Given the persistence of splenomegaly, absolute monocyte counts of 2280/mmc, 9% blasts, PTPN11 mutation, monosomy 7, circulating myeloid precursors, and WBC 16,300/mmc, a diagnosis of JMML was made, and bone marrow transplant was considered as the treatment of choice. Here, PTPN11 is linked to juvenile myelomonocytic leukemia.