UC Irvine

‘Disseminated intravascular coagulation (DIC)’ occurs commonly in critical illnesses such as sepsis, trauma, cancer, and complications of surgery and pregnancy. Mortality is very high. The pathogenesis has been ascribed to tissue factorinitiatedcoagulation disorder, resulting in disseminated microblood clots that are made of platelets, plasma factors, fibrins, and blood cells. True DICdepletes coagulation factors and consumes platelets, and activates fibrinolysis. ‘DIC’ isassumed to orchestrate thrombocytopenia, microangiopathic hemolytic anemia and hypoxic multiorgan dysfunction syndrome, and causes hemorrhagic disorder due to depleted coagulation factors. In contrast,disseminated intravascular microthrombosis (DIT) occurs in thrombotic thrombocytopenic purpura (TTP) and TTP-like syndrome due to ADAMTS13 deficiency or insufficiency. The pathogenesis is due to formation of intravascular‘microthrombi’ composed of complexes of platelets and unusually large von Willebrand factor multimers. Interestingly, DIT also occurs in the same critically ill patients as ‘DIC’ does. Following activation of complement system,the terminal complex C5b-9 causes endotheliopathy via channel formation to the endothelial cell membrane. Endotheliopathy activates microthrombotic pathway and initiates microthrombogenesis, leading to endotheliopathyassociatedDIT. DIT results in TTP-like syndrome with hematologic phenotype of consumptive thrombocytopenia, microangiopathic hemolytic anemia, and multiorgan dysfunction syndrome. In reinterpretation of ‘DIC’, the truelesion is ‘microthrombi’ but not microblood clots. Thus, ‘DIC’ is endotheliopathy-associated DIT. This concept reconciles all the clinical features of ‘DIC’, and dramatically changes our understanding of pathophysiological mechanism inhemostasis and thrombosis. This new paradigm should assist the physician with correct diagnostic evaluation and treatment intervention.