Deciphering the individual contribution of absolute neutrophil and monocyte counts to thrombosis risk in polycythemia vera and essential thrombocythemia

In addition to its adverse effect on survival and leukemic transforma-tion, in both polycythemia vera (PV) and essential thrombocythemia(ET), leukocytosis has been implicated as a risk factor for thrombosis,in both of these myeloproliferative neoplasms (MPNs).1Recent stud-ies have underscored anatomical and biologic differences as well ascommon traits between arterial (AT) and venous (VTE) thrombosis.Consequently, different sets of risk factors for AT versus VTE in PVversus ET, have been promoted; in PV, these include prior AT event,hypertension, and hyperlipidemia, for AT, and prior venous event,older age, major hemorrhage, and leukocytosis, for VTE2,3; in ET, thecorresponding variables for AT include prior AT event, age > 60 years,cardiovascular risk factors, presence ofJAK2V617F, and leukocytosisand, for VTE, male gender.