<prompt> Answer this question truthfullyWhat is the definition of myelomonocytic leukemia in young individuals?  <response>: <reason> About 80 of JMML patients have some sort of genetic abnormality in their leukemia cells that can be identified with laboratory testing. This includes:15-20 of patients with neurofibromatosis 1 NF1 25 of patients with mutations in one of the RAS family of oncogenes only in their leukemia cells Another 35 of patients with a mutation in a gene called PTPN11 again, only in their leukemia cells. 