Disseminated intravascular clotting associated with Fc-receptor IIa-mediated platelet activation in a patient with endocarditis after aortic valve replacement.

This report describes fatal disseminated cardiovascular thrombosis associated with Fc-receptor IIa-mediated platelet activation during surgery for aortic valve replacement in a patient with endocarditis. The patient's serum contained antibodies which strongly activated platelets via the Fc-receptor IIa. Antibodies did not bind to platelet factor 4 or aprotinin and binding was independent of heparin. The mechanisms and differential diagnosis for such a complication are discussed. Our data show for the first time in a patient with endocarditis that, beside HIT, other immune complexes can induce massive intravascular coagulation via platelet Fc-receptor IIa activation.