Polycythemia, Erythrocytosis (Polycythaemia)

Polycythemia is an increase in hemoglobin levels in the blood. The cause of polycythemia can be either a decrease in the total volume of blood plasma (relative polycythaemia) or an increase in the total volume of red blood cells in the blood (absolute polycythaemia).

Absolute polycythemia can develop as a primary disease (see Polycythemia vera) or as a secondary disease, accompanying various respiratory diseases or blood diseases that lead to oxygen deficiency in the tissues. Absolute polycythemia can also occur if a person develops certain tumors, such as kidney carcinoma.