Thrombotic thrombocytopenic purpura (TTP) is a rare, though severe, inherited or acquired disease caused by severe deficiency of the Von Willebrand factor-cleaving serine protease, ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) [2]. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.