Genetic or acquired deficiency of ADAMTS13 causes thrombotic thrombocytopenic purpura (TTP), a life-threatening disease, in which microvascular thrombi forms in arterioles and capillaries[10], while a paucity of large vWF multimers caused by mutations in the A2 domain is associated with the bleeding disorder, type 2A von Willebrand disease (vWD)[3,13,14]. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.