Dynamic changes in absolute immature platelet count suggest the presence of a coexisting immune process in the setting of thrombotic thrombocytopenic purpura.

Abstract

Previous studies have indicated the usefulness of absolute immature platelet counts (A-IPCs) in the management and diagnostic algorithm of thrombotic thrombocytopenic purpura (TTP). Specifically a threefold increase in A-IPC from baseline may be diagnostic of TTP. Here, A-IPC was used to understand a coexisting immune dysregulation complicating TTP treatment. A 17-year-old previously healthy female was admitted with altered mental status, petechiae, anemia, thrombocytopenia, and schistocytes on peripheral smear. Daily therapeutic plasma exchange (TPE) and corticosteroids were started for suspected TTP supported by ADAMTS13 activity of less than 5%, inhibitormore than8, and more than threefold A-IPC increase from baseline post-TPE initiation. Despite daily TPE, the patient had significant and unexpected decreases in platelet (PLT) counts and A-IPCs during her hospital course. After each PLT count decline, response to TPE and immunosuppression led to increasingly prolonged count recovery with subsequent episodes. Decreases in both PLTs and A-IPCs indicated that both mature and immature PLTs were being cleared from circulation. Recovery occurred once A-IPC dynamics indicated restored negative feedback in relation to PLT count. Serial monitoring of A-IPC dynamics was indicative of coexisting processes in the setting of ADAMTS13 deficiency. Uncoupling of the expected A-IPC and PLT count seen in TTP suggested the presence of such an immune process in addition to TTP with high ADAMTS13 inhibitor. Monitoring of A-IPC is a clinically valuable, rapid, and noninvasive thrombopoietic measurement when TTP is suspected.