GSTM1 and acquired polycythemia vera: According to the revised World Health Organization (WHO) classification of myeloid neoplasms from 2016, there are clear diagnostic criteria for PV, including haemoglobin (Hb) > 16.5 g/dL in men and Hb > 16 g/dL in women, or haematocrit (Hct) > 49% in men and Hct > 48% in women, or red blood cell (RBC) mass > 25% above mean normal predicted value [1].