Cardiobacterium hominis endocarditis associated with very severe thrombocytopenia and platelet autoantibodies.

Severe thrombocytopenia is a life-threatening condition. It is often associated with immune-mediated platelet destruction or myeloablative chemotherapy. Infective endocarditis has been associated with thrombocytopenia, which, as in sepsis, tends to be mild and is often the result of several pathological mechanisms. We report a case of Cardiobacterium hominis endocarditis associated with very severe thrombocytopenia and bleeding in a patient who refused platelet transfusion. Platelet autoantibodies directed against glycoprotein (Gp) IIb/IIIa and Gp Ib/IX were detected during active infection using a glycoprotein-specific assay. Successful treatment of C. hominis endocarditis was associated with loss of platelet autoantibodies and recovery of the platelet count. This report illustrates that the development of platelet autoantibodies can contribute to very severe thrombocytopenia in occasional patients with infective endocarditis.