In general, HMMs are classified into three groups (Table 1), namely (1) myeloid neoplasms with germline predisposition and pre-existing platelet disorder (RUNX1, ANKRD26, and ETV6), (2) myeloid neoplasms with germline predisposition and potential organ dysfunction (GATA2, SAMD9, SAMD9L, etc.), and (3) myeloid neoplasms with germline predisposition without a preexisting platelet disorder or organ dysfunction (CEBPA and DDX41). The gene discussed is RUNX1; the disease is myeloid neoplasm.