SHP2 is involved in the regulationof multiple cell processes, including proliferation, survival, differentiation,and migration, and its functional upregulation contributes to oncogenesisand underlies developmental disorders.1 Somatically acquired, gain of function mutations in PTPN11 are the major cause of juvenile myelomonocytic leukemia (JMML),3 a rare and aggressive myelodysplastic/myeloproliferativedisorder of early childhood with a very poor prognosis, for whichno drugs are presently available. Here, PTPN11 is linked to juvenile myelomonocytic leukemia.