An abnormal increase in the proportion of red cells in the blood.
Abnormal increase in the number of erythrocytes in the blood, often associated with pulmonary or heart disease, or exposure to high altitudes for a long period, but in many cases of unknown cause.
Condition of increased numbers of red cells in the blood to increase the amount of hemoglobin available to carry oxygen.
An increase in the number of red blood cells circulating in the bloodstream; also known as erythrocytosis (from erythrocyte, the medical term for red blood cell). The added mass of blood cells causes the blood to be thicker than normal and increases blood volume. A person with polycythemia is at increased risk of blood clots that can lead to heart attack, stroke, or thrombophlebitis (inflammation of the veins).
An increase in the hemoglobin concentration of the blood. This may be due either to a decrease in the total volume of the plasma (relative polycythemia) or to an increase in the total volume of the red cells (absolute polycythemia). The latter may occur as a primary disease or as a secondary condition in association with various respiratory or circulatory disorders that cause deficiency of oxygen in the tissues and with certain tumors, such as carcinoma of the kidney.
An excess of red blood cells. In a newborn, it may reflect hemoconcentration due to hypovolemia or prolonged intrauterine hypoxia, or hypervolemia due to intrauterine twin-to-twin transfusion or placental transfusion resulting in delayed clamping of the umbilical cord.
An increase in the number of red cells in the circulating blood. The upper limits of normality are 6.5 million red cells per cubic millimeter of blood, but in polycythemia this may reach 7-14 million per cubic millimeter. The condition is merely a symptom and may be caused by any dehydrating illness such as the diarrhea of cholera, which concentrates the blood; by a diminution in the available oxygen, such as is experienced at high altitudes; by certain heart diseases marked by cyanosis; by emphysema, asthma, and fibrosis or growths which interfere with normal ventilation of the lungs; by chronic poisoning with chemical agents such as arsenic, phosphorus, carbon monoxide, or aniline derivatives. Cirrhosis of the liver, tuberculosis of the spleen, and conditions associated with splenic enlargement are rare causes.