Polycythemia - Definition

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Polycythemia, or polyglobulia, constitutes an abnormal increase in the total red blood cell volume in the blood. Of the different forms of this condition, there is primary polycythemia, where overactive bone marrow function causes overproduction of red blood cells, usually due to a bone marrow disease, such as polycythemia vera. There is also secondary polythemia, potentially manifesting following a decrease of blood oxygen, thus common at high altitude where there is less oxygen in the air. Other potential causes are various respiratory disorders or certain tumors or hemoglobin-related diseases. Polycythemia causes increased viscosity of the blood, leading to higher risks of thrombosis. Commonly reported symptoms include headaches, high blood pressure, and tinnitus, where one hears a ringing or whistling in the ears.