FAMILIAL ASSOCIATION OF AUTOIMMUNE THROMBOCYTOPENIA AND HYPERTHYROIDISM

An association between thrombocytopenia and thyrotoxicosis in a single individual is well documented, and the theories for this event includ e a common immunologic cause or a thyrotoxic-induced decrease in plate let survival. We report the first description of the coexistence of au toimmune thrombocytopenic purpura (AITP) and Graves' disease in severa l members of the same family, in which four females were thrombocytope nic and two of these were also hyperthyroid. All four patients had hig h titers of antiplatelet antibodies, and the two hyperthyroid cases we re positive for thyroid-stimulating immunoglobulins (TSI). The familia l occurrence of two autoimmune disorders is very uncommon, and suggest s a genetic etiology. The HLA phenotype was determined and the antigen s B8 and DR3, which are reported with high frequency in both diseases, were present in three patients. Although the etiologic cause is still unknown, our findings further support the theory that a genetic predi sposition underlies autoimmune disease.