Chronic mountain sickness (CMS) is a disease that can develop during extended time living at a high altitude. It is also known as "Monge's disease", after its first description in 1925 by Carlos Monge. While acute mountain sickness is experienced shortly after ascent to high altitude, chronic mountain sickness may develop after many years of living at high altitude. In medicine, high altitude is defined as over 2500 metres (8200 ft), but most cases of CMS occur at over 3000 m (10000 ft). Recently it has been correlated with increased expression of the genes ANP32D and SENP1.