U2AF1 and essential thrombocythemia: Conversely, MIPSS-ET included male sex; age >60 years; leukocyte count ≥11 × 109/L; and the presence of mutations in SRSF2, SF3B1, U2AF1, or TP53. A recent sub-analysis of the ET cohort included in the MIPSS-ET demonstrated that ASXL1/RUNX1/EZH2 mutations were associated with a decreased risk of arterial thrombosis, suggesting a different underlying biology [96].