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Abstract
Neutropenia is a decrease in circulating neutrophils in the peripheral blood. The absolute neutrophil count (ANC) number defines neutropenia. An abnormal ANC value contains fewer than 1500 cells per mm3. Mature neutrophils are produced by precursors in the bone marrow. The total body neutrophil content can be divided conceptually into the following 3 compartments: the bone marrow, the blood, and the tissues. In the marrow, the neutrophils exist in 2 divisions—the proliferative, or mitotic, compartment (myeloblasts, promyelocytes, myelocytes) and the maturation-storage compartment metamyelocytes, bands, polys). Neutrophils leave the marrow storage compartment and enter the blood without reentry into the marrow. In the blood, 2 compartments also are present, the marginal compartment and the circulating compartment. Some neutrophils do not circulate freely (marginal compartment) but are adherent to the vascular surface, and these constitute approximately half the total neutrophils in the blood compartment. Neutrophils leave the blood pool in a random manner after 6-8 hours and enter the tissues, where they are destined for cellular action or death. Thus, if the process producing neutropenia is unknown, measurements of the blood neutrophil number, ANC, often must be supplemented by bone marrow examination to determine whether adequate production of neutrophils or increased destruction of neutrophils exists. As already mentioned, the first investigation on suspicion of neutropenia is a CBC/FBC. By this procedure the neutrophil count is measured. If the neutrophil count is low it is normal to repeat the CBC/FBC to be certain that the neutropenia continues. In patients with SCN the neutrophil count may vary slightly, but in contrast to cyclic neutropenia it always remains at a very low level. Sometimes the neutrophil count can be normal because of a cyclical change, but at other times it is very low. In this case your physician may suspect cyclic neutropenia, then he/she will arrange for blood samples (CBC/FBC) to be taken three times per week for at least six weeks to see whether there is a regular cyclical pattern of neutrophil counts.