JAK2 and acquired polycythemia vera: World Health Organization 2016 diagnostic laboratory criteria for PV requires that a Hb level of 165 g/L in men and 160 g/L for women or a HCT value of 49% in men and 48% in women and a characteristic JAK2/V617F mutation or JAK2 exon 12 mutation.[9] Nevertheless, in some patients who are eventually diagnosed with PV, the Hb and PLT counts may show a normal-to-borderline increases at the onset of acute stroke, then followed by gradual increase.[10] The patient in our case had no medical history prior to this hospitalization, including a history of atherosclerosis.