Re-exacerbation of thrombotic thrombocytopenic purpura shortly after initial response to plasma exchange and rituximab in patients with high anti-ADAMTS13 inhibitor titers

We previously described 4 patients (cases 1 to 4) with acquired thrombotic thrombocytopenic purpura (TTP) and showed that rituximab exhibited both shortand long-term favorable effects. In this paper, we report 4 additional patients (cases 5 to 8) with TTP who showed variable disease severities and antiADAMTS13 inhibitor titers. These 4 patients were treated using plasma exchange (PEx) and steroids, and 3 received 4 doses of rituximab weekly, which resulted in a long-term complete response. In the 8 patients with TTP we encountered, 4 had an anti-ADAMTS13 inhibitor titer of >5.0 BU/mL at presentation. Although all 4 patients were treated with PEx, highor standard-dose steroids, and weekly rituximab, inhibitor rebound associated with the recurrence of thrombocytopenia and elevation of LDH levels was noted in 3 patients shortly after the initial response, while two developed the recurrence of neurological manifestations, which required intravenous sedation under mechanical ventilation. Thus, the dosage and administration schedule of rituximab should be optimized for patients with high inhibitor titers, and additional immunosuppressive agents may be considered in refractory cases. On the other hand, 5 patients previously had an episode of infectious disease that preceded the presentation, which suggested that infection is a triggering factor for the development of TTP.