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.