Data are presented for 283 consecutive patients in whom ADAMTS13 was measured immediately before their first plasma exchange treatment (November 13, 1995 through December 31, 2009). Patients were assigned to clinical categories based on their clinical features during their initial episode and without knowledge of the results of the ADAMTS13 measurement, as previously described.¹⁷  Chemotherapeutic agents were mitomycin C (4), gemcitabine (4), carmustine (1), and pentostatin (1). The calcineurin inhibitor was cyclosporine (2). Other drugs were alendronate, clopidogrel, cocaine, ticlopidine, trimethoprim-sulfamethoxazole, and vancomycin (1 each). Other autoimmune disorders included immune thrombocytopenic purpura/Evan syndrome (5), antiphospholipid antibody syndrome (2), scleroderma (2), Wegener granulomatosis (2), and once each for bronchiolitis obliterans with organizing pneumonia, Hamman-Rich syndrome, periarteritis nodosa, Sjögren syndrome, and unspecified vasculitis. Other disorders included multiorgan failure (11) and congenital hemolytic anemia (1).