Contributor: Gordon K. Klintworth
Autoimmune hemolytic anemia is an autoimmune disease and a heterogenous type of hemolytic anemia [anemia - hemolytic]. The anemia is a manifestation of hypersensitivity type II [hypersensitivity - type II] in which hemolysis results from cytotoxic IgG or IgM antibodies against cell surface antigens. These antibodies usually activate the complement system. The activity of some of these antibodies is maximal at body temperature; less often most activity is at a lower temperature. The hemoglobin concentration in the peripheral blood falls below the normal range as a result from a diminution in the number of erythrocytes or in the quanity of hemoglobin within the erythrocytes. The anemia follows blood destruction as a result of hemolysis. The erythrocyte survival is shortened because of an immune response against autologous erythrocytes. In most cases (80-90%) the hemolysis takes place with maximum reactivity at 37ºC (warm-antibody autoimmune hemolytic anemia [anemia - warm-antibody autoimmune hemolytic]); in other cases the maximal activity is at <37ºC (cold-antibody autimmune hemolytic anemia [anemia - cold-antibody autoimmune hemolytic]). Warm-antibody autoimmune hemolytic anemia may be idiopathic or be secondary to other disorders, such as lymphocytic lymphoma [lymphoma - lymphocytic], chronic lymphocytic leukemia [leukemia - chronic lymphocytic, collagen vascular disease (especially systemic lupus erythematosus], a viral infection, some inflammatory disorders (such as ulcerative colitis) and certain solid tumors. Jaundice is a prominent feature of autoimmune hemolysis and the sclera becomes yellow. The anemia may produce edema of the optic nerve head, as well as hemorrhages [hemorrhage - retina] and exudates in the retina. The frequency and severity of retinal hemorrhage depends partly on the coexistence of anemia and thrombocytopenia.