Conversely, expression of leukemogenic alleles of Ptpn11, such as Ptpn11D61Y[7] or Ptpn11E76K[8], in the hematopoietic compartment results in a fatal myeloproliferative neoplasm (MPN), featuring leukocytosis, anemia and hepatosplenomegaly. This evidence concerns the gene PTPN11 and myeloproliferative neoplasm.