Long-term remission induced by low-dose rituximab for relapsed and refractory thrombotic thrombocytopenic purpura: A report of two cases.

Thrombotic thrombocytopenic purpura (TTP) is acquired in the majority of cases. Traditional therapy consists of plasma exchange (PEX), as well as the administration of certain immunosuppressive agents including steroids. A standard dose of rituximab (RTX) at 375 mg/m2 weekly for 4 consecutive weeks was recently demonstrated to have significant activity in patients with acquired TTP. To date, clinicians have limited experience using low-dose RTX. In the present study, 2 patients were treated with low-dose RTX at 100 mg weekly for 4 consecutive weeks as a salvage therapy following failure to respond to PEX and other immunosuppressive agents. Prior to RTX therapy, the patients had severely deficient ADAMTS13 activity and detectable anti-ADAMTS13 inhibitors. The patients achieved complete remission and presented long-term stabilization during follow-up. Repeated detection during follow-up demonstrated that the patients had 100% ADAMTS13 activity and undetectable anti-ADAMTS13 antibodies. Although further investigation in a prospective clinical trial is required, the use of low-dose RTX seems to be as effective as a standard dose for patients with relapsing or refractory acquired TTP.