Hemolysis

accelerated destruction of erythrocytes, releasing hemoglobin

Definition
Common causes for hemolysis are (sometimes congenital) defects in the erythrocytes themselves (e.g. of their enzymes or cytoskeleton), mechanical disruption (as may be brought about also be the changed shape of erythrocytes in e.g. sickle cell disease), and antibody-mediated immune responses (as may be encountered after mismatched blood transfusion).