Comparison of MDS/MPN-RS-T (n = 158) and MDS/MPN-U with BM RS ≥ 15% (MDS/MPN-U-RS; n = 25) did not reveal significant differences in frequency of thrombosis, OS, or LFS, although SF3B1 mutation frequency was higher in the former (93% versus 59%; P = 0.0005). The gene discussed is SF3B1; the disease is myelodysplastic syndrome.