Sir,The recent report on thrombotic thrombocytopenic purpura (TTP) after transfusion of ABO incompatible blood is very interesting.[1] Solak et al. hypothesized that the TTP might be due to “transfusion of ABO incompatible blood” or “open cardiac surgery.”[1] Solak et al. also noted that “TTP secondary to ABO incompatible blood transfusion has never been reported in the literature until date.”[1] What the exact mechanism in the present case is still a myth and the data on confounding morbidity (such as occult cancer) in the present case is not well presented. In fact, it is no doubt that ABO incompatibility can induce TTP. The previous reports on TTP after ABO mismatched liver and renal transplantations are good example.[23] Hence, the cases of ABO blood transfusion should be no doubt for the pathogenesis of TTP.