VWF and thrombotic thrombocytopenic purpura: For instance, primary aHUS has been linked to von Willebrand factor (VWF),20,21 a coagulation factor that is involved in the development of TTP and that can interact with CFH.22 Along the same line, the multicomponent protein network of the coagulation pathway is interlinked with the complement through several crossover points.23 It is perhaps for this reason that gene defects in thrombomodulin can lead to aHUS.24,25