TTP and HUS are caused by different pathophysiological mechanisms: through inherited or acquired deficiency in the vWF-cleaving protease ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13) in TTP, endothelial injury related to Shigatoxin-producing Enterobacteriaceae in typical post-diarrhoea HUS and unleashed complement activation in atypical HUS. The gene discussed is ADAMTS13; the disease is hemolytic-uremic syndrome.