VWF and atypical hemolytic-uremic syndrome: Two key events are involved in the pathogenesis of D+HUS: altered Von Willebrand factor (VWF) activity (for example, as seen with 'a disintegrin and metalloproteinase with thrombospondin motif-13' (ADAMTS13) deficiency) and site-specific activation and/or apoptosis of microvascular endothelial cells.