Barbui and Tefferi [11] proposed revising WHO diagnostic criteria for PV and adopted by WHO in 2016 [12] as follows: 1) increased RCM, and/or Hb>16.5 g in men, >16 g in women or Hct>49% in men, >48% in women; 2) BM morphology consistent with WHO criteria; and 3) presence of JAK2 mutation; minor criterion: serum EPO levels. Here, EPO is linked to acquired polycythemia vera.