ADAMTS13 and thrombotic thrombocytopenic purpura: The most common physiologic condition present in the immune-mediated forms, which is often associated with severe ADAMTS13 deficiency, is pregnancy.29,36,72,73 Immune-mediated TMA in pregnancy should be distinguished from a number of pregnancy-associated TMAs such as preeclampsia, hemolysis with elevated liver enzymes and low platelets (HELLP) syndrome, acute fatty liver of pregnancy, and antiphospholipid syndrome.74,75 Accurate diagnosis is essential since plasma exchange is indicated for pregnancy-associated TTP while fetal-placental delivery is therapeutic for HELLP syndrome.