Post-transfusion purpura.

We report two cases of purpura characterised by severe immune thrombocytopenia which appeared one to two weeks after blood transfusion during elective surgery. Both patients had antibodies to the platelet P1A1 antigen and displayed high levels of platelet-bindable IgG and IgM in their serum; they were treated with glucocorticoids and recovered after four weeks. One case relapsed following a further transfusion of packed red cells. Theories of pathogenesis, methods of diagnosis, and alternative forms of therapy are reviewed.