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

 

Bibliography

 

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.