Case report: successful treatment of an idiopathic acquired factor VIII inhibitor with unusual features.

A patient with an idiopathic acquired factor VIII inhibitor is described. Unusual features of this patient's illness were measurable factor VIII (4 to greater than 20%) despite the presence of inhibitor, and continued spontaneous bleeding despite these factor VIII levels. Successful treatment on both a short-term and a long-term basis--with neutralizing doses of human factor VIII concentrate and with chlorambucil, respectively--is reported. It is concluded that in patients with this type of inhibitor factor VIII, assays may not provide a reliable prediction of the potential for bleeding and that chlorambucil therapy warrants further study.