- The JAK2 V617F activating tyrosine kinase mutation is an infrequent event in both "atypical" myeloproliferative disorders and myelodysplastic syndromes. Steensma, D.P., Dewald, G.W., Lasho, T.L., Powell, H.L., McClure, R.F., Levine, R.L., Gilliland, D.G., Tefferi, A. Blood (2005)