Which of these is not a feature of C.M.L?
**Core Concept**
Chronic Myeloid Leukemia (CML) is a type of myeloproliferative neoplasm characterized by the uncontrolled growth of mature and immature granulocytes. The hallmark of CML is the presence of the Philadelphia chromosome, resulting from a reciprocal translocation between chromosomes 9 and 22.
**Why the Correct Answer is Right**
The Philadelphia chromosome creates a fusion gene, BCR-ABL, which encodes a constitutively active tyrosine kinase. This leads to the continuous activation of downstream signaling pathways, promoting cell proliferation and survival. The clinical features of CML include an elevated white blood cell count, splenomegaly, and bone marrow fibrosis.
**Why Each Wrong Option is Incorrect**
**Option A:** CML is often associated with a high neutrophil count, which is a correct feature of the disease. Therefore, this option is incorrect.
**Option B:** Bone marrow fibrosis is a common finding in CML, making this option incorrect.
**Option C:** The Philadelphia chromosome is a hallmark of CML, making this option incorrect.
**Clinical Pearl / High-Yield Fact**
The BCR-ABL fusion gene is a key driver of CML pathogenesis, and its presence is diagnostic for the disease. This knowledge is crucial for differentiating CML from other myeloproliferative neoplasms.
**Correct Answer:** D