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  1. This term is used to differentiate between the leucocytosis and leukemia.
  2. In leukocytosis or neutrophilia there is an increase in the count from 10,000 to 25,000 / µL (microliter).

The differentiating point from leukemia

  1.  In the leukemoid reaction, the neutrophils are mature and not clonally derived.
  2. There is a persistent increase in TLC above 50,000/cmm and no evidence of leukemia.
  3. Blood count comes to normal after treating the cause.
  4. Increased blast cells are not seen in the leukemoid reaction.
  5. A count above 100,000 /µL is more suggestive of the myeloproliferative disorder with very few exceptions.

Differential diagnosis includes:

  1. Chronic myeloid leukemia.

Causes of Leukemoid reaction:

  1. Severe infection like Clostridium, Tuberculosis, Pertussis and Infectious mononucleosis.
  2. Visceral larva migration leads to eosinophilia.
  3. Tuberculosis gives rise monocytosis.
  4. Leukemoid lymphocytosis is seen in Tuberculosis, Whooping cough and infectious mononucleosis.
  5. Intoxication.
  6. malignancies.
  7. Severe hemorrhage.
  8. Acute hemolysis.
  9. Drugs like Sulfa, Dapsone, Glucocorticoids, and use of G-CSF factor.
  10. Diabetic ketoacidosis.
  11. Ischemic colitis.
  12. Hepatic necrosis.

Difference between Leukemoid reaction and chronic myelocytic leukemia

Test                                             Leukemoid reaction                        Chronic myeloid leukemia 
WBC count usually <50,000/cmm usually >50,000/cmm
Basophils absent usually increased count
platelets normal Increased
Eosinophil normal Increased
Hemoglobin usually normal usually low
Band form these are prominent  all stages (myelocytes)
Toxic granules and Dohle bodies              these are present toxic granules ± to 0
Spleen usually not present usually enlarged
Philadelphia chromosome absent present in 90% of the cases
Leucocytes Alk.phosphatase (LAP) > 100 < 10
History  short long

Possible References Used

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