The term polycythemia is applied to conditions in which the number of circulating red corpuscles is increased. Erythrocytosis indicates a symptomatic response to anoxia, which may occur in cardiac or pulmonary disease, or at high altitudes. Erythrocytosis is also produced by hypertrophy or tumors of the adrenal cortex, by certain poisons, such as aniline and its derivatives, phosphorus, and occasionally by some metals.
Erythremia or polycythemia vera is a chronic disease of obscure origin, with an increase in the total blood volume and the number of red blood cells. The patients have a plethoric complexion, splenic and hepatic enlargement and a variety of neurologic and vasomotor disturbances. Venous thromboses, bleeding tendency, varicosities and phlebitis, or arterial occlusion are common, due to alteration in the blood. Thrombi in the cerebral vessels may lead to hemiplegia or paresis. The red cell count varies from 7 to 10 million, as a rule. The hemoglobin may reach as high as 25 Gram (140%). The individual red corpuscles appear normal. Leukocytosis is frequently present, and the platelet count may reach 4 million. Some patients develop leukemia.
