POSTTRANSFUSION PURPURA - CLINICAL AND IMMUNOLOGICAL INVESTIGATIONS IN 38 PATIENTS

Background: Posttransfusion purpura (PTP) is characterized by severe thrombocytopenia and hemorrhagic diathesis about 1 week following blood transfusion. Only few studies exceed the description of single cases. Materials and Methods: Clinical data from 38 patients were analyzed. Platelet antibodies were studied by complement binding, immunofluorescence, MAIPA assay and acid elution techniques. Results: All patients were female. The mean age at onset was 60.7 years (35-78 years). 4 patients received whole blood, 28 were transfused with packed RBC. 11 of 13 patients (85%) had febrile, non hemolytic adverse reactions during the transfusion. The interval between transfusion and onset of purpura extended from 2 to 14 days, with a peak at 7 and 8 days. Hemorrhagic symptoms lasted 10.1 days. The minimal platelet count was 7.0x10(3)/mu l. The platelet count increased to over 50x10(3)/mu l after 13.9 days (n=26), and to over 100x10(3)/mu l after 17.0 days (n=22). 2 patients died of hemorrhagic complications. 24 patients were treated with glucocorticoids, 20 with intravenous immunoglobulins (ivIG), 17 of these received both therapies. 14 of 19 patients (74%) responded well to ivIG. In contrast, platelet transfusions produced no adequate increment, in 6 cases they provoked febrile reactions. 35 sera (92.1%) contained anti-Zw(a), either alone or together with anti-HLA or in 1 case with anti-Br-a. Anti-Bak(a) and anti-Bak(b) were found in 1 case each. In 5 patients, anti-Zw(a) could be eluted from autologous Zw(a)-negative platelets. Conclusions: The broad clinical spectrum of PTP could be shown. Since 5% of the patients succumb to bleeding complications, the application of ivIG as therapy of choice is recommended. The phenomenon of elution of alloantibodies from autologous platelets is interpreted as a consequence of 'pseudospecificity' which may play a role in the pathogenesis of PTP.