High-Dose Intravenous ?-Immunoglobulin Infusion in the Treatment of Thrombotic Thrombocytopenic Purpura

To the Editor.—Finn and coworkers concluded in their recent article that intravenous γ-immunoglobulin infusion produced a remission in one patient with thrombotic thrombocytopenic purpura (TTP) after more conventional treatment failed.¹ Analysis of the data presented in Fig 2 suggests that the response to treatment occurred prior to the administration of intravenous γ-immunoglobulin on day 13. Specifically, the decrease in the lactic dehydrogenase level began on day 12. In addition, the platelet count response following vincristine sulfate administered on days 7 and 8 is similar to previous observations of patients with TTP successfully treated with only vincristine.² After a dose of vincristine, the platelet count usually decreases for three to five days and then increases promptly. This effect of vincristine therapy on platelet production and survival has been substantiated in animal studies as well as in humans.³ Unfortunately, Finn et al did not provide a platelet count