GSTM1 and chronic mountain sickness: Chronic mountain sickness is a maladaptive syndrome secondary to excessive erythrocytosis (EE), defined by an international consensus as a [Hb] of ≥21 g dL−1 in men and ≥19 g dL−1 in women (León‐Velarde et al., 2005) and including symptoms such as breathlessness, palpitations, sleep disturbance, cyanosis, dilatation of veins, paraesthesia, headache and tinnitus, although the exact pathophysiological mechanisms underlying EE and CMS symptoms remain unclear (Stauffer et al., 2020).