A rare case of orbital involvement in Riedel's thyroiditis.

We report a case of Riedel's thyroiditis in a 59-yr-old Caucasian female. She presented hypothyroidism and a stony hard, painful goiter. Due to fever, a high sedimentation rate and a high C-reactive protein (CRP), as well as high levels of anti-thyroid peroxidase antibodies (anti-TPOab), differential diagnostic considerations included acute and subacute thyroiditis as well as Hashimoto's thyroiditis and thyroid malignancy. At the same time the patient had clinical and radiological features of bilateral orbital pseudotumor with lacrimal gland involvement. During L-thyroxine therapy orbital symptoms and signs improved and thyroid size decreased. This case report serves as a reminder of differential diagnostic considerations in the etiology of goiter as well as ophthalmopathy. Although extremely rare, orbital sclerosing fibrosis can be seen in conjunction with Riedel's thyroiditis as part of multifocal fibrosclerosis.