The V617F mutation of the JAK2 gene was discovered in 2005 [3], and subsequently mutations of the thrombopoetin receptor gene (MPL) [4,5]; mutations of the JAK2 exon-12 [6]; and, finally, mutations of the calreticulin gene (CALR) [6] were demonstrated to be associated with MPN pathogenesis in 2006, 2007, and 2013, respectively. The gene discussed is CALR; the disease is myeloproliferative disorder.