ABSTRACT
Chronic mountain sickness (CMS) afflicts people who are native or long-time residents of high altitude. It is characterized by excessive erythrocytosis. It can be classified as primary (without identified cause) or secondary (due to underlying conditions). CMS usually begins insidiously in adult life, often during the fourth decade, as progressive hypoxemia stimulates erythrocytosis. The clinical picture disappears when the patient moves to lower altitudes. Therefore, the primary etiology of CMS is presumed to be hypoxemia.
