Rituximab in the treatment of relapsed thrombotic thrombocytopenic purpura

Several reports have defined nonfamilial thrombotic thrombocytopenic purpura (TTP) as an autoimmune disorder caused by antibodies to von Willebrand's factor-cleaving protease (vWF-CP). This raises the possibility that rituximab, a monoclonal antibody against CD20 present in B-lymphoid cells, may have utility in the treatment of TTP. We report five consecutively treated patients with relapsed TTP who responded rapidly to immune suppression by rituximab at our institution. These two male and three female patients had a median age of 37 years (27-70). The median time from diagnosis to therapy was 24 months (8-60). Prior therapies included plasma exchange and corticosteroids in all cases, splenectomy ( 4), vincristine and aspirin (3), and azathioprine (2). The median number of plasma exchanges received prior to therapy was 59 (21-158). The cohort had a median platelet count of 48 x 10(9)/l (23-110), median hemoglobin of 9 g/dl (8-11), and median lactate dehydrogenase of 632 IU/l (311-945) prior to administration of rituximab. Analysis of vWF-CP activity demonstrated absent or decreased activity with detectable inhibitors in four patients. All patients attained a complete response. The median time to response after the first dose of rituximab was 5 weeks. Responses are maintained in all patients from 10 to 21 months after treatment. This report adds to the evidence that rituximab has efficacy in nonfamilial TTP and warrants further study.