What condition is characterized by an increased number of white blood cells?

Leukemia is characterized by an increased number of white blood cells due to the uncontrolled proliferation of these cells in the bone marrow and their subsequent release into circulation. In this condition, the normal regulation of blood cell production is disrupted, leading to the overproduction of immature or abnormal white blood cells. This can result in a variety of symptoms, including fatigue, fever, frequent infections, and easy bruising or bleeding because it can interfere with normal blood cell function.

Anemia is primarily related to a decrease in red blood cells or hemoglobin levels, which negatively impacts oxygen transport. Thrombocytopenia involves a reduced platelet count, leading to increased risk of bleeding. Hemophilia is a genetic disorder primarily affecting the blood’s ability to clot due to deficiencies in clotting factors, which is also not associated with an increase in white blood cells. Thus, among the given choices, leukemia is distinctly identified by its hallmark of elevated white blood cell counts.