Recent research has shown that functional deletion mutations in LNK, an important hematopoietic suppressor gene, lead to a > 10-fold increase in hematopoietic stem cell numbers owing to superior hematopoietic stem cell self-renewal [6] and gives rise to myeloproliferative neoplasms characterized by platelet and leukocyte overproduction [7]. The gene discussed is SH2B3; the disease is myeloproliferative neoplasm.