An acquired factor V inhibitor: clinical and laboratory features.

A sixty-five year old white male presented with an acquired Factor V inhibitor after an episode of cholecystitis and cefotaxime therapy. Plasma Factor V activity was less than 1%. He developed lower gastrointestinal bleeding a week after onset of coagulopathy, and was treated with plasmapheresis, fresh frozen plasma, oral cyclophosphamide, and prednisone. The coagulopathy resolved within four days of treatment, and within two weeks of presentation. Laboratory studies revealed an IgG inhibitor to Factor V that closely mimicked the more commonly encountered lupus anticoagulant. We would like to alert clinicians to this entity because, in contrast to a lupus anticoagulant, the acquired Factor V inhibitor can be associated with clinical bleeding as in our patient, and requires therapy prior to any surgical procedures.