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Definition of Leukopenia, Neutropenia, and Monocytopenia

by Mary Territo, MD

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 recognized as a decrease in the total WBC count, because lymphocytes account for only 20 to 40% of the total WBC count.

Monocytopenia was not previously thought to be a distinct entity; however, recent evidence suggests that deficiency or absence of monocytes can occur in patients with mutations of the hematopoietic transcription factor gene, GATA2 . Affected patients sometimes present with nontuberculous mycobacterial infection especially at cutaneous sites (ie, MonoMAC syndrome) or with genital human papillomavirus infection that has a high risk of progression to genital cancer. There is risk of progression to other hematologic disorders (eg, bone marrow failure, acute myelogenous leukemia, chronic myelomonocytic leukemia). Monocytopenia is diagnosed by CBC with differential. Treatment is experimental and may include interferon, antibodies, and allogeneic hematopoietic stem cell transplantation, depending on the severity of the condition and the development of secondary hematologic disorders.

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