Which term describes a disease characterized by an increase in white blood cells?

The term that describes a disease characterized by an increase in white blood cells is leukocytosis. This condition specifically refers to a higher than normal number of leukocytes, or white blood cells, in the bloodstream. Leukocytosis can occur in response to various factors such as infections, inflammation, stress, or more serious conditions like leukemia, where abnormal white blood cells are produced.

Leukemia does involve an increase in white blood cells, but it is a specific type of cancer affecting blood and bone marrow and characterized by the production of abnormal white blood cells. Thus, while related and sometimes resulting in leukocytosis, leukemia itself denotes a more complex and specific pathological condition rather than the general increase of leukocytes implied by leukocytosis.

In contrast, terms like anemia relate to the deficiency of red blood cells or hemoglobin, while leucopenia indicates a decreased number of white blood cells. Therefore, when focusing solely on the definition of an increase in white blood cells, leukocytosis is the most appropriate term.