In a survey of 172 RUNX1mut AML cases, the activating mutation JAK2V617F occurred more frequently in germline RUNX1 AML cases compared with sporadic RUNX1 AML cases, and activating mutations in MPL and inactivating mutations in the JAK2 inhibitor SH2B3 (encoding the LNK protein) occurred solely in germline RUNX1mut AML (18). The gene discussed is JAK2; the disease is acute myeloid leukemia.