hemolysis (hĬmŏl´ĬsĬs), destruction of red blood cells in the bloodstream. Although new red blood cells, or erythrocytes, are continuously created and old ones destroyed, an excessive rate of destruction sometimes occurs. The dead cells, in sufficiently large numbers, overwhelm the organ that destroys them, the spleen, so that serum pigments resulting from hemoglobin breakdown appear in the blood serum. Jaundice is caused by overloading the liver with pigment. Large-scale destruction of red blood cells, from any of a variety of causes, results in anemia. Rh disease, or erythroblastosis fetalis, is a hemolytic disease of newborns caused by an immune reaction between fetal red blood cells and maternal antibodies to them. Some hemolytic conditions, e.g., those in which red blood cells are fragile and rupture easily, are treated by removal of the spleen to slow cell breakdown or by administration of steroids. Autoimmune hemolytic conditions result from splenomegaly. The spleen not only sequesters red blood cells, but produces antibodies against the body's red blood cells. This is a potentially lethal condition that occurs more often in women than men.

haemolysis The breakdown of red blood cells. A normal occurrence, chiefly in the blood sinuses of the spleen, when the cells are ageing after 3–4 months in circulation, but it can happen abnormally in the circulating blood, causing haemolytic anaemia. In either case, the cells become more fragile than normal, disintegrate, and shed their contents. Normally the haemoglobin is broken down and recycled, so its iron is not lost. When free haemoglobin is released in the plasma, some products are retained, but excessive amounts are excreted from the kidneys (haemoglobinuria). Fragility of cells in a blood sample can be assessed by placing them in a series of salt solutions of progressively lower osmolality than the blood itself, which causes them to swell, and finding the osmolality at which they burst.

Stuart Judge

haemolysis (hi-mol-i-sis) n. the destruction of red blood cells (erythrocytes). Within the body, haemolysis may result from poisoning, infection, or the action of antibodies; it may occur in mismatched blood transfusions. It usually leads to anaemia. See also laking.

haemolysis The breakdown of red blood cells. It may be due to the action of disease-causing microorganisms, poisons, antibodies in mismatched blood transfusions, or certain allergic reactions. It produces anaemia.

haemolysis (hemolysis) The rupture of red blood cells and the dissolution of their contents.