JAK2 and Splenomegaly: In the entire cohort, in univariate analysis, JAK2 mutation (HR:2.3, 95% CI: 1.2–4.8, p = 0.026), elevated WBC count (>11 × 109/L) (HR: 2.1, 95% CI: 1.1–4.3, p = 0.043) and absence of splenomegaly at diagnosis (HR: 3.3, 95% CI: 1.0–11.0, p = 0.053) were associated with increased risk of thrombosis.