Neutropenia

DEFINITION
Neutrophil count < 2900 neutrophils/mL in dogs and < 2500 neutrophils/mL in cats Can develop alone or as a component of pancytopenia Often accompanied by a left shift and toxic change (e.g., cytoplasmic basophilia, cytoplasmic vacuolation, Döhle bodies, and toxic granulation)

PATHOPHYSIOLOGY
Results from one of three mechanisms—(1) deficient neutrophil production in the bone marrow, (2) cells shifting from the circulating neutrophil pool to the marginal neutrophil pool in the blood, and (3) reduced neutrophil survival because of excessive tissue demand or immune-mediated destruction of cells
Most commonly associated with infection, because emigration of neutrophils from the blood into the tissues exceeds the rate at which the bone marrow can replace them.