Although the Janus family of kinases (JAK1, JAK2, JAK3, and TYK2) has been extensively characterized and investigated, the role of Janus kinase activation in the pathogenesis and therapy of human malignancies was not fully appreciated until recently when multiple studies identified a recurrent somatic mutation in the JAK2 tyrosine kinase (JAK2V617F) in the majority of patients with BCR-ABL-negative myeloproliferative neoplasms (MPN), polycythemia vera, essential thrombocytosis, and primary myelofibrosis.
The recent discovery of the new mutation affecting the Janus tyrosine kinase 2 (JAK2V617F), more frequently observed in patients with polycythemia vera, is seen in approximately 35% to 57% of patients with CIMF.