ADAMTS13 and thrombotic thrombocytopenic purpura: Acquired TTP is a rare, autoimmune disease characterized by antibodies, usually IgG, directed against ADAMTS-13, with an annual incidence of 0.2–1 per 100,000.43 In its most common, characteristic form, TTP begins abruptly and virulently, occasionally after a febrile, viral-like prodrome; a minor infection or pregnancy may be the trigger.44,45 Thrombocytopenia and fragmentation hemolysis are severe, and central neurologic signs exist at presentation or supervene quickly, out of proportion to renal signs.