Which condition is characterized by lymphocytosis?

Chronic lymphocytic leukemia (CLL) is characterized by lymphocytosis, which refers to an elevated level of lymphocytes in the blood. In CLL, the body produces a higher-than-normal number of abnormal B lymphocytes that can accumulate and crowd out normal blood cells. This condition often leads to symptoms such as swollen lymph nodes, fatigue, and susceptibility to infections.

The other conditions have different hematologic profiles: Acute myeloid leukemia typically presents with an increase in myeloblasts rather than lymphocytes. Chronic myeloid leukemia is distinguished by a proliferation of myeloid cells and is often associated with the Philadelphia chromosome. Acute lymphoblastic leukemia primarily involves lymphoblasts but is characterized by an acute presentation and a predominance of immature lymphoid cells, which can lead to increased lymphocyte counts as well, though the overall picture differs from CLL and often includes a variety of cell lineages. Thus, CLL is the specific condition that prominently features lymphocytosis.