Investigation and management of erythrocytosis

Mithoowani et al discuss the management of erythrocytosis. The condition refers to an erythrocyte count above the sex-specific normal range and can be subclassified into relative erythrocytosis, caused by a reduction in plasma volume, or absolute erythrocytosis, caused by increased erythrocyte mass. Primary erythrocytosis refers to autonomous production of erythrocytes, typically from a myeloproliferative neoplasm (polycythemia vera [PV]). In contrast, secondary erythrocytosis is caused by a physiologically appropriate response to elevated serum erythropoietin levels. Up to 4% of ambulatory men and 0.4% of ambulatory women in Canada have erythrocytosis, based on hemoglobin levels greater than 165 g/L or 160 g/L, respectively. Differentiating PV from other causes of erythrocytosis is critical because early recognition and treatment of PV can prevent many of its vasomotor and thrombotic complications. PV vera is rare, with an incidence and prevalence of 0.84 and 22 per 100 000, respectively. Although the prevalence of secondary erythrocytosis is difficult to estimate, it is higher than that of PV. Here, a contemporary approach to differentiating PV from other causes of erythrocytosis, and the review of the natural history, diagnosis and management of PV are summarized.