Myeloproliferative Disorders Are Associated with an Increase in Levels of Prothrombotic and Inflammatory Markers Despite Cytoreductive Therapy.

Thrombotic complications are frequent in patients with Essential Thrombocythaemia (ET) and Polycythaemia Vera (PV). A raised haematocrit and thrombocytosis have been implicated in the pathogenesis but events still occur on treatment. We hypothesized that there was a role for other prothrombotic and inflammatory pathways in the aetiology of thrombosis in MPD, and so assessed these parameters in 101 patients and 51 controls. Assays and results are listed in table below. Standard methods of thromboelastography, flow cytometry, RVVT assays and ELISAs were used. 72 ET and 29 PV patients were included: median age 58 years (range17–89), disease duration 84 months (range 2–384) and platelet counts 473 × 10⁹/l (range 207–1780). 59 (58%) patients had the JAK2 V617F mutation. 51 (50%) had thrombosis with 23 patients developing the events post-diagnosis. 82 (81%) patients were receiving anti-platelet agents and 76 (75%) cytoreductive therapy. Comparison with clinical features revealed V617F positive patients to be older with significantly higher haemoglobin and PCV and greater levels of E-selectin and C3a, contrary to the higher platelet activation recently shown by Arellano-Rodrigo (2006). The only parameters that correlated with previous thrombosis were older age, longer disease duration and increased CD63 levels +/− ADP stimulation. Cytoreductive therapy was associated with lower levels of VEGF (p=0.01) but no other parameters. In conclusion, assessment of haemostatic, endothelial, complement, angiogenic and inflammatory markers shows evidence of increased activation in patients with MPD. Of these parameters, only the angiogenic marker was reduced by cytoreductive therapy and none appear to be associated with the risk of thrombosis.