[Approach to the Patient with Polycythemia]

Polycythemia is defined as an elevation of age and sex - adjusted hematocrit. While Polycythemia vera (PV) is a myeloproliferative neoplasm caused by JAK2 mutations leading to an autonomous proliferation of red blood cells. Most cases of polycythemia seen in general practice represent relative polycythemia or are secondary to other causes. Secondary erythrocytosis is most often due to chronic hypoxia, the use of erythropoietin-stimulating drugs such as androgens or SGLT2 inhibitors or erythropoietin -secreting tumors. Relative polycythemia results from chronic plasma volume contraction. Rarely, hereditary erythrocytosis may be a cause of polycythemia. In this review we outline our diagnostic approach to patients with polycythemia, focusing on identifying secondary causes. We suggest that when polycythemia is isolated, secondary and hereditary causes should be considered initially. If polycythemia is accompanied by leukocytosis or thrombocytosis, the initial investigations should be testing for JAK2 mutations and serum erythropoietin levels. Polycythemia vera is characterized by headache, visual disturbances, pruritus, erythromelalgia and splenomegaly. Treatment includes phlebotomy, low-dose aspirin, and cytoreductive agents. In secondary polycythemia, there are no clear guidelines regarding the desired hematocrit and management should be individualized to treat the cause. Phlebotomy is the only modality used to lower the hematocrit when this is required. A systematic clinical approach that prioritizes the exclusion of secondary causes before genetic testing may prevent unnecessary investigations and enable focused, effective patient care.