ID1 and myeloproliferative disorder: Id1-overexpressing mice died roughly one year after BMT compared to control mice, and sick mice showed 1) myeloid/erythroid cell hyperplasia and increased numbers of immature cells in the BM, 2) splenomegaly and extramedullary hematopoiesis, and 3) peripheral blood monocytosis, indicating that these mice succumbed to a MPN that did not progress to AML (39).