The majority of acquired neutropenic states are either due to viral infections or are iatrogenic as a result of drugs ( Table,!).
Table 1 Acquired neutropenic states
A mild self-limiting reduction in absolute neutrophil count is most commonly seen following an acute influenza infection. Neutropenia develops during the acute viremic phase of the infection and can persist for up to a week without serious sequelae. Concomitant diminution of other cell lines is unusual in this setting, and diagnosis is aided by a history of an influenza-like illness and reactive lymphocytes with toxic granulation of the neutrophils on the blood film. Protracted neutropenia can occasionally occur with viral hepatitis, Kawasaki disease, and infectious mononucleosis. The mechanism of neutropenia is unclear but probably results from direct suppression of myelopoiesis and increased utilization of neutrophils.
Severe bacterial sepsis can also cause neutropenia, probably as a result of direct damage of myeloid precursors by bacterial endotoxin and increased adherence of neutrophils to the vascular endothelium. Bacterial-induced neutropenia tends to be more common in patients with reduced marrow neutrophil reserve, due to either a primary hematological disease or previous treatment with myelosuppressive drugs or irradiation. Some patients are malnourished or have a history of alcohol abuse. Chronic infections causing splenomegaly, such as tuberculosis, brucellosis, kala-azar, and malaria, also cause neutropenia, but this is probably secondary to splenic sequestration.
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