Chronic Mountain Sickness

Avinell Abdool


Chronic Mountain Sickness (CMS) is a pathological finding that is commonly found amongst individuals that have taken up permanent residence in high altitude environments (altitudes of over 8,200 feet)1. Clinical manifestations of CMS include but are not limited to the following1;

  • HA
  • Dizziness
  • Tinnitus
  • Breathlessness
  • Palpitations
  • Sleep Disturbances
  • Fatigue
  • Loss of appetite
  • Confusion
  • Cyanosis
  • Dilation of veins


CMS is the outcome of progressive loss of ventilation rate, which subsequently results in hypoxemia and polycythemia2. Polycythemia is defined as by excessive erythrocytosis (EE; Hb >/= 19g/dL for women and Hb >/= 21 g/dL for men) which along with a hypoxic environment can result in pulmonary hypertension2. In advanced conditions of Chronic Mountain Sickness there can be cor-pulmonlae and congestive heart failure2 .

A study was conducted in the University of San Diego by Dr. Gabriel Haddad that researched the adaption of the Peruvian population in high altitude conditions3. It was found that CMS is highest in the Andeans (approximately 18 %), lesser in Tibetans (1%-11%) and completely absent in the Ethiopian population3. From these data points it appeared that there was was a genetic correlation between CMS sufferers and ethnicity3. In addition, this finding added another factor that mystified the conclusive pathogenesis of CMS3. By understanding exact pathogenesis of CMS, it would not only benefit those who are at potential risk for the disease but also those living at sea level, where hypoxia plays a role in certain pathology ( such as stroke, cardiac ischemia, Obstructive sleep apnea and Sickle Cell Disease)3 .

A cohort of 94 individuals were gathered and were equally categorized into CMS and non CMS subjects3. These individuals originated from Cerro de Pasco, which has an elevation of greater than 14,000 feet3. Genetic tools and a custom algorithm were utilized and the researchers identified 11 regions on the genome that contained 38 genes that proved to be statistically significant3. Nine of the eleven genes were tested in fruit flies in hypoxic experiments3. The experiment consisted of fruit flies that had these genes and ones that did not have the genes3. It was concluded that individuals with these molecular adaptions were better able to adapt to physiological stress such as hypoxia when compared to individuals that did not have this adaption3. The results of this study allowed researchers to better understand the correlation between genetics and individuals who strive in hypoxic environments3.



Figure 1- D.melanogaster (fruit fly)3



Figure 2-Cerro de Pasco3




  1. Villafuerte FC, Corante N. Chronic Mountain Sickness: Clinical Aspects, Etiology, Management, and Treatment. High Altitude Medicine & Biology. 2016;17(2):61-69. doi:10.1089/ham.2016.0031.
  2. Chronic mountain sickness and high altitude pulmonary hypertension. High Altitude Medicine and Physiology 5E. 2012:333-346. doi:10.1201/b13633-23.
  3. Stobdan T, Akbari A, Azad P, et al. New Insights into the Genetic Basis of Monges Disease and Adaptation to High-Altitude. Molecular Biology and Evolution. 2017. doi:10.1093/molbev/msx239.