Thrombotic thrombocytopenic purpura (TTP) is a rare but potentially fatal hematologic emergency characterized by the formation of microvascular platelet-rich thrombi due to a severe deficiency of ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 motif, member 13) [1]. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.