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80% of patients with chronic autoimmune thrombocytopenic purpura (ATP) may reach normalization of platelet count after steroids or splenectomy. In some of these cases a bleeding tendency may still persist and this has been attributed to abnormalities of platelet function resulting from the effect of platelet-bound antibodies. We have studied 49 ATP patients in order to assess the frequency and the pattern of this immune thrombopathia, and the correlation with the levels of platelet associated IgG (PAIgG). Only 3 patients (6%) had prolonged bleeding time and persistence of mucocutaneous haemorrhages, whereas 36% presented an altered platelet aggregation pattern. Platelet serotonin content, platelet and plasma beta-thromboglobulin concentration, and malondialdehyde generation after thrombin stimulus were found also altered, but the findings were not clearly correlated with the concentration of PAIgG.

In 23 patients with untreated idiopathic thrombocytopenic purpura (TP), the relation of thrombokinetics to quantitative determinations of megakaryocytes in bone marrow sections was studied. The megakaryocytes were classified into maturation stages, and platelet sizes were determined. Megarkaryocyte number and volume per microliter of bone marrow were significantly higher in ITP as compared to controls. The megakaryocyte number and volume were inversely related to the peripheral platelet count. Platelet production rate was significantly increased in ITP and related to the megakaryocyte number and volume. The megakaryocytes were shifted towards more immature forms in ITP, suggesting an increased turnover rate of the expanded recognizable metakaryocyte compartment. Platelet size was significantly increased in ITP, and the mean platelet diameter was 1.6 times normal. There was a significant relationship between platelet size and platelet production rate, as well as an inverse relationship between platelet size and platelet mean life-span (MLS). There was also a significant correlation between platelet size and the proportion of young megakaryocytes.

A new modification of the microtitre complement fixation test, (CFT), is described for the detection of platelet-bound antibodies (PBA). The test was positive in 12 out of 16 patients, (75%), with active autoimmune thrombocytopenic purpura (AITP). It was negative in four patients who were in remission of AITP when tested, in 10 patients with non-immune thrombocytopenia and in 51 normal blood donors. This is a semi-quantitative method in which suspensions of the patients' own platelets consume complement and therefore prevent the lysis of sensitised sheep red cells (SRBC). Sera from some of these cases were also tested for serum anti-platelet antibody (SPA) and immune complexes. The possible mechanisms and the relevance of positive results are discussed.

With radioactive chromium, platelet kinetic studies were carried out in four patients with onyalai, a form of thrombocytopenic purpura occurring in the African Negro. Results were compared with those of White patients suffering from idiopathic thrombocytopenic purpura. In the onyalai patients platelet life-span was considerably reduced, and this was associated with a definite rise in radioactivity over the spleen in three of the four cases. In two patients remission was associated with steroid therapy, while in the other two remission followed splenectomy after steroids had failed to raise the platelet count. These findings are similar to those in White patients with idiopathic thrombocytopenic purpura.