Chronic mountain sickness

Chronic mountain sickness
Classification and external resources
Specialty emergency medicine
ICD-10 T70.2
ICD-9-CM E902.0
DiseasesDB 29615

Chronic mountain sickness (CMS or Monge's disease) is a disease in which the proportion of blood volume that is occupied by red blood cells increases (polycythemia) and there is an abnormally low level of oxygen in the blood (hypoxemia). CMS can develop during extended time living at a high altitude. The most frequent symptoms of CMS are headache, dizziness, tinnitus, breathlessness, palpitations, sleep disturbance, fatigue, anorexia, mental confusion, cyanosis, and dilation of veins.

CMS was first described 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.[1][2]


Although CMS generally affects people native to altitudes higher than 3000 m, it does not affect populations around the world equally. A recent study by Sahota and Panwar (2013)[3] reviewed CMS prevalence rates around the world and found the highest rates were found in Andean countries of South America and the lowest rates in people native to the East African Mountains of Ethiopia. Third party CMS prevalence rates reported from the study are summarized below:


CMS is characterised by polycythemia (with subsequent increased hematocrit) and hypoxemia, which both improve 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 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.

Clinical diagnosis by laboratory indicators have ranges of Hb > 200 g/L, Hct > 65%, and arterial oxygen saturation (SaO2) < 85% in both genders.


Treatment involves descent from altitude, where the symptoms will diminish and the hematocrit return to normal slowly. Acute treatment at altitude involves bleeding (phlebotomy), removal of circulating blood, to reduce the hematocrit; however this is not ideal for extended periods. Carbonic anhydrase inhibitors have been shown to improve chronic mountain sickness by reducing erythropoietin and the resulting polycytemia, which resulted in better arterial O2 and lower heart rate.[4]

  1. Zhou D, Udpa N, Ronen R, Stobdan T, Liang J, Appenzeller O, Zhao HW, Yin Y, Du Y, Guo L, Cao R, Wang Y, Jin X, Huang C, Jia W, Cao D, Guo G, Gamboa JL, Villafuerte F, Callacondo D, Xue J, Liu S, Frazer KA, Li Y, Bafna V, Haddad GG. Whole-genome sequencing uncovers the genetic basis of chronic mountain sickness in Andean highlanders. Am J Hum Genet. 2013 Sep 5;93(3):452-62. doi:10.1016/j.ajhg.2013.07.011. Epub 2013 Aug 15. PMID 23954164
  2. Cole, Amy M.; Nayia Petousi; Gianpiero L. Cavalleri; Peter A. Robbins (2014). "Genetic Variation in SENP1 and ANP32D as Predictors of Chronic Mountain Sickness". High Altitude Medicine & Biology. 15 (4): 497–499. doi:10.1089/ham.2014.1036. ISSN 1557-8682. PMC 4273201Freely accessible. PMID 25225945.
  3. Sahota, Inderjeet; Nidhi Panwar (September 2013). "Prevalence of Chronic Mountain Sickness in high altitude districts of Himachal Pradesh". Indian Journal of Occupational and Environmental Medicine. 17 (3): 94–100. doi:10.4103/0019-5278.130839. PMC 4035612Freely accessible. PMID 24872667.
  4. Richalet, Jean-Paul; Maria Rivera; Patrick Bouchet; Eduardo Chirinos; Igor Onnen; Olivier Petitjean; Annick Bienvenu; Francçoise Lasne; Stéphane Moutereau; Fabiola León-Velarde (2005). "Acetazolamide: a treatment for chronic mountain sickness". American Journal of Respiratory and Critical Care Medicine. 172 (11): 1427–1433. doi:10.1164/rccm.200505-807OC. ISSN 1073-449X. PMID 16126936.
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