The relation of constitutive EPOR activation with erythroleukemia pathogenesis was introduced early during the 1990s, as the erythroblastosis-inducing spleen focus-forming virus (SFFV) was found to activate EPOR [23], while activating point mutations of the EPOR also promoted tumorigenesis [24]. The gene discussed is EPOR; the disease is erythroleukemia.