Guglielmelli P, Coltro G, Mannelli F, Rotunno G, Loscocco GG, Mannarelli C, et al. ASXL1 mutations are prognostically significant in primary myelofibrosis, but not myelofibrosis following essential thrombocythemia or polycythemia vera. This evidence concerns the gene ASXL1 and myelofibrosis.