Polycythemias

Polycythemia, also called erythrocytosis, is an increase in the number of circulating red blood cells per volume of blood, as reflected by an elevated hematocrit or hemoglobin level. The three major categories of polycythemia are relative polycythemia, secondary polycythemia, and polycythemia vera. Included in this chapter are discussions on initial evaluation; familial polycythemia; and polycythemia caused by renal and hepatic disorders, drug use, and appropriate increases in erythropoietin production. A flowchart depicts an approach to the evaluation of a patient with polycythemia. Other figures depict the oxygen-hemoglobin dissociation curve characteristic of various polycythemias and a gene mutation associated with familial polycythemia. This review contains 3 highly rendered figures and 27 references.