JAK2 and acquired polycythemia vera: In contrast to a 1993 report in which polycythemia vera (PV) was not confirmed by testing for JAK2 (V617F and exon 12) mutations, [9] recent studies have shown that secondary polycythemia and PV have similar rates of thromboembolism, [10] suggesting that secondary polycythemia also warrants intervention to reduce the risk of thrombosis in this cohort.