Key Takeaways

✅ Polycythemia or erythrocytosis are terms used interchangeably to describe an elevated hematocrit (Hct) or hemoglobin (Hb).

✅ Hb is a more appropriate physiological measure in a patient with anemia; Hct is a more appropriate physiological measure in a patient with polycythemia.

✅ The Hct is the primary determinant of blood viscosity, which in turn affects total peripheral resistance and cardiac output.

✅ An elevated Hct can lead to symptoms of hyperviscosity.

✅ Polycythemia may be apparent (relative) or absolute.

✅ Absolute polycythemia may be primary or secondary.

✅ Acquired primary polycythemia = polycythemia vera.

✅ Polycythemia vera may be associated with elevated white cell and platelet count, increased serum uric acid and LDH, and low serum erythropoietin level.

✅ Polycythemia vera is diagnosed using established diagnostic criteria.

✅ Treatment of polycythemia vera is based on risk for thrombosis and includes a combination of phlebotomy, cytoreductive therapy and aspirin. Treatment is not curative and does not reduce transformation risk. Its goal is to reduce the risk of thrombosis.

✅ Treatment of secondary polycythemia involves treating the underlying cause, where applicable.

✅ Complications of polycythemia vera include hyperviscosity syndrome, thrombosis, bleeding, pruritis, erythromelalgia and transformation to acute leukemia.