UC Irvine

Hemostasis, endowed to human to protect lives, is a process of logical blood clotting system to prevent blood loss in vascular injury. However, the notion that deadly thrombosis occurs as a result of normal hemostasis in intravascular injury could encounter with conceptual skepticism because the term ‘thrombosis’ automatically conjures up as serious disease. According to ‘two-path unifying theory’, normal hemostasis is initiated only by vascular injury through activated unusually large von Willebrand factor (ULVWF) path and/or activated tissue factor (TF) path. When these two equally important paths are unified in normal hemostasis, clotting at external bodily injury site is initiated for wound healing, but in intravascular injury ‘blood clots’ is formed to produce a disease called ‘thrombosis’. As microthrombi from ULVWF path and fibrin clots from TF path become unified, macrothrombus would be formed via thrombogenesis. However, if ULVWF path and TF path cannot be unified due to lone ULVWF path activation, partial hemostasis produces only microthrombi seen in endotheliopathy-associated vascular microthrombotic disease. In real life, in-vivo fibrin clot cannot be formed alone via normal hemostasis because bleeding vascular injury always activates both ULVWF and TF paths. Without vascular injury, microthrombi due to activated ULVWF path occur in ADAMTS13 deficiency in thrombotic thrombocytopenic purpura, and fibrin clots due to activated TF path occur in acute promyelocytic leukemia. These two conditions can be called pathologic hemostasis. Three thrombogenic pathways produce three thrombotic disorders, which include macrothrombosis, microthrombosis and true DIC through macrothrombogenesis, microthrombogenesis and fibrinogenesis in both physiologic and pathological hemostasis.