JAK2 and myelodysplastic syndrome: These predilections are unsurprising, since these mutations are defining features of the associated malignancies: for example, SF3B1 mutations are characteristic of the MDS subtype refractory anemia with ring sideroblasts (RARS), whereas mutations occurring in JAK2, CALR, and MPL are MPN-defining mutations (84, 86, 87, 90, 91, 100, 101, 113, 146, 147).