Polycythemia

POLYCYTHEMIA (from Greek polys- many and Latin globulus- little ball), an increase beyond normal levels (over 5.5 million per 1 mm³) in the number of red blood cells per unit volume of blood. P. is often observed as a symptom in various pathological conditions. Such symptomatic P. may arise from blood concentration - in cases of diarrhea, fasting, profuse sweating, dehydration, or from acute difficulties in tissue respiration, for example, in congenital and decompensated heart defects with anoxemia, or at high altitudes (see Mountain sickness). Most of these symptomatic P. cases have a reversible, sometimes transient character. From a practical standpoint, the more significant are those acute P. that serve as manifestations of an independent disease of the blood-forming system - polycythemia (see).