________ polycythemia can be due to loss of plasma (dehydration)

________ polycythemia can be due to loss of plasma (dehydration)

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

Answer: (B)

Dehydration reduces plasma volume, so the red blood cell mass stays the same while the blood becomes more concentrated. This raises hematocrit and hemoglobin levels without an actual increase in red cell production, which is the hallmark of relative polycythemia. In contrast, true polycythemia involves increased red cell mass, as seen in secondary polycythemia (driven by elevated EPO) or polycythemia vera (a clonal myeloproliferative disorder). So dehydration-like plasma volume loss causes relative polycythemia, not a true rise in red cell production.

Dehydration reduces plasma volume, so the red blood cell mass stays the same while the blood becomes more concentrated. This raises hematocrit and hemoglobin levels without an actual increase in red cell production, which is the hallmark of relative polycythemia. In contrast, true polycythemia involves increased red cell mass, as seen in secondary polycythemia (driven by elevated EPO) or polycythemia vera (a clonal myeloproliferative disorder). So dehydration-like plasma volume loss causes relative polycythemia, not a true rise in red cell production.