The Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) are a group of chronic, clonal stem-cell disorders characterized by increased production of mature blood cells. MPNs include polycythemia vera (PV) with increased red blood cells count and often elevated leucocyte and platelet counts, essential thrombocythemia (ET) with increased platelet count and in some patients also slightly elevated leucocyte count and primary myelofibrosis (PMF), subdivided into prefibrotic myelofibrosis (PreMF) and classic primary myelofibrosis with overt bone marrow fibrosis. 1 The majority of patients with MPNs, particularly those with PV (98%), presents with the JAK2V617F mutation in the Janus kinase 2 gene (JAK2), which causes constitutive signalling of various cytokine receptors. [2][3][4] Other phenotypic driver mutations in the calreticulin (CALR) and thrombopoietin receptor (MPL) genes are found in 25%-30% of patients with ET and 5%-10% of patients with PMF. [5][6][7][8] Thrombotic events represent the most frequent complication, especially in ET and PV, and may occur years before the diagnosis of MPNs and particularly within the first 3 months after diagnosis. 9-11 Among the most prominent risk factors for thrombosis in ET and PV are age above 60 years and a previous thrombosis. 12