PTPN11 and juvenile myelomonocytic leukemia: JMML is a myeloproliferative disorder characterized by excessive proliferation of myelomonocytic cells, and somatic PTPN11 variants have been identified in 34% of JMML cases as well as in a small percentage of myelodysplastic syndrome, acute myeloid leukemia, and acute lymphoblastic leukemia cases in patients without NS (Tartaglia et al., 2003; Loh, 2004; Tartaglia, 2004).