________ polycythemia is due to increased erythropoietin (chronic hypoxia, tumors)

• A. Primary
• B. Secondary
• C. Polycythemia Vera
• D. Relative

Answer: (B)

Secondary polycythemia is when the rise in red cell mass is driven by increased erythropoietin. In chronic hypoxia, the kidneys sense low oxygen and upregulate EPO, stimulating more RBC production. The same occurs with tumors that secrete erythropoietin, such as renal cell carcinoma, hepatocellular carcinoma, or cerebellar hemangioblastoma. Because EPO is elevated, the marrow keeps making red cells to compensate for hypoxia or due to ectopic EPO production. This contrasts with primary polycythemia (polycythemia vera), where an intrinsic clonal expansion of red cell precursors happens with normal or low EPO, and relative polycythemia, where plasma volume is reduced but EPO and red cell production are not the primary drivers.