What is a leukomoid reaction (leukocyte disorder)?

A leukomoid reaction is a significant increase in white blood cell count (typically above 50,000 cells/μL) that occurs in response to severe infection, inflammation, or certain malignancies, but is not leukemia. This condition represents an exaggerated physiological response to stress or infection. The elevated white blood cell count primarily involves mature neutrophils, though other cell lines may be affected. Common causes include severe bacterial infections (particularly pneumonia, meningitis, and sepsis), burns, severe hemorrhage, poisoning, and solid tumors that produce growth factors. To distinguish a leukomoid reaction from leukemia, physicians typically examine the peripheral blood smear for normal cell maturation, check for the absence of blast cells, and may perform additional tests like leukocyte alkaline phosphatase (LAP) scoring, which is typically elevated in leukomoid reactions but low in leukemias. Management focuses on treating the underlying cause rather than the elevated white count itself. The prognosis depends on the primary condition, with the white cell count typically normalizing once the underlying problem is resolved.