Complete response of acquired FV inhibitor to rituximab.

Abstract

in the surgery. His hematology investigation results on day 6 post-operation showed: platelets 119 × 10/L, prothrombin time (PT) 17 s [reference range (RR): 10–13 s], activated partial thromboplastin time (APTT) 38.5 s (RR: 22.6–33.2 s), thrombin time (TT) 15.5 s (RR: 16.3–19.2 s), fibrinogen by Clauss assay 4.92 g/L, quantitative d-dimer 18,730 μg/L FEU, and FV activity of 64.2 %. A total of 29 units of fresh frozen plasma (FFP) were transfused in the post-operative period before the onset of coagulation inhibitor for suspected liver disease and/or disseminated intravascular coagulation, in view of the slightly prolonged PT and APTT and increased d-dimer level. However, on day 10 post-operation there was prolongation of PT to 63.7 s and APTT to 87.1 s. The PT and APTT were correctable down to 15.3 and 33.3 s, respectively immediately after 1:1 mixing with normal plasma, but the mixture was prolonged to 16.4 and 36.8 s, respectively after incubation at 37 °C for 1 h and to 18.5 and 41.3 s, respectively, after 2 h. The FV activity of the patient was markedly reduced to 2.2 % and multiple dilution analysis showed non-parallelism. The platelet FV level was not determined and the possibility of FV mal-distribution was not entirely excluded. Assay of other coagulation factors showed: FVII 71 %, FVIII 187 %, FIX 99 % and FX 73 %. A diagnosis of acquired FV inhibitor was made. A Bethesda assay based on PT showed an inhibitor level of 2.2 BU/mL. Instead of an APTT-based Bethesda assay, the PT-based assay was employed since FV assay in the laboratory was also PT based. The patient experienced no significant bleeding problems. The patient was initially treated by intravenous immunoglobulin, plasmapheresis and platelet transfusion. Steroids were not given due to concurrent chest infection. There was no improvement in the PT and APTT. The patient was then started on rituximab (Mabthera, Roche) at a dose of 375 mg/ Dear Sir, Acquired factor V (FV) inhibitor is a rare coagulopathy of varying clinical severity that ranges from asymptomatic laboratory abnormality to life-threatening bleeding [1]. The majority of previously described cases developed acquired FV inhibitor after exposure to bovine thrombin preparations [2]. However, due to the increasing use of recombinant forms of thrombin, acquired FV inhibitor now arises due to other precipitating factors, such as surgery, antibiotics (especially of the β-lactam group), blood transfusion, cancer, and autoimmune disorders [1]. Treatment of acquired FV inhibitor entails control of bleeding and eradication of the autoantibody [3]. We report a patient with acquired FV inhibitor who showed complete durable response to anti-CD20 monoclonal antibody rituximab, and review the literature on this new treatment modality for this condition. An 87-year-old Chinese man who had a recent radical gastrectomy for stomach remnant cancer presented with blood streaked tracheal aspirate. No fibrin glue was used