Following the description of the JAK2V617F mutation [2, 3], additional somatic driver mutations were discovered in JAK2 wild-type patients, including JAK2 exon12 mutations in PV [4] and thrombopoietin receptor (MPL) [5, 6] and calreticulin (CALR) mutations in ET and PMF [7, 8]. Here, JAK2 is linked to acquired polycythemia vera.