[Orbital pseudotumors and Riedel's thyroiditis: case report].

Introduction: We report a case of a patient with orbital pseudotumors associated with Riedel's thyroiditis. This association of unknown etiology may be related to idiopathic multifocal fibrosclerosis that includes retroperitoneal fibrosis, mediastinal fibrosis, sclerosing cholangitis, Riedel's thyroiditis, and orbital pseudotumors.

Case Report: A 44-year-old woman was referred for a bilateral inflammatory malignant exophthalmos with progressive optical neuropathy (bilateral visual acuity<1/20). Imaging studies demonstrated bilateral exophthalmos (grade III) with compression of the both optic nerves by extensive tumoral infiltration. The general work-up showed a compressive goiter, with the histopathologic examination establishing the diagnosis of Riedel's thyroiditis. Orbital biopsy and antithyroid antibody testing were not contributive. Systemic corticosteroid associated with total thyroidectomy resulted in regression of the symptoms within 3 months.

Discussion: The coexistence of bilateral orbital pseudotumor and Riedel's thyroiditis is the most common situation found for idiopathic multifocal fibrosclerosis. We discuss the differential diagnosis with thyroid-associated orbitopathy and orbital lymphoma. This observation is original because the diagnosis was reached by ophthalmic manifestation. The ophthalmologist should be able to identify this pathology to optimize the diagnostic and the therapeutic strategy.

Conclusion: In case of exophthalmos, a complete assessment should be made, including radiological and histopathological orbital and thyroid work-up.