Neutrophil production and kinetics: Neutropenia and neutrophilia

Neutrophils are the body’s primary defense against bacterial pathogens. Changes in neutrophil count are frequently encountered in clinical medicine in that increased or decreased neutrophil counts are common with infections and other disorders. Thus, neutrophil changes most often represent a response to an underlying disorder, and they may be the first clue to its presence. At other times, high or low neutrophil counts can be a crucial indicator of a primary hematologic disorder. Increased neutrophils are characteristic of chronic myeloid leukemia and other myeloproliferative disorders, and decreased neutrophils can signal aplastic anemia, myelodysplastic syndrome, acute leukemia, or other disorders perturbing bone marrow function. This chapter will not focus on primary hematologic disorders, but rather will deal with normal neutrophil kinetics, more common aberrations, and briefly consider esoteric disorders that primarily affect myeloid cells.