What laboratory findings are characteristic of polycythemia vera?

Polycythemia vera (PV) is a myeloproliferative neoplasm characterized by the overproduction of red blood cells, which can also include increased production of white blood cells and platelets. The correct choice highlights that leukocytosis (elevated white blood cell count) and thrombocytosis (elevated platelet count) are often observed in patients with PV.

In PV, the bone marrow is stimulated to produce more of not just red blood cells, but also leukocytes and platelets. This is attributed to a neoplastic change, primarily due to mutations in the JAK2 gene in many patients. Consequently, it is common for patients to present with both elevated leukocyte and platelet counts, reflecting the hyperproliferative nature of the disease.

The other choices do not accurately characterize PV. In PV, erythropoietin levels are usually low, not elevated, because the excessive red blood cell production leads to feedback inhibition on erythropoietin synthesis. Hypervolemia (increased blood volume) could occur due to increased red cell mass causing increased viscosity, but it is not a defining laboratory finding. Lastly, a decrease in hemoglobin would not be characteristic of PV, as the condition