KRAS and Splenomegaly: The expression of KRAS A146T in hematopoietic stem cells led to a myelodysplastic syndrome/myeloproliferative neoplasm with a delayed onset compared to mice expressing KRAS G12D in the same cells, and these animals died with severe anemia and splenomegaly at an older age than KRAS G12D-expressing mice (61).