Phenotypically related to pCMML, juvenile myelomonocytic leukemia (JMML) is a pediatric neoplasm often initiated by germline (CBL, NF1, PTPN11) or somatic (NRAS, KRAS, CBL, RRAS) RAS-activating mutations and is described as a bona fide RASopathy26,27. The gene discussed is PTPN11; the disease is juvenile myelomonocytic leukemia.