Chronic mountain sickness (CMS) is a disease that can develop during extended time living at altitude. It is also known as 'Monge’s disease' , after its first description in 1925 by Carlos Monge Medrano^[1]. The acute form of mountain or altitude sickness is acute mountain sickness, and is experienced shortly after ascent to high altutude by those unacclimatised to such altitudes. In contrast, chronic mountain sickness may develop after many years of living at high altitude. In medicine, high altitude is defined as over 2500 metres, but most cases of CMS occur at over 3000 m. Altitude sickness, also known as acute mountain sickness (AMS) or altitude illness is a pathological condition that is caused by lack of adaptation to high altitudes. ...

CMS is characterised by polycythaemia (increased haematocrit) and hypoxaemia which both decrease on descent from altitude. CMS is believed to arise because of an excessive production of red blood cells, which increases the oxygen carrying capacity of the blood ^[2] but may cause increased blood viscosity and uneven blood flow through the lungs (V/Q mismatch). However, CMS is also considered an adaptation of pulmonary and heart disease to life under chronic hypoxia at altitude.^[3] Polycythemia is a condition in which there is a net increase in the total circulating erythrocyte (red blood cell) mass of the body. ... The hematocrit (Ht) or packed cell volume (PCV) is the proportion of blood that is occupied by red blood cells. ... Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. ...

The most frequent symptoms and signs of CMS are headache, dizziness, tinnitus, breathlessness, palpitations, sleep disturbance, fatigue, anorexia, mental confusion, cyanosis, and dilation of veins.^[4] Tinnitus (ti-NIGHT-us or TIN-i-tus[1]) is the perception of sound in the absence of a corresponding external sound. ... A palpitation is an abnormal, rapid beating of the heart, brought on by overexertion, disease or drugs. ... Anorexia (deriving from the Greek α(ν)- (a(n)-, a prefix that denotes absence) + όρεξη (orexe) = appetite) is the decreased sensation of appetite. ... Cyanosis refers to the bluish coloration of the skin due to the presence of deoxygenated hemoglobin in blood vessels near the skin surface. ...

Clinical diagnosis by laboratory indicators have ranges of: Hb > 200 g/L, Hct >65%, and arterial oxygen saturation (SaO2) <85% in both genders.^[5] See drugs, medication, and pharmacology for substances that treat patients. ... 3-dimensional structure of hemoglobin Hemoglobin or haemoglobin is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. ... The hematocrit (Ht) or packed cell volume (PCV) is the proportion of blood that is occupied by red blood cells. ...

Treatment involves descent from altitude, where the symptoms will diminish and the haematocrit return to normal slowly. Acute treatment at altitude involves bleeding, removal of circulating blood, to reduce the haematocrit; however this is not ideal of extended periods.

References

1. ↑ Monge CC, Whittembury J. Chronic mountain sickness. Johns Hopkins Med J. 1976 Dec;139 SUPPL:87-9. PMID 1011412
2. ↑  Online calculator explaining blood oxygen content
3. ↑ Zubieta-Castillo G Sr, Zubieta-Calleja GR Jr, Zubieta-Calleja L. Chronic mountain sickness: the reaction of physical disorders to chronic hypoxia. J Physiol Pharmacol. 2006 Sep;57 Suppl 4:431-42.
4. ↑ Wu TY. Chronic mountain sickness on the Qinghai-Tibetan plateau. Chin Med J (Engl). 2005 Jan 20;118(2):161-8. PMID 15667803
5. ↑ Chinese Medical Association for High Altitude Medicine. Recommendation for the classification and diagnostic criteria of high altitude disease in China. Chin High Alt Med J (Chin) 1996;6:2-5.