Different criteria of Hb and Ht have been published for the diagnosis of erythrocytosis, with the consensus that Hb > 185 g/L and Ht > 0.52 in men and Hb > 165 g/L and Ht > 0.48 in women in at least two separate blood counts at 2 months apart requires further investigations (Patnaik and Tefferi, 2009; Keohane et al., 2013; McMullin, 2014, 2016; Bento, 2018). The gene discussed is GSTM1; the disease is polycythemia.