JAK2 and essential thrombocythemia: Last but not least, the chronic myeloid stimulation hypothesis allows for many different initial causes and thus would explain why the JAK2-V617F mutation and to a lesser degree the MPL exon 10 and CALR exon 9 mutations are associated with very different diseases (ET, PV, PMF, RARS-T, and splanchnic thrombosis for JAK2-V617F; ET, PMF, and RARS-T for MPL and CALR mutations).