JAK2 and acquired polycythemia vera: Mutations other than JAK2 were frequently observed in resistant patients, which were reclassified as PV with TP53 disruption/aneuploidy (16.4%), PV with spliceosome/chromatin mutations (37.7%), PV with homozygous JAK2 mutation (27.9%), and PV with heterozygous JAK2 mutation (16.4%), whereas the corresponding figures in controls were 1.7%, 11.9%, 44%, and 41%, respectively (p < 0.0001, Supplemental Table 2).