BCSE Practice Exam 2026 – Complete Study Resource

Chronic mountain sickness, also known as Monge's disease, is primarily characterized by an increase in blood viscosity due to elevated levels of hematocrit and red blood cells. When individuals ascend to high altitudes, the body responds to lower oxygen levels by producing more red blood cells (a process known as erythropoiesis). This increase in red blood cell mass is aimed at improving the oxygen-carrying capacity of blood to compensate for the reduced oxygen availability.

However, when the hematocrit—a measurement of the proportion of blood volume that is occupied by red blood cells—becomes excessively high, it can lead to increased blood viscosity. This thicker blood can disrupt normal circulation, causing various symptoms associated with chronic mountain sickness, including headaches, fatigue, and increased risk of cardiovascular problems. Thus, the factor that directly contributes to the condition's pathology through the mechanism of increased blood viscosity is indeed the increased hematocrit and red blood cells. This understanding is crucial in managing and potentially preventing chronic mountain sickness in high-altitude environments.