Riedel’s Thyroiditis in Multifocal Fibrosclerosis: CT and MR Imaging Findings

Summary: Riedel’s thyroiditis is a rare disorder of un-known etiology and may be seen isolated or as a part of multifocal fibrosclerosis. It is important to distinguish Rie-del’s thyroiditis from thyroid carcinoma. Reports about imaging features of Riedel’s thyroiditis are limited in the radiologic literature. We describe herein CT and MR im-aging features of Riedel’s thyroiditis in a case of multifocal fibrosclerosis with previously unreported radiologic observations. Multifocal fibrosclerosis is a rare syndrome char-acterized by fibrosis involving multiple organ sys-tems (1). Varying combinations of involvement have been reported: Riedel’s thyroiditis, retroperi-toneal fibrosis, orbital pseudotumor, mediastinal fi-brosis, and sclerosing cholangitis (1–4). Althoug