An estimated 40% of BCS patients and 28% of PVT patients without an MPN diagnosis carry the JAK2 V617F gene mutation [11], while 71–100% of patients with overt MPN and SVT test positive for JAK2 V617F, which is significantly higher than the JAK2 positivity reported for other VTEs within the course of MPN [33]. This evidence concerns the gene JAK2 and myeloproliferative disorder.