Antibodies to platelet membrane glycoprotein antigens in three cases of infectious mononucleosis‐induced thrombocytopenic purpura

Infectious mononucleosis may occasionally be complicated by purpura, but the mechanism of the thrombocytopenia is not known in detail. In the present study, 3 children with mononucleosis-associated purpura were found to have marked elevations of platelet-associated immunoglobulins and circulating platelet binding IgG and IgM. Employing electrophoretically (SDS-PAGE) separated normal platelet membrane proteins in an immunoblot assay, serum IgG and IgM antibodies were found to be directed to antigenic determinants situated on glycoprotein GP IIb (140 kDa) in all patients, but also on smaller proteins of molecular weights between 30 and 52 kDa. 24 control sera were negative. Positive reactions were eliminated after absorption of sera with fresh platelets. These results demonstrate autoantibodies to platelet surface membrane proteins in infectious mononucleosis-induced purpura and suggest a transient autoantibody-mediated platelet destruction as the cause of thrombocytopenia in these patients.