Anti-erythrocyte autoimmunization in hydatid disease.

A 73-year-old man with hydatid disease developed autoimmune hemolytic anemia due to IgM cold agglutinin with anti-I specificity. Hemolysis decreased after initiating mebendazole therapy. The cysts notably diminished in size and the red cell autoantibodies disappeared at the end of this treatment. On the basis of these observations, 44 patients with hydatid disease were investigated. One patient showed IgM cold autoantibody with no signs of anemia. In addition, cleavage fragments of C3 were detected on the erythrocyte membranes of 6 patients, following chronic activation of the complement system. We suggest that parasitic antigens may evoke antibodies cross-reacting with the red blood cells of the host.