Background: Riedel thyroiditis is a rare, chronic inflammatory disease of the thyroid, characterized by a dense fibrosis that replaces normal thyroid parenchyma. In literature descriptions of individual cases of Riedel thyroiditis can be found.
Case report: We present an euthyroid patient with multinodular goiter who was diagnosed with Riedel thyroiditis using pathology. Imaging diagnostic methods (Ultrasonography, X-ray computed tomography, Magnetic resonance imaging, Radionuclide imaging) or various tests of thyroid function cannot confirm the diagnosis of Riedel thyroiditis.
Conclusion: Only level of IgG4 may be helpful for the diagnosis of Riedel thyroiditis, while pathology is used for its definitive confirmation.
Keywords: Riedel thyroiditis; histopathology.