High-dose intravenous immunoglobulin treatment in two patients with acquired factor V inhibitors.

We report two patients who developed acquired factor V (FV) inhibitors not related to exposure to bovine thrombin. Associated conditions were found in one patient (surgery, antibiotic administration) but none in the other one. Bleeding complications occurred only in the patient with idiopathic FV inhibitor, leading to packed red cell infusion. Laboratory findings showed the presence of specific FV inhibitors with titers of 5.5 and 5 Bethesda units, respectively. These two patients received high-dose intravenous immunoglobulin and FV levels normalized within a few days with a concomitant disappearance of FV inhibitors.