TTP is characterized by an abnormal accumulation of unusually large multimers of vonWillebrand factor (VWF) caused by insufficient or absent activity of a disintegrinand metalloprotease with a thrombospondin type 1 motif, member 13 (ADAMTS13), whichhas the function of fragmenting VWF multimers acquired by autoantibodies (TTPa) orinherited due to mutations in the ADAMTS13 gene in the congenitalform. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.