Increased IgA in a subject with positive anti-thyroid autoantibodies - a case report

Introduction: Increased concentrations of antithyroid autoantibodies are found in inflammatory diseases as well as in thyroid autoimmune disorders. The aim of this report is to present increased IgA concentrations in a female patient with positive anti-thyroid autoantibodies. Results throughout 13 months of follow-up are presented. Materials and methods: The levels of thyroid hormones and antibodies in the serum samples were measured using microparticle enzyme-immunoassay. IgA was determined by two immunochemical methods, immuno-turbidimetric method and radial immunodiffusion, respectively. Results: Initial thyroid function tests showed normal values of T3, T4 and thyroid stimulating hormone (TSH), and increased values of thyroid peroxidase autoantibodies (anti-TPO), anti-thyroglobulin (anti-Tg) autoantibodies and IgA. The patient underwent treatment with single daily dose of levothyroxine. The elevated initial levels of anti-TPO stabilized with the administration of levothyroxine, while anti-Tg remained increased. IgA determined by immuno-turbidimetric method was significantly increased during the follow-up period. Repeated determination of IgA by radial immunodiffusion revealed lower IgA concentrations. Conclusion: Possible false increased IgA values could be a result of both, interferences of goat anti-IgA antibodies from reagents, and cross-reactivity with endogenous anti-Tg autoantibodies in serum, respectively. Further investigations are needed to ascertain the cause of increased IgA values in patient with positive anti-thyroid autoantibodies.