Which is not seen in polycythemia vera –
**Core Concept**
Polycythemia vera (PV) is a myeloproliferative disorder characterized by the excessive production of erythrocytes, leukocytes, and platelets due to mutations in the JAK2 gene, leading to uncontrolled cell proliferation and subsequent increased viscosity of the blood.
**Why the Correct Answer is Right**
Polycythemia vera typically presents with an increased red blood cell mass, leukocytosis, and thrombocytosis. The increased red blood cell mass can lead to hyperviscosity, which can cause symptoms such as headaches, dizziness, and visual disturbances. However, thrombotic events are a significant complication of PV, and splenomegaly is a common finding due to extramedullary hematopoiesis. The JAK2 mutation is present in the majority of PV cases, leading to constitutive activation of the JAK/STAT signaling pathway.
**Why Each Wrong Option is Incorrect**
**Option A:** Typically seen in PV, as it is a direct consequence of the JAK2 mutation and the subsequent increase in erythropoietin-independent erythropoiesis.
**Option B:** Also commonly seen in PV, as the increased red blood cell mass can lead to hyperviscosity, which can cause symptoms such as headaches, dizziness, and visual disturbances.
**Option C:** Not typically seen in PV, as the disease is characterized by an increase in red blood cells, not a decrease. Anemia is more commonly associated with myelodysplastic syndromes or other myeloproliferative disorders.
**Clinical Pearl / High-Yield Fact**
PV is a classic example of a myeloproliferative disorder that can mimic other conditions, such as essential thrombocytopenia or chronic myeloid leukemia. A high index of suspicion and careful clinical evaluation are necessary to diagnose PV accurately.
**Correct Answer: C.**