Severely Deficient ADAMTS13 Activity Predicts Relapse of Immune-Mediated Thrombotic Thrombocytopenic Purpura in Pregnancy.

It is commonly accepted that severely deficient ADAMTS13 activity in remission increases the risk for relapse, but relapse in severely deficient ADAMTS13 activity in patients with immune-mediated thrombotic thrombocytopenic purpura (iTTP) is not uniform. Mouse models and published studies have suggested that a “second hit” is required in addition to severely deficient ADAMTS13 activity to lead to clinical relapse. Our initial published experience led us to preliminarily conclude that pregnancy could serve as the second hit in addition to severely deficient ADAMTS13 activity and lead to relapse. The aim of this study was to evaluate the risk of relapse and outcomes of pregnant patients with a diagnosis of iTTP.