Decreased bone density in splenectomized Gaucher patients receiving enzyme replacement therapy

Imiglucerase, cholecalciferol, and bone-diet in skeletal health management of type I Gaucher disease patients: a pilot study and systematic review

Skeletal anomalies represent a characteristic feature of type 1 Gaucher disease (GD1). Here we evaluated the impact of an integrated therapy comprising enzyme-replacement therapy (ERT), cholecalciferol, and a normocalcemic-normocaloric-hyposodic diet (bone diet) on bone health in GD1 patients. We also performed a systematic review to compare our results with available data. From January 1, 2015 to February 28, 2019, all GD1 patients referred to Federico II University were enrolled and treated with the integrated therapy. Bone turnover markers and bone mineral density (BMD) were evaluated at baseline (T0) and after 24 months (T24). We enrolled 25 GD1 patients, all showing 25-hydroxy vitamin D (25OHD) levels < 50 nmol/l (hypovitaminosis D) at T0. Response to cholecalciferol treatment was effective, showing a direct relationship between 25OHD levels before and after treatment. At T0, 2 GD1 patients showed fragility fractures, 5 the Erlenmeyer flask deformity, 3 osteonecrosis, and 7 a BMD Z-score ≤ -2. Overall, GD1 patients with bone anomalies showed higher C-terminal telopeptide levels compared with those without bone anomalies. No new bone anomalies occurred during 2 years of follow-up. At T24, BMD remained stable across the entire study cohort, including in patients with bone anomalies. The systematic review showed that our study is the first that evaluated all bone health parameters. Hypovitaminosis D is prevalent in GD1 patients. The response to cholecalciferol treatment was effective but different to healthy subjects and in patients with metabolic bone disorders. Integrated therapy including ERT, cholecalciferol, and bone diet guarantees bone health.

[Misdiagnosis of Gaucher disease in real life: Retrospective study of the French Gaucher's disease registry]

INTRODUCTION

Gaucher disease is an autosomal recessive genetic disorder. It is caused by a deficiency of the lysosomal enzyme, glucocerebrosidase which leads to an accumulation of glucosylceramide in the macrophages. Splenomegaly, hepatomegaly, cytopenias (anemia, thrombocytopenia) and bone disorders are the main symptoms. The diagnosis is often delayed, leading to unnecessary investigations and treatments, and delaying the specific treatment. The primary objective of our study was to establish, in patients who had a diagnostic delay of more than one year, the reported misdiagnoses before the final diagnosis. The secondary objectives were to investigate the risk factors associated with error and delayed diagnosis.

METHODS

Retrospective study including patients with Gaucher disease from the French Gaucher Disease Registry. Collection of data by a single investigator from a standardized form.

RESULTS

Among 83 patients with a known diagnostic delay, 13 patients (15 %) had one or two misdiagnoses. These included osteo-articular diagnoses (osteomyelitis, osteoarthritis, arthritis, osteochondritis, rheumatic fever, n=8), haematological diagnoses (gestational thrombocytopenia, immunological thrombocytopenia, n=4), infectious diagnoses (visceral leishmaniasis, mononucleosis, n=2) and hemochromatosis. The osteo-articular and infectious diagnoses concerned the child and the adolescent while the haematological diagnoses and the hemochromatosis concerned the adult. No factors were found associated with misdiagnoses. Patients with a diagnostic delay greater than one year were less likely to have hepatosplenomegaly as the first symptom.

CONCLUSION

There is a risk of diagnostic error related to phenotypic heterogeneity and lack of specificity of Gaucher disease symptoms. This study helps to better identify the misdiagnoses associated with Gaucher disease.

Cancer risk and gammopathies in 2123 adults with Gaucher disease type 1 in the International Gaucher Group Gaucher Registry

There are numerous reports of cancers in Gaucher disease (GD) from mostly small single-center studies; however, precise risk estimates and cancer types involved have not been delineated. We conducted a study involving 2123 patients with GD type 1 (GD1) to assess the incidence of hematological malignancies, gammopathies, and solid tumors in an international observational study, the International Cooperative Gaucher Group Gaucher Registry (Clinicaltrials.gov: NCT00358943). Risk for cancer overall and for each type of malignancy was compared to the United States (US) population using the Surveillance, Epidemiology, and End Results database. Natural history of gammopathy was determined through assessing the progression from a diagnosis of monoclonal gammopathy of unknown significance (MGUS) to multiple myeloma (MM). Risk for hematological malignancies was more than four times higher than expected compared to the general population: non-Hodgkin lymphoma was approximately three times higher; MM was approximately nine times higher. Age-specific incidence rates of MGUS were unexpectedly high among younger patients. The 10-year cumulative incidence of MM after diagnosis of MGUS was 7.9%, comparable to the general population. Compared to the general US population, GD1 patients were at higher risk for solid malignancies of liver (2.9 times), kidney (2.8 times), melanoma (2.5 times), and breast (1.4 times). Colorectal, prostate, and lung cancer risks were lower than expected. These findings help advance care of patients with GD1 by supporting recommendations for individualized monitoring for malignancies and antecedents such as MGUS for MM and provoke important questions of the role of glucosylceramide and related sphingolipids in cancer biology.

Endocrine and metabolic disorders in patients with Gaucher disease type 1: a review

Background

Gaucher disease (GD) is one of the most prevalent lysosomal storage diseases and is associated with hormonal and metabolic abnormalities, including nutritional status disorders, hypermetabolic state with high resting energy expenditures, peripheral insulin resistance, hypoadiponectinaemia, leptin and ghrelin impairments, hypolipidaemia, linear growth deceleration and growth hormone deficiency, delayed puberty, hypocalcaemia and vitamin D deficiency. Specific treatments for GD such as enzyme replacement therapy and substrate reduction therapy display significant effects on the metabolic profile of GD patients.

Main body of the abstract

Hormonal and metabolic disturbances observed in both adult and paediatric patients with Gaucher disease type 1 (GD1) are discussed in this review. The PubMed database was used to identify articles on endocrine and metabolic disorders in GD1. GD1 appears to facilitate the development of disorders of nutrition, glucose metabolism and vitamin D insufficiency. Metabolic and hormonal diseases may have a significant impact on the course of the underlying disease and patient quality of life.

Conclusions

Conditions relating to hormones and metabolism can be wide-ranging in GD1. Obtained findings were intrinsic to GD either as a deleterious process or a compensatory response and some changes detected may represent co-morbidities. Actively seeking and diagnosing endocrine and metabolic disorders are strongly recommended in GD1 patients to optimize healthcare.

A multicenter, open-label, phase III study of Abcertin in Gaucher disease

BACKGROUND

Gaucher disease (GD) is caused by a deficiency in the lysosomal enzyme glucocerebrosidase. Enzyme replacement therapy (ERT) is recommended for clinical improvement.

METHODS

The efficacy and safety of a new imiglucerase, Abcertin, were assessed in 7 Egyptian patients with treatment-naïve type 1 GD. Each patient was administered a biweekly 60 U/kg dose of Abcertin for 6 months. The primary endpoint was the change in hemoglobin concentration. The secondary endpoints were changes from baseline in platelet counts, spleen and liver volumes, biomarker levels, skeletal parameters, and bone mineral density.

RESULTS

The hemoglobin concentration increased by a mean of 1.96 ± 0.91 g/dL (range 1.11-2.80 g/dL) or 20.6% (P = .001). Statistically significant increases in the platelet count and decreases in the spleen volume and biomarker levels were also observed. There were no severe drug-related adverse events. One patient developed anti-imiglucerase antibodies without neutralizing activity.

CONCLUSION

Our study results demonstrate the efficacy and safety of Abcertin in patients with type 1 GD. This suggests that Abcertin can be an alternative ERT option for type 1 GD.

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

According to European legislation, a disease can be considered rare or "orphan" when it affects less than 1 subject of 2000 (1). Often these diseases affecting the pediatric age, are complex diseases and chronically debilitating and for this motive need the intervention of multidisciplinary skills specific. Among the rare disease as affecting the skeleton more than 400 are characterized by dysplastic changes of the skeleton (2). Alongside the disorders affecting the skeleton primitively, many systemic diseases can have a bone involvement. Among these, the Gaucher disease (GD), an heterogeneous lysosomal storage determined by hereditary enzyme deficiency of β-glucosidase. Patients with this disease have skeletal disorders of varying severity (Erlenmeyer flask deformity, lytic lesions and osteonecrosis, pathological fractures) that affects both the bone marrow, both mineralized bone with progressive damage of the tissue. The bone disease is the most debilitating of GD and can have a significant impact on the quality of life of patients. Thorough evaluations by monitoring biochemical markers of bone turnover and instrumental, with a quantitative and qualitative evaluation of the bone, are of fundamental importance to intervene early so they can prevent complications irreversible.

The clinical spectrum and pathophysiology of skeletal complications in lysosomal storage disorders

Lysosomal storage disorders affect multiple organs including the skeleton. Disorders with prominent skeletal symptoms are type 1 and 3 Gaucher disease, the mucopolysaccharidoses, the glycoproteinoses and pycnodysostosis. Clinical manifestations range from asymptomatic radiographical evidence of bone pathology to overt bone crises (Gaucher), short stature with typical imaging features known as dysostosis multiplex (MPS), with spine and joint deformities (mucopolysaccharidoses, mucolipidosis), or osteopetrosis with pathological fractures (pynodysostosis). The pathophysiology of skeletal disease is only partially understood and involves direct substrate storage, inflammation and other complex alterations of cartilage and bone metabolism. Current treatments are enzyme replacement therapy, substrate reduction therapy and hematopoietic stem cell transplantation. However, effects of these interventions on skeletal disease manifestations are less well established and outcomes are highly dependent on disease burden at treatment initiation. It is now clear that adjunctive treatments that target skeletal disease are needed and should be part of future research agenda.

Gaucher disease and bone manifestations

Gaucher disease is a relatively rare metabolic disease caused by the inherited deficiency of the lysosomal enzyme glucocerebrosidase. Gaucher disease affects multiple organs, among which is the skeleton. Bone involvement occurs frequently in Gaucher disease, and is one of its most debilitating features, reducing the quality of life of patients. Bone status is an important consideration for treatment to ameliorate symptoms and reduce the risk of irreversible complications. We have conducted a systematic review of all the various aspects of Gaucher disease, focusing on different skeletal manifestations, pathophysiology of bone alterations, clinical symptoms, and current diagnostic and therapeutic approaches.

Long-term effectiveness of enzyme replacement therapy in children with Gaucher disease: results from the NCS-LSD cohort study

OBJECTIVES

To determine the effectiveness of enzyme replacement therapies (ERT) for children with Gaucher disease (GD).

DESIGN

A longitudinal cohort study including prospective and retrospective clinical data. Age- and gender-adjusted treatment effects were estimated using generalised linear mixed models. Children on treatment contributed data before and during treatment. Children not on treatment contributed natural history data.

PARTICIPANTS

Consenting children (N = 25, aged 1.1 to 15.6 years) with a diagnosis of GD (14 with GD1 and 11 with GD3) who attended a specialist treatment centre in England. At recruitment, 24 patients were receiving ERT (mean treatment duration, 5.57 years; range 0-13.7 years).

OUTCOME MEASURES

Clinical outcomes chosen to reflect disease progression, included platelet count; haemoglobin and absence/presence of bone pain.

RESULTS

Duration of ERT was associated with statistically significant improvements in platelet count (p < 0.001), haemoglobin (p < 0.001), and reported bone pain (p = 0.02). The magnitude of effect on haematological parameters was greater in children with GD3 than in those with GD1.

CONCLUSIONS

These data provide further evidence of the long-term effectiveness of ERT in children with GD.

Long-term effectiveness of enzyme replacement therapy in adults with Gaucher disease: results from the NCS-LSD cohort study

OBJECTIVES

To determine the effectiveness of enzyme replacement therapies (ERT) for adults with Gaucher disease (GD).

DESIGN

A longitudinal, multi-centre cohort study, including prospective and retrospective clinical data. Age- and gender-adjusted treatment effects were estimated using generalised linear mixed models. Treated patients contributed data before and during treatment. Untreated patients contributed natural history data.

PARTICIPANTS

Consenting adults (N = 150, aged 16 to 83 years) with a diagnosis of GD who attended a specialist treatment centre in England. At recruitment, 131 patients were receiving ERT (mean treatment duration, 10.8 years; range 0-18 years).

OUTCOME MEASURES

Clinical outcomes chosen to reflect disease progression, included platelet count; haemoglobin; absence/presence of bone pain; spleen and liver volumes and AST levels.

RESULTS

One hundred and fifty adults were recruited. Duration of ERT was associated with statistically significant improvements in platelet count (p < 0.001), haemoglobin (p < 0.001), liver and spleen volumes (p < 0.001) and AST levels (p = 0.02).

CONCLUSIONS

These data provide further evidence of the long-term effectiveness of ERT in adults with GD.

Modelling Gaucher disease progression: long-term enzyme replacement therapy reduces the incidence of splenectomy and bone complications

Long-term complications and associated conditions of type 1 Gaucher Disease (GD) can include splenectomy, bone complications, pulmonary hypertension, Parkinson disease and malignancies. Enzyme replacement therapy (ERT) reverses cytopenia and reduces organomegaly. To study the effects of ERT on long-term complications and associated conditions, the course of Gaucher disease was modelled.

The cohort consisted of all diagnosed GD patients in the Netherlands. Mutually exclusive disease states were defined as ‘asymptomatic’, ‘signs/symptoms’, ‘recovery’, ‘splenectomy’, ‘bone complication’, ‘multiple complications’ and ‘malignancy’. A natural history (NH) cohort was delineated based upon historical data on Dutch patients before ERT was available. Cumulative incidence curves were composed for progression from each disease state to the next. Two scenarios were applied for the ERT cohort: time to complications was calculated from A. start of ERT; B. entering the previous disease state.

Median time for the development of signs and/or symptoms was 30.1 years (N = 73). In the NH cohort (N = 42), 9% had developed a bone complication after 10 years in the signs/symptoms phase, while 21% had undergone a splenectomy. In the ERT cohort (N = 29 (A), N = 28 (B)), 12% (A) or 4% (B) had developed a bone complication after 10 years in this phase and no patient was splenectomized. No patients in the NH cohort recovered, compared to 50% in the ERT cohort after 3.6 years (N = 28 (A)) or 22.4 years (N = 27 (B)) of treatment. Median time from a first to a second complication was 11 years in the NH cohort (N = 31), whereas 16 respectively 14 percent had developed a second complication after 10 years in the ERT cohort (N = 17, scenario A/B). Fourteen percent (scenario A/B) developed an associated malignancy after 10 years in the phase ‘multiple complications’ (N = 23). Associated malignancies occurred almost exclusively in advanced disease stages, therefore it is suggested that ERT reduces their incidence

Long-term ERT for GD can reduce the incidence of splenectomy and bone complications. As ERT prevents progression to more advanced stages of GD it will most likely result in a reduction of associated malignancies.

Bone disease in patients with Gaucher disease

Gaucher disease is an inborn error of metabolism due to a deficiency of the lysosomal enzyme glucocerebrosidase. As a result of this deficiency, the substrate glucocerebroside accumulates in the liver, spleen, bone and bone marrow. Bone involvement can lead to abnormalities in bone growth, bone remodeling, bone infarcts, aseptic necrosis, osteonecrosis, increased fracture risk and lytic bone lesions. Patients may experience bone pain and bone crises related to bone infarcts. There is evidence of abnormal bone metabolism in both bone resorption and bone formation based upon biochemical abnormalities found in patients. In addition, both immunological and coagulation abnormalities have in part been implicated in the causation of bone disease. Treatment with enzyme replacement therapy and substrate reduction therapy has led to improvement in both the symptoms and the radiographic abnormalities seen in these patients. It is unknown whether these treatments lower fracture risk.

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.

Bone turnover markers in patients with type 1 Gaucher disease

Bone complications occur frequently in Gaucher disease (GD) and reduce the quality of life of these patients. Skeletal involvement is an important indication for treatment to ameliorate symptoms and reduce the risk of irreversible and debilitating disease. Bone biomarkers have been used to assess disease status and the response to therapy in a number of bone disorders. Here, we examine the literature for evidence of abnormalities in bone turnover markers in patients with type 1 GD to assess whether they might be useful for the assessment of bone involvement in GD. We have found that bone biomarkers in GD show highly variable results which do not currently support their routine use for clinical assessment of bone status, as an indication for therapy initiation, or for monitoring the response to therapy. A greater understanding of bone markers and their relation to the bone manifestations of GD is required.

Miscellaneous non-inflammatory musculoskeletal conditions. Gaucher disease and bone

Gaucher disease (GD) is an inherited lysosomal storage disorder affecting multiple organs. Non-neuronopathic GD, the most common form, can present with hepatosplenomegaly, anaemia, bleeding tendencies, thrombocytopenia, skeletal pathologies, growth retardation and, in severe cases, with pulmonary disease. The bone manifestations include bone infarcts, avascular bone necrosis, lytic lesions, osteosclerosis, fractures due to osteoporosis and, rarely, acute osteomyelitis. Bone pain of varying intensity, fractures and joint collapses increase the patients' morbidity and impair their mobility and quality of life. Currently available therapies - enzyme replacement therapy and substrate reduction therapy - have shown to improve blood count and the visceral manifestations within a short time. Beneficial effects have also been documented on bone pain, bone crises and the extent of osteoporosis. The article focusses on the bone pathologies of GD including its pathophysiology, current diagnostics, clinical management and therapeutic effects of enzyme replacement therapy, substrate reduction therapy and bone-specific therapies.

Biomarkers for osteonecrosis in Gaucher disease

INTRODUCTION

The search for surrogate biomarkers of osteonecrosis, a disabling complication of Gaucher disease, has intensified in the last decade. Biomarkers that predict osteonecrosis and monitor the effectiveness of therapies would improve clinical practice and enrich the molecular exploration of this disorder.

AREAS COVERED

Here we discuss advances in biomarker research with special reference to those biomarkers associated with Gaucher disease and investigated in the context of enzyme therapy. Much progress has been made in the diversification of treatment for the condition and several biomarker molecules, which may ultimately improve risk assessment for osteonecrosis, have been identified.

EXPERT OPINION

The discovery of prospective biomarkers of osteonecrosis such as CCL18/PARC, CXCL8/IL-8, CCL5/RANTES, CCL3/MIP-1α, CCL4/MIP-1β, particularly during recurrent episodes occurring despite enzyme treatment, has the potential radically to change practices in the management of Gaucher disease and should improve therapeutic monitoring and prognostic evaluation. Ultimately, exploration of this field will provide the basis for a refined mechanistic understanding of pathogenesis.

Therapeutic approaches to bone pathology in Gaucher disease: past, present and future

Enzyme replacement therapy (ERT) is effective for the treatment of the systemic manifestations of Gaucher disease (GD) and can have a significant impact on skeletal manifestations. Bone involvement is broad and can occur in otherwise clinically asymptomatic individuals. The heterogeneity in GD-related bone disease may implicate multiple pathological processes such as disruption of coordinated bone cell activity, in addition to the physical impact of Gaucher cells causing vascular occlusion. Accumulated data suggests that earlier treatment initiation decreases skeletal complications and that bone disease may require a longer duration of treatment and higher dose than is necessary for organ involvement and hematopoietic manifestations. However, in some patients, bone manifestations persist and even worsen despite ERT, regardless of dose or duration of treatment. Treating skeletal disease should be considered of equal importance as treating visceral and hematologic manifestations. When treatment decisions involve multiple enzyme preparations and other therapeutic modalities such small molecules, the choice should be tailored on an individual basis with continuing evaluation.

Gaucher disease: a systematic review and meta-analysis of bone complications and their response to treatment

Type 1 Gaucher disease (GD1) is an inherited lysosomal storage disease, which is often managed by enzyme replacement therapy (ERT). The bone response to ERT is usually slower than visceral and hematological responses. There is uncertainty as to whether an increase in the dosage of ERT has a beneficial effect. The aim of our study was to determine whether or not there is sufficient evidence to make a definitive statement about the effects of ERT and substrate reduction therapy (SRT) on bone marrow infiltration and bone mineral density (BMD) in GD1. We conducted a systematic review of all studies examining the effects of ERT and SRT on bony complications of GD1 published before July 2008. The studies were identified by a computerized search with use of Medline, Embase, The Cochrane Database of Systematic Reviews, The Cochrane Central Register of Controlled Trials (CCTR), and bibliographies of papers subsequently retrieved from the search. Three hundred studies were grouped according to whether they deal with the natural history of GD1 or therapeutic issues, and 17 studies were included in the review. The results from our systematic review suggest that further investigations, such as better analysis of the Gaucher Registry, are needed on the effects of ERT and SRT on bony complications of GD1. Studies on the effects of the newly identified velaglucerase and the plant-derived glucocerebrosidase on bony complications of GD1 are also needed.

Baseline characteristics and outcome in Romanian patients with Gaucher disease type 1

BACKGROUND/AIM

To present clinical and genetic characteristics of all Romanian patients with Gaucher disease type 1, in whom specific diagnosis has been confirmed by enzymatic and molecular methods and to analyze their outcome with and without enzymatic replacement therapy (ERT).

PATIENTS, METHODS

There are fifty patients (F/M - 1.63/1) with Gaucher disease type 1. Clinical status, haemoglobin, thrombocytes, hepatic/splenic volume, bone mineral density and severity score were assessed at baseline and every six months thereafter. Thirty-nine patients (78%) received imiglucerase (44.4+/-13.6 U/kg/2 weeks) for 3.1+/-1.4 years.

RESULTS

Based on general prevalence data, our group represents 22.7% of the expected total number of patients with Gaucher disease type 1 in Romania. Mean age was 15.5 years at clinical onset and 28.9 years at confirmation of diagnosis. The genotype N370S/L444P was frequent in our group (35.9% of alleles). Anaemia, thrombocytopenia, splenomegaly and bone disease were present at 38%, 70%, 100% and 84%, respectively. Mean values for haemoglobin, thrombocytes, hepatic volume and chitotriosidase normalized after 0.5, 1.5, 2.5 and 3 years of ERT, respectively. Splenomegaly regressed from 14.4 x N (normal) to 3.06 x N over four years of treatment. Bone disease was ameliorated under ERT, yet bone mineral density worsened in patients treated with 30 U/kg/2 weeks.

CONCLUSIONS

The genotype N370S/L444P is frequent in our patients, in line with the severe phenotypes. ERT improved haematological parameters and visceromegaly, without a clear benefit for bone mineral density. To attain therapeutic goals, an early treatment start with optimal dosage is mandatory.

The pharmacological chaperone isofagomine increases the activity of the Gaucher disease L444P mutant form of beta-glucosidase

Gaucher disease is caused by mutations in the gene that encodes the lysosomal enzyme acid beta-glucosidase (GCase). We have shown previously that the small molecule pharmacological chaperone isofagomine (IFG) binds and stabilizes N370S GCase, resulting in increased lysosomal trafficking and cellular activity. In this study, we investigated the effect of IFG on L444P GCase. Incubation of Gaucher patient-derived lymphoblastoid cell lines (LCLs) or fibroblasts with IFG led to approximately 3.5- and 1.3-fold increases in L444P GCase activity, respectively, as measured in cell lysates. The effect in fibroblasts was increased approximately 2-fold using glycoprotein-enrichment, GCase-immunocapture, or by incubating cells overnight in IFG-free media prior to assay, methods designed to maximize GCase activity by reducing IFG carryover and inhibition in the enzymatic assay. IFG incubation also increased the lysosomal trafficking and in situ activity of L444P GCase in intact cells, as measured by reduction in endogenous glucosylceramide levels. Importantly, this reduction was seen only following three-day incubation in IFG-free media, underscoring the importance of IFG removal to restore lysosomal GCase activity. In mice expressing murine L444P GCase, oral administration of IFG resulted in significant increases (2- to 5-fold) in GCase activity in disease-relevant tissues, including brain. Additionally, eight-week IFG administration significantly lowered plasma chitin III and IgG levels, and 24-week administration significantly reduced spleen and liver weights. Taken together, these data suggest that IFG can increase the lysosomal activity of L444P GCase in cells and tissues. Moreover, IFG is orally available and distributes into multiple tissues, including brain, and may thus merit therapeutic evaluation for patients with neuronopathic and non-neuronopathic Gaucher disease.

The female Gaucher patient: the impact of enzyme replacement therapy around key reproductive events (menstruation, pregnancy and menopause)

BACKGROUND

The principal manifestations of type 1 Gaucher disease (GD) (increased risk of bleeding, anaemia, splenomegaly, hepatomegaly and bone disease) are likely to affect females during reproductive events such as menarche and menstruation; fertility, pregnancy, parity, delivery and lactation; and menopause. In order to determine the optimal management of female Gaucher patients based on available data, we examine reproductive events and GD in untreated and alglucerase and/or imiglucerase-treated females.

METHODS

A panel of international clinicians experienced in the management of GD reviewed and presented evidence from peer-reviewed literature, a pharmacovigilance database on imiglucerase, and their own clinical experience to support discussions and recommendations. Nine panel members completed a 130-item-questionnaire on the outcomes of the management of female patients in their clinical practice. Results, covering menarche (137 females), menstruation (261 reports), fertility (295 females), pregnancy (416 pregnancies in 247 women) and menopause (45 women) were analysed. Data from a recent Canadian survey on 50 patients with 39 pregnancies, the imiglucerase pharmacovigilance database (100 pregnancies), and relevant literature (56 items covering 398 pregnancies in 205 women) were also reviewed.

KEY RESULTS

Menarche: May be delayed in girls with GD. Menorrhagia: Appears to be more common in GD than in the non-Gaucher population and may be ameliorated by alglucerase and/or imiglucerase treatment (menorrhagia in 67/133 (50.4%) untreated females compared with 37/128 (28.9%) treated; Mann-Whitney U test: p=0.001). Fertility: There is no evidence of decreased fertility in GD. Pregnancy: Pregnancy in GD may be complicated by haematological disease, organomegaly and bone involvement. GD diagnosis occurs frequently during pregnancy. Questionnaire results demonstrate: a reduced risk of spontaneous abortion in women treated with alglucerase and/or imiglucerase (untreated: 26/189 (13.8%); treated 1/58 (1.7%) chi(2)p=0.010); reduced risk of Gaucher-related complications during delivery (untreated 43/109 (39.4%); treated 3/46 (6.5%) chi(2)p<0.0005): and a reduced risk of Gaucher-related complications during the post partum period (untreated 15/71 (21.1%); treated 3/43 (7%) chi(2)p=0.014). There is no evidence to date of any untoward effect of alglucerase and/or imiglucerase on the fetus, or on infants breast fed by mothers receiving alglucerase and/or imiglucerase. Menopause: The impact of GD on menopause requires further study especially in relation to bone pathology.

CONCLUSIONS

On the basis of this review, GD may have an impact on reproductive events in affected women. Enzyme therapy may have benefits in reducing menorrhagia, spontaneous abortions and complications associated with delivery and the postpartum period.

Enzyme replacement therapy for Gaucher disease

Gaucher disease is the most common lysosomal storage disease, and the first lysosomal storage disease for which a specific therapy has been developed. Enzyme replacement therapy, with glucocerebrosidase purified from human placentae, was introduced in 1991. Recombinant human glucocerebrosidase, produced by Chinese hamster ovary cells in tissue culture, became available in 1994 and has replaced the placenta-derived product. These therapies have revolutionized the care of patients with type 1 Gaucher disease, reversing many of the pathological consequences of this disease, and preventing further progression. Furthermore, they have served as a model for the treatment of other lysosomal storage diseases and inborn errors of metabolism.

Randomized, controlled trial of miglustat in Gaucher's disease type 3

OBJECTIVE

To evaluate the efficacy and safety of miglustat, concomitant with enzyme replacement therapy (ERT), in patients with Gaucher's disease type 3 (GD3).

METHODS

This 24-month, phase II, open-label clinical trial of miglustat in GD3 was conducted in two phases. During the initial 12 months, patients were randomized 2:1 to receive miglustat or "no miglustat treatment." The randomized phase was followed by an optional 12-month extension phase in which all patients received miglustat. All patients received ERT during the 24-month period. The primary efficacy end points were change from baseline to months 12 and 24 in vertical saccadic eye movement velocity as determined by the peak amplitude versus amplitude regression line slope. Secondary end points included changes in neurological and neuropsychological assessments, pulmonary function tests, liver and spleen organ volumes, hematological and clinical laboratory assessments, and safety evaluations.

RESULTS

Thirty patients were enrolled, of whom 21 were randomized to miglustat and 9 to "no miglustat treatment." Twenty-eight patients entered the 12-month extension phase. No significant between-group differences in vertical saccadic eye movement velocity or in the other neurological or neuropsychological evaluations were observed. Organ volumes and hematological parameters remained stable in both treatment groups, but improvement in pulmonary function and decrease of chitotriosidase levels were observed with miglustat compared with patients receiving ERT alone.

INTERPRETATION

Miglustat does not appear to have significant benefits on the neurological manifestations of GD3. However, miglustat may have positive effects on systemic disease (pulmonary function and chitotriosidase activity) in addition to ERT in patients with GD3.

The pharmacokinetics and tissue distribution of the glucosylceramide synthase inhibitor miglustat in the rat

Miglustat (Zavesca) is a reversible inhibitor of glucosylceramide synthase, which catalyses the first step in the glucosylceramide biosynthetic pathway, and is approved for therapy in patients with type 1 Gaucher disease. The present report describes the pharmacokinetic profile of miglustat in the rat with a focus on tissue distribution. Experiments were performed with radiolabeled miglustat itself and with a perbutyrated prodrug, the latter being readily converted to miglustat during gastrointestinal absorption and first pass metabolism. Miglustat was well absorbed and exhibited an oral bioavailability of 40-60%. Tissue distribution studies indicated the presence of miglustat in a number of organs and tissues that are considered of importance for the long-term therapeutic benefit, in particular the central nervous system, bone and lung. Miglustat was eliminated via renal clearance by a combination of glomerular filtration and active secretion. Hepatic clearance was negligible, as was the role of metabolism in the overall elimination process of miglustat in the rat.

Gaucher disease: New developments in treatment and etiology

Gaucher disease (GD) is an autosomal recessive disease which if undiagnosed or diagnosed late results in devastating complications. Because of the heterozygous nature of GD, there is a wide spectrum of clinical presentation. Clinicians should be aware of this rare but potentially treatable disease in patients who present with unexplained organomegaly, anemia, massive splenomegaly, ascites and even cirrhosis of unknown origin. The treatment options for adult type GD include enzyme replacement treatment (ERT) and substrate reduction treatment (SRT) depending on the status of the patient. Future treatment options are gene therapy and “smart molecules” which provide specific cure and additional treatment options. In this review, we present the key issues about GD and new developments that gastroenterologists should be aware of.

Management of non-neuronopathic Gaucher disease with special reference to pregnancy, splenectomy, bisphosphonate therapy, use of biomarkers and bone disease monitoring

Enzyme replacement was introduced as treatment for non-neuronopathic Gaucher disease more than 15 years ago. To ensure the best use of this costly ultra-orphan agent, a systematic disease management approach has been proposed by an international panel; this includes the development, by consensus, of achievable treatment goals. Here we critically review these goals and monitoring guidelines and incorporate emerging experience of the disease in the therapeutic era, as well as contemporary clinical research. This review makes recommendations related specifically to the management of pregnancy; the appropriate use of splenectomy and bisphosphonate treatment; the relevance of biochemical markers to disease monitoring; and the use of semi-quantitative methods for assessing bone marrow infiltration. In addition, we identify key areas for development, including the requirement for a validated index of disease severity; the need to correlate widely used biomarkers with long-term disease outcomes, and the desirability of establishing agreed standards for monitoring of bone disease particularly in infants and children with Gaucher disease.

Improvement of bone disease by imiglucerase (Cerezyme) therapy in patients with skeletal manifestations of type 1 Gaucher disease: results of a 48-month longitudinal cohort study

Sims KB, Pastores GM, Weinreb NJ, Barranger J, Rosenbloom BE, Packman S, Kaplan P, Mankin H, Xavier R, Angell J, Fitzpatrick MA, Rosenthal D. Improvement of bone disease by imiglucerase (Cerezyme) therapy in patients with skeletal manifestations of type 1 Gaucher disease: results of a 48-month longitudinal cohort study. Clin Genet 2008: 73: 430–440. © Blackwell Munksgaard, 2008

Progressive skeletal disease accounts for some of the most debilitating complications of type 1 Gaucher disease. In this 48-month, prospective, non-randomized, open-label study of the effect of enzyme replacement therapy on bone response, 33 imiglucerase-naïve patients (median age 43 years with one or more skeletal manifestations such as osteopenia, history of bone crisis, or other documented bone pathology) received imiglucerase 60 U/kg/2 weeks. Substantial improvements were observed in bone pain (BP), bone crises (BC), and bone mineral density (BMD). Improvements in BP were observed at 3 months (p < 0.001 vs baseline) and continued progressively throughout the study, with 39% of patients reporting pain at 48 months vs 73% at baseline. Eleven of the 13 patients with a pre-treatment history of BC had no recurrences. Biochemical markers for bone formation increased; markers for bone resorption decreased. Steady improvement of spine and femoral neck BMD, measured using dual-energy X-ray absorptiometry was noted. Mean Z score for spine increased from −0.72 ± 1.302 at baseline to near-normal levels (−0.09 ± 1.503) by month 48 (p = 0.042) and for femoral neck from −0.59 ± 1.352 to −0.17 ± 1.206 (p = 0.035) at month 36. This increase was sustained at 48 months. With imiglucerase treatment, patients should anticipate resolution of BC, rapid improvement in BP, increases in BMD, and decreased skeletal complications.

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.

Outcome of enzyme replacement therapy in patients with Gaucher disease type I. The Romanian experience

AIM

This study reports the first evaluation of therapeutic response in Romanian patients with Gaucher disease type I, after therapy with Cerezyme recently became available in our country.

PATIENTS AND METHODS

24 patients (11-50 years) received Cerezyme 20-60 U/kg every two weeks for at least 18 months. Haemoglobin, platelet count, volume of the liver and spleen, plasma chitotriosidase and the severity score were assessed every 6 months; skeletal radiography and osteodensitometry were also monitored.

RESULTS

Eleven patients were splenectomized before start of therapy. Eight patients had anaemia (mean haemoglobin 9.4 g/dl) and 14 patients, of whom 13 were without splenectomy, had thrombocytopenia (mean 65,692/mm3). Haemoglobin values normalized after 6 months and the platelet count increased to 147,818/mm3 after 18 months of treatment. Splenomegaly improved (mean 13.8x to 5.6x normal), hepatomegaly improved (mean 1.4x to 1.06x normal), the severity score decreased (mean 15.9 to 8.4), plasma chitotriosidase levels showed a reduction from 40,956 to 11,266 nmol/h per ml plasma. Bone disease improved clinically in all patients; bone radiography and osteodensitometry showed no further disease progress. We observed a mean weight gain of 4.3 kg, an improvement in quality of life, and the absence of therapeutic adverse events.

CONCLUSIONS

Enzyme replacement therapy administered for 18 months in Romanian patients with Gaucher disease type I led to a marked improvement in haematological parameters and hepato- and splenomegaly. In the majority of patients we observed no further progress of bone disease; for an improvement in skeletal disease, a longer treatment period is required.

Recommendations for the management of the haematological and onco-haematological aspects of Gaucher disease

Current knowledge of the haematological and onco-haematological complications of type 1 Gaucher disease has been reviewed with the aim of identifying best clinical practice for treatment and disease management. It was concluded that: (i) Awareness of typical patterns of cytopenia can help clinicians distinguish haematological co-morbidities. (ii) Red blood cell studies and complete iron metabolism evaluation at baseline are recommended. (iii) Haemoglobin levels defining anaemia should be raised and used in Gaucher disease treatment and monitoring. (iv) Surgeons should be aware of potential bleeding complications during surgery in Gaucher patients. The higher incidence of multiple myeloma in Gaucher disease suggests that Gaucher patients should have their immunoglobulin profile determined at diagnosis and monitored every 2 years (patients <50 years) or every year (patients >50 years). If monoclonal gammopathy of undetermined significance (MGUS) is found, general MGUS guidelines should be followed. Future studies should focus on the utility of early treatment to prevent immunoglobulin abnormalities and multiple myeloma.

Evidence-based recommendations for monitoring bone disease and the response to enzyme replacement therapy in Gaucher patients

BACKGROUND

Bone disease is a serious complication of Gaucher disease. Untreated, it can result in pain, permanent bone damage and disability. Enzyme replacement therapy reverses many of the clinical signs of Gaucher bone disease but early assessment and treatment, and regular monitoring, are essential in optimising outcomes.

SCOPE

In September 2005, a group of European experts met to review current knowledge and identify best practice and unmet needs in the monitoring of Gaucher bone disease and the response to enzyme replacement therapy.

METHODS

Medline searches of peer-reviewed literature (no date restrictions) were conducted and supplemented by additional information considered relevant by panellists to furthering discussions.

FINDINGS AND CONCLUSIONS

The group's recommendations included: currently used biochemical bone markers are not clinically practical or reliable; plain X-rays should not be the sole method of assessing bone disease; MRI is the most sensitive method for monitoring bone marrow infiltration by Gaucher cells; semi-quantitative methods for assessing bone marrow infiltration in routine clinical practice should use readily available technology, include an assessment of Gaucher cell infiltration in the lumbar spine and femur, and be validated for inter-rater reliability and in comparison to other methods; a multidisciplinary approach is required for the treatment of Gaucher patients; all Gaucher patients should receive a comprehensive initial radiologic evaluation for bone disease and ongoing radiological monitoring at least once every 2 years.

Enzyme replacement therapy and bony changes in Egyptian paediatric Gaucher disease patients

BACKGROUND

In Gaucher disease, the infiltration of the bone marrow by glucocerebroside-laden macrophages (Gaucher cells) triggers a diverse pattern of skeletal disease that results in crippling complications. Reliable ascertainment of the severity and pattern of skeletal disease is essential to determine disease status and the response to enzyme replacement therapy (ERT). Although there is ample documentation of reversal of haematological and visceral disease by ERT, there is a paucity of data on skeletal response to ERT in children.

AIM

To delineate the pattern of bone disease in children with Gaucher disease in Egypt and to evaluate its response to ERT.

METHOD

Twenty-two children with Gaucher disease were treated with ERT. Phenotyping by clinical, laboratory and radiological criteria was performed at baseline and following 11.2 +/- 4 months of ERT. Genotyping for glucocerebrosidase (GBA) mutations was performed by gene sequencing, and genotype-phenotype correlations were performed.Results. Two-thirds of the patients were from consanguineous pedigrees and 14/22 patients were homozygous or compound heterozygous for L444P and D409H mutations. Bone involvement was detected by plain radiology in 11 children (50%) and in 16 (73%) by magnetic resonance imaging (MRI). There was no correlation of severity of bone involvement and GBA genotype. ERT ameliorated bone disease: 10 of the 11 children with abnormal radiographic findings at baseline showed improvement in skeletal lesions; while 9/16 showed improvement of marrow disease by MRI. Radiographic sensitivity and specificity were 62% and 82% compared to MRI for detection of bone involvement in this patient population. At baseline, bone pain was present in 5 patients and ERT resulted in complete symptomatic remission in all of them. ERT was associated with significant improvement in growth parameters and amelioration of haematological and visceral involvement.

CONCLUSION

Symptomatic and radiological skeletal disease is common in children with Gaucher disease in Egypt. MRI is the most accurate technique for detecting early skeletal involvement. There was no correlation between severity of skeletal involvement and GBA genotype. ERT was effective in ameliorating radiological manifestations of skeletal disease and achieving complete remission of bone pain.

Recombinant glucocerebrosidase uptake by Gaucher disease human osteoblast culture model

Bone lesions are a major cause of morbidity in Gaucher disease (GD) type I. Enzyme replacement therapy (ERT) has been successful in treating many symptoms of type I GD but skeletal response lags behind. Local exogenous glucocerebrosidase supplementation in bone lesions via a drug delivery system may overcome this limitation. Although local enzyme supplementation aims to target lipid-engorged macrophages (Gaucher Cells) in bone compartment, enzyme uptake by osteoblasts is not excluded. To investigate the ability of human osteoblasts to internalize recombinant glucocerebrosidase (rGCR), we have used an artificial GD human osteoblasts cell culture system. MG63 human osteoblasts were treated with conduritol B epoxide (CBE) to induce complete and prolonged inhibition of endogenous glucocerebrosidase activity of cells. rGCR uptake by glucocerebrosidase-inactivated osteoblasts was examined using (125)I-radiolabelling, Western blot analysis and measurement of glucocerebrosidase activity. Analysis of radiolabeled enzyme uptake by CBE treated osteoblasts showed 67.9% of internalized protein in cell extract. Enzyme internalization was also observed by Western blot analysis where the amount of mature form of glucocerebrosidase protein recognized by the glucocerebrosidase antibody was increased following the administrations of rGCR. Moreover, enzymatic activity measurement showed 23.9% of glucocerebrosidase activity of control cells. The rGCR internalization by MG63 osteoblast seems to be partially mediated by mannose receptors. These data provide evidence that MG63 human osteoblasts are able to internalize rGCR.

Improved intracellular delivery of glucocerebrosidase mediated by the HIV-1 TAT protein transduction domain

Enzyme replacement therapy (ERT) for Gaucher disease designed to target glucocerebrosidase (GC) to macrophages via mannose-specific endocytosis is very effective in reversing hepatosplenomegaly, and normalizing hematologic parameters but is less effective in improving bone and lung involvement and ineffective in brain. Recombinant GCs containing an in-frame fusion to the HIV-1 trans-activator protein transduction domain (TAT) were expressed in eukaryotic cells in order to obtain active, normally glycosylated GC fusion proteins for enzyme uptake studies. Despite the absence of mannose-specific endocytic receptors on the plasma membranes of various fibroblasts, the recombinant GCs with C-terminal TAT fusions were readily internalized by these cells. Immunofluorescent confocal microscopy demonstrated the recombinant TAT-fusion proteins with a mixed endosomal and lysosomal localization. Thus, TAT-modified GCs represent a novel strategy for a new generation of therapeutic enzymes for ERT for Gaucher disease.

Haemorheology in Gaucher disease

In Gaucher disease, a deficiency of glucocerebrosidase results in the accumulation of glucocerebroside within the lysosomes of the monocyte-macrophage system. Prior to the availability of enzyme replacement therapy (ERT), splenectomy was often indicated for hypersplenism. Haemorheological abnormalities could be expected in view of the anaemia and abnormal lipid metabolism in these patients and the role of the spleen in controlling erythrocyte quality.

OBJECTIVES

To investigate the effect of Gaucher disease on blood and plasma viscosity, erythrocyte aggregation and erythrocyte deformability, and to determine whether observed rheological differences could be attributed to splenectomy.

METHODS

Haematological and haemorheological measurements were made on blood collected from 26 spleen-intact patients with Gaucher disease, 16 splenectomised patients with Gaucher disease, 6 otherwise healthy asplenic non-Gaucher disease subjects and 15 healthy controls.

RESULTS

No haemorheological differences could be demonstrated between spleen-intact patients with Gaucher disease and the control group. Compared to controls, both asplenic Gaucher disease and asplenic non-Gaucher disease study groups had a reduced MCHC (P = 0.003 and 0.005, respectively) and increased whole blood viscosity at 45% haematocrit (Hct), relative viscosity and red cell aggregation index - all measured at low shear (P < 0.05 for all). Additionally, asplenic patients with Gaucher disease alone showed an increased MCV (P = 0.006), an increased whole blood viscosity at 45% Hct measured at high shear (P = 0.019), and a reduced relative filtration rate (P = 0.0001), compared to controls.

CONCLUSION

These observations demonstrate a direct and measurable haemorheological abnormality in Gaucher disease only revealed when there is no functioning spleen to control erythrocyte quality.

Gaucher disease: pathological mechanisms and modern management

Gaucher disease, the most common lysosomal storage disorder, is caused by the defective activity of the lysosomal enzyme, acid-beta-glucosidase (GlcCerase), leading to accumulation of glucosylceramide (GlcCer), particularly in cells of the macrophage lineage. Nearly 200 mutations in GlcCerase have been described, but for the most part, genotype-phenotype correlations are weak, and little is known about the down-stream biochemical changes that occur upon GlcCer accumulation that result in cell and tissue dysfunction. In contrast, the clinical course of Gaucher disease has been well described, and at least one treatment is available, namely enzyme replacement therapy. One other treatment, substrate reduction therapy, has recently been marketed, and others are in early stages of development. This review, after discussing pathological mechanisms, evaluates the advantages and disadvantages of existing therapies.

Gaucher disease and bone: laboratory and skeletal mineral density variations during a long period of enzyme replacement therapy

The usefulness of bone turnover markers in Gaucher disease is still unclear and their utility in monitoring the effects of enzyme replacement therapy (ERT) on bone metabolism has not yet been investigated exhaustively. Skeletal involvement seems to improve slowly during ERT, but only a few studies evaluating bone mineral density (BMD) changes during a long follow-up period have been reported. The aim of this study was to assess the efficacy of ERT on bone involvement in a group of 12 type I Gaucher disease (GD I) patients by monitoring biochemical indices of bone resorption/formation and BMD measured by dual energy x-ray absorptiometry (DEXA). Serum (calcium, phosphorus, bone alkaline phosphatase isoenzyme, carboxyterminal propeptide of type I procollagen (PICP), carboxyterminal telopeptide of type I collagen (ICTP), osteocalcin, intact parathyroid hormone) and urinary (calcium, phosphorus, hydroxyproline and free deoxypyridinoline) markers of bone metabolism and lumbar BMD were measured at baseline, after 6 and 12 months, and then every year for a mean ERT follow-up period of 4.5 years (range 4.4-6 years). Twelve healthy adult subjects matched for age and sex were tested as negative controls. A significant decrease of PICP was detected in the patient group at baseline (mean value 100.52 ng/ml vs 142.45 ng/ml, p = 0.017), while ICTP was remarkably higher: mean value 3.93 ng/ml vs 2.72 ng/ml, p = 0.004 (two-sided Student's t-test). No changes in bone formation indices were observed during the follow-up period, while urinary calcium excretion increased significantly from 0.065 to 0.191 mg/mg creatinine (p = 0.0014) (repeated measures ANOVA). A significant BMD improvement was also detected after an average ERT period of 4.5 years: Z-score increased from -0.81 to -0.56 (p = 0.005) (two-sided Student's t-test). These data evidenced the ineffectiveness of the biochemical markers used in monitoring ERT efficacy in GD I skeletal involvement, whereas DEXA was demonstrated to be a reliable method with which to follow up BMD improvement.

Enzyme replacement therapy reduces Gaucher cell burden but may accelerate osteopenia in patients with type I disease - a histological study

Enzyme replacement treatment (ERT) is effective in controlling the clinical and biochemical manifestation of type I Gaucher disease. Little is known on the evolution of bone marrow histology caused by ERT. We compared the pretreatment trephine bone marrow biopsies in five patients (F32, F41, F50, M55, and M46) with the control biopsies performed after 26-32 months of imiglucerase treatment. The planimetric estimates revealed significant decrease in Gaucher cell burden in all the patients. The post-ERT values ranged from 24% to 65% of the initial total volumes occupied by the Gaucher cells. This resulted mainly from disappearance of Gaucher cells, and to a lesser extent from their shrinkage. Normal hemopoiesis was markedly increased in four of five patients, fat tissue in all the five patients. Surprisingly, the estimated volumes of trabecular bone in the control biopsies were significantly smaller than in the pre-ERT trephines (0.61%, 0.64%, 0.64%, 0.97%, and 0.22% of the initial volumes, P = 0.043). The bone loss correlated rather with the degree of reconstitution of normal hemopoiesis than with the decrease in the Gaucher cell burden. The histological response did not correlate strictly with initial clinical parameters and the genotype, with different reactions to ERT in two sibs (cases 3 and 4). Particularly, ERT alleviated bone manifestations in all four patients with previous bone pains or fractures. ERT may accelerate progress of osteopenia in men and premenopausal women. The clinical significance of this phenomenon remains to be established. Its mechanism may be linked to increased osteolytic activity exerted directly or indirectly by regenerating hemopoietic cells.