[Posttransfusion purpura: identification of a new platelet antigen Leka. A case].

A young female patient with Gardner's syndrome developed post-transfusion purpura. Serological studies demonstrated the presence of an antibody directed not against PlA1 but against a new antigen, Leka. This is the first case of post-transfusion purpura not associated with immunization against the PlA1 antigen.