Immunoblot analyses of platelet multimerin. Washed platelet lysates from several affected family members (*) were compared with dilutions of normal pooled platelet lysate (NP) and analyzed using nonreduced multimer gels and immunoblotting with monoclonal antimultimerin (JS-1). A short exposure of the multimers in the normal pooled lysate is shown for comparison. Similar multimerin abnormalities were found in patient II-13.