Leukemoid reaction

Last revised by Rohit Sharma on 12 Mar 2024

A leukemoid reaction refers to a marked increase in white blood cells (>50000 cells/mL), typically neutrophils, which manifests as an acute inflammatory reaction that can mimic leukemia.


Leukemoid reactions often occur from accelerated release of cells from the bone marrow.

Features that differentiate it from leukemia include:

  • no immature cells

  • no basophilia

  • no monocytosis

  • no increase in increased leukocyte alkaline phosphatase (LAP)

  • absence of the BCR-ABL1 translocation

  • bone marrow is hypercellular but otherwise normal

  • severe infection

  • intoxication

  • other malignancies

  • severe hemorrhage

  • acute hemolysis

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