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 include a common immunologic cause or a thyrotoxic-induced decrease in platelet survival. We report the first description of the coexistence of autoimmune thrombocytopenic purpura (AITP) and Graves' disease in several members of the same family, in which four females were thrombocytopenic and two of these were also hyperthyroid. All four patients had high titers of antiplatelet antibodies, and the two hyperthyroid cases were positive for thyroid-stimulating immunoglobulins (TSI). The familial occurrence of two autoimmune disorders is very uncommon, and suggests a genetic etiology. The HLA phenotype was determined and the antigens 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 predisposition underlies autoimmune disease.