Rituximab as a Treatment Option for Acquired Inhibitors.

The incidence of acquired Factor VIII (FVIII) inhibitors is 0.2–1.0 case/million/year with a mortality range of 7.9 to 22%. Management consists of treating the bleeding episode and eradicating the autoantibody. First line therapy for the latter includes immunosuppressive agents with all of their potentially serious side effects. On this study, we add 5 patients to the scant published literature of individuals treated with Rituximab, a monoclonal antibody against CD20⁺ B cells. The patients had bleeding episodes from moderate to severe and presented with a prolonged partial thromboplastin time (PTT) that did not correct with a 1:1 mix with normal plasma. Inhibitors were confirmed by a low FVIII level and the Bethesda assay. Summarized clinical and laboratory data are shown in the table below. All the patients received Rituximab 375 mg/m² once weekly × 4 doses. Patients 2–5 received Rituximab exclusively and patient 1 received two initial weeks of prednisone and cyclophosphamide followed by Rituximab. There were no adverse reactions to Rituximab. Complete remission was defined as clinical improvement associated with disappearance of the FVIII antibody and normalization of the factor VIII level. All the patients are currently in complete remission with no relapse, and with a post Rituximab time of more than 36 months for patients 1 and 5, and 12 months for patients 2–4. Rituximab appears to be a safe and well tolerated alternative to cytotoxic agents and it should be studied more thoroughly in prospective randomized studies.