Acquired thrombotic thrombocytopenic purpura (TTP) is a rare thrombotic microangiopathy due to the development of autoantibodies against the VWF-cleaving protease ADAMTS13. ADAMTS13-specific circulating immune complexes (CICs) have been described in patients with acquired TTP, but their clinical relevance remained to be established. The aim of this study was to assess the association between ADAMTS13-specific CICs and ADAMTS13-related measurements, clinical and laboratory markers of disease severity, and occurrence of TTP relapse, in autoimmune TTP patients.