EPO and Increased total leukocyte count: JAK2V617F activates erythropoietin (EPO), thrombopoietin (TPO), and granulocyte-colony stimulating factor (G-CSF) receptors in the absence of ligands, whereas exon-12 mutations activate the EPO receptor, resulting in erythroid-dominant myeloproliferation and reduced leukocytosis and thrombocytosis [10].