Abstract

Background: Bleeding diathesis is a common manifestation of Gaucher disease, usually attributed to thrombocytopenia due to hypersplenism and bone marrow infiltration by Gaucher cells. Hemorrhagic manifestations are not restricted to thrombocytopenic patients, and other mechanisms, e.g. platelet function defect, manifested in abnormal aggregation, have also been implicated.

Aim: to evaluate platelet adhesion properties in Gaucher patients.

Methods: Platelet function was studied in 44 Gaucher patients with a platelet count of ≥130×109/L, using a novel method for quantitative analysis of whole blood platelet interaction with immobilized plasma ligands under flow conditions, the Impact-R [Cone and Plate(let) analyzer] test. The results were compared to platelet function of 51 obligatory Gaucher carriers, 20 healthy volunteers and 5 transgenic Gaucher mice. Platelet’s glucocerebrosidase function was tested in platelet’s extract by incubation with C6-NBD-glucosylceramide, and by testing the fluorescence intensity of the end product, C6-NBD-ceramide.

Results: Adhesion defect, manifested by surface coverage (SC) < 7.0%, was found in 70.4% of the patients (SC 5.1%±3.1), in 41.2% of the Gaucher carriers (SC 7.7%±2.8) and only in 20% of the control group (SC 8.7%±3.2, P=0.0007 and 0.09, respectively). This defect was independent of platelet count, or hematocrit. Further support for this observation was found in transgenic Gaucher mice, who also had low platelet adhesion compared to wild type mice (SC of 2.7%±0.6 vs. 12.5%±2.9, respectively). Average size of platelet aggregates was lower in Gaucher patients with bleeding tendency, compared to those with no bleeding history (23.5 μm2±12 and 29.2±10, p=0.026). A trend for lower SC in bleeders vs. non bleeders was also found (4.3±3.7 vs. 6.4±3.9, p=0.069). No difference was found in platelet counts between bleeder and non-bleeders (p=0.13). Surface coverage was higher in splenectomized patients and in patients receiving enzyme replacement therapy. Highest SC was observed in patients under both treatment modalities, SC= 8±4.6, compared to those treated with one modality, 4.9±3.7, and untreated ones, 3.3±2.3 (p=0.01). These differences were independent of platelet count. In order to elucidate the potential role of glucoceramide in the adhesion defect, we tested platelet’s glucocerebrozidase function in patients and controls. The specific activity thus calculated in 5 mildly thrombocytopenic Gaucher patients was 0.02–0.08 pmol/min/μgr protein compared to specific activity of 0.14-0.15 pmol/min/μg protein in platelet homogenate of 3 healthy volunteers.

Conclusions: platelet adhesion defect is common in Gaucher disease, which may account for bleeding events in some patients with normal platelet count. Accumulation of glucoceramide in Gaucher platelets may be responsible for this defect. Further studies into the potential role of the stored material in the adhesion defect and bleeding phenomena in Gaucher is warranted.

Disclosures: David Varon is a founder of Matis-Medical Inc developing the CPA technology.; This study was supported in part by DiaMed Switzerland.

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