Thrombotic thrombocytopenic purpura (TTP) is a rare, lifethreatening thrombotic microangiopathy (TMA) often occurring in adulthood with a sudden, unpredictable onset.1 Deficiency of ADAMTS13 enzyme activity represents the central feature of TTP and is traditionally attributed to either a congenital or acquired condition. This evidence concerns the gene ADAMTS13 and thrombotic microangiopathy.