Two contrasting disorders exemplify disturbances in this pathway—thrombotic thrombocytopenic purpura, where either an inherited deficiency of ADAMTS13 or the development of autoantibodies to ADAMTS13 results in a small vessel and arterial thrombotic phenotype, or type 2 von Willebrand’s Disease, in which large vWF multimers are defective or absent, resulting in a lifelong bleeding disorder. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.