ADAMTS13 and thrombotic thrombocytopenic purpura: In patients with low ADAMTS13 levels during clinical remission, the risk of TTP relapse is 30–50%, therefore lifelong monitoring of ADAMTS13 is part of current patients’ follow-up, allowing pre-emptive rituximab treatment in case of ADAMTS13 relapse (i.e., reduction of ADAMTS13 activity levels below 20%) [14, 15].