Domain structure of JAK2 with an outline of associated mutations. AML, acute myeloid leukemia; CEL, chronic eosinophilic leukemia; DS-B-ALL, Down syndrome–associated B-ALL; ET, essential thrombocythemia; HL, Hodgkin lymphoma; MPN, myeloproliferative neoplasm; PMF, primary myelofibrosis; RARS-T, refractory anemia with ring sideroblasts and thrombocytosis.