To unify the definition and diagnostic criteria of CMS, the Sixth World Congress on Mountain Medicine and High Altitude Physiology redefined CMS as excessive erythrocytosis (Hb ≥ 190 g/L in female patients; Hb ≥ 210 g/L in male patients), severe hypoxemia, and, in some cases, moderate to severe pulmonary hypertension [9], and a quantitative CMS diagnostic criterion - the CMS score, based on symptoms and the Hb concentration, was also proposed and approved by the International CMS Consensus Working Group [9]. The gene discussed is GSTM1; the disease is pulmonary arterial hypertension.