High-dose intravenous IgG in adults with autoimmune thrombocytopenia.

A study of the effect of high-dose intravenous IgG in 25 adults with autoimmune thrombocytopenia confirmed the predictable rise in the platelet count seen during the infusion and previously reported in children. Unlike the data based on children, there was no sustained response unless the IgG infusion was closely associated with splenectomy. There was no correlation between the presence of platelet autoantibodies or the Ig class of the autoantibody and the pattern of response to the infusion. The initial platelet response appears to be the result of transient blockade of the reticuloendothelial system, including the macrophage Fc receptor mechanism. The long-term response in some patients requires another explanation and may be due to a more specific immunosuppressive effect of the high-dose IgG infusion. Splenectomy may have an additive effect by removing a major site of platelet autoantibody production.