U2AF1 (U2 small nuclear RNA auxiliary factor—chromosome 21q22) mutations are seen in ~10% of patients with CMML and have thus far lacked an independent prognostic effect.60 The mutational hot spots for U2AF1 include S34F, Q157 and R158H.16ZRSR2 mutations (zinc finger, RNA-binding motif and serine/arginine-rich factor—chromosome Xp22.2) are very infrequent and once again do not have an independent prognostic impact.60 Here, U2AF1 is linked to chronic myelomonocytic leukemia.