Scientists say they have discovered why some humans develop chronic mountain sickness (CMS) while other people can adapt to high altitudes. According to a study published in the American Journal of Human Genetics, it is all in the genes.

Researchers from the University of California-San Diego (UCSD) say they have decoded a genetic basis for chronic mountain sickness, also known as Monge's disease, which could potentially lead to the development of new treatments.

The team conducted their research based on previous studies showing that many people who live in high-altitude regions, such as the Andes mountain region of South America, are not adapted to their environment and continue to suffer from CMS.

Around 140 million people have permanently settled within high-altitude regions, the researchers say. These environments have low-oxygen conditions, which can cause residents to suffer from hypoxia - low levels of oxygen in the blood, causing CMS.

CMS usually develops after spending an extended time living in altitudes over 3,000 meters. Symptoms include headache, depression, fatigue and sleepiness. People with the disease can often have strokes or heart attacks during early adulthood as a result of the decrease in oxygen getting to organs and tissues.

Two genes found to cause chronic mountain sickness

For the study, the researchers recruited 20 Peruvian residents of the Andes region: ten residents who suffered from CMS and ten residents without the disease. Their genetic variation was measured using whole genome sequencing.

Two genes were identified - ANP32D and SENP1. According to the study authors, both genes showed increased presence in residents who suffered from CMS, compared with those who did not have the disease.

The researchers looked to assess whether "down-regulating" these genes would limit the symptoms of hypoxia, and they looked at a species with corresponding gene sequences - the fruit fly.

Gabriel Haddad, distinguished professor and chair of the Department of Pediatrics at UCSD, explains:

"While a number of published articles have described an association between certain genes and the ability for humans to withstand low oxygen at high levels, it was very hard to be sure if the association was causal.

We found that flies with these genes down-regulated had a remarkably enhanced survival rate under hypoxia."

Potential treatment for heart and brain disease

The researchers say that the findings in this study may lead to potential treatments, not only for those living at high altitudes, but also for those at any altitude who suffer from cardiovascular and brain diseases related to low oxygen levels.

Further research will involve conducting whole genome sequencing on 100 participants to determine if biomarkers - a substance used as an indicator of a biological state - exist to predict CMS.

The researchers have already taken skin samples from the 100 participants, which will be "reprogramed" into pluripotent stem cells (IPS). The study authors add that the IPS cells, if they have the capacity to become glia or red blood cells, may be used to "test the resilience to low oxygen levels."