abo incompatible blood transfusions are rare , result in haemolytic transfusion reactions ( htr ) , and they can be fatal in 2 to 6% of cases . it is enough to transfuse only 10 - 15 ml of abo incompatible blood to cause following symptoms of acute htr : fever , hypotension , disseminated intravascular coagulation ( dic ) , complement - induced acute intravascular hemolysis and acute renal failure . in adults , thrombotic thrombocytopenic purpura ( ttp ) is idiopathic in approximately one - third of cases and in the remainder it is encountered in a variety of potentially triggering clinical situations ( so - called secondary ttp ) , including pregnancy , malignancies , drugs , infection , auto - immune disorders and after haemopoietic stem cell transplantation . secondary thrombotic ttp is a life - threatening condition and is characterized by an aggressive course , it requires prompt treatment at the outset . in case of delayed or inadequate treatment mortality rate may be close to 100% . to date , there is no report in the literature about secondary ttp caused by abo incompatible blood transfusion . we present a case of ttp developed after a htr in the setting of cardiac bypass surgery . a 64-year - old male patient developed nausea , vomiting and chills during red blood cell ( rbc ) suspension transfusion on the second day of coronary by - pass surgery . caring physicians recognized an error in labeling of the rbc suspension . with a preliminary diagnosis of abo incompatible transfusion reaction , hemoglobin values dropped and lactate dehydrogenase ( ldh ) and serum creatinine levels started to increase proportionally . urine color was darkened with a gradual development of oligo - anuria and acute kidney injury ( aki ) . on the 7 day of transfusion , ttp was diagnosed according to following criteria : thrombocytopenia , microangiopathic anemia , increase in ldh level , and development of aki . after 11 and 15 sessions of hemodialysis and plasmapheresis , respectively , platelet , ldh , urea , creatinine levels and urine output improved . the patient showed a dramatic improvement , and plasmapheresis and hemodialysis were stopped subsequently . on the 41 day of admission he had bloody diarrhea and c. difficile toxin a was found to be positive in feces and vancomycin was administered for pseudo - membranous enterocolitis . on the 50 day , multiple infarctions were seen on cranial ct that was performed for the evaluation of confusion . blood urea , creatinine and ldh levels increased , hemoglobin and platelet levels decreased again . the pertinent laboratory data and major interventions are chronologically illustrated in [ table 1 ] . every 1 of 14000 blood transfusions are erroneous , and among them 1 of 13000 are abo incompatible . the pathogenesis of htr is most likely related with activation of complement and hemostatic system , which leads to attachment of host antibodies to red blood cell antigens of incompatible donors blood . as a result , it can modify the intravascular hemolysis and initiate symptoms such as nausea , vomiting , chills , fever and dark appearance of urine , which were evident in our patient during and after transfusion . in addition , studies presented relation between abo groups , clearance of ultra large von willebrand factor multimers ( ulvwf ) , deficiency of adamts13 and risk of ttp development . adamts13 is a circulating zinc metalloprotease , responsible to cleave the ulvwf , thereby the multimers become progressively smaller due to cleavage by adamts13 . deficiency of adamts13 leads to a shift of plasma ulvwf multimers to larger sizes , adhesion with platelets and its aggregation , leading to endothelial injury with activation of thrombosis cascade . data from terrell et al . demonstrated that blood group  o  is an independent risk factor for ttp associated with severe adamts13 deficiency . o  abo blood group , but we could not documented the adamst13 deficiency due to unavailability of the lab technique at our institution at that time . the initiating mechanism of secondary ttp include drug toxicity , radiation and high - dose chemotherapy , angioinvasive fungal or viral infections , surgery and acute graft versus host disease . ttp also appear to differ in their response to therapy . primary or idiopathic form responds to plasmapheresis 80% of the cases whereas this rate is very low in secondary forms . the clinical course of our patient showed a severe relapse despite an initial complete biochemical and clinical response . recently canadian apheresis group conducted a phase ii trial to test the beneficial effects of rituximab in idiopathic ttp . in this form of the disease , actually this study was planned after reporting of many cases in which rituximab was shown to be beneficial . and the authors concluded that autoimmune deficiency of adamts 13 may be due to yet unidentified autoantibodies and while plasmapheresis clears circulating autoantibodies , treatment modalities such as rituximab precludes further antibody production via blockage of b cells . postoperative ttp have been described after a number of surgical operations , most common of which is open heart surgery . ttp developed after five to nine days after surgical operation in most of the case reports . however , it has been proposed that extensive endothelial damage during surgery may lead to release of high - molecular weight von willebrand factor ( hmw - vwf ) multimers in substantial amounts sufficient to overwhelm the capacity of the vwf - cleaving enzyme . however , despite thousands of cabg operations worldwide at each year , only a handful of cases have been reported . this may in part be related to presence of confounding factors such as blood loss , hemodilution , severe infection , dic , and heparin induced thrombocytopenia commonly in the early course of cabg . another explanation may be the rare patients who have genetically low levels of cleavage enzyme . ttp secondary to abo incompatible blood transfusion has never been reported in the literature to date . we hypothesize a potential mechanism which may account for the development of ttp in this setting . however , ttp developed in our patient in the setting of open heart surgery . after the abo incompatible blood transfusion , dic usually develops if sufficient amount of incompatible blood is transfused . we know that dic is self - limited provided that underlying inciting disease is well controlled . however , thrombocytopenia in our patient developed 1 week after the offending event and lasted for weeks despite normal coagulation tests ( inr and aptt ) , which is unusual in the setting of dic . another supporting finding in favor of ttp was a favorable response to plasmapheresis performed with fresh frozen plasma . it is very difficult to discriminate whether transfusion of abo incompatible blood or open cardiac surgery or the combination of the two actually initiated the process . perhaps , both factors worked hand - in - hand . however , one clinical observation supports our hypothesis of blood transfusion as the initiating factor . none of the ttp cases secondary to surgery had relapsed unless the patient underwent a second operation . however , this was not the case in our patient who developed a relapse after near complete improvement of laboratory and clinical parameters . despite initial recovery , he developed a second bout which was complicated by multiple cerebral thrombi and subsequently died . given the complex picture of early postoperative phase of cabg and the presence of potential confounders , many cases of postoperative ttp may have been missed . prompt recognition is of utmost importance because of not only high mortality rate when left untreated but also to institute specific therapies availability of efficient therapeutic maneuvers to our knowledge , this is the first report of ttp secondary to abo incompatible blood transfusion .
the triggers of secondary thrombotic thrombopcytopenic purpura ( ttp ) include drug toxicity , radiation and high - dose chemotherapy , angioinvasive infections , surgery and acute graft versus host disease . 
 ttp secondary to surgery have been reported in a number of cases . 
 most of the cases have been occurred after open heart surgery . 
 extensive endothelial damage is held responsible as the initiating mechanism in postoperative ttp cases . 
 however , there is no report of secondary ttp describing development owing to abo incompatible blood transfusion . here 
 , we describe a patient who developed ttp after transfusion of abo incompatible blood during hospitalization for bypass surgery . 
 we also propose a hypothesis which may account for the possible underlying mechanism .