GSTM1 and chronic mountain sickness: Patients with chronic mountain sickness (CMS) or Monge’s disease (Monge 1942; Monge and Whittembury 1976) develop severe polycythemia, in which a hemoglobin concentration [Hb] of > 21 g/dl in men and > 19 g/dl in women is considered typical (Vasquez and Villena 2001; Leon-Velarde et al., 2005; Villafuerte and Corante 2016).