Acquired thrombotic thrombocytopenic purpura without detectable anti-ADAMTS13 antibodies: a possible underlying autoimmune mechanism.

In up to 25% of patients with acquired TTP, anti-ADAMTS13 antibodies are not identified, the mechanism resulting from ADAMTS13 deficiency remains unidentified (uTTP). In this study, we provide further insights on clinical presentation and outcome of uTTP. In patients with baseline undetectable anti-ADAMTS13 antibodies, usual features of iTTP (young age, cerebral involvement, severe thrombocytopenia) with no other associated context than a history of systemic autoimmune disease or pregnancy, should prompt to consider the diagnosis of iTTP.