Abstract
The mechanism of cyclic thrombocytopenia developing in a 36-year-old woman was studied. The distribution of platelet size differed depending on phases in the cycle, per cent macrothrombocytes being maximal at the lowest platelet count and decreasing as platelet counts rose. On the other hand, serial examinations of the bone marrow revealed neither megakaryocytic hypoplasia nor significant changes in the ploidy of megakaryocyte nuclei during the cycle. In addition, the platelet cycle was not accompanied with such a cyclic pattern of either peripheral reticulocytes or neutrophils. These observations suggested that the platelet cycle in this patient would be ascribable to variation in the destruction rate of platelets rather than their production rate, although the half survival of platelets was short as 0.8 days even at the peak platelet count. The accelerated platelet destruction was not related to periodic changes of the endometrium since hysterectomy did not result in disapperarance of the cyclic pattern of platelets. During our observation the periodicity of platelet counts was apparent when she received prednisolome, while sever thrombocytopenia persisted without administration of the corticosteroid.
