A patient presents with fever and erythema with marked leukocytosis (WBC 57,000). The described response is best labeled as which of the following?

• A. Leukemoid reaction
• B. Leukemia
• C. Lymphoma
• D. Eosinophilia

Answer: (A)

Reactive neutrophilia due to infection, known as a leukemoid reaction, best fits this scenario. A WBC count around 57,000 can occur in a significant inflammatory or infectious process as the bone marrow releases neutrophils to fight the stimulus. The fever and erythema point to inflammation or infection driving this response, not a malignant clone.

What distinguishes a leukemoid reaction from leukemia is the nature of the cells and the clinical context. In a leukemoid reaction, the neutrophil predominance comes from a reactive process, often with a left shift (more immature neutrophils) but without malignant blasts, and the leukocyte alkaline phosphatase score is typically normal or elevated. In leukemia, malignant proliferation leads to abnormal cells (often blasts) in the blood and marrow, with possible anemia, thrombocytopenia, and a different smear and lab pattern.

Lymphoma would involve lymphoid lineage and usually presents with lymphadenopathy or organ involvement rather than isolated extreme neutrophilic leukocytosis. Eosinophilia points to an eosinophil-predominant process rather than a broad neutrophilic response.

So, the description aligns with a leukemoid reaction—the body’s reactive, infection-driven surge of neutrophils.