Somatic translocations and mutations of RUNX1 are causative of haematological diseases such as myelodysplastic syndrome, acute myeloid leukaemia, acute lymphoblastic leukaemia, chronic myelomonocytic leukaemia and acute megakaryoblastic leukaemia with familial platelet disorder. The gene discussed is RUNX1; the disease is chronic myelomonocytic leukemia.