Coexisting JAK2V617F and CALR Exon 9 Mutation in Essential Thrombocythemia

Classic "BCR-ABL1-negative" MPN is an operational sub-category of MPN that includes polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) harboring JAK2V617F as the most common mutation. JAK2V617F can be detected in about 95 % of patients with PV while remaining 5 % of PV patients carry a somatic mutation of JAK2 exon 12. Approximately one-third of patients with ET or PMF do not carry any mutation in JAK2 or MPL. In December 2013, mutations were described in calreticulin (CALR) gene in 67-71 and 56-88 % of JAK2V617F and MPL negative patients with ET and PMF, respectively. Since this discovery CALR mutations have been reported to be mutually exclusive with JAK2V617F or MPL mutations. However recently few studies (eleven published reports) reported the coexistence of JAK2V617F and CALR in MPN. In the present study we are reporting JAK2V617F positive ET patient from our center with coexisting CALR exon 9 mutation type c.1214_1225del12 (p.E405_D408del) that was never reported before as a coexisting mutation and describing in detail the clinical outcomes.