AUTOIMMUNE THROMBOCYTOPENIA (AITP) AND THYROID AUTOIMMUNE-DISEASE (TAD) - OVERLAPPING SYNDROMES

The pathogenesis of thrombocytopenia associated with TAD and the occur rence of overlapping traits between TAD and AITP are still a matter of debate. For this reason, we investigated for the presence and specifi city of platelet and thyroid autoantibodies in 18 TAD patients with th rombocytopenia, 19 TAD patients without thrombocytopenia and in 22 pat ients with primary AITP without clinical signs of TAD. Platelet-associ ated IgG and/or specific circulating platelet autoantibodies were dete cted in 83% of patients with TAD and thrombocytopenia, in 10% of patie nts with TAD without thrombocytopenia and in 86% of patients with prim ary AITP. The reactivity of serum autoantibodies, assayed by MoAb immo bilization of platelet antigens (MAIPA), was directed against platelet glycoproteins Ib and/or IIb/IIIa in 50% of the patients with TAD and thrombocytopenia, as in 46% of the patients with primary AITP. Thyroid autoantibodies were found in 89% of patients with TAD and thrombocyto penia, in 95% of patients with TAD without thrombocytopenia, and in 18 % of patients with primary AITP. Thyrotropin (TSH) levels determined i n three of four AITP patients with thyroid autoantibodies revealed a s ubclinical hyperthyroidism in one patient. The present study supports the autoimmune aetiology of thrombocytopenia associated with TAD, sinc e the prevalence and specificity of platelet autoantibodies are simila r in TAD and primary AITP. The results indicate also that there exists an overlap between thyroid and platelet autoimmunity with or without clinical manifestations.