Gaucher disease: the role of the specialist on metabolic bone diseases

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.

Taliglucerase alfa in the longterm treatment of children and adolescents with type 1 Gaucher disease: the Albanian experience

Introduction

Enzyme replacement therapy is already recognized as the gold standard of care for patients with Gaucher disease. Taliglucerase alfa is one of the three alternatives recommended for treatment of Gaucher disease in children and adults.

Aim

This study aims to evaluate the long-term efficacy and safety of Taliglucerase alfa in children and adolescents with Type 1 Gaucher disease.

Patients and methods

Over a six-year period, we monitored the efficacy of continuous treatment in 10 patients by assessing various parameters, including hemoglobin concentration, platelet count, liver and spleen volume, bone mineral density, glucosylsphingosine level, chitotriosidase activity, and growth parameters. Safety was evaluated by immunogenicity and adverse event monitoring.

Results

The mean age of patients was 13.4 ± 3.6 years and the treatment duration was 60.24 ± 13.4 months. From baseline to end line the parameters change as follows: hemoglobin concentration improved from 12.7 (±1.3) to 14.6 (±1.5) and platelet count from 180 (±74) to 198 (±79). The spleen volume, was reduced by 46% (p = 0,007). The chitotriosidase activity decreased from 4,019.7 (±3,542.0) nmoles/ml/hr to 2,039.5 (±1,372.2) nmoles/ml/hr (46% reduction). Glucoylsphingosine level dropped from 119.2 (±70.4) ng/ml to 86.2 (±38.1) ng/ml, indicating a reduction of 28%. Bone mineral density Z-score, improved from -1.47 (±1.76) to -0.46 (±0.99) (69.7% reduction). Out of the 1,301 total administrations, our patients reported only 37 (2.8%) infusion-related adverse events which were mild and transitory.

Conclusion

Taliglucerase alfa exhibits good efficacy and a safe profile in the treatment of children and adolescents with Type 1 Gaucher disease.

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.

TRAP5b and RANKL/OPG Predict Bone Pathology in Patients with Gaucher Disease

Background and objective: Bone involvement occurs in 75% of patients with Gaucher disease (GD), and comprises structural changes, debilitating pain, and bone density abnormalities. Osteoporosis is a silent manifestation of GD until a pathologic fracture occurs. Thus, early diagnosis is crucial for identifying high-risk patients in order to prevent irreversible complications. Methods: Thirty-three patients with GD were assessed prospectively to identify predictive markers associated with bone density abnormalities, osteopenia (OSN), and osteoporosis (OSR). Subjects were categorized into three cohorts based on T- or Z-scores of bone mineral density (BMD). The first GD cohort consisted of those with no bone complications (Z-score ≥ −0.9; T-scores ≥ −1), the second was the OSN group (−1.8 ≥ Z-score ≥ −1; −2.5 ≥ T-score ≥ −1), and the third was the OSR group (Z-score ≤ −1.9; T-scores ≤ −2.5). Serum levels of TRAP5b, RANKL, OPG, and RANK were quantified by enzyme-linked immunosorbent assays. Results: TRAP5b levels were increased in GD patients, and showed a positive correlation with GD biomarkers, including plasma glucosylsphingosine (lyso-Gb1) and macrophage activation markers CCL18 and chitotriosidase. The highest level of TRAP5b was measured in patients with osteoporosis. The elevation of RANKL and RANKL/OPG ratio correlated with osteopenia in GD. Conclusion: TRAP5b, RANKL, and RANKL/OPG elevation indicate osteoclast activation in GD. TRAP5b is a potential bone biomarker for GD with the ability to predict the progression of bone density abnormalities.

The International Collaborative Gaucher Group GRAF (Gaucher Risk Assessment for Fracture) score: a composite risk score for assessing adult fracture risk in imiglucerase-treated Gaucher disease type 1 patients

Background

Fractures in Gaucher disease type 1 (GD1) patients cause significant morbidity. Fracture risk may be decreased by enzyme replacement therapy (ERT) but not eliminated. When considering initiation of treatment, it is useful to know to what extent fixed patient-specific factors determine risk for future fractures beyond standard risk factors that change with time and treatment, such as decreased bone mineral density. We developed a tool called the GRAF score (Gaucher Risk Assessment for Fracture) that applies 5 widely available characteristics (sex, age at treatment initiation [ATI], time interval between diagnosis and treatment initiation, splenectomy status, history of pre-treatment bone crisis) and provides a practical method to assess future fracture risk when imiglucerase ERT is initiated.

Methods

Inclusion criteria: GD1 patients in the International Collaborative Gaucher Group Gaucher Registry as of September 2019 initially treated with alglucerase/imiglucerase; known splenectomy status; at least one skeletal assessment on treatment (3216 of 6422 patients). Data were analyzed by ATI group (< 18, ≥ 18 to < 50, or ≥ 50 years of age) using Cox proportional hazards regression with all 5 risk factors included in the multivariable model. A composite risk score was calculated by summing the contribution of each parameter weighted by the strength of its association (regression coefficient) with fracture risk.

Results

Patients were followed from the date of treatment initiation (or age 18 years for patients if treatment started earlier) to the date of first adult fracture (n = 288 first fracture endpoints), death, or end of follow-up. The GRAF score for each ATI group was associated with a 2.7-fold increased risk of adult fracture for each one-point increase (p < 0.02 for < 18 ATI, p < 0.0001 for ≥ 18 to < 50 ATI and ≥ 50 ATI).

Conclusions

The GRAF score is a tool to be used with bone density and other modifiable, non-GD-specific risk factors (e.g. smoking, alcohol intake, frailty) to inform physicians and previously untreated GD1 patients about risk for a future fracture after starting imiglucerase regardless of whether there is an eventual switch to an alternative ERT or to substrate reduction therapy. GRAF can also help predict the extent that fracture risk increases if initiation of treatment is further delayed.

Gaucher Disease in Bone: From Pathophysiology to Practice

Gaucher disease (GD) is a rare, genetic lysosomal disorder leading to lipid accumulation and dysfunction in multiple organs. Involvement of the skeleton is one of the most prevalent aspects of GD and a major cause of pain, disability, and reduced quality of life. Uniform recommendations for contemporary evaluation and management are needed. To develop practical clinical recommendations, an international group of experienced physicians conducted a comprehensive review of 20 years' of the literature, defining terms according to pathophysiological understanding and pointing out best practice and unmet needs related to the skeletal features of this disorder. Abnormalities of bone modeling, reduced bone density, bone infarction, and plasma cell dyscrasias accompany the displacement of healthy adipocytes in adult marrow. Exposure to excess bioactive glycosphingolipids appears to affect hematopoiesis and the balance of osteoblast and osteoclast numbers and activity. Imbalance between bone formation and breakdown induces disordered trabecular and cortical bone modeling, cortical bone thinning, fragility fractures, and osteolytic lesions. Regular assessment of bone mineral density, marrow infiltration, the axial skeleton and searching for potential malignancy are recommended. MRI is valuable for monitoring skeletal involvement: It provides semiquantitative assessment of marrow infiltration and the degree of bone infarction. When MRI is not available, monitoring of painful acute bone crises and osteonecrosis by plain X-ray has limited value. In adult patients, we recommend DXA of the lumbar spine and left and right hips, with careful protocols designed to exclude focal disease; serial follow-up should be done using the same standardized instrument. Skeletal health may be improved by common measures, including adequate calcium and vitamin D and management of pain and orthopedic complications. Prompt initiation of specific therapy for GD is crucial to optimizing outcomes and preventing irreversible skeletal complications. Investing in safe, clinically useful, and better predictive methods for determining bone integrity and fracture risk remains a need. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Gene variants of osteoprotegerin, estrogen-, calcitonin- and vitamin D-receptor genes and serum markers of bone metabolism in patients with Gaucher disease type 1

Purpose

Osteopathy/osteoporosis in Gaucher disease type 1 (GD1) shows variable responses to enzyme replacement therapy (ERT); the pathogenesis is incompletely understood. We aimed to investigate the effects of several gene variants on bone mineral density (BMD) and serum markers of bone metabolism in GD1.

Patients and methods

Fifty adult Caucasian patients with GD1/117 controls were genotyped for gene variants in the osteoprotegerin (TNFRSF11B; OPG), estrogen receptor alpha, calcitonin receptor (CALCR), and vitamin D receptor (VDR) genes. In patients and 50 matched healthy controls, we assessed clinical data, serum markers of bone metabolism, and subclinical inflammation. BMD was measured for the first time before/during ERT (median 6.7 years).

Results

Forty-two percent of patients were splenectomized. ERT led to variable improvements in BMD. Distribution of gene variants was comparable between patients/controls. The AA genotype (c.1024+283G>A gene variant; VDR gene) was associated with lower Z scores before ERT vs GA (P=0.033), was encountered in 82.3% of patients with osteoporosis and was more frequent in patients with pathological fractures. Z score increases during ERT were higher in patients with the CC genotype (c.9C>G variant, TNFRSF11B; OPG gene; P=0.003) compared with GC (P=0.003). The CC genotype (c.1340T>C variant, CALCR gene) was associated with higher Z scores before ERT than the TT genotype (P=0.041) and was absent in osteoporosis. Osteocalcin and OPG were lower in patients vs controls; beta crosslaps, interleukin-6, and ferritin were higher.

Conclusions

We suggest for the first time a protective role against osteoporosis in GD1 patients for the CC genotype of the c.9C>G gene variant in the TNFRSFB11 (OPG) gene and for the CC genotype of the c.1340T>C gene variant (CALCR gene), while the AA genotype of the c.1024+283G>A gene variant in the VDR gene appears as a risk factor for lower BMDs. Serum markers suggest decreased osteosynthesis, reduced inhibition of osteoclast activation, increased bone resorption, and subclinical inflammation during ERT.

Actual reason for bone fractures in the case of a patient followed-up with the osteogenesis imperfecta: Gaucher's Disease

Gaucher's disease (GD) is a rare disease characterized by a β-glucocerebroside accumulation in the reticulo-endothelial system. Patients may refer to the clinic with complaints of bone pain, hepatosplenomegaly, anemia, thrombocytopenia, growth retardation, interstitial pulmonary disease, pulmonary hypertension, and skeletal disorders. Skeletal system involvement is observed commonly in Gaucher patients and a significant cause of morbidity. Our patient was followed for several years as a glass child - osteogenesis imperfecta and he had joint deformities due to skeletal fractures. We wanted to present this case to raise awareness of GD's skeletal involvement and effects of late diagnosis.