Since PV patients can be characterized by an abnormal increase in the number of three types of blood cells – erythrocytes, granulocytes, and platelets [14] – the model for PV should involve hematopoietic transcription factors such as GATA-1, GATA-2 [15,16], C/EBPε and Fli-1 [17,18] that correspond to each lineage. This evidence concerns the gene CEBPE and acquired polycythemia vera.