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Leukemoid Reaction

The term "leukemoid reaction" is used to describe a condition where peripheral white blood cells on a stained blood smear may have some resemblance to leukemia cells. Quantatively, in a leukemoid reaction, the neutrophil count may be as high as 50.0 X 109/L with more immature cells, particularly myelocytes, than are usually present in toxic left-shift syndromes.

The presence of immature cells in a leukemoid reaction awakens thoughts of leukemia. Great care must be taken to make a distinct differentiation between aberrant white blood cell proliferations (possible leukemia) and a benign but exaggerated granulocytic proliferative response (leukemoid reaction). The leukocyte alkaline…

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 Leukemoid Reactions — Not Always Caused by Infection

Markedly elevated peripheral white blood cell counts with neutrophilia have been termed leukemoid reactions. Although definitions differ, most involve a white blood cell count ≥25,000 × 109/µL with a predominance of granulocytes, a shift toward more-immature forms such as band neutrophils and metamyelocytes, and the absence of dysplastic changes. Although infection is presumed to account for most instances of leukemoid reaction, other conditions may be causative.

Articles of Interest

Leukemoid Reaction - Causes, Diagnosis, and Treatment

A leukemoid reaction is a short-term rapid increase in the count of white blood cells that can sometimes mimic the condition of leukemia. The reaction usually occurs in response to infections, tumors, or pharmacological drug side effects.

Leukemoid Reaction – A Tale of 50 Years

The definition, however has become more elaborate, and now reads as ‘a hematological disorder, characterized by a leukocyte count >50,000 cells/µL, significant increase in mature neutrophil counts in the peripheral blood, accompanied by a differential count showing marked left shift, signs of neutrophil activation in the absence of basophilia and dysplastic changes’. Over the last fifty years, most advances have been in terms of expanding the number of underlying causes as well as the use of alternative diagnostic modalities when standard hematological methods fail to establish the diagnosis.

Leukemoid reaction: A 21st-century cohort study

Leukemoid reaction (leukocyte count >50 cells ×109 L) is a rare but extremely relevant finding. Since little has been published on this condition's clinical relevance and prognosis, we investigated leukemoid reaction in patients with a white blood cell count of >50 × 109 L, including etiology and outcomes.

Differential Diagnosis of Leukemoid Reaction

Patients with leukemoid reaction were more likely to have an infection, be hospitalized and die.

Sick Flags: Leukemoid Reaction...

Leukemoid reactions in KD are rarely reported in the literature, and there is limited discussion of what degree to expect. In the setting of KD, this is reported more frequently in infants and can be accompanied by other cell-line changes that create concern for oncologic processes.

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Deranged Physiology

In a good-going leukemoid reaction, the granulocyte progenitor cells are too rushed to produce mature neutrophils. Typically, early neutrophil precursors swarm uselessly in the peripheral blood (eg, myelocytes, metamyelocytes) and the more severe the reaction, the earlier and less mature the circulating forms. So, is it leukemoid reaction or is it in fact a neutrophilic leukemia? How does one discriminate between the two? The most important aetiology to rule out is a myeloid leukaemia. A bone marrow biopsy soon reveals which is which.

WikEM

Markedly elevated leukocyte (particularly neutrophil) count without hematologic malignancy. Cutoff is variable, 25-50k.