In a large (879 patients) PMF collaborative study, ASXL1 mutations were identified in 20% of patients and were associated with older age, presence of constitutional symptoms, leukocytosis and circulating blasts.52 In systemic mastocytosis, ASXL1 mutations were seen in 9 (14%) of 62 patients and predicted for a shortened OS.53 In AML, ASXL1 mutations have been found to be mutually exclusive with the favorable NPM1 mutations, with some,54, 55 but not all,56 studies demonstrating an independent prognostic impact. The gene discussed is ASXL1; the disease is acute myeloid leukemia.