What is leukemia primarily characterized by?

Leukemia is primarily characterized by a progressive increase in abnormal white blood cells. This condition affects the blood and bone marrow, leading to the overproduction of these dysfunctional cells, which can interfere with the body’s ability to fight infections, control bleeding, and carry oxygen. Unlike normal white blood cells, the abnormal ones proliferate uncontrollably, crowding out healthy cells and leading to various health complications.

In the context of leukemia, it's important to note that while there may also be effects on red blood cells and platelets due to the overall disruption in blood cell production, the defining feature is indeed the abnormal increase in white blood cells.