[Post-transfusion purpura. An unknown cause of acute immune thrombocytopenia. 4 new cases].

Post-transfusion purpura is characterized by the occurrence of acute immune thrombocytopenia 5 to 10 days after transfusion of platelet-containing blood products in subjects who had been alloimmunized to specific platelet antigens. Four cases are reported here. Three of these 4 patients, who had a rare PLA1 platelet phenotype, had developed, during a previous sensitization (pregnancy n = 2, transfusion n = 1), an allo antibody directed against PLA1 antigen. The fourth patient presented a specific anti-PLA2 antibody. Thrombocytopenia (platelet count between 4 and 40 x 10(9)/1) appeared 1 to 12 days after the responsible transfusion and showed as haematomas (n = 3) or haemoptysis (n = 1). One patient was asymptomatic and remained untreated. The remaining 3 patients received corticosteroids orally associated, in one case, with infusions of human immunoglobulin concentrates. Thrombocytopenia was corrected within 5 to 13 days. In such cases, whenever another blood transfusion is necessary, a preventive treatment with perfectly platelet-free blood products is mandatory. Platelet depletion by freezing-thawing of red cell concentrates is probably not always sufficient, since recurrence was observed with such a product in one of our patients. The exact cause of immune destruction of autologous platelet remains a mystery.