Arthritis associated with antithyroid therapy in a 15-year-old girl.

A 15-year-old white girl with autoimmune thyroiditis developed arthritis 3 weeks after starting therapy with the antithyroid drug thiamazole. Because an adverse drug reaction of thionamide therapy was suspected, thiamazole was withdrawn, and symptoms disappeared rapidly. Thionamide therapy is indicated for hyperthyroidism and has been widely used since 1948.