Leukemoid Reaction

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  • Markedly elevated leukocyte (particularly neutrophil) count without hematologic malignancy
  • Cutoff is variable, 25-50k[1]

Literature Review

Retrospective review of 135 patients with WBC >25k [2]

  • 48% infection
  • 15% malignancy
  • 9% hemorrhage
  • 12% glucocorticoid or granulocyte colony stimulating therapy

Retrospective review of 173 patients with WBC >30k [3]

  • 48% infection (7% C. difficile)
  • 28% tissue ischemia
  • 7% obstetric process (vaginal or cesarean delivery)
  • 5% malignancy

Observational study of 54 patients with WBC >25k [4]

  • Consecutive patients presenting to the emergency department
  • Compared to age-matched controls with moderate leukocytosis (12-24k)
  • Patients with leukemoid reaction were more likely to have an infection, be hospitalized and die.

Clinical Features

  • Signs/symptoms of underlying pathology or asymptomatic

Differential Diagnosis

Differential Diagnosis of Leukemoid Reaction


  • Treat underlying condition


External Links


  1. Sakka V, Tsiodras S, Giamarellos-Bourboulis EJ, Giamarellou H. An update on the etiology and diagnostic evaluation of a leukemoid reaction. Eur J Intern Med. 2006;17(6):394-398. doi:10.1016/j.ejim.2006.04.004.
  2. Reding MT, Hibbs JR, Morrison VA, Swaim WR, Filice GA. Diagnosis and outcome of 100 consecutive patients with extreme granulocytic leukocytosis. Am J Med. 1998;104(1):12-16.
  3. Potasman I, Grupper M. Leukemoid reaction: spectrum and prognosis of 173 adult patients. Clin Infect Dis. 2013;57(11):e177-e181. doi:10.1093/cid/cit562.
  4. Lawrence YR, Raveh D, Rudensky B, Munter G. Extreme leukocytosis in the emergency department. QJM. 2007;100(4):217-223. doi:10.1093/qjmed/hcm006.