Abstract:

Objectives: Acquired factor inhibitor is a rare disorder and can cause life-threatening bleeding. Consequently, we report the efficacy and safety of our patients with acquired factor inhibitor treated with immunosuppressive drugs. Materials and Methods: We retrospectively investigated acquired factor inhibitor patients who were followed and treated in our center between November 2018 and March 2022. Results: A total of seven patients, four of whom were male, with a median age of 65 (43-76) were included. Acquired factor inhibitor was associated with malignancy (n=3), advanced age (n=2), postpartum period (n=1) and lupus anticoagulant (n=1). Median follow-up time was 9 months (range, 2-46). High inhibitor titres were detected in four patients [median: 7.06 BU/mL (range, 5.76-100)] and all of them were treated with immunosuppressive drugs (metilprednisone in combination with cyclophosphamide, rituximab). The overall response rate was 100% (n=4) with 50% complete response and 50% partial response and one patient who developed the inhibitor in the postpartum period responded to single agent rituximab. To achieve the hemostatic target, recombinant activated clotting factor VII (rFVIIa) and activated prothrombin complex concentrate (aPCC) were used in two out of four patients with active bleeding. Hemostasis was achieved successfully. Three patients developed a low-titre factor inhibitor and immunosuppressive drugs were not started for inhibitor elimination. Coagulation assays disappeared when the underlying condition was self-limited. Conclusion: Clinical presentation of factor inhibitors is highly variable and optimal treatment is not clearly established. Rituximab might be a promising treatment for therapy-resistant factor inhibitor and bleeding control was achieved with rFVIIa and aPCC. Treatment plan of patients with low-titre factor inhibitor should be provided considering the clinical situation and underlying disease.

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