How is secondary erythrocytosis different from primary erythrocytosis?

Secondary erythrocytosis is caused by external conditions that lead to an increased number of red blood cells (RBCs). This can occur in response to various factors such as chronic hypoxia, which may stem from long-term exposure to high altitudes, chronic respiratory disorders, or conditions that result in lower oxygen levels in the blood. The body's compensatory mechanism to these low oxygen levels includes increasing erythropoietin (a hormone that stimulates RBC production) to enhance the oxygen-carrying capacity of the blood.

In contrast, primary erythrocytosis, often associated with polycythemia vera, is a condition driven by a mutation in the stem cells that leads to an overproduction of RBCs independent of these external stimuli. Thus, the distinction lies in the origin of the erythrocytosis, with secondary arising from external factors rather than an intrinsic disease of the hematopoietic system.

Other options do not correctly describe secondary erythrocytosis, as it is specifically linked to increased RBC production due to external triggers, rather than a decrease or any impact on white blood cells.