Definition
A leukemoid reaction is an increase in the white blood cell count, which can mimic leukemia. The reaction is actually due to an infection or another disease and is not a sign of cancer.
Blood counts often return to normal when the underlying condition is treated.
References
Nasr MR, Hutchison RE. Leukocytic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 34.
Rice L, Zieske AW, Jung M. Neutrophilic leukocytosis, neutropenia, monocytosis, and monocytopenia. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 49.