Thrombocytopenia associated with gold therapy: a drug-induced autoimmune disease?

We studied 13 patients with rheumatoid arthritis (RA) and gold-induced thrombocytopenia. Platelet-specific autoantibodies of the IgG and often also of the IgM class were detected by immunofluorescence on the patient's platelets and in ether eluates from these platelets. In nine patients we also detected autoantibodies in the serum. The antibodies were unreactive with platelets from patients with Glanzmann's disease in most cases, and were not EDTA dependent. Thus, they had the serological characteristics of true autoantibodies. The reaction of the antibodies with platelets was not influenced by the addition of extra gold. By atomic absorption spectrophotometry we found that the ether eluates, which were often strongly reactive with donor platelets, were free of gold. This indicated that the autoantibodies in the thrombocytopenic patients were not dependent on gold for their reaction. The possibility is raised that gold treatment of rheumatoid arthritis patients induces or enhances the formation of platelet-specific autoantibodies, and that gold-induced thrombocytopenia is a drug-induced autoimmune disease.