ADAMTS13 and thrombotic thrombocytopenic purpura: Mannucci et al. [7] showed that low levels of ADAMTS-13 are found in a significant portion of cases of systemic lupus erythematosus (SLE) and other systemic connective tissue diseases, highlighting the risk of TTP in SLE patients and the importance of the rare TTP cases with a positive Coombs test.