neutrophilia

Neutrophilia is an elevation of neutrophils in the peripheral blood. It is typically defined by an absolute neutrophil count (ANC) above the upper limit of normal, commonly ANC greater than about 7.0 x 10^9/L in adults, though exact thresholds vary by laboratory. Neutrophilia can be transient or persistent and may occur with or without a left shift (increased immature neutrophils such as bands).

Causes of neutrophilia are diverse and can be broadly grouped into physiologic and pathologic categories. Physiologic neutrophilia occurs in response to acute stress, intense exercise, seizures, smoking, pregnancy, or after administration of certain drugs such as corticosteroids or epinephrine, which promote demargination of neutrophils. Pathologic neutrophilia includes bacterial or significant inflammatory infections; autoinflammatory or autoimmune diseases; tissue necrosis (for example, myocardial infarction, trauma, burns); extrinsic factors such as exposure to drugs that stimulate neutrophil production (G-CSF) or cause demargination; and hematologic conditions such as myeloproliferative neoplasms, leukemias, or other malignancies.

Evaluation typically starts with a complete blood count with differential, review of clinical context, and repeat testing to confirm persistence. Distinction from leukocytosis due to other white cell lineages relies on the differential and, when indicated, tests such as the leukocyte alkaline phosphatase (LAP) score, cytogenetics, and molecular studies to assess for myeloproliferative disorders or leukemia. A left shift or toxic changes may accompany infection, while a normal LAP score with marked neutrophilia may raise concern for a myeloproliferative process.

Management focuses on treating the underlying cause. In many cases, neutrophilia resolves with control of infection or inflammation. Rare cases with very high neutrophil counts or suspected leukostasis may require specialist hematology input and cytoreductive measures.