ABSTRACT
PURPOSE: The platelet synthesis is extremely variable after intravenous immunoglogulin injection (IVIG) in acute idiopathic thrombocytopenic purpura (ITP). To investigate the size variation of platelet according to the time sequence of ITP, the relationship between platelet number and mean platelet volume (MPV) was analyzed. METHODS: Twenty acute ITP patients who showed abrupt increase of platelets within 48 hours after IVIG were selected. We checked the platelet number and MPV, thereafter analyzed the relationship. RESULTS: At the early phase of ITP before IVIG, MPV was normal or slightly decreased. However, as the number of platelet increased after IVIG, MPV increased together until platelet count reached 100, 000/mm3. The MPV decreased afterward, therefore the platelet mass was preserved. CONCLUSION: At the early phase of ITP before the increase of platelet, MPV decreased in spite of low number of platelet. After IVIG, there was an abrupt increase of MPV with platelet number. There might be some contributing factors for these, particularly IL-6, IL-11 and thrombopoietin. Now, we need more experimental data to explain these findings.