Many studies in different ethnic populations have demonstrated the presence of ADAMTS13 mutations in patients with TTP.16,26,48,68,81–106 Some aspects emerging from studies of ADAMTS13 congenital deficiency in mice could help to unravel the role of ADAMTS13 and UL-VWF multimers in the pathogenesis of TMAs. This evidence concerns the gene VWF and thrombotic thrombocytopenic purpura.