What condition is characterized by an increased white blood cell count?

Leukocytosis is characterized specifically by an increased white blood cell count. This condition can occur in response to a variety of factors, including infections, inflammation, stress, or certain medical conditions like leukemia. The elevation in white blood cells is typically a physiological response that helps the body fight off infections or diseases.

Anemia relates to a deficiency in red blood cells or hemoglobin, not white blood cells. Thrombocytopenia is a condition marked by a low platelet count, affecting the blood's ability to clot but not influencing white blood cell levels. Leukopenia refers to a decreased white blood cell count, which would contradict the increased levels seen in leukocytosis. Therefore, leukocytosis is the only option directly associated with an increase in white blood cells.