ASXL1 and myeloproliferative neoplasm: ASXL1 (additional sex combs like 1) is a gene that is mutated in a number of hematological neoplasms including Myelodysplastic Syndrome (MDS), Acute Myeloid Leukemia (AML), Myeloproliferative Neoplasms (MPN), Chronic Myelomonocytic Leukemia (CMML) and Chronic Myeloid Leukemia (CML).