Mutations of SHP2 have also been linked to various childhood leukaemia including juvenile myelomonocytic leukaemia (JMML) and acute myelogenous leukaemia (AML), making SHP2 the first proto-oncogene identified in the protein tyrosine phosphatase family (reviewed in [11], [13]). The gene discussed is PTPN11; the disease is juvenile myelomonocytic leukemia.