Prevalence of nonthyroid specific autoantibodies in autoimmune thyroid diseases

To clarify the involvement of polyclonal activation of autoimmune reaction in organ-specific autoimmune diseases, we investigated the prevalence of nonthyroid specific autoantibodies in 50 patients with autoimmune thyroid diseases (22 patients with Graves' disease and 28 with Hashimoto's disease) and in 50 age- and sex-matched controls. None of the 100 subjects had any clinical manifestations or laboratory data indicating any other immunological, infectious, hepatic, or malignant diseases. The prevalence of positive antibodies to nucleus, smooth muscle, and single-stranded DNA in the patients (26%, 36%, and 34%, respectively) was higher than that in the control group (8%, 4%, and 4%, respectively), although neither group was positive for autoantibodies against double-stranded DNA, extractable nuclear antigen, SS-A, SS-B, mitochondria, or rheumatoid factor. Furthermore, 66% of the patients had at least one autoantibody to nucleus, smooth muscle, or single-stranded DNA. In conclusion, patients with autoimmune thyroid diseases show high prevalence of autoantibody against not only thyroid-specific, but also nonthyroid-specific antigens. These results are consistent with the concept that immune reaction of patients with organ-specific autoimmune diseases may be polyclonally accelerated to the production of antibodies against both organ and nonorgan specific autoantigens.