Disappearance of factor VIII autoantibodies preceding autoimmune haemolytic anaemia

We describe a previously healthy woman who at the age of 44 years developed a factor VIII inhibitor, that over the years increased to a maximum level of 3600 Bethesda units (BU) mL(-1) in 1978. The epitope specificity of the factor VIII inhibitor was investigated and antibodies directed against the A2 and C2, domains of factor VIII were detected. The majority of these anti bodies were of subclass IgG4. Over the years, the inhibitor titre gradually decreased and in 1989, the inhibitor could no longer be detected. Shortly after, the patient developed auto-immune haemolytic anaemia. A possible lin k between the disappearance of factor VIII inhibitors and the development o f other autoantibodies may be explained by concomitant development of antii diotypic antibodies that neutralize the activity of factor VIII inhibitors. We were unable to detect anti-idiotypic antibodies, which could explain th e decline in factor VIII inhibitor titre in this patient.