Polycythemia(redirected from megakaryocytosis)
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polycythemia(pŏl'ēsīthē`mēə), condition characterized by an increase in the production of red blood cells, or erythrocytes, in the blood. Primary polycythemia, also called erythremia, or polycythemia vera, is a chronic, progressive disease, most common in middle-aged men. It is characterized by overgrowth of the bone marrow, abnormally increased red blood cell production, and an enlarged spleen. Symptoms, include headache, inability to concentrate, and pain in the fingers and toes. There is a danger of blood clotting or hemorrhage (see thrombosisthrombosis
, obstruction of an artery or vein by a blood clot (thrombus). Arterial thrombosis is generally more serious because the supply of oxygen and nutrition to an area of the body is halted.
..... Click the link for more information. ). Primary polycythemia is treated by radiation, periodic removal of some blood (phlebotomy), or chemotherapy with antimetabolite drugs, e.g., CytoxanCytoxan
, trade name for the drug cyclophosphamide, used to inhibit growth of tumors and rapidly proliferating cells. It is used in the treatment of leukemia, Hodgkin's disease, and lymphosarcoma and other solid tumors.
..... Click the link for more information. . In secondary polycythemia, or erythrocytosis, the proliferation of red blood cells results from the body's attempt to compensate for other conditions, such as prolonged lack of oxygen at high altitudes or chronic lung or heart insufficiency. Certain tumors are also associated with increased red blood cell production. In secondary polycythemia the treatment is directed toward the underlying cause.
an increase in the total quantity of blood in the human body. A distinction is made between polycythemia vera, in which the increase in erythrocytes, up to 8–10 million in 1cu mm of blood, is greater than the increase in the total volume of blood plasma, and hypervolemia, which is characterized chiefly by an increase in the volume of plasma. The latter may be of cardiac origin or may be due to water retention in the vascular system after copious drinking. The normal ratio of the volume of blood cells to that of plasma is 45:55.
an increase in the number of erythrocytes in the blood. Spurious, or relative, polycythemia results from a reduction in the volume of blood plasma and is caused by loss of fluid, as from heavy perspiration or from diarrhea. Secondary polycythemia is characterized by an absolute increase in the number of erythrocytes, as with oxygen deficiency in the mountains, heart disease, or pulmonary emphysema. Secondary polycythemia accompanied by an increase in the volume of blood plasma is called polycythemia vera, or erythremia.