Leukopenia is a reduction in the circulating WBC count to < 4000/μL. It is usually characterized by a reduced number of circulating neutrophils, although a reduced number of lymphocytes, monocytes, eosinophils, or basophils may also contribute. Thus, immune function is generally greatly decreased.

Neutropenia is a reduction in blood neutrophil count to < 1500/μL in whites and < 1200/μL in blacks. It is more serious when accompanied by monocytopenia and lymphocytopenia. Lymphocytopenia, in which the total number of lymphocytes is < 1000/μL in adults, is not always reflected in the total WBC count, because lymphocytes account for only 20 to 40% of the count.

Last full review/revision August 2012 by Mary Territo, MD

Content last modified November 2012