Which condition is characterized by an excess of white blood cells?

Leukocytosis is the condition characterized by an excess of white blood cells in the bloodstream. This increase can occur in response to various stimuli, such as infections, inflammation, stress, or more serious conditions like leukemia. White blood cells, or leukocytes, play a crucial role in the immune response, and their elevation indicates that the body is reacting to a stimulus, potentially signaling an underlying health issue.

Leukopenia, on the other hand, refers to a deficiency of white blood cells, which can leave an individual more susceptible to infections. Anemia generally involves a shortage of red blood cells or hemoglobin, affecting the body's ability to transport oxygen but is not related to white blood cell levels. Primary anemia is a specific type of anemia, and while it also does not pertain to white blood cell counts, it specifically refers to blood disorders that cause low red blood cell counts.

Thus, the correct choice reflects the direct relationship between leukocytosis and elevated white blood cell counts, emphasizing its role in diagnosing and monitoring various medical conditions.