Post-transfusion purpura: a survey of 12 Danish cases with special reference to immunoglobulin G subclasses of the platelet antibodies

SUMMARY. The clinical and immunological data of 12 Danish cases of post-transfusion purpura (PTP) are summarized. All patients but one were women. All except one had thrombocytopenic purpura which occurred 4–11 days after transfusion, usually with a nadir of the platelet count below 10times109 1-1. The typical haemorrhagic symptoms were cutaneous bleedings, melena and haematuria lasting from 3 to 12 days. The time until normalization of platelet count varied from 3 to 50 days after onset. One patient had recurrence of PTP and one patient died due to intracranial haemorrhage. Ten of the HPA-la negative patients (83%) had platelet-specific HPA-la antibodies and two HPA-lapositive individuals had anti-HPA-lbantibodies. In 10 patients, HLA antibodies were also detectable and in one patient a delayed haemolytic transfusion reaction due to anti-E was seen. All of seven patients investigated had anti-HPA antibodies of both IgGl and IgG3 subclasses during the thrombocytopenic period while all of 10 patients had anti-HPA of only the IgGl subclass after recovery from PTP Thus, the destruction of autologous platelets in PTP seems to be associated with the presence of anti-HPA of the IgG3 subclass which may be of importance in the pathogenesis of PTP.