polycythemia [päl΄i sī thē′mē ə]
an abnormal increase in the number and concentration of circulating red blood corpuscles

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pol·y·cy·the·mi·a (pŏl'ē-sī-thēʹmē-ə) n.
A condition marked by an abnormally large number of red blood cells in the circulatory system.
  [poly- + cyto- + -hemia.]

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      abnormal increase in red blood cells (erythrocyte) and hemoglobin in the circulation, a situation that results in thickened blood, retarded flow, and an increased danger of clot formation within the circulatory system. Polycythemia may be relative (e.g., after blood-plasma loss), transient (as when a large number of red blood cells suddenly enter the circulation from storage), or absolute (i.e., reflecting an increase in actual mass of red cells in the body). Relative and transient, or secondary, polycythemia disappear when the condition to which they are secondary is eliminated. Absolute polycythemia, when the cause is known, is called erythrocytosis; this may accompany congenital heart disease, some hemoglobin defects, pulmonary disease (e.g., emphysema, silicosis), the Pickwickian syndrome (a form of obesity), and living at high altitudes.

      The situation in which excess red blood cells occur without known cause is called erythremia, primary polycythemia, or polycythemia vera. Symptoms include headache, dizziness, difficulty in breathing, skin changes (e.g., tendency to bruise), an enlarged spleen, and red discoloration of the face and sometimes the extremities. Certain blood-clotting factors are not produced in adequate amounts, and consequently hemorrhages may occur from ulcers or minor wounds. Duodenal ulcer and gout occur with increased frequency in persons with erythremia. The disease is relatively common in Jews, affects men more often than women, and usually appears at middle age or later. Treatment is aimed at reducing the volume of red blood cells.

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Universalium. 2010.

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