Which statement best characterizes chronic myelogenous leukemia?

Which statement best characterizes chronic myelogenous leukemia?

• A. Philadelphia chromosome negative
• B. Elevated lymphocyte count only
• C. Philadelphia chromosome positive
• D. No splenomegaly

Answer: (C)

Chronic myelogenous leukemia is driven by a specific genetic change: a translocation between chromosomes 9 and 22 that creates the BCR-ABL fusion gene on the Philadelphia chromosome. This fusion produces a constitutively active tyrosine kinase, causing unchecked proliferation of myeloid cells and a characteristic high white cell count with cells at many stages of maturation, often accompanied by splenomegaly and basophilia. Because of this molecular hallmark, the best characterization is that the disease is Philadelphia chromosome positive. The other statements don’t fit the typical picture: an elevated lymphocyte count alone points more to chronic lymphocytic leukemia; absence of splenomegaly runs counter to the common presentation of CML; and Philadelphia chromosome negativity is not the defining feature of classic CML (though rare variants exist).

Chronic myelogenous leukemia is driven by a specific genetic change: a translocation between chromosomes 9 and 22 that creates the BCR-ABL fusion gene on the Philadelphia chromosome. This fusion produces a constitutively active tyrosine kinase, causing unchecked proliferation of myeloid cells and a characteristic high white cell count with cells at many stages of maturation, often accompanied by splenomegaly and basophilia. Because of this molecular hallmark, the best characterization is that the disease is Philadelphia chromosome positive.

The other statements don’t fit the typical picture: an elevated lymphocyte count alone points more to chronic lymphocytic leukemia; absence of splenomegaly runs counter to the common presentation of CML; and Philadelphia chromosome negativity is not the defining feature of classic CML (though rare variants exist).