CALR and myeloproliferative disorder: It was not until 2005 that technological advances in DNA sequencing led to the discovery of the JAK2V617F mutation [3,4,5,6], the most frequent driver mutation in MPN, followed by the identification of additional driver mutations in exon 12 of JAK2 [7], the thrombopoietin receptor MPL [8,9] and calreticulin (CALR) genes [10,11].