CML vs Leukemoid reaction
How to tell CML and Leukemoid reaction apart when a board question makes them look alike.
CML is BCR-ABL clonal myeloid disease with low LAP; leukemoid reaction is reactive neutrophilia with high LAP.
Side by side
Chronic myeloid leukemia causes clonal granulocytic expansion with splenomegaly, basophilia, Philadelphia chromosome t(9;22), BCR-ABL, and low leukocyte alkaline phosphatase.
Leukemoid reaction is reactive neutrophilia from infection, inflammation, stress, or cytokine drive, often with toxic granulation, high LAP, and no BCR-ABL.
BCR-ABL tyrosine kinase signaling drives myeloid proliferation from a clonal hematopoietic stem cell.
Inflammatory cytokines stimulate normal marrow to release neutrophils and immature granulocytes as a reactive process.
BCR-ABL positivity, Philadelphia chromosome, basophilia, low LAP, and very high WBC with all granulocyte stages support CML.
High LAP, toxic granulation, Dohle bodies, clear infectious trigger, and absence of BCR-ABL support leukemoid reaction.
The trap
Both can show very high neutrophil counts and left shift, so BCR-ABL, basophils, LAP, and clinical trigger decide.
Watch it explained
The repair move
For extreme neutrophilia, separate clonal myeloid growth from reactive marrow response.
Try a free question
CoreA patient has weight loss, splenomegaly, leukocytosis with all stages of granulocyte maturation, basophilia, low LAP, and BCR-ABL. Which diagnosis is most likely?
Show answer and explanation
Answer: A. CML. BCR-ABL with basophilia, splenomegaly, and low LAP points to CML.
Why the other choices are tempting
- B. Leukemoid reaction has high LAP and no BCR-ABL.
- C. AML is acute myeloblast expansion rather than chronic granulocytic maturation.
- D. CLL has mature lymphocytes and smudge cells.
- E. Polycythemia vera is a JAK2-driven erythrocytosis phenotype.
Flashcards
Tap a card to flip it.
What genetic clue defines CML?
Philadelphia chromosome t(9;22) producing BCR-ABL defines CML.
What LAP pattern supports CML?
Low leukocyte alkaline phosphatase supports CML.
Quick answers
What is the fastest way to tell CML from Leukemoid reaction?
CML is BCR-ABL clonal myeloid disease with low LAP; leukemoid reaction is reactive neutrophilia with high LAP.
What is the key clue for CML?
Chronic myeloid leukemia causes clonal granulocytic expansion with splenomegaly, basophilia, Philadelphia chromosome t(9;22), BCR-ABL, and low leukocyte alkaline phosphatase.
What is the key clue for Leukemoid reaction?
Leukemoid reaction is reactive neutrophilia from infection, inflammation, stress, or cytokine drive, often with toxic granulation, high LAP, and no BCR-ABL.
What is the common trap with CML vs Leukemoid reaction?
Both can show very high neutrophil counts and left shift, so BCR-ABL, basophils, LAP, and clinical trigger decide.