Leukemoid reaction

Background

Significant leukocytosis and neutrophilia in the absence of a hematologic malignancy
- e.g. WBC ≥30-50 with ≥50% granulocytes

Infections
- Sepsis, pneumonia, urinary tract infection
- Clostridioides difficile colitis (often quite high)
- Disseminated tuberculosis
- Severe shigellosis
- Postpartum Clostridium sordellii
Inflammation
- Pancreatitis
- Mesenteric inflammatory pseudotumor
Malignancies
- Carcinomas (lung, oropharyngeal, gastrointestinal, genitourinary)
- Hodgkin lymphoma
- Melanoma
- Sarcoma
Drugs
- Corticosteroids
- Minocycline
- Recombinant hematopoietic growth factors
Miscellaneous
- Splenectomy
- Ethylene glycol intoxication
- Severe hemorrhage or acute hemolysis
- Alcoholic steatohepatitis


Characteristic	Leukemoid reaction	Chronic myeloid leukemia	Chronic neutrophilic leukemia
Peripheral blood film	Mature neutrophils with a left shift	Immature cells, basophils, and eosinophils	Marked neutrophilia without immagure cells
LAP score	high	low	high
Vitamin B12	variable or high	high	high
Bone marrow	myeloid hyperplasia, orderly maturation, normal morphology	basophilia, eosinophilia, monocytosis, slight increase in blasts and reticulin fibrosis	myeloid hyperplasia, orderly maturation, normal morphology, but with packed bone marrow, slight increase in reticulin
Cytogeneic analysis	normal	BCR/ABL translocation	present in 35%
Serum G-CSF	high	low	low
Clonality studies	polyclonal	monoclonal	monoclonal