bone mineral density (BMD), and EM deformity. Thirty-nine patients with GD were classified into cohorts based on the presence and severity of bone manifestations. The serum levels of sclerostin and DKK-1 were quantified by enzyme-linked immunosorbent assays. The highest level of sclerostin was measured in GD patients with pain, BMI, and EM deformity. The multiparameter analysis demonstrated that 95% of GD patients with pain, BMI, and EM deformity had increased levels of sclerostin. The majority of patients with elevated sclerostin also have osteopenia or osteoporosis. Moreover, circulating sclerostin level increase with age, and GD patients have elevated sclerostin levels when compared with healthy control from the same age group. Pearson's linear correlation analysis showed a positive correlation between serum DKK-1 and sclerostin in healthy controls and GD patients with normal bone mineral density. However, the balance between sclerostin and DKK-1 waned in GD patients with osteopenia or osteoporosis. In conclusion, the osteocyte marker, sclerostin, when elevated, is associated with bone pain, BMI, and EM flask deformity in GD patients. The altered sclerostin/DKK-1 ratio correlates with the reduction of bone mineral density. These data confirm that the Wnt signaling pathway plays a role in GD-associated bone disease. Sclerostin and bone pain could be used as biomarkers to assess patients with a high risk of BMI and EM flask deformities.

Ultrasound findings of finger, wrist and knee joints in Mucopolysaccharidosis Type I

INTRODUCTION

Musculoskeletal findings in MPS can progress after enzyme replacement. Our aim was to examine synovial recesses, tendons, retinacula and pulleys using ultrasonography for structural and inflammatory changes.

MATERIAL AND METHODS

The wrist, metacarpophalangeal (MCP), proximal and distal interphalangeal (PIP and DIP) joints, the finger flexor tendons and the knee including entheses of quadriceps and patella tendons were assessed clinically. Ultrasonography of the various synovial recesses of the wrist as well as the extensor retinaculum, carpal tunnel, MCP, PIP and DIP joints of the second finger, extensor and flexor tendons, A1-5 pulleys and the knee joint including relevant entheses followed. Significance of differences between patient values and available normative data were assessed using t-tests.

RESULTS

Ultrasonography showed significant abnormal intraarticular material in the wrist without a clear distribution to synovial recesses and without effusions. Doppler signals were found in a perisynovial distribution and not intrasynovial as expected in in inflammatory arthritis. Findings were similar in the knee but not the fingers. Flexor and extensor tendons were also mostly normal in their structure but significant thickening of retinaculae and the flexor tendon pulleys was seen (p<0.0001 compared to normal).

CONCLUSION

MPS I patients showed intraarticular deposition of abnormal material in the wrist and knee but not in the finger joints where significant thickening of retinaculae/pulleys controlling tendon position was dominant. No ultrasound findings of inflammatory pathology were demonstrated but rather a secondary reaction to abnormal deposition and direct damage of GAG.

Hurdles in treating Hurler disease: potential routes to achieve a "real" cure

Mucopolysaccharidoses (MPSs) are multiorgan devastating diseases for which hematopoietic cell transplantation (HCT) and, to a lesser extent, enzyme replacement therapy have substantially altered the course of the disease. Furthermore, they have resulted in increased overall survival, especially for Hurler disease (MPS-1). However, despite the identification of clinical predictors and harmonized transplantation protocols, disease progression still poses a significant burden to patients, although at a slower pace. To design better therapies, we need to understand why and where current therapies fail. In this review, we discuss important aspects of the underlying disease and the disease progression. We note that the majority of progressive symptoms that occur in "hard-to-treat" tissues are actually tissues that are difficult to reach, such as avascular connective tissue or tissues isolated from the circulation by a specific barrier (eg, blood-brain barrier, blood-retina barrier). Although easily reached tissues are effectively cured by HCT, disease progression is observed in these "hard-to-reach" tissues. We used these insights to critically appraise ongoing experimental endeavors with regard to their potential to overcome the encountered hurdles and improve long-term clinical outcomes in MPS patients treated with HCT.

Enzyme therapy: a forerunner in catalyzing a healthy society?

INTRODUCTION

The use of enzymes in various industries has been prevalent for centuries. However, their potency as therapeutics remained latent until the late 1950 s, when scientists finally realized the gold mine they were sitting on. Enzyme therapy has seen rapid development over the past few decades and has been widely used for the therapy of myriad diseases, including lysosomal storage disorders, cancer, Alzheimer's disease, irritable bowel syndrome, exocrine pancreatic insufficiency, and hyperuricemia. Enzymes are also used for wound healing, the treatment of microbial infections, and gene therapy.

AREAS COVERED

This is a comprehensive review of the therapeutic use of enzymes that can act as a guidepost for researchers and academicians and presents a general overview of the developments in enzyme therapy over the years, along with updates on recent advancements in enzyme therapy research.

EXPERT OPINION

Although enzyme therapy is immensely beneficial and induces little auxiliary damage, it has several drawbacks, ranging from high cost, low stability, low production, and hyperimmune responses to the failure to cure a variety of the problems associated with a disease. Further fine-tuning and additional clinical efficacy studies are required to establish enzyme therapy as a forerunner to catalyzing a healthy society.

Characterization of mesenchymal stem cells in mucolipidosis type II (I-cell disease)

Mucolipidosis type II (ML-II, I-cell disease) is a fatal inherited lysosomal storage disease caused by a deficiency of the enzyme N-acetylglucosamine-1-phosphotransferase. A characteristic skeletal phenotype is one of the many clinical manifestations of ML-II. Since the mechanisms underlying these skeletal defects in ML-II are not completely understood, we hypothesized that a defect in osteogenic differentiation of ML-II bone marrow mesenchymal stem cells (BM-MSCs) might be responsible for this skeletal phenotype. Here, we assessed and characterized the cellular phenotype of BM-MSCs from a ML-II patient before (BBMT) and after BM transplantation (ABMT), and we compared the results with BM-MSCs from a carrier and a healthy donor. Morphologically, we did not observe differences in ML-II BBMT and ABMT or carrier MSCs in terms of size or granularity. Osteogenic differentiation was not markedly affected by disease or carrier status. Adipogenic differentiation was increased in BBMT ML-II MSCs, but chondrogenic differentiation was decreased in both BBMT and ABMT ML-II MSCs. Immunophenotypically no significant differences were observed between the samples. Interestingly, the proliferative capacity of BBMT and ABMT ML-II MSCs was increased in comparison to MSCs from age-matched healthy donors. These data suggest that MSCs are not likely to cause the skeletal phenotype observed in ML-II, but they may contribute to the pathogenesis of ML-II as a result of lysosomal storage-induced pathology.

Imaging of non-neuronopathic Gaucher disease: recent advances in quantitative imaging and comprehensive assessment of disease involvement

Gaucher disease is an inherited metabolic disorder resulting in deficiency of lysosomal enzyme β-glucocerebrosidase causing the accumulation of abnormal macrophages (“Gaucher cells”) within multiple organs, most conspicuously affecting the liver, spleen, and bone marrow. As the most common glycolipid metabolism disorder, it is important for radiologists encountering these patients to be familiar with advances in imaging of organ and bone marrow involvement and understand the role of imaging in clinical decision-making. The recent advent of commercially available, reliable, and reproducible quantitative MRI acquisitions to measure fat fractions prompts revisiting the role of quantitative assessment of bone marrow involvement. This manuscript reviews the diverse imaging manifestations of Gaucher disease and discusses more optimal quantitative approaches to ascertain solid organ and bone marrow involvement with an emphasis on future applications of other quantitative methods including elastography.

Clinical presentation and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are estimated to affect1 in 25,000 live births although specific rates vary between the ethnic origin and country. MPS are a group of lysosomal storage disorders, which cause the buildup of GAG(s) due to insufficient or absent GAG-degrading enzymes. With seven types of MPS disorders and eleven subtypes, the MPS family presents unique challenges for early clinical diagnosis due to the molecular and clinical heterogeneity between groups and patients. Novel methods of early identification, particularly newborn screening through mass spectrometry, can change the flow of diagnosis, allowing enzyme and GAG quantification before the presentation of clinical symptoms improving outcomes. Genetic testing of patients and their families can also be conducted preemptively. This testing enables families to make informed decisions about family planning, leading to prenatal diagnosis. In this review, we discuss the clinical symptoms of each MPS type as they initially appear in patients, biochemical and molecular diagnostic methods, and the future of newborn screening for this group of disorders.

Thoracolumbar kyphosis in patients with mucopolysaccharidoses: clinical outcomes and predictive radiographic factors for progression of deformity

AIMS

Clinical and radiological data were reviewed for all patients with mucopolysaccharidoses (MPS) with thoracolumbar kyphosis managed non-operatively or operatively in our institution.

METHODS

In all 16 patients were included (eight female: eight male; 50% male), of whom nine had Hurler, five Morquio and two Hunter syndrome. Six patients were treated non-operatively (mean age at presentation of 6.3 years; 0.4 to 12.9); mean kyphotic progression +1.5(o)/year; mean follow-up of 3.1 years (1 to 5.1) and ten patients operatively (mean age at presentation of 4.7 years; 0.9 to 14.4); mean kyphotic progression 10.8(o)/year; mean follow-up of 8.2 years; 4.8 to 11.8) by circumferential arthrodesis with posterior instrumentation in patients with flexible deformities (n = 6).

RESULTS

In the surgical group (mean age at surgery of 6.6 years; 2.4 to 16.8); mean post-operative follow-up of 6.3 years (3.5 to 10.3), mean pre-operative thoracolumbar kyphosis of 74.3(o) (42(o) to 110(o)) was corrected to mean of 28.6(o) (0(o) to 65(o)) post-operatively, relating to a mean deformity correction of 66.9% (31% to 100%). Surgical complications included a deep wound infection treated by early debridement, apical non-union treated by posterior re-grafting, and stable adjacent segment spondylolisthesis managed non-operatively. Thoracolumbar kyphosis > +38(o) at initial presentation was identified as predicting progressively severe deformity with 90% sensitivity and 83% specificity.

DISCUSSION

This study demonstrates that severe thoracolumbar kyphosis in patients with MPS can be effectively treated by circumferential arthrodesis. Severity of kyphosis at initial presentation may predict progression of thoracolumbar deformity. Patients with MPS may be particularly susceptible to post-operative complications due to the underlying connective tissue disorder and inherent immunological compromise.

TAKE HOME MESSAGE

Clinical and radiological data were reviewed for all patients with mucopolysaccharidoses with thoracolumbar kyphosis managed non-operatively or operatively in our institution.

Can Macrosomia or Large for Gestational Age Be Predictive of Mucopolysaccharidosis Type I, II and VI?

BACKGROUND

The objective of the study was to compare mean values for birth body length and weight between patients with mucopolysaccharidosis (MPS) and the general population.

METHODS

A retrospective analysis of birth anthropometric data was performed for patients (n = 103) with MPS I, II, and VI. Two-tailed t tests were used to compare mean values for body length and weight at birth between patients with MPS and the general population.

RESULTS

Mean values for birth body length and weight for all studied groups were greater than in the general population. For body length the differences were statistically significant. When considered individually, 53% of patients were large for gestational age (LGA) and 30% were macrosomic. The highest percentage of LGA was observed in MPS II males and MPS VI females (55% and 56%, respectively), while the highest percentage of macrosomia was observed in MPS VI males (36%).

CONCLUSION

At the time of birth, MPS patients were larger than those in the general population. High birth weight and/or LGA can be suggestive of MPS disease and should raise suspicion aiding early disease recognition.

Bone marrow adipose tissue: formation, function and regulation

The human body requires an uninterrupted supply of energy to maintain metabolic homeostasis and energy balance. To sustain energy balance, excess consumed calories are stored as glycogen, triglycerides and protein, allowing the body to continue to function in states of starvation and increased energy expenditure. Adipose tissue provides the largest natural store of excess calories as triglycerides and plays an important role as an endocrine organ in energy homeostasis and beyond. This short review is intended to detail the current knowledge of the formation and role of bone marrow adipose tissue (MAT), a largely ignored adipose depot, focussing on the role of MAT as an endocrine organ and highlighting the pharmacological agents that regulate MAT.

Lysosomal storage disorders: A review of the musculoskeletal features

The lysosomal storage disorders are a collection of progressive, multisystem disorders that frequently present in childhood. Their timely diagnosis is paramount as they are becoming increasingly treatable. Musculoskeletal manifestations often occur early in the disease course, hence are useful as diagnostics clues. Non-inflammatory joint stiffness or pain, carpal tunnel syndrome, trigger fingers, unexplained pain crises and short stature should all prompt consideration of a lysosomal storage disorder. Recurrent ENT infections, hepatosplenomegaly, recurrent hernias and visual/hearing impairment - especially when clustered together - are important extra-skeletal features. As diagnostic and therapeutic options continue to evolve, children with lysosomal storage disorders and their families are facing more sophisticated options for screening and treatment. The aim of this article is to highlight the paediatric presentations of lysosomal storage disorders, with an emphasis on the musculoskeletal features.

Impaired bone remodeling and its correction by combination therapy in a mouse model of mucopolysaccharidosis-I

Mucopolysaccharidosis-I (MPS-I) is a lysosomal storage disease (LSD) caused by inactivating mutations of IDUA, encoding the glycosaminoglycan-degrading enzyme α-l-iduronidase. Although MPS-I is associated with skeletal abnormalities, the impact of IDUA deficiency on bone remodeling is poorly defined. Here we report that Idua-deficient mice progressively develop a high bone mass phenotype with pathological lysosomal storage in cells of the osteoblast lineage. Histomorphometric quantification identified shortening of bone-forming units and reduced osteoclast numbers per bone surface. This phenotype was not transferable into wild-type mice by bone marrow transplantation (BMT). In contrast, the high bone mass phenotype of Idua-deficient mice was prevented by BMT from wild-type donors. At the cellular level, BMT did not only normalize defects of Idua-deficient osteoblasts and osteocytes but additionally caused increased osteoclastogenesis. Based on clinical observations in an individual with MPS-I, previously subjected to BMT and enzyme replacement therapy (ERT), we treated Idua-deficient mice accordingly and found that combining both treatments normalized all histomorphometric parameters of bone remodeling. Our results demonstrate that BMT and ERT profoundly affect skeletal remodeling of Idua-deficient mice, thereby suggesting that individuals with MPS-I should be monitored for their bone remodeling status, before and after treatment, to avoid long-term skeletal complications.

Ultrasonographic Features of Hip Joints in Mucopolysaccharidoses Type I and II

OBJECTIVES

The primary aim of this study was to assess the ultrasonographic features of hip joints in patients with mucopolysaccharidosis (MPS) type I and II in comparison with healthy population. The secondary aims were to correlate these features with clinical measures and to evaluate the utility of ultrasound in the diagnosis of MPS disease.

MATERIALS AND METHODS

Sixteen MPS I (n = 3) and II (n = 13) patients were enrolled in the present study and underwent clinical and radiological evaluation, and bilateral high-resolution ultrasonography (US) of hip joints. The distance from the femoral neck to joint capsule (synovial joint space, SJS), joint effusion, synovial hyperthrophy, and local pathological vascularization were evaluated. The results were compared to the healthy population and correlated with clinical and radiological measures.

RESULTS

1. There was a difference in US SJS between children with MPS disease and the normative value for healthy population (7mm). Mean values of SJS were 15.81 ± 4.08 cm (right hip joints) and 15.69 ± 4.19 cm (left joints). 2. No inflammatory joint abnormalities were detected in MPS patients. 3. There was a clear correlation between US SJS and patients' age and height, while no clear correlation was observed between SJS and disease severity.

CONCLUSIONS

1. Patients with MPS I and II present specific features in hip joint ultrasonography. 2. The data suggests that ultrasonography might be effective in the evaluation of hip joint involvement in patients with MPS and might present a valuable tool in facilitating the diagnosis and follow up of the disease.

Molecular Genetics and Metabolism Report Long-term follow-up of post hematopoietic stem cell transplantation for Hurler syndrome: clinical, biochemical, and pathological improvements

Mucopolysaccharidosis type I (MPS I; Hurler Syndrome) is a lysosomal storage disease caused by a deficiency of the enzyme α-L-iduronidase which affects multiple organs such as central nervous system (CNS), skeletal system, and physical appearance. Hematopoietic stem cell transplantation (HSCT) is recommended as a primary therapeutic option at an early stage of MPS I with a severe form to ameliorate CNS involvement; however, no description of pathological improvement in skeletal dysplasia has been investigated to date. We here report a 15-year-old male case with MPS I post-HSCT. This patient received successful HSCT at the age of 2 years and 1 month, followed for over 10 years. His activity of daily living including cognitive performance has been kept normal and the present height and weight are 162 cm and 55 kg. Bone deformity has been still developed, resulting in hemiepiphysiodesis of bilateral medial proximal tibia at 12 years of age and successive arthrodesis of thoraco-lumbar spine at 13 years of age; however, skeletal histopathology from surgical remnants showed substantial improvement in bone lesion with markedly reduced occurrence and cell size of vacuolated cells. After a series of surgical procedures, he became ambulant and independent in daily activity. The levels of GAGs in blood were substantially reduced. In conclusion, this long-term post-HSCT observation should shed light on a new aspect of therapeutic effect associated with skeletal pathology and GAG levels as a biomarker, indicating that HSCT is a primary choice at an early stage for not only CNS but skeletal system in combination of appropriate surgical procedures.

Neonatal bone marrow transplantation prevents bone pathology in a mouse model of mucopolysaccharidosis type I

Neonatal bone marrow transplantation (BMT) could offer a novel therapeutic opportunity for genetic disorders by providing sustainable levels of the missing protein at birth, thus preventing tissue damage. We tested this concept in mucopolysaccharidosis type I (MPS IH; Hurler syndrome), a lysosomal storage disorder caused by deficiency of α-l-iduronidase. MPS IH is characterized by a broad spectrum of clinical manifestations, including severe progressive skeletal abnormalities. Although BMT increases the life span of patients with MPS IH, musculoskeletal manifestations are only minimally responsive if the timing of BMT delays, suggesting already irreversible bone damage. In this study, we tested the hypothesis that transplanting normal BM into newborn MPS I mice soon after birth can prevent skeletal dysplasia. We observed that neonatal BMT was effective at restoring α-l-iduronidase activity and clearing elevated glycosaminoglycans in blood and multiple organs. At 37 weeks of age, we observed an almost complete normalization of all bone tissue parameters, using radiographic, microcomputed tomography, biochemical, and histological analyses. Overall, the magnitude of improvements correlated with the extent of hematopoietic engraftment. We conclude that BMT at a very early stage in life markedly reduces signs and symptoms of MPS I before they appear.

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.

Characterization of joint disease in mucopolysaccharidosis type I mice

Mucopolysaccharidoses (MPS) are lysosomal storage disorders characterized by mutations in enzymes that degrade glycosaminoglycans (GAGs). Joint disease is present in most forms of MPS, including MPS I. This work aimed to describe the joint disease progression in the murine model of MPS I. Normal (wild-type) and MPS I mice were sacrificed at different time points (from 2 to 12 months). The knee joints were collected, and haematoxylin-eosin staining was used to evaluate the articular architecture. Safranin-O and Sirius Red staining was used to analyse the proteoglycan and collagen content. Additionally, we analysed the expression of the matrix-degrading metalloproteinases (MMPs), MMP-2 and MMP-9, using immunohistochemistry. We observed progressive joint alterations from 6 months, including the presence of synovial inflammatory infiltrate, the destruction and thickening of the cartilage extracellular matrix, as well as proteoglycan and collagen depletion. Furthermore, we observed an increase in the expression of MMP-2 and MMP-9, which could conceivably explain the degenerative changes. Our results suggest that the joint disease in MPS I mice may be caused by a degenerative process due to increase in proteases expression, leading to loss of collagen and proteoglycans. These results may guide the development of ancillary therapies for joint disease in MPS I.

Enhanced differentiation of osteoclasts from mononuclear precursors in patients with Gaucher disease

Gaucher disease (GD) is an autosomal recessive disorder caused by deficiency of β-glucocerebrosidase. Storage of glucosylceramide in reticuloendothelial cells results in multiorgan pathology including bone disease. Established skeletal disease may remain problematic despite Gaucher-specific treatment. Both osteopenia and osteonecrosis have been described but the underlying pathophysiology, in particular the role of monocyte-derived osteoclasts is not well defined. The objective of this study was to explore the effect of glucocerebrosidase deficiency, inhibition and replacement on osteoclast development and function. In cultures derived from GD patients, or where GBA was chemically inhibited multinucleate giant cells expressing markers of osteoclast differentiation occurred earlier and in greater numbers compared to normal controls and the functional capacity of osteoclasts for bone resorption was enhanced. Increases in osteoclast number and activity correlated with radiological markers of active bone disease. Abnormalities were reversed by addition of specific therapies and were attenuated by co-culture with cells derived from healthy controls (HCs). Numbers of osteoblast lineage cells in the peripheral blood were mismatched to osteoclast precursors indicating uncoupling of osteoblast-osteoclast regulation which may further impact on bone remodelling. Elucidation of the underlying mechanisms of these changes will suggest rational therapies for the most disabling aspect of this condition.

High prevalence of femoral head necrosis in Mucopolysaccharidosis type III (Sanfilippo disease): a national, observational, cross-sectional study

BACKGROUND

Sanfilippo disease, or Mucopolysaccharidosis type III (MPS III), is a lysosomal storage disorder and a member of the mucopolysaccharidoses (MPSs). MPS III is clinically characterized by progressive neurodegeneration. Skeletal disease is not felt to be an important clinical component in MPS III patients, unlike in the other MPSs. We conducted radiographic studies in a relatively large group of MPS III patients and detected a high prevalence of osteonecrosis of the femoral head (ONFH).

METHODS

Thirty-three patients were included in the study. All the patients underwent an X-ray of the pelvis (anteroposterior view). All the X-rays were evaluated by a single, blinded radiologist using a modified Ficat classification system for ONFH (the stages ranged from 0 to IV, with increasing stages signifying more severe abnormalities). Clinical symptoms possibly related to hip disease were recorded. The patients were divided into different phenotypes based on mutational analysis and their plasma heparan sulfate (HS) levels.

RESULTS

In 21 of the 33 patients, the disease severity could be predicted by genotype. In 11 of the 12 remaining patients, the phenotype could be assessed via the plasma HS levels. Eight patients (24%) exhibited signs of ONFH (Ficat stage≥I), and 6 (75%) of them had bilateral changes. None of the patients with attenuated MPS III (n=14) had ONFH. In 6 of the patients with a severe phenotype, hip dysplasia was detected as an additional finding. The 7 patients with Ficat stages ≥ II reported hip pain.

CONCLUSIONS

Femoral head disease, which resembles ONFH, is common in patients with the severe MPS III phenotype. An evaluation of hip disease should be included in follow-up visits with MPS III patients.

Enzyme replacement therapy for Mucopolysaccharidosis Type I among patients followed within the MPS Brazil Network

Mucopolysaccharidosis type I (MPS I) is a rare lysosomal disorder caused by deficiency of alpha-L-iduronidase. Few clinical trials have assessed the effect of enzyme replacement therapy (ERT) for this condition. We conducted an exploratory, open-label, non-randomized, multicenter cohort study of patients with MPS I. Data were collected from questionnaires completed by attending physicians at the time of diagnosis (T1; n = 34) and at a median time of 2.5 years later (T2; n = 24/34). The 24 patients for whom data were available at T2 were allocated into groups: A, no ERT (9 patients; median age at T1 = 36 months; 6 with severe phenotype); B, on ERT (15 patients; median age at T1 = 33 months; 4 with severe phenotype). For all variables in which there was no between-group difference at baseline, a delta of ≥ ± 20% was considered clinically relevant. The following clinically relevant differences were identified in group B in T2: lower rates of mortality and reported hospitalization for respiratory infection; lower frequency of hepatosplenomegaly; increased reported rates of obstructive sleep apnea syndrome and hearing loss; and stabilization of gibbus deformity. These changes could be due to the effect of ERT or of other therapies which have also been found more frequently in group B. Our findings suggest MPS I patients on ERT also receive a better overall care. ERT may have a positive effect on respiratory morbidity and overall mortality in patients with MPS I. Additional studies focusing on these outcomes and on other therapies should be performed.

Capturing phenotypic heterogeneity in MPS I: results of an international consensus procedure

Background

Mucopolysaccharidosis type I (MPS I) is traditionally divided into three phenotypes: the severe Hurler (MPS I-H) phenotype, the intermediate Hurler-Scheie (MPS I-H/S) phenotype and the attenuated Scheie (MPS I-S) phenotype. However, there are no clear criteria for delineating the different phenotypes. Because decisions about optimal treatment (enzyme replacement therapy or hematopoietic stem cell transplantation) need to be made quickly and depend on the presumed phenotype, an assessment of phenotypic severity should be performed soon after diagnosis. Therefore, a numerical severity scale for classifying different MPS I phenotypes at diagnosis based on clinical signs and symptoms was developed.

Methods

A consensus procedure based on a combined modified Delphi method and a nominal group technique was undertaken. It consisted of two written rounds and a face-to-face meeting. Sixteen MPS I experts participated in the process. The main goal was to identify the most important indicators of phenotypic severity and include these in a numerical severity scale. The correlation between the median subjective expert MPS I rating and the scores derived from this severity scale was used as an indicator of validity.

Results

Full consensus was reached on six key clinical items for assessing severity: age of onset of signs and symptoms, developmental delay, joint stiffness/arthropathy/contractures, kyphosis, cardiomyopathy and large head/frontal bossing. Due to the remarkably large variability in the expert MPS I assessments, however, a reliable numerical scale could not be constructed. Because of this variability, such a scale would always result in patients whose calculated severity score differed unacceptably from the median expert severity score, which was considered to be the 'gold standard'.

Conclusions

Although consensus was reached on the six key items for assessing phenotypic severity in MPS I, expert opinion on phenotypic severity at diagnosis proved to be highly variable. This subjectivity emphasizes the need for validated biomarkers and improved genotype-phenotype correlations that can be incorporated into phenotypic severity assessments at diagnosis.

Restricted joint range of motion in patients with MPS II: correlation with height, age and functional status

AIM

The aims of the study were to assess shoulder range of motion (ROM) in patients with mucopolysaccharidosis type II (MPS II) and to correlate joint mobility with patients' height, age and functional status.

METHODS

Passive ROM and Z-score of height were followed in 29 patients with MPS II (mean age 11.5 years, range 2-29 years) between the years 2005 and 2010. Passive ROM was measured by a goniometer, and height, by a stadiometer. Functional status was assessed by an age-appropriate health assessment questionnaire (HAQ).

RESULTS

(i) A strong correlation was observed between patients' age and Z-score of patients' height (R = 0.78, p < 0.001). (ii) A medium correlation was observed between Z-score of patients' height and passive shoulder flexion and abduction (R = 0.697, p < 0.001 and R = 0.63, p < 0.001, respectively). The progression of restriction was slower in attenuated patients. (iii) Restrictions in shoulder flexion and abduction were already observed before the second year of life. (iv) ROM limitations intensified and became more severe with age. (v) Activities of daily living depended on cognitive impairment of patients with MPS II.

CONCLUSION

Range of motion limitations in patients with MPS II correlate with patients' height, increase with patients' age and are more pronounced in a severe form of MPS II.

Pathogenesis of skeletal and connective tissue involvement in the mucopolysaccharidoses: glycosaminoglycan storage is merely the instigator

The mucopolysaccharidoses (MPSs) are a series of rare genetic disorders in which progressive bone and joint disease represents a key source of morbidity for patients. The recent introduction of enzyme replacement therapy for many of the MPSs has led to a need for increased physician awareness of these rare conditions in order to ensure that treatment is initiated at a time that leads to optimal benefit for patients. In addition, the current experiences of the clinical responsiveness of patient's symptoms to enzyme replacement approaches have also fuelled an interest in the development of alternative and adjunctive therapeutic approaches directed particularly to the rheumatological aspects of disease. Understanding the underlying pathogenesis of the MPSs is a key element for advancements in both of these areas. This review highlights the current knowledge underlying the pathophysiology of disease symptoms in the MPSs and underscores the importance and role of pathogenic cascades.

Natural history of Polish patients with mucopolysaccharidosis type VI

The aim of the study was to describe the natural history, anthropometric features, range of motion (ROM) and molecular characteristics of Polish patients with mucopolysaccharidosis (MPS) VI. Clinical heterogeneity was observed and two major clinical phenotypes of the disease were distinguished, rapidly advancing and relatively attenuated. Two patients developed symptoms early in life presenting with short stature, significant skeletal malformations and other clinical abnormalities. In two other patients, height was only slightly decreased and MPS features developed later in the course of the disease. All patients had similar characteristics at the time of birth but showed significant differences in body proportions when compared with the healthy population. Differences between healthy and affected children increased with age and were reflected in phenotypes. Analysis of ROM showed impairments at multiple joints, although to a various degree in different patients. Restriction in upper extremity ROM was observed since the second year of life, while restriction in lower extremity ROM developed later and influenced stereotype of walking. These limitations intensified with the patients’ age, which made self-care more difficult or impossible. The molecular analysis revealed that the milder phenotype may be associated with the R152W mutation, which suggests a specific genotype-phenotype correlation.

Sphingolipids: the nexus between Gaucher disease and insulin resistance

Sphingolipids constitute a diverse array of lipids in which fatty acids are linked through amide bonds to a long-chain base, and, structurally, they form the building blocks of eukaryotic membranes. Ceramide is the simplest and serves as a precursor for the synthesis of the three main types of complex sphingolipids; sphingomyelins, glycosphingolipids and gangliosides. Sphingolipids are no longer considered mere structural spectators, but bioactive molecules with functions beyond providing a mechanically stable and chemically resistant barrier to a diverse array of cellular processes. Although sphingolipids form a somewhat minor component of the total cellular lipid pool, their accumulation in certain cells forms the basis of many diseases. Human diseases caused by alterations in the metabolism of sphingolipids are conventionally inborn errors of degradation, the most common being Gaucher disease, in which the catabolism of glucosylceramide is defective and accumulates. Insulin resistance has been reported in patients with Gaucher disease and this article presents evidence that this is due to perturbations in the metabolism of sphingolipids. Ceramide and the more complex sphingolipids, the gangliosides, are constituents of specialised membrane microdomains termed lipid rafts. Lipid rafts play a role in facilitating and regulating lipid and protein interactions in cells, and their unique lipid composition enables them to carry out this role. The lipid composition of rafts is altered in cell models of Gaucher disease which may be responsible for impaired lipid and protein sorting observed in this disorder, and consequently pathology. Lipid rafts are also necessary for correct insulin signalling, and a perturbed lipid raft composition may impair insulin signalling. Unravelling common nodes of interaction between insulin resistance and Gaucher disease may lead to a better understanding of the biochemical mechanisms behind pathology.

Low bone mass in Pompe disease: muscular strength as a predictor of bone mineral density

Pompe disease is an inherited metabolic myopathy caused by deficiency of acid alpha-glucosidase. The introduction of enzyme replacement therapy as treatment for the disease may change prospects for patients and may require that more attention be paid to co-morbidities such as osteoporosis.

METHODS

Bone mineral status was assessed in children and adults with Pompe disease and compared with reference values by means of dual energy X-ray absorptiometry (DXA) technology (GE Lunar DPX, GE Health Care). Bone mineral density (BMD) of the total body and the lumbar spine (L2-L4) was measured in adults and children; BMD of the femoral neck was measured in adults only. Exclusion criteria were: age<4 years, severe contractures, and inability to transfer the patient.

RESULTS

46 patients were enrolled in the study; 36 adults and 10 children. The BMD was significantly lower in Pompe patients than in healthy individuals. Sixty-seven percent of patients had a BMD Z-score below -1, 26% were classified as osteoporosis/low bone mass for chronological age (T-score<-2.5 in adults or Z-score<-2 in children), 66% had a BMD Z-score below -1 of the femoral neck, and 34% had a BMD Z-score below -1 for the lumbar spine. Osteoporosis/low bone mass for chronological age was more frequent in patients who were wheelchair-bound, but was also observed in ambulant patients. We found a significant correlation between proximal muscle strength and total body BMD. Of the 10 children, 8 (all four patients with the classic infantile form) had a low BMD.

CONCLUSION

Low BMD is a frequent finding in patients with Pompe disease and may be causally related to decreased proximal muscle strength. BMD should be monitored at regular intervals. Children deserve specific attention.

Efficacy of recombinant human alpha-L-iduronidase (laronidase) on restricted range of motion of upper extremities in mucopolysaccharidosis type I patients

The aims of the study were to assess the effectiveness of enzyme replacement therapy (ERT) with laronidase on the range of motion (ROM) of upper extremities and influence on activities of daily living (ADLs) of patients with mucopolysaccharidosis type I (MPS I). The ROM of 17 patients with MPS I was followed from the first year of life until the introduction of ERT and after 52-208 weeks of treatment. In all patients (group 1, n = 10), passive ROM was assessed. In patients with Hurler/Scheie or Scheie phenotype (group 2, n = 7) both passive and active ROM, as well as daily life activities, were evaluated. Passive and active ROM was measured by a goniometer, while a health assessment questionnaire was used to assess activities of daily living. The data since the first months of life until the beginning of treatment were obtained by retrospective review of patients' charts. Restriction in ROM of the upper extremities of patients with MPS I was observed from the first year of life. These limitations intensified and became more severe with the patients' age, making patients' self-care more difficult or even impossible. Introduction of ERT led to slower progression of symptoms, especially in the passive range of motion in all patients. Additionally, patients with normal mental development, or only slightly delayed (group 2), who underwent active physical rehabilitation (including mobilisation of nerve system, passive techniques for joint mobility, active gymnastics for muscle power, as well as massage and the training of families for therapy at home) showed improvement in active movement followed by enhanced self-care.

Mucopolysaccharidosis type-IS presenting with onset of carpal tunnel syndrome at adolescence

Mucopolysaccharidosis type I (MPS I) results from deficiency of the lysosomal enzyme alpha-L iduronidase. Three subtypes, based on severity of clinical findings, have been described, of which MPS type IS (also called Scheie syndrome) is the mildest form. A woman (age, 30 years) and her little brother (age, 21 years) presented to our clinic complaining of atrophy of the thenar muscles, numbness in both hands, and contractures in the finger joints. Electrophysiologic examination showed severe carpal tunnel syndrome for both patients. Findings of cardiac and ocular involvements and decreased level of alpha-L iduronidase confirmed the diagnosis of Scheie syndrome. Enzyme replacement therapy was initiated for the further prevention of musculoskeletal and other organ complications. Delayed diagnosis of MPS type-IS and the musculoskeletal findings are discussed in these 2 familial patients.

Anthropometric data of 14 patients with mucopolysaccharidosis I: retrospective analysis and efficacy of recombinant human alpha-L-iduronidase (laronidase)

OBJECTIVES

Our goal was to evaluate growth patterns in terms of body height, weight, head and chest circumference in patients with mucopolysaccharidosis type I (MPS I) without treatment and after enzyme replacement therapy (ERT) with alpha-l-iduronidase (laronidase).

PATIENTS AND METHODS

Anthropometric features of 14 patients with MPS I were followed from birth until the introduction of ERT (group 1-1st year of life, group 2 3rd year of life), after 52-260 weeks of ERT and periodically during treatment. The data since birth until beginning of treatment was obtained by retrospective review of patients' charts. Patients received intravenous laronidase at 100 U/kg (0.58 mg/kg) weekly for 52-260 weeks.

RESULTS

Patients from group 1 (n=7) and group 2 (n=7) had similar characteristics at the time of birth but showed significant difference when compared with healthy population. Growth patterns were associated significantly with the MPS I at birth. After 96-260 weeks of ERT, patients receiving laronidase (group 1) compared with group 2 did not show statistically significant improvement.

CONCLUSIONS

Anthropometric features of patients with MPS I significantly differ from the healthy population. Children with MPS I grew considerably slower, and differences between healthy and affected children increased with age. In studied patients with MPS I, laronidase did not appear to alter the growth patterns.

Characterization of Gaucher disease bone marrow mesenchymal stromal cells reveals an altered inflammatory secretome

Gaucher disease causes pathologic skeletal changes that are not fully explained. Considering the important role of mesenchymal stromal cells (MSCs) in bone structural development and maintenance, we analyzed the cellular biochemistry of MSCs from an adult patient with Gaucher disease type 1 (N370S/L444P mutations). Gaucher MSCs possessed a low glucocerebrosidase activity and consequently had a 3-fold increase in cellular glucosylceramide. Gaucher MSCs have a typical MSC marker phenotype, normal osteocytic and adipocytic differentiation, growth, exogenous lactosylceramide trafficking, cholesterol content, lysosomal morphology, and total lysosomal content, and a marked increase in COX-2, prostaglandin E2, interleukin-8, and CCL2 production compared with normal controls. Transcriptome analysis on normal MSCs treated with the glucocerebrosidase inhibitor conduritol B epoxide showed an up-regulation of an array of inflammatory mediators, including CCL2, and other differentially regulated pathways. These cells also showed a decrease in sphingosine-1-phosphate. In conclusion, Gaucher disease MSCs display an altered secretome that could contribute to skeletal disease and immune disease manifestations in a manner distinct and additive to Gaucher macrophages themselves.

Myopathy in Gaucher disease

Gaucher disease is a recessively inherited lysosomal storage disorder, caused by deficiency of glucocerebrosidase activity. Affected individuals usually present with hepatosplenomegaly, anaemia, thrombocytopenia, and skeletal diseases. A wide range of neurological manifestations have also been recognized in Gaucher patients including acute neurological deterioration in infancy, mental retardation, ocular motor apraxia, seizure, and parkinsonism. Although muscle weakness is not an uncommon finding in patients with Gaucher disease, the aetiology of weakness is not well understood. We prospectively investigated seven Gaucher patients and found that four of them (patients 1-4) had mild to moderate degree of proximal-predominant symmetrical muscle weakness in four limbs. By history, three patients (patients 1-3) developed insidious onset of nonprogressive muscle weakness in four limbs with easy muscle fatigue from adolescence. A needle electromyographic study detected some small, brief polyphasic waves in these four patients. Muscle biopsy in one patient (patient 1) showed a few atrophic type II muscle fibres without infiltration of Gaucher cells. Three patients (patients 1-3) continuously received enzyme replacement therapy with imiglucerase and their muscle strength seemed improved after two years. We concluded that Gaucher disease may be associated with myopathy.

Lysosomal storage diseases as differential diagnoses to rheumatic disorders

PURPOSE OF REVIEW

To describe the latest findings on lysosomal storage diseases relevant to rheumatologists, including literature findings on the natural history, clinical features, diagnostic measures, and treatment.

RECENT FINDINGS

Many relevant investigations are based on large lysosomal storage disease registries. The steadily growing number of patients has resulted in an increasingly accurate description of the natural history of the diseases and permits the investigation of special problems, including monitoring the long-term safety and effectiveness of treatment. For Gaucher disease, several semi-quantitative and quantitative techniques have been proposed to measure bone marrow involvement and thus to monitor the effectiveness of enzyme replacement therapy. Given the unspecific symptoms of Fabry disease during childhood, several studies highlight the importance of a thoroughly recorded family history in making the correct diagnosis. Two investigations describe the specific features of Fabry disease in women.

SUMMARY

Given the rheumatologist's awareness of lysosomal storage diseases, the latest findings on the natural history of lysosomal storage diseases allow earlier diagnosis and treatment. The results of enzyme replacement therapy are promising, but large studies with control groups carried out over a longer period of time are lacking.

Mechanism of glycosaminoglycan-mediated bone and joint disease: implications for the mucopolysaccharidoses and other connective tissue diseases

We have previously shown that glycosaminoglycan (GAG) storage in animal models of the mucopolysaccharidoses (MPS) leads to inflammation and apoptosis within cartilage. We have now extended these findings to synovial tissue and further explored the mechanism underlying GAG-mediated disease. Analysis of MPS rats, cats, and/or dogs revealed that MPS synovial fibroblasts and fluid displayed elevated expression of numerous inflammatory molecules, including several proteins important for lipopolysaccharide signaling (eg, Toll-like receptor 4 and lipoprotein-binding protein). The expression of tumor necrosis factor, in particular, was elevated up to 50-fold, leading to up-regulation of the osteoclast survival factor, receptor activator of nuclear factor-kappaB ligand, and the appearance of multinucleated osteoclast-like cells in the MPS bone marrow. Treatment of normal synovial fibroblasts with GAGs also led to production of the prosurvival lipid sphingosine-1-phosphate, resulting in enhanced cell proliferation, consistent with the hyperplastic synovial tissue observed in MPS patients. In contrast, GAG treatment of normal chondrocytes led to production of the proapoptotic lipid ceramide, confirming the enhanced cell death we had previously observed in MPS cartilage. These findings have important implications for the pathogenesis and treatment of MPS and have further defined the mechanism of GAG-stimulated disease.

Atteintes ostéoarticulaires de la maladie de Gaucher chez l'adulte: de la physiopathologie au traitement

Gaucher disease frequently has severe osteoarticular manifestations that may be disabling. Ischemic phenomena cause the most serious complications and lead to irreversible lesions. Aseptic osteonecrosis of the hip is the most disabling complication; it causes intense early bone pain and often joint collapse and secondary osteoarthritis in young adults. Localized or systemic bone fragility explains osteopenia, osteoporosis, and fractures (vertebral collapse with irreversible kyphosis causing chronic morbidity). Although no double-blind randomized studies have assessed the bone effects of enzyme replacement therapy, it has been shown effective in reducing bone pain in about half of all treatment-naive patients within 1 to 2 years and in improving bone mineral density after 3 years. In open-label trials, substrate reduction therapy (miglustat) reduced both bone pain and bone marrow infiltration. Specific treatment for bone fragility, with bisphosphonates for example, should be considered after rigorous individualized evaluation and assessment of other risk factors.

Fractures in children with Pompe disease: a potential long-term complication

BACKGROUND

Pompe disease (glycogen storage disease type II or acid maltase deficiency) is an autosomal recessive disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). Classic infantile-onset disease, characterized by cardiomegaly and profound weakness, leads to death in the first year of life from cardiorespiratory failure. Reversal of cardiomyopathy and improved motor function have been shown in clinical trials of rhGAA enzyme replacement therapy (ERT) with alglucosidase alfa (Myozyme), recently approved for clinical use. Increased survival potentially unmasks long-term complications of this previously lethal disease, including risk of skeletal fracture, recently identified at our institution and not previously reported in children with Pompe disease.

OBJECTIVE

To report the risk of fracture in children with Pompe disease with increased survival with ERT.

MATERIALS AND METHODS

We present four cases of fracture in patients with classic infantile Pompe disease treated with ERT at our institution, and review a study database for additional reports of fracture in this population.

RESULTS

We review 19 fractures in 14 children with Pompe disease on ERT.

CONCLUSION

Radiologists should be familiar with and vigilant for the association of fractures and increased survival on ERT in children with Pompe disease. We discuss potential mechanisms, implications for radiographic surveillance, potential intervention, and needs for further research.

Enzymatic biodegradable micro-reactors for therapeutic applications

Poly(epsilon-caprolactone) is a well known biocompatible polymer, widely used as drug immobilization systems. In this work poly(epsilon-caprolactone) microparticles with average size between 5 and 25 microm have been prepared by O/W emulsion evaporation method. Inside the microparticles, we have encapsulated Glucose Oxidase with the aim of preparing micro-reactors for enzymatic therapy. These microparticles were structurally characterized and its enzymatic activity analyzed in order to improve the enzyme entrapment. Thus, at the optimum synthesis conditions the enzyme entrapped in the microparticles showed an enzymatic activity of (29.9 +/- 2.1)% comparing with the same amount of free enzyme. Moreover the microparticles maintained a (70.4 +/- 3.2)% of their initial enzymatic activity after placing them in buffer solution for two weeks.

Current and emerging therapies for the lysosomal storage disorders

Targeted treatments for the lysosomal storage disorders (LSDs), in the form of enzyme replacement and/or substrate depletion, have been shown to be relatively safe and effective in reversing core disease features in selected clinical subtypes (including Gaucher disease types I and III, Fabry disease and the Hurler-Scheie syndrome). These approaches have expanded the therapeutic options available to patients with rare genetic disorders, beyond palliative measures (such as liver or kidney transplantation for end-organ failure) and cellular replacement through bone marrow transplantation. Present efforts are focused on the development of novel strategies, including chaperone-mediated enzyme enhancement and genetically engineered stem cell therapy. In the coming decades, a broadening therapeutic horizon for patients with inborn errors of metabolism is anticipated, and the growing experience in the management of patients with LSDs will serve as an instructive model. Among the many challenges will be determination of the extent to which these therapies have modified the course of disease beyond merely extending the age of survival, but also enabling a meaningful patient quality of life, and the minimisation of current resource use. The projected lifetime acquisition costs of newly introduced therapeutic options also raises several issues, related to equitable access and the large opportunity costs for other therapeutic areas, that will need to be addressed by healthcare policy makers and third-party payers.

Total hip replacement in identical twins with Scheie Mucopolysaccharidosis

Investigation performed at the Hospital for Special Surgery, New York, USA Scheie Syndrome is an autosomal recessive metabolic storage disease with distinct skeletal findings known as "dysostosis multiplex". This paper reports on identical twins with Scheie Syndrome who required total hip arthroplasty for early osteoarthritis of the hip. The surgical approach and exposure was particularly demanding due to the stiffness imposed by the soft tissues arising from infiltration of glycosaminoglycans. The small femoral head and acetabulum limited the diameter of the acetabular component and subsequently the prosthetic head diameter that could be safely utilized without compromising the thickness of the polyethylene liner. Twenty-two millimeter heads with a standard polyethylene insert were therefore utilized in the two arthroplasties performed in 1998 in the first twin, and a 28 mm head with a highly cross linked polyethylene liner, in the arthroplasty performed on the second twin in 2003. This is a relevant issue considering that these patients required an arthroplasty at a young age. Hip arthroplasty relieved pain, improved ambulation and provided a better range of motion in our two patients. There were no peri-operative complications. Long-term survivorship of total hip replacement in this population is not yet known. (Hip International 2005; 15: 55-8).