Quantification of bone involvement in Gaucher disease: MR imaging bone marrow burden score as an alternative to Dixon quantitative chemical shift MR imaging--initial experience

Deep learning-based quantification of osteonecrosis using magnetic resonance images in Gaucher disease

Gaucher disease is one of the most common lysosomal storage disorders. Osteonecrosis is a principal clinical manifestation of Gaucher disease and often leads to joint collapse and fractures. T1-weighted (T1w) modality in MRI is widely used to monitor bone involvement in Gaucher disease and to diagnose osteonecrosis. However, objective and quantitative methods for characterizing osteonecrosis are still limited. In this work, we present a deep learning-based quantification approach for the segmentation of osteonecrosis and the extraction of characteristic parameters. We first constructed two independent U-net models to segment the osteonecrosis and bone marrow unaffected by osteonecrosis (UBM) in spine and femur respectively, based on T1w images from patients in the UK national Gaucherite study database. We manually delineated parcellation maps including osteonecrosis and UBM from 364 T1w images (176 for spine, 188 for femur) as the training datasets, and the trained models were subsequently applied to all the 917 T1w images in the database. To quantify the segmentation, we calculated morphological parameters including the volume of osteonecrosis, the volume of UBM, and the fraction of total marrow occupied by osteonecrosis. Then, we examined the correlation between calculated features and the bone marrow burden score for marrow infiltration of the corresponding image, and no strong correlation was found. In addition, we analyzed the influence of splenectomy and the interval between the age at first symptom and the age of onset of treatment on the quantitative measurements of osteonecrosis. The results are consistent with previous studies, showing that prior splenectomy is closely associated with the fractional volume of osteonecrosis, and there is a positive relationship between the duration of untreated disease and the quantifications of osteonecrosis. We propose this technique as an efficient and reliable tool for assessing the extent of osteonecrosis in MR images of patients and improving prediction of clinically important adverse events.

A Real-World Investigation of MRI Changes in Bone in Patients with Type 1 Gaucher Disease Treated with Velaglucerase Alfa: The EIROS Study

Background/Objectives: Gaucher disease type 1 (GD1) is characterized by hepatosplenomegaly, thrombocytopenia, and disabling bone manifestations requiring regular MRI monitoring. The EIROS study assessed the real-world impact of velaglucerase alfa on GD1 bone disease, using MRI data collected in French clinical practice. Methods: MRIs collected retrospectively from treatment initiation and prospectively during follow-up (12-months) were analyzed centrally by a blinded expert radiologist to evaluate bone infiltration using the Bone Marrow Burden (BMB) score and a qualitative method (stable, improved or worsened for the spine and femur). Abdominal MRIs were also centrally analyzed to assess hepatosplenomegaly. Bone manifestations, hepatosplenomegaly, and hematologic parameters were analyzed from medical records. Results: MRI data were available for 20 patients: 6 treatment-naive patients and 14 patients who switched to velaglucerase alfa from another GD treatment. Interpretable MRIs for BMB scoring were available for seven patients for the spine and one patient for the femur. Qualitative assessments (n = 18) revealed stability in spine and femur infiltration in 100.0% and 84.6% of treatment-switched patients (n = 13), respectively, and improvements in 80.0% and 60.0% of treatment-naive patients (n = 5), respectively; no worsening of bone infiltration was observed. Liver, spleen, and hematologic parameters improved in treatment-naive patients and remained stable in treatment-switched patients. Conclusions: The qualitative real-world data support findings from clinical trials suggesting the long-term effectiveness of velaglucerase alfa on GD1 bone manifestations. When MRI assessment by radiologists with experience of GD is not possible, a simplified qualitative assessment may be sufficient in clinical practice for monitoring bone disease progression and treatment response.

Fat fraction quantification of bone marrow in the lumbar spine using the LiverLab assessment tool in healthy adult volunteers and patients with Gaucher disease

BACKGROUND

Magnetic Resonance Imaging is used for evaluation of bone in Gaucher disease (GD), but a widely available quantitative scoring method remains elusive.

AIMS

The study purpose was to assess the reproducibility of the LiverLab tool for assessing bone marrow fat fraction (FF) and determine whether it could differentiate GD patients from healthy subjects.

METHODS

Ten healthy volunteers and 18 GD patients were prospectively recruited. FF was calculated at L3, L4 and L5. GD patient bone marrow burden (BMB) score assessed by one observer. Inter and intra-rater agreement assessed with Bland-Altman data plots. Differences in FF between healthy volunteers versus GD patients and between subjects treated versus not treated assessed using two-sample t-tests. In GD patients, the relationship between FF, BMB and glucosylsphingosine was determined using the Pearson's correlation coefficient.

RESULTS

Healthy volunteer mean FF was 0.36, standard deviation (SD) 0.10 (range 0.20-0.57). Intra and inter-rater SD were both 0.02. GD patient mean FF was 0.40, SD 0.13 (range 0.09-0.57). No statistical difference was shown between healthy volunteers and GD patients (P = 0.447) or between GD patients whether on enzyme replacement therapy or not (P = 0.090). No significant correlation between mean FF and total BMB (r = -0.525, P = 0.253) or between FF and glucosylsphingosine levels (r = 0.287, P = 0.248).

CONCLUSION

Excellent reproducibility of LiverLab FF measurements across studies and observers is comparable to Dixon quantitative chemical shift imaging (QCSI). Lack of statistical difference between GD patients and controls may be explained by limited patient numbers, active treatment or mild disease severity in untreated patients.

Advantages of digital technology in the assessment of bone marrow involvement in Gaucher's disease

Gaucher disease (GD) is a genetic lysosomal disorder characterized by high bone marrow (BM) involvement and skeletal complications. The pathophysiology of these complications is not fully elucidated. Magnetic resonance imaging (MRI) is the gold standard to evaluate BM. This study aimed to apply machine-learning techniques in a cohort of Spanish GD patients by a structured bone marrow MRI reporting model at diagnosis and follow-up to predict the evolution of the bone disease. In total, 441 digitalized MRI studies from 131 patients (M: 69, F:62) were reevaluated by a blinded expert radiologist who applied a structured report template. The studies were classified into categories carried out at different stages as follows: A: baseline; B: between 1 and 4 y of follow-up; C: between 5 and 9 y; and D: after 10 years of follow-up. Demographics, genetics, biomarkers, clinical data, and cumulative years of therapy were included in the model. At the baseline study, the mean age was 37.3 years (1-80), and the median Spanish MRI score (S-MRI) was 8.40 (male patients: 9.10 vs. female patients: 7.71) (p < 0.001). BM clearance was faster and deeper in women during follow-up. Genotypes that do not include the c.1226A>G variant have a higher degree of infiltration and complications (p = 0.017). A random forest machine-learning model identified that BM infiltration degree, age at the start of therapy, and femur infiltration were the most important factors to predict the risk and severity of the bone disease. In conclusion, a structured bone marrow MRI reporting in GD is useful to standardize the collected data and facilitate clinical management and academic collaboration. Artificial intelligence methods applied to these studies can help to predict bone disease complications.

Venglustat combined with imiglucerase for neurological disease in adults with Gaucher disease type 3: the LEAP trial

Gaucher disease type 3 is a chronic neuronopathic disorder with wide-ranging effects, including hepatosplenomegaly, anaemia, thrombocytopenia, skeletal disease and diverse neurological manifestations. Biallelic mutations in GBA1 reduce lysosomal acid β-glucosidase activity, and its substrates, glucosylceramide and glucosylsphingosine, accumulate. Enzyme replacement therapy and substrate reduction therapy ameliorate systemic features of Gaucher disease, but no therapies are approved for neurological manifestations. Venglustat is an investigational, brain-penetrant, glucosylceramide synthase inhibitor with potential to improve the disease by rebalancing influx of glucosylceramide with impaired lysosomal recycling. The Phase 2, open-label LEAP trial (NCT02843035) evaluated orally administered venglustat 15 mg once-daily in combination with maintenance dose of imiglucerase enzyme replacement therapy during 1 year of treatment in 11 adults with Gaucher disease type 3. Primary endpoints were venglustat safety and tolerability and change in concentration of glucosylceramide and glucosylsphingosine in CSF from baseline to Weeks 26 and 52. Secondary endpoints included change in plasma concentrations of glucosylceramide and glucosylsphingosine, venglustat pharmacokinetics in plasma and CSF, neurologic function, infiltrative lung disease and systemic disease parameters. Exploratory endpoints included changes in brain volume assessed with volumetric MRI using tensor-based morphometry, and resting functional MRI analysis of regional brain activity and connectivity between resting state networks. Mean (SD) plasma venglustat AUC0-24 on Day 1 was 851 (282) ng•h/ml; Cmax of 58.1 (26.4) ng/ml was achieved at a median tmax 2.00 h. After once-daily venglustat, plasma concentrations (4 h post-dose) were higher compared with Day 1, indicating ∼2-fold accumulation. One participant (Patient 9) had low-to-undetectable venglustat exposure at Weeks 26 and 52. Based on mean plasma and CSF venglustat concentrations (excluding Patient 9), steady state appeared to be reached on or before Week 4. Mean (SD) venglustat concentration at Week 52 was 114 (65.8) ng/ml in plasma and 6.14 (3.44) ng/ml in CSF. After 1 year of treatment, median (inter-quartile range) glucosylceramide decreased 78% (72, 84) in plasma and 81% (77, 83) in CSF; median (inter-quartile range) glucosylsphingosine decreased 56% (41, 60) in plasma and 70% (46, 76) in CSF. Ataxia improved slightly in nine patients: mean (SD, range) total modified Scale for Assessment and Rating of Ataxia score decreased from 2.68 [1.54 (0.0 to 5.5)] at baseline to 1.55 [1.88 (0.0 to 5.0)] at Week 52 [mean change: -1.14 (95% CI: -2.06 to -0.21)]. Whole brain volume increased slightly in patients with venglustat exposure and biomarker reduction in CSF (306.7 ± 4253.3 mm3) and declined markedly in Patient 9 (-13894.8 mm3). Functional MRI indicated stronger connectivity at Weeks 26 and 52 relative to baseline between a broadly distributed set of brain regions in patients with venglustat exposure and biomarker reduction but not Patient 9, although neurocognition, assessed by Vineland II, deteriorated in all domains over time, which illustrates disease progression despite the intervention. There were no deaths, serious adverse events or discontinuations. In adults with Gaucher disease type 3 receiving imiglucerase, addition of once-daily venglustat showed acceptable safety and tolerability and preliminary evidence of clinical stability with intriguing but intrinsically inconsistent signals in selected biomarkers, which need to be validated and confirmed in future research.

Long-term effects of eliglustat on skeletal manifestations in clinical trials of patients with Gaucher disease type 1

PURPOSE

Most patients with Gaucher disease have progressive and often disabling skeletal manifestations. We examined the long-term effect of eliglustat treatment on bone outcomes in clinical trials in adults with Gaucher disease type 1.

METHODS

Data from 4 completed phase 2 and 3 trials were evaluated in treatment-naïve patients or patients switching to eliglustat from enzyme replacement therapy (ERT).

RESULTS

Overall, 319 of 393 (81%) eliglustat-treated patients remained in their trials until completion or commercial eliglustat became available. Mean eliglustat treatment duration ranged from 3.3 to 6.5 years. In treatment-naïve patients and ERT-switch patients, frequency and severity of bone pain decreased during eliglustat treatment. Mean lumbar spine T-scores shifted from abnormal to normal in treatment-naïve patients and remained in the healthy reference range or improved modestly in ERT-switch patients. Mean total bone marrow burden score shifted from marked-to-severe to moderate in treatment-naïve patients and remained moderate in ERT-switch patients. MIP-1β (marker of active bone disease) was elevated at baseline and decreased to the healthy reference range in treatment-naïve patients and remained in the healthy reference range among ERT-switch patients.

CONCLUSION

These findings confirm the long-term efficacy of eliglustat on skeletal complications of Gaucher disease in treatment-naïve and ERT-switch patients.

Quantitative assessment of the exposure-efficacy relationship of glucocerebrosidase using Markovian elements in Gaucher patients treated with enzyme replacement therapy

AIMS

The aims of this study are (i) to develop a population pharmacokinetic model of enzyme activity in Gaucher-type 1 (GD1) patients after intravenous administration of enzyme replacement therapy (ERT) and, (ii) to establish an exposure-efficacy relationship for bone marrow infiltration to propose dose adjustments according to patient covariate values.

MATERIALS AND METHODS

A prospective follow-up, semi-experimental multi-centre study was conducted in four hospitals to evaluate the pharmacokinetics, efficacy and safety of ERT in GD1 patients. 25 individuals with 266 glucocerebrosidase (GCase) observations in plasma and leukocytes and 14 individuals with 68 Spanish Magnetic Resonance Imaging (S-MRI) observations were enrolled.

RESULTS

A two concatenated compartments with zero-order endogenous production and first-order distribution (CL₁ =3.85 x10^-1 L/d) and elimination (CL₂ = 1.25 L/d) allowed to describe GCase observations in plasma and leucocytes, respectively. An exponential time-dependency (k_T =6.14 x10^-1 d^-1 ) effect on CL₁ was incorporated. The final exposure-efficacy model was a longitudinal logistic regression model with a first-order Markov element. An Emax function (EC₅₀ =15.73 U/L and Emax=2.33) linked steady-state concentrations of GCase in leucocytes to the probability of transition across the different S-MRI stages.

CONCLUSION

A population pharmacokinetic model successfully characterized the leukocyte activity-time profiles of GCase following intravenous administration of ERT in GD1 patients together with an exposure-efficacy relationship in bone marrow using markovian elements. The information obtained from this study could be of high clinical relevance in individualization of ERT in GD1 patients, as this could lead to anticipate decision-making regarding clinical response in bone and optimal dosing strategy. NONSTANDARD ABBREVIATIONS: -2LL: -2xlog(likelihood); ERT: enzyme replacement therapy; GCase: glucocerebrosidase activity; GD1: Gaucher disease type 1; GOF: goodness-of-fit plots; IIV: inter-individual variability; NLME: non-linear mixed effects modelling; OFV: objective function value; pc-VPC: prediction-corrected visual predictive check; PK: pharmacokinetic; RSE: relative standard error; RUV: residual unexplained variability, S-MRI: Spanish Magnetic Resonance Imaging, TDM: therapeutic drug monitoring.

Bone marrow burden score is not useful as a follow-up parameter in stable patients with type 1 Gaucher disease after 5 years of treatment

INTRODUCTION

Gaucher disease (GD) is one of the most prevalent lysosomal disorders, with an estimated incidence of 1 in 40,000 live births worldwide. Skeletal involvement is one of the main features of GD, causing morbidity and impacting long-term quality of life in patients with type 1 GD.

OBJECTIVES

To characterize bone marrow infiltration in patients with type 1 GD followed at the Gaucher Disease Referral Center of Porto Alegre, Brazil, and to assess whether the Bone Marrow Burden score (BMB) correlates with clinical or laboratory parameters. We also evaluated whether the BMB score is a suitable parameter for long-term follow-up of patients with type 1 GD.

METHODS

All included patients underwent magnetic resonance imaging for BMB score calculation at baseline, 1 year, and every other year thereafter or as clinically indicated from 2012 to 2018.

RESULTS

The BMB score tended to decrease during the first 5 years of treatment, at a rate of -1.08 points per year; after the 5-year mark, BMB tended to remain stable.

CONCLUSIONS

The BMB score is useful for response monitoring in the first five years of treatment. We recommend that, after 5 years of treatment, MRI for BMB evaluation should only be performed in non-adherent patients or in those who develop symptoms of acute skeletal disease.

Qualitative and quantitative magnetic resonance imaging evaluation of bone tissue vaso-occlusive events in patients with sickle cell disease

OBJECTIVE

To evaluate the association between bone changes due to vaso-occlusive events in sickle cell disease (SCD) revealed by conventional MRI sequences and the fat fraction obtained using a 6-point DIXON technique (FFdix), in an attempt to use quantitative data as a biomarker for bone complications.

METHODS

Cross-sectional study, with 48 SCD patients, 26-homozygous (HbSS), and 22-compound heterozygous (HbSC). Forty-eight healthy individuals paired by age, weight, and sex with SCD patients. All participants underwent lumbar spine and pelvis MRI. Conventional sequences: bone complications related to vaso-occlusive events-femoral head avascular necrosis, bone infarctions, "H"-shaped vertebrae, bone marrow necrosis. Six-point DIXON technique: quantitative evaluation of the bone marrow at pre-established sites (lumbar vertebrae, sacrum, iliacs, femoral heads, greater femoral trochanters, femoral necks). Pearson's correlation, ROC curve, and binary logistic regression analysis were performed.

RESULTS

The most frequent findings in the SCD group included femoral head avascular necrosis (75%), bone infarctions (58.3%), "H"-shaped vertebrae (58.3%), and typical imaging findings of bone marrow necrosis (8.3%). Cortical bone thickness in the proximal femoral diaphysis in patients with SCD was moderately negatively correlated with FFdix in lumbar vertebrae, iliacs, femoral necks, and first sacral vertebrae. The ROC curves and odds ratios demonstrated excellent performance of FFdix in all the evaluated anatomical sites and identified patients having bone complications.

CONCLUSIONS

FFdix could serve as a potential biomarker in SCD because of its association with bone complications secondary to vaso-occlusive events in patients with SCD, especially in femoral heads, femoral necks, and iliacs.

Sclerotic bone lesions caused by non-infectious and non-neoplastic diseases: a review of the imaging and clinicopathologic findings

Bone sclerosis is a focal, multifocal, or diffuse increase in the density of the bone matrix on radiographs or computed tomography (CT) imaging. This radiological finding can be caused by a broad spectrum of diseases, such as congenital and developmental disorders, depositional disorders, and metabolic diseases. The differential diagnosis can be effectively narrowed by an astute radiologist in the light of the clinical picture and typical findings on imaging. Some of these lesions are rare and have been described as case reports and series in the literature. This article aims to collate the clinical-radiologic findings of non-infectious and non-neoplastic causes of bone sclerosis with relevant imaging illustrations.

Skeletal involvement in Gaucher disease: extent of bone disease, splenic volume, and quality of life

Objective

To investigate the correlations among the extent of bone involvement, splenic volume, and quality of life in patients with Gaucher disease.

Materials and Methods

This was a descriptive, prospective cross-sectional study of 18 patients with Gaucher disease who underwent 3-T magnetic resonance imaging of both femurs and the lumbar spine. Semiquantitative analyses were performed on the basis of the bone marrow burden (BMB) score. We looked for linear relationships among the variables splenic volume, quality of life score, and BMB score.

Results

We identified a linear relationship between the BMB scores and splenic volume. The quality of life score showed no statistically significant relationship with splenic volume or the BMB score.

Conclusion

The linear relationship between the BMB score and the splenic volume indicates that the extent of bone disease is greater in individuals with splenomegaly. No correlation was found between the BMB and quality of life scores, illustrating the insidious and silent progression of Gaucher disease.

Applications of the Dixon technique in the evaluation of the musculoskeletal system

The acquisition of images with suppression of the fat signal is very useful in clinical practice and can be achieved in a variety of sequences. The Dixon technique, unlike other fat suppression techniques, allows the signal of fat to be suppressed in the postprocessing rather than during acquisition, as well as allowing the visualization of maps showing the distribution of water and fat. This review of the Dixon technique aims to illustrate the basic physical principles, to compare the technique with other magnetic resonance imaging sequences for fat suppression or fat quantification, and to describe its applications in the study of diseases of the musculoskeletal system. Many variants of the Dixon technique have been developed, providing more consistent separation of the fat and water signals, as well as allowing correction for many confounding factors. It allows homogeneous fat suppression, being able to be acquired in combination with several other sequences, as well as with different weightings. The technique also makes it possible to obtain images with and without fat suppression from a single acquisition. In addition, the Dixon technique can be used as a quantitative method, allowing the proportion of tissue fat to be determined, and, in more updated versions, can quantify tissue iron.

Mapping the medullar adiposity of lumbar spine in MRI: A feasibility study

PURPOSE

The bone medullar adiposity is a marker of bone quality to the point that there is a need to investigate the factors which influence or not the density and distribution of this fat in the spine, especially at the lumbar level. The purpose was to test the feasibility of a Dixon three-point technique and investigate the vertebral marrow fat distribution.

MATERIAL AND METHODS

A sagittal sequence Iterative Decomposition of Water and Fat with Echo Asymmetry and Least-squares Estimation (IDEAL) IQ was performed on the lumbar spine of 46 subjects who were not suffering from any bone disease (21 women and 25 men, aged 18-77 years). Medulla adiposity was determined directly from the measurement of the fat fraction in each vertebral body (T12 to S1) obtained on the fat cartography automatically generated by the IDEAL sequence.

RESULTS

Average vertebral fat fraction was 36.48% (SD 12.82), with a tendency to increase with age and to higher values among men. We observed a craniocaudal gradient of the fat fraction (β = 1.37; p < 0,001; SD 0.11) increasing with age in the lumbar spine from T12 to L5. Through multivariate analysis, this gradient was adjusted for sex, weight and height of the subjects.

CONCLUSION

This feasibility study shows the existence of a physiological craniocaudal gradient of vertebral medullar adiposity from T12 to L5. This gradient increases with age but it is independent of sex or BMI. The IDEAL sequence allows quick and reproducible measurement of the spine vertebral medullar adiposity.

What's New for Clinical Whole-body MRI (WB-MRI) in the 21st Century

Whole-body MRI (WB-MRI) has evolved since its first introduction in the 1970s as an imaging technique to detect and survey disease across multiple sites and organ systems in the body. The development of diffusion-weighted MRI (DWI) has added a new dimension to the implementation of WB-MRI on modern scanners, offering excellent lesion-to-background contrast, while achieving acceptable spatial resolution to detect focal lesions 5 to 10 mm in size. MRI hardware and software advances have reduced acquisition times, with studies taking 40-50 min to complete.The rising awareness of medical radiation exposure coupled with the advantages of MRI has resulted in increased utilization of WB-MRI in oncology, paediatrics, rheumatological and musculoskeletal conditions and more recently in population screening. There is recognition that WB-MRI can be used to track disease evolution and monitor response heterogeneity in patients with cancer. There are also opportunities to combine WB-MRI with molecular imaging on PET-MRI systems to harness the strengths of hybrid imaging. The advent of artificial intelligence and machine learning will shorten image acquisition times and image analyses, making the technique more competitive against other imaging technologies.

Acoustic radiation force impulse point shear wave elastography of the liver and spleen in patients with Gaucher disease type 1: Correlations with clinical data and markers of disease severity

PURPOSE

To evaluate the feasibility of acoustic radiation force impulse point shear wave elastography (ARFI-pSWE) of the liver and spleen in patients with Gaucher disease type 1 (GD1), and to assess correlations between organ stiffness and clinico-radiologic data, particularly the GD1 Severity Scoring System (GD-DS3).

MATERIALS AND METHODS

We retrospectively evaluated the results of ARFI-pSWE as measures of liver and spleen stiffness in 57 patients with GD1. The feasibility of the method was assessed. Correlations between elastography data and clinical data related to the metabolic syndrome, laboratory tests, and GD1-related clinico-radiologic data (bone marrow burden score, GD-DS3) were assessed.

RESULTS

ARFI-pSWE provided reliable results (i.e. standard deviation <30% of the mean value between the measurements) in 50/57 patients. Significant liver fibrosis was present in 35/50 patients (70%). Liver stiffness significantly correlated with GD-DS3 score (p = .03), and number of fulfilled criteria of metabolic syndrome (p = .03). Spleen stiffness significantly correlated with age (p = .021), body mass index (p = .002), number of fulfilled criteria of metabolic syndrome (p = .02), and several laboratory parameters (alanine aminotransferase, gamma glutamyltranspeptidase, triglycerides, cholesterol), and nearly significantly with GD-DS3 score (p = .059).

CONCLUSION

ARFI-pSWE is a useful tool for a more detailed assessment of disease severity in patients with GD1, which adds relevant information to the standard clinical scores. Thus, elastography might allow for extended therapy monitoring, especially in patients with significant liver fibrosis. Spleen elastography showed promising results; thus, its role should be further investigated.

Glucocerebrosidase: Functions in and Beyond the Lysosome

Glucocerebrosidase (GCase) is a retaining β-glucosidase with acid pH optimum metabolizing the glycosphingolipid glucosylceramide (GlcCer) to ceramide and glucose. Inherited deficiency of GCase causes the lysosomal storage disorder named Gaucher disease (GD). In GCase-deficient GD patients the accumulation of GlcCer in lysosomes of tissue macrophages is prominent. Based on the above, the key function of GCase as lysosomal hydrolase is well recognized, however it has become apparent that GCase fulfills in the human body at least one other key function beyond lysosomes. Crucially, GCase generates ceramides from GlcCer molecules in the outer part of the skin, a process essential for optimal skin barrier property and survival. This review covers the functions of GCase in and beyond lysosomes and also pays attention to the increasing insight in hitherto unexpected catalytic versatility of the enzyme.

Gaucher disease status and treatment assessment: pilot study using magnetic resonance spectroscopy bone marrow fat fractions in pediatric patients

OBJECTIVE

To assess magnetic resonance spectroscopy (MRS) bone marrow fat fractions' ability to discern between untreated Gaucher disease patients and healthy controls based on assessment of bone marrow infiltration and evaluate response to enzyme replacement therapy (ERT) on serial imaging.

METHODS

This retrospective case-controlled study compared conventional MRI and bone marrow MRS findings in six pediatric and young adult Gaucher disease patients with age- and sex-matched controls, examining femoral neck and lumbar spine bone marrow fat fractions and bone marrow burden (BMB) scores. Separate analysis of six patients with serial imaging on ERT was performed with analysis of fat fractions, BMB scores, organ volumes, and serum chitotriosidase.

RESULTS

Untreated patients had significantly lower femoral and lumbar spine fat fractions than controls (0.32 versus 0.67, p = 0.041 and 0.17 versus 0.34, p = 0.041, respectively). Total BMB scores were significantly higher in patients (8.0 versus 3.5, p = 0.015). In patients on ERT with average follow-up of 3.5 years, femoral neck fat fraction was the sole significant predictor of treatment duration (R square: 0.804, p < 0.001) when adjusted for age. Femoral neck fat fraction also correlated with lumbar spine fat fraction, liver volume and chitotriosidase (p < 0.05). MRS test-retest reliability was excellent (Pearson correlations: 0.96, 0.99; p-values <0.001). BMB inter-rater reliability was good overall with an intra-class correlation coefficient of 0.79 for total score, although lumbar spine score reliability was poor at 0.45.

CONCLUSION

MRS-derived bone marrow fat fractions appear capable of detecting Gaucher disease severity and monitoring treatment-related changes as a predictor of ERT duration in pediatric and young adult patients.

Rare GBA1 genotype associated with severe bone disease in Gaucher disease type 1

Introduction

Gaucher disease (GD) type 1 is a lysosomal disease characterised by hepatosplenomegaly, anemia, thrombocytopenia, bone changes, and bone marrow infiltration. The disease is caused by biallelic pathogenic variants in GBA1 which codes for glucocerebrosidase, an enzyme involved in the catabolic pathway of complex lipids.

Aims

To report on the case of two sisters with GD type 1 who bear a genotype never reported in the literature.

Case report

Patient 1 is a 47-year-old female diagnosed at 42 years of age with chronic lumbar pain, mild splenomegaly, slightly reduced platelets and normal hemoglobin values, severe Bone Marrow Burden (BMB) score, high chitotriosidase activity, and low glucocerebrosidase. Patient 2 is a 50-year-old female, sister of patient 1, who was diagnosed after familial screening. At 45 years of age, she had osteonecrosis of the left femur and a total hysterectomy because of uncontrollable bleeding. At first evaluation, she had bone pain with a high BMB score, mild splenomegaly, normal hemoglobin, normal platelets count, elevated chitotriosidase activity, and low glucocerebrosidase activity. Both patients were found to be compound heterozygotes for the p.Glu388Lys and the p.Ser405Asn variants in GBA1.

Conclusions

This is the first family with GD and this combination of variants which causes a phenotype remarkable for severe bone disease with no or mild hematological manifestations.

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.

A Comprehensive Study of Bone Manifestations in Adult Gaucher Disease Type 1 Patients in Argentina

Gaucher disease (GD) is the most prevalent lysosomal storage disease, and bone involvement is the most disabling condition. The aim of the present study was to evaluate bone involvement in adult patients with GD, using an observational cross-sectional study. Patients were evaluated using X-rays, bone densitometry (BMD), trabecular bone score (TBS), magnetic resonance imaging (MRI), and biochemical bone markers. Thirty-two type 1GD patients were included (mean age: 40 ± 16 years). Patients had received velaglucerase for 2.7 ± 1.4 years; 19/32 had been treated previously with imiglucerase. Ninety-four percent of subjects met therapeutic goals for hematological parameters, and eight were splenectomized (SPX). Nineteen patients had irreversible bone lesions (IL), i.e., avascular necrosis, bone infarction, and/or vertebral fractures. MRI showed marrow infiltration in 71% of patients. Patients with IL had higher bone marrow burden than those without (p = 0.001). All SPX patients had IL, a higher prevalence of bone marrow edema (p = 0.02), and lower TBS (p = 0.03) than non-SPX patients. Only 18.7% of patients had abnormal BMD, with no correlation with fractures (FX). TBS values were < 1350 in 53% of patients and tended to be lower in those with FX (p = 0.06). Patients with P1NP in the lower quartile had lower TBS (p = 0.03) than those with P1NP in the higher quartiles. TBS correlated moderately but not significantly with P1NP (r = 0.32) and BMB (r = - 0.44). A high prevalence of IL was documented. Bone quality was more affected than BMD in fracture patients. Low bone formation, active bone marrow infiltration, and splenectomy might be implicated in IL.

Chitotriosidase on treatment-naïve patients with Gaucher disease: A genotype vs phenotype study

BACKGROUND

Chitotriosidase (ChT) is used as a biomarker for the follow-up of patients with Gaucher disease (GD), once his activity is extremely elevated and declines during ERT. However, some variants in the CHIT1 gene affect ChT activity.

METHODS

To assess association between ChT genotype, and clinical/biochemical features of GD were performed CHIT1 genotyping for: c.1049_1072dup24, p.Gly102Ser, p.Gly354Arg, c.1155_1156 + 2delGAGT, c.1156 + 5_1156 + 8delGTAA, p.Ala442Val/Gly and the rearrangement delE/I-10.

RESULTS

Were evaluated 42 patients with GD from Southern Brazil. Pretreatment ChT activity was available for 32 patients. Allelic frequencies found for dup24, p.Gly102Ser and p.Ala442Gly were 0.14, 0.32 and 0.12, respectively. Only one patient presented reduced ChT activity (dup24 homozygous). Comparison between wild homozygous and heterozygous for dup24 showed that both differ in relation to the ChT activity before (15,230 vs 6936 nmol/h/mL, p < .001), but not after treatment (5212 vs 3045 nmol/h/mL, p = .227).

CONCLUSIONS

Pretreatment ChT activity was not correlated with clinical/biochemical features. There was a reduction of 63% in the ChT activity after 12 months on treatment (p < .001). There is no evidence that higher ChT levels are associated with a more severe symptomatology in untreated GD patients. The pretreatment ChT levels appear to be mainly dependent on the presence/absence of the dup24 allele.

Improvement in bone marrow infiltration in patients with type I Gaucher disease treated with taliglucerase alfa

Preliminary data suggest a positive effect of taliglucerase alfa on the bone marrow infiltration of Gaucher cells. In this investigator-initiated study, we report the impact of taliglucerase alfa on the bone marrow fat fraction (FF) in 26 patients assessed by quantitative chemical shift imaging (QCSI). Of 15 treatment-naïve patients (median age 48 [range 24-68] years), eight had baseline FF ≤ 0.3, six of those with a FF ≤ 0.23 ('bone at risk'). All significantly improved from a median baseline FF of 0.24 (0.15-0.32) to 1st year FF of 0.37 (0.25-0.54) and 2nd year FF of 0.42 (0.27-0.59) (p = 0.01). Among the 11 'switch-over' patients (median age 42 [range 33-69] years; median imiglucerase exposure 8 [range 1-17] years), eight had baseline FF ≤ 0.3, five of those with FF < 0.23. All, but one, significantly improved from a median baseline FF of 0.17 (0.08-0.28) to 1st year FF of 0.3 (0.05-0.34) and 2nd year FF of 0.34 (0.08-0.44) (p = 0.03). Two elderly female patients (age 43 and 58 years, with 17 years imiglucerase exposure) who remained at the same enzyme replacement therapy dose, increased from baseline FF of 0.13 and 0.19 to 0.26 at 1 year. Although the number of observations is small, we hypothesize that switching to taliglucerase may result in an improved bone marrow response. A larger study is needed to assess the early benefit of taliglucerase alfa in adult patients with type 1 Gaucher disease on the bone marrow compartment.

How we manage Gaucher Disease in the era of choices

Treatment of Gaucher Disease (GD) is now beset with the abundance of therapeutic options for an individual patient, making the choice of therapy complex for both expert and non-expert clinicians. The pathogenesis of all disease manifestations is a gene mutation-driven deficiency of glucocerebrosidase, but the clinical expression and response of each of the clinical manifestations to different therapies can be difficult to predict. Enzyme replacement therapy has been available since 1991 and is well-established, with known efficacy and minimal toxicity. Of interest, the three available enzymes are distinct molecules and were registered as new products, not biosimilars. Oral substrate reduction therapy has undergone a revitalisation with a newly approved agent in this class for which some efficacy and toxicity questions have been raised. Herein we present our approach to the management of GD in the era of choices, including a new algorithm for how to manage a newly diagnosed patient.

Recent advances in the diagnosis and management of Gaucher disease

INTRODUCTION

Gaucher disease, the autosomal recessive deficiency of the lysosomal enzyme glucocerebrosidase, is associated with wide phenotypic diversity including non-neuronopathic, acute neuronopathic, and chronic neuronopathic forms. Overlap between types can render definitive diagnoses difficult. However, differentiating between the different phenotypes is essential due to the vast differences in clinical outcomes and response to therapy. Genotypic information is helpful, but cannot always be used to make clinical predictions. Current treatments for Gaucher disease, including enzyme replacement therapy and substrate reduction therapy, can reverse many of the non-neurological manifestations, but these therapies must be administered continually and are extremely costly.

AREAS COVERED

We reviewed the literature concerning the varied clinical presentations of Gaucher disease throughout the lifetime, along with treatment options, management goals, and current and future research challenges. A PubMed literature search was performed for relevant publications between 1991 to January 2018.

EXPERT COMMENTARY

Interest and research in the field of Gaucher disease is rapidly expanding. However, significant barriers remain in our ability to predict phenotype, assess disease progression using objective biomarkers, and determine optimal treatment strategy on an individual basis. As the field grows, we anticipate identification of genetic modifiers, new biomarkers, and small-molecule chaperone therapies, which may improve patient quality of life.

Correlating liver stiffness with disease severity scoring system (DS3) values in Gaucher disease type 1 (GD1) patients

Gaucher disease (GD) is an autosomal-recessive lysosomal storage disease caused by a deficiency of the enzyme, glucocerebrocidase, resulting in accumulation of lipid-laden storage cells in multiple organs such as bone marrow, liver, spleen, and lungs. Type 1 Gaucher disease is the most common form of this condition in which the brain and spinal cord (the central nervous system) are not affected. The Gaucher disease severity scoring system (GD-DS3) is typically used to assess disease severity accounting for skeletal, hematologic, and visceral disease. In addition to being time consuming for the clinician to calculate the scores, some of the assessments are subjective and may falsely increase or decrease disease severity. The purpose of this study was to determine if there is a correlation between liver stiffness values obtained from MR elastography (MRE) and the GD-DS3 score. An IRB approved, HIPAA compliant retrospective study was performed. All patients with type 1 GD imaged with MRE between 2011 and 2016 were included in this study. Clinical and imaging data was collected. Two pediatric radiologists analyzed MR images from abdomen and thigh studies independently to determine bone marrow involvement using a semi-quantitative scoring system with one reviewer analyzing a subset of studies to determine inter-observer reliability. The collected data was used to calculate a GD-DS3 score for all patients. GD-DS3 scores were compared with liver MRE stiffness values. Clinical MRE scores were plotted against GD-DS3 severity scores for 31 patients (15 males, 16 females; median age 27years, age range: 4-67years). The median GD-DS3 score was 4 (range: 1-10.1) and median MRE value was 2.43kPa (range: 1.30-5.20kPa). A significant positive correlation was found between MRE and GD-DS3 scores; Pearson's correlation coefficient value of r=0.47, p<0.001 for all scores, r=0.68, p<0.001 for complete scores and r=0.46, p<0.07 for incomplete scores. The inter-observer variation of bone marrow burden showed only fair agreement with a Kappa coefficient of 0.26. There is a significant positive correlation between increasing liver stiffness and increasing composite GD-DS3 scores. This supports the use of MRE, a non-invasive reproducible quantitative test, as both an additional assessment and independent marker for monitoring disease severity and progression in GD.

Combined miglustat and enzyme replacement therapy in two patients with type 1 Gaucher disease: two case reports

BACKGROUND

Intravenous enzyme replacement therapy is a first-line therapy for Gaucher disease type 1, and substrate reduction therapy represents an oral treatment alternative. Both enzyme replacement therapy and substrate reduction therapy are generally used as monotherapies in Gaucher disease. However, one randomized study and several case reports have described combination therapy over short time periods.

CASE PRESENTATION

We report two female Gaucher disease type 1 patients of mainly Anglo-Saxon descent, where combined enzyme replacement therapy and miglustat substrate reduction therapy were administered to overcome refractory clinical symptoms. The first patient was diagnosed at age 17 and developed Gaucher disease-related bone manifestations that worsened despite starting imiglucerase enzyme replacement therapy. After switching to miglustat substrate reduction therapy, her bone symptoms improved, but she developed tremors and eventually switched back to enzyme replacement therapy. Miglustat was later recommenced in combination with ongoing enzyme replacement therapy due to continued bone pain, and her bone symptoms improved along with maintained visceral manifestations. Enzyme replacement therapy was subsequently tapered off and the patient has since been successfully maintained on miglustat. The second patient was diagnosed aged 3, and commenced imiglucerase enzyme replacement therapy aged 15. After 9 years on enzyme replacement therapy she switched to miglustat substrate reduction therapy and her core symptoms were maintained/stable for 3 years. Imiglucerase enzyme replacement therapy was later added as a boost to therapy and her symptoms were subsequently maintained over a 2.3-year period. However, miglustat was discontinued due to her relocation, necessitating an increase in enzyme replacement therapy dose. Overall, both patients benefited from combination therapy.

CONCLUSION

While the majority of Gaucher disease type 1 patients will not need treatment with both substrate reduction therapy and enzyme replacement therapy, the current case reports demonstrate that judicious use of combination therapy may be of benefit in some cases.

In vitro osteoclastogenesis from Gaucher patients' cells correlates with bone mineral density but not with Chitotriosidase

Gaucher disease (GD) is caused by mutations on the gene encoding for the lysosomal enzyme glucocerebrosidase. Type I GD (GD1) patients present anemia, hepatosplenomegaly and bone alterations. In spite of treatment, bone alterations in GD patients persist, including poor bone mineral density (BMD). Mechanisms leading to bone damage are not completely understood, but previous reports suggest that osteoclasts are involved. Chitotriosidase (CHIT) is the most reliable biomarker used in the follow up of patients, although its correlation with bone status is unknown. The aim of this work was to study the pro-osteoclastogenic potential in patients and to evaluate its correlation with CHIT activity levels and clinical parameters. PBMCs from treated patients and healthy controls were cultured in the presence of M-CSF, and mature osteoclasts were counted. BMD, blood CHIT activity and serum levels of CTX, BAP, and cytokines were evaluated in patients. We found that blood CHIT activity and osteoclast differentiation were significantly increased in patients, but no correlation between them was observed. Interestingly, osteoclast numbers but not CHIT, presented a negative correlation with BMD expressed as Z-score. CTX, BAP and serum cytokines involved in bone remodeling were found altered in GD1 patients. These results show for the first time a correlation between osteoclast differentiation and BMD in GD1 patients, supporting the involvement of osteoclasts in the bone pathology of GD1. Our results also suggest that an altered immune response may play an important role in bone damage.

A Review of Gaucher Disease Pathophysiology, Clinical Presentation and Treatments

Gaucher disease (GD, ORPHA355) is a rare, autosomal recessive genetic disorder. It is caused by a deficiency of the lysosomal enzyme, glucocerebrosidase, which leads to an accumulation of its substrate, glucosylceramide, in macrophages. In the general population, its incidence is approximately 1/40,000 to 1/60,000 births, rising to 1/800 in Ashkenazi Jews. The main cause of the cytopenia, splenomegaly, hepatomegaly, and bone lesions associated with the disease is considered to be the infiltration of the bone marrow, spleen, and liver by Gaucher cells. Type-1 Gaucher disease, which affects the majority of patients (90% in Europe and USA, but less in other regions), is characterized by effects on the viscera, whereas types 2 and 3 are also associated with neurological impairment, either severe in type 2 or variable in type 3. A diagnosis of GD can be confirmed by demonstrating the deficiency of acid glucocerebrosidase activity in leukocytes. Mutations in the GBA1 gene should be identified as they may be of prognostic value in some cases. Patients with type-1 GD-but also carriers of GBA1 mutation-have been found to be predisposed to developing Parkinson's disease, and the risk of neoplasia associated with the disease is still subject to discussion. Disease-specific treatment consists of intravenous enzyme replacement therapy (ERT) using one of the currently available molecules (imiglucerase, velaglucerase, or taliglucerase). Orally administered inhibitors of glucosylceramide biosynthesis can also be used (miglustat or eliglustat).

DOENÇA DE GAUCHER TIPO 1 NO ESQUELETO: REVISÃO DA AMÉRICA LATINA

RESUMO A doença de Gaucher (DG) é a doença de depósito lisossômico mais prevalente, que se caracteriza pelo acúmulo de glicosilceramida e glucosilesfingosina em todos os tecidos do corpo. Com o advento da terapia de reposição de enzimas, o prognóstico dos pacientes com DG melhorou acentuadamente. Ainda assim, as manifestações esqueléticas associadas à DG respondem lentamente à terapia de reposição de enzimas e são as que contribuem de forma mais significativa para a morbidade do paciente. Esta revisão das manifestações ósseas da DG apresenta as mais recentes teorias sobre a sua fisiopatologia e uma revisão sistemática de estudos com pacientes latino-americanos que relataram a frequência das manifestações ósseas e os efeitos da terapia de reposição de enzimas sobre seu tratamento. Concluímos, destacando a importância da identificação precoce e do manejo adequado das doses apropriadas da terapia de reposição de enzimas para reduzir a morbidade causada pela DG.

Glucosylsphingosine is a key biomarker of Gaucher disease

Gaucher disease (GD) involves the accumulation of glucosylceramide (GL1) and its deacylated lysolipid, glucosylsphingosine (lyso-GL1) which is implicated in mediating immune dysregulation and skeletal disease. The aim of our study was to assess plasma Lyso-GL1 as a biomarker of GD and its response to therapy. Plasma lyso-GL1 in 169 patients with GD type 1 (GD1) was measured by LC-MS/MS. Significant predictors of plasma LGL1 were assessed by Pearson's correlation coefficient, Wilcoxon Mann Whitney test and multiple linear regression. Propensity scores were used to match patients on treatment mode: Enzyme Replacement Therapy (ERT) vs. Eliglustat Tartrate SRT (ELI-SRT). Plasma Lyso-GL1 levels in healthy controls averaged 1.5 ng/ml (1.3-1.7; 95% CI). In untreated GD patients, the levels were massively elevated (180.9 ng/ml: 95% CI, 145.4-216.5) and imiglucerase ERT resulted in marked reduction (89 ng/ml: 95% CI, 69.2-129.4) (P < 0.001). Lyso-GL1 correlated with chitotriosidase (r = 0.59 P < 0.001), CCL18 (r = 0.62 P <0.001), hepatomegaly (r = 0.28 P < 0.001), splenomegaly (r = 0.27 P = 0.003), splenectomy (P = 0.01) and treatment mode (P < 0.001). By multiple linear regression, the strongest predictors of lyso-GL1 were age (P < 0.001), splenectomy (P = 0.02), Chitotriosidase (P < 0.001) and CCL18 levels (P = 0.001). After propensity score matching to obtain comparable groups of patients on ERT vs ELI-SRT, lyso-GL1 levels were lower among patients receiving ELI-SRT by 113 ng/ml (95% CI: 136-90.3 ng/ml P < 0.001). Plasma lyso-GL1 is a key biomarker of GD. ERT reduced lyso-GL1 levels. By propensity scoring, ELI-SRT resulted in greater reduction of lyso-GL1 than ERT. Am. J. Hematol. 91:1082-1089, 2016. © 2016 Wiley Periodicals, Inc.

Imiglucerase in the management of Gaucher disease type 1: an evidence-based review of its place in therapy

Introduction

Gaucher disease is the first lysosomal disease to benefit from enzyme replacement therapy, thus serving as model for numerous other lysosomal diseases. Alglucerase was the first glucocerebrosidase purified from placental extracts, and this was then replaced by imiglucerase – a Chinese hamster ovary cell-derived glucocerebrosidase.

Aim

The aim was to review the evidence underlying the use of imiglucerase in Gaucher disease type 1

Evidence review

Data from clinical trials and Gaucher Registries were analyzed.

Conclusion

Imiglucerase has been prescribed and found to have an excellent efficacy and safety profile. We report herein the evidence-based data published for 26 years justifying the use of imiglucerase.

Comparison of Bone Mineral Density by Dual-Energy X-Ray Absorptiometry and Bone Strength by Speed-of-Sound Ultrasonography in Adults With Gaucher Disease

Patients with the lysosomal disorder Gaucher disease (GD) are at risk of osteoporosis and/or avascular necrosis, but to date, no adequate biomarkers are available to ascertain individual predilections. Bone mineral density by dual-energy X-ray absorptiometry (DXA) has traditionally been used to monitor trends. With the availability of a speed-of-sound (SOS) ultrasonography to assess bone strength/elasticity, we aimed to ascertain whether these modalities are complimentary or comparable so SOS, with no radiation risk, might be used more routinely as a potential biomarker. A prospective comparative study in adult GD patients undergoing routine follow-up of bone mineral density T- and Z-scores at forearm (FA), femoral neck, and lumbar spine, and SOS Z-scores at FA was initiated. Interpretation was by qualitative categorization of Z-scores. The kappa measure of agreement beyond chance was calculated between pairs of measurements and the McNemar test was then applied. This noninterventional trial (ClinicalTrials.gov Identifier: NCT02067247) was approved by the institutional ethics committee. There were 89 patients (ages 21-78 years, 61% female, 62% common Ashkenazi genotype, 18% splenectomized, and 18% with avascular necrosis/fractures). When comparing Z-scores at FA by DXA and SOS, only 39.3% correlated, while the remaining results were in disagreement; no trend was noted. Similarly, when comparing Z-scores at the femoral neck by DXA with those at FA by SOS, 44.9% of the results were in agreement; no trend was noted; and Z-scores at the lumbar spine by DXA with FA by SOS, 46% were in agreement and no trend was noted. DXA at the 3 sites did not track in the same direction or the same magnitude of difference with SOS at FA in adult patients with GD. Due to the fundamental differences between the 2 measurements and their clinical correlates, plus the lack of long-term follow-up to assess outcome, the potential added value of the measurements at the FA by SOS in patients with GD awaits further studies.

Standardization of MRI and Scintigraphic Scores for Assessing the Severity of Bone Marrow Involvement in Adult Patients With Type 1 Gaucher Disease

OBJECTIVE

MRI and (99m)Tc-sestamibi scintigraphy are used to estimate bone marrow infiltration in patients with Gaucher disease (GD), but comparison of data obtained at different institutions is difficult because different scores are employed for semiquantitative assessment. We developed normalized scores for comparing data both within a single method (MRI) and between different methods (MRI versus scintigraphy).

MATERIALS AND METHODS

We evaluated 51 patients with type 1 GD (26 women, 25 men; mean age ± SD, 36.3 ± 10.9 years old). T1- and T2-weighted turbo spin-echo sequences at 1.5 T served to derive the bone marrow burden score (0-16), the vertebra-disk ratio (VDR), the Terk score (0-3), and the Spanish-MRI score (S-MRI, 0-24). Scintigraphy was scored between 0 and 8. Each score was normalized into four categories: 0 = normal, 1 = mild, 2 = intermediate, 3 = severe involvement. Interobserver and intraobserver agreements were evaluated by kappa statistics; nonparametric statistics with Bonferroni correction assessed correlations among the various original and normalized scores.

RESULTS

Interobserver agreement was excellent for the original scores (κ = 0.730-0.843) and even more so for the normalized scores (κ = 0.775-0.940). Intraobserver agreement kappa values ranged from 0.753 to 0.937 for the original scores and 0.851 to 1.000 for the normalized scores. Highly significant correlations were found among the various original scores (r = 0.42-0.86, p values between 0.0296 and < 0.0001), except for VDR versus S-MRI and Terk. Normalization generally induced marginal reductions in statistical significance, whereas S-MRI versus VDR reached statistical significance with the normalized scores.

CONCLUSION

Our data indicate no significant loss of statistical information is caused by the normalization we employed. Our approach therefore facilitates comparison of different scores obtained in different institutions with different imaging modalities.

A multicenter, open-label extension study of velaglucerase alfa in Japanese patients with Gaucher disease: Results after a cumulative treatment period of 24months

Enzyme replacement therapy (ERT) with exogenous glucocerebrosidase is indicated to treat symptomatic Gaucher disease (GD), a rare, inherited metabolic disorder. ERT with velaglucerase alfa, which is produced in a human cell line using gene activation technology, was studied in a 12-month phase III trial in Japanese patients with type 1 or 3 GD who were switched from imiglucerase ERT (n=6); the current, open-label, 12-month extension study was designed to assess longer-term safety and efficacy. Two adult and three pediatric patients (aged <18years) were enrolled into the extension study. Every-other-week intravenous infusions were administered for 63-78weeks at average doses between 51.5 and 60.7units/kg. Three non-serious adverse events were considered related to velaglucerase alfa treatment, but no patient discontinued from the study. Six serious but non-drug-related adverse events were reported. No patient tested positive for anti-velaglucerase alfa antibodies. Hemoglobin concentrations, platelet counts, and liver and spleen volumes (normalized to body weight) in these patients were generally stable over a cumulative 24-month period from the baseline of the parent trial. The data suggest that velaglucerase alfa was well tolerated and maintained clinical stability in Japanese GD patients over 2years after switching from imiglucerase. ClinicalTrials.gov identifier NCT01842841.

Magnetic resonance imaging and BMB score in the evaluation of bone involvement in Gaucher's disease patients

Objective

To evaluate by magnetic resonance imaging changes in bone marrow of patients undergoing treatment for type I Gaucher’s disease.

Materials and Methods

Descriptive, cross-sectional study of Gaucher’s disease patients submitted to 3 T magnetic resonance imaging of femurs and lumbar spine. The images were blindly reviewed and the findings were classified according to the semiquantitative bone marrow burden (BMB) scoring system.

Results

All of the seven evaluated patients (three men and four women) presented signs of bone marrow infiltration. Osteonecrosis of the femoral head was found in three patients, Erlenmeyer flask deformity in five, and no patient had vertebral body collapse. The mean BMB score was 11, ranging from 9 to 14.

Conclusion

Magnetic resonance imaging is currently the method of choice for assessing bone involvement in Gaucher’s disease in adults due to its high sensitivity to detect both focal and diffuse bone marrow changes, and the BMB score is a simplified method for semiquantitative analysis, without depending on advanced sequences or sophisticated hardware, allowing for the classification of the disease extent and assisting in the treatment monitoring.

Quantification of Bone Marrow Involvement in Treated Gaucher Disease With Proton MR Spectroscopy: Correlation With Bone Marrow MRI Scores and Clinical Status

OBJECTIVE

The objective of our study was to use proton MR spectroscopy (MRS) to quantitatively evaluate bone marrow infiltration by measuring the fat fraction (FF) and to compare the FF with semiquantitative bone marrow MRI scores and clinical status in children treated for type 1 Gaucher disease (GD).

SUBJECTS AND METHODS

Over a 2-year period, we prospectively evaluated 10 treated GD patients (six males, four females; median age, 15.1 years) and 10 healthy age-matched control subjects (five males, five females; median age, 15.3 years) using 3-T proton MRS of L5 and the femoral neck. Water and lipid AUCs were measured to calculate the FF. Two blinded pediatric musculoskeletal radiologists performed a semiquantitative analysis of the conventional MR images using the bone marrow burden score and modified Spanish MRI score. We evaluated symptoms, spleen and liver volumes, platelet levels, hemoglobin levels, and bone complications.

RESULTS

In the femur, the FF was higher in the control subjects (median, 0.71) than the GD patients (0.54) (p = 0.02). In L5, the difference in FF--higher FF in control subjects (0.37) than in GD patients (0.26)--was not significant (p = 0.16). In both groups and both regions, the FF increased with patient age (p < 0.02). Semiquantitative scores showed no differences between control subjects and treated GD patients (p > 0.11). Eight of 10 GD patients were asymptomatic and two had chronic bone pain. The median age of patients at symptom onset was 4.0 years, the median age of patients at the initiation of enzyme replacement therapy was 4.3 years, and the median treatment duration was 10.2 years. Hemoglobin level, platelet count, and liver volume at MRI were normal. Mean pretreatment spleen volume (15.4-fold above normal) decreased to 2.8-fold above normal at the time of MRI (p = 0.01).

CONCLUSION

Proton MRS detected FF differences that were undetectable using conventional MRI; for that reason, proton MRS can be used to optimize treatment of GD patients.

Bone marrow involvement in Gaucher disease at MRI : what long-term evolution can we expect under enzyme replacement therapy?

PURPOSE

To study the long-term evolution of the bone marrow burden (BMB) score at MRI in patients with Gaucher disease (GD) under enzyme replacement therapy (ERT).

MATERIAL AND METHODS

Forty patients treated for GD were retrospectively studied in a referral centre. BMB scores were assessed on spine and femur MR examinations performed between January 2003 and June 2014. The long-term evolution of the BMB scores was analyzed using a linear mixed model.

RESULTS

A total of 121 MRI examinations were performed during the study period with a mean follow-up of 7.1 years ± 5.6, an average rate of 3.1 MR examinations ± 1.7 per patient and an interval of 2.3 years ± 1.1 between examinations. Patients had received ERT during 12 years on average ± 6.7. The trend of BMB scores with time decreased significantly by 15% (P = 0.008) during the total study period and 39% (P = 0.01) during the first 5 years of treatment. No changes in BMB scores were observed after five years of treatment.

CONCLUSION

In Gaucher patients, the trend of MRI BMB scores with time decreased significantly under ERT the first 5 years of treatment before a long-term stabilization.

KEY POINTS

• Bone marrow infiltration of Gaucher patients responds to enzyme replacement therapy • MRI BMB score decreases mainly during the first five years of treatment • MRI BMB score tends to stabilize after five years of treatment • MR examinations could be limited after five years of treatment.

Evaluation of bone involvement in patients with Gaucher disease: a semi-quantitative magnetic resonance imaging method (using ROI estimation of bone lesion) as an alternative method to semi-quantitative methods used so far

OBJECTIVE

The aim of this study was to evaluate bone involvement in patients with Gaucher disease (GD) and to propose a novel semi-quantitative magnetic resonance imaging (MRI) staging.

METHODS

MRI of the lumbar spine, femur, and tibia was performed in 24 patients with GD and 24 healthy controls. We also measured circulating levels of C-C motif ligand-3 (CCL-3) chemokine, C-telopeptide of collagen type-1 (CTX), and tartrate-resistant acid phosphatase isoform type-b (TRACP-5b).

RESULTS

We used the following staging based on MRI data: stage I: region of interest (ROI) 1/2 of normal values and bone infiltration up to 30%; stage II: ROI 1/3 of normal values and bone infiltration from 30 to 60%; stage III: ROI 1/4 of normal values and bone infiltration from 60% to 80%; and stage IV: detection of epiphyseal infiltration, osteonecrosis and deformity regardless of the ROI's values. All but two patients had abnormal MRI findings: 9 (37.5%), 6 (25%), 3 (12.5%), and 4 (16.7%) had stages I-IV, respectively. Patients with GD had elevated chitotriosidase, serum TRACP-5b, and CCL-3 levels (P < 0.001).

CONCLUSIONS

We propose an easily reproducible semi-quantitative scoring system and confirm that patients with GD have abnormal MRI bone findings and enhanced osteoclast activity possibly due to elevated CCL-3.

[Cathepsin K as a biomarker of bone involvement in type 1 Gaucher disease]

BACKGROUND AND OBJECTIVE

Gaucher disease is an inherited disorder caused by deficit of acid β-glucocerebrosidase, responsible for the degradation of glucosylceramide to ceramide and glucose. Although the disorder is primarily hematologic, bone is the second most commonly affected structure. Cathepsin K (CATK) is an enzyme involved in bone remodelling process. It has been proposed that determination of its serum concentrations may provide additional information to other biomarkers.

PATIENTS AND METHODS

The study included 20 control subjects and 20 Gaucher type 1 patients from Andalusia and Extremadura regions. We analyzed the biomarkers of bone remodelling: the bone alkaline phosphatase (B-ALP), the N-terminal propeptide of type 1 procollagen (P1NP), the β carboxyterminal telopeptide of type 1 collagen (CTx) and the CATK through electrochemiluminescence and immunoassay techniques.

RESULTS

There is an increase in levels of CATK, CATK/P1NP and CATK/B-ALP ratios in type 1 Gaucher patients compared to the control group. Considering the existence of skeletal manifestations in the patient group, the CATK and CATK/P1NP ratio showed higher levels in patients with bone damage compared to those without it.

CONCLUSIONS

Although imaging studies are the gold standard for monitoring bone disease in type 1 Gaucher patients, the utility of CATK should be considered as a possible indicator of bone damage in these patients. Furthermore, this parameter can be used in the monitoring of the treatment of bone pathology.