JAK2 and deep vein thrombosis: In PV patients, the JAK2 variant allele frequency (VAF) is highly heterogeneous at diagnosis, with median value around 50%, and correlates with some phenotypic traits; in a previous study a VAF > 75% was associated with higher rate of thrombotic events after diagnosis [10], and a recent study including a large cohort of Chinese patients reported a 4.6 times higher incidence of thrombosis in PV patients with JAK2V617F VAF ≥ 50% [11].