JAK2V617F allele burden is associated with thrombotic mechanisms activation in polycythemia vera and essential thrombocythemia patients.

The clinical courses of polycythemia vera (PV) and essential thrombocythemia (ET) are characterized by thrombohemorrhagic diathesis. Several groups have suggested an association between JAK2V617F mutation and thrombosis. We hypothesized a relationship between JAK2V617F allele burden, cellular activation parameters, and thrombosis. We evaluated a group of PV and ET patients using flow cytometry: platelet CD62P, CD63, and dense granules, platelet-leukocyte aggregates (PLA), leukocyte CD11b and monocyte tissue factor (TF) expression. All patients had increased baseline platelet CD62P and CD63 expression (p < 0.05); 71 % of PV and 47 % of ET presented with a storage pool disease. Leukocyte CD11b, TF, and PLA were elevated in all patients. TF was higher in PV compared to ET (p < 0.05) and platelet-neutrophil [polymorphonuclear (PMN)] aggregates were increased in ET versus PV (p < 0.05). In ET, PLA were correlated with platelet numbers (p < 0.05). In all patients, JAK2V617F allele burden was directly correlated with monocyte CD11b. Patients with JAK2V617F allele burden >50 % presented higher levels of leukocyte activation. In ET, thrombosis was associated with JAK2V617F mutation (p < 0.05, χ (2) = 5.2), increased monocyte CD11b (p < 0.05) and with platelet-PMN aggregates (p < 0.05). In ET patients, hydroxyurea does not significantly reduce the activation parameters. Our data demonstrate that JAK2V617F allele burden is directly correlated with activation parameters that drive mechanisms that favor thrombosis.