Monocytic and myelomonocytic AML subtypes as defined by the French-American-British (FAB) classification (AML M4 and M5) and patients with FLT3-ITD mutations, and abnormalities involving the MLL gene on 11q23 have been identified as risk factors for hyperleukocytosis [5,15,16,17]. The gene discussed is KMT2A; the disease is acute myeloid leukemia.