SummaryA 33-year-old euthyroid woman presented with diplopia of sudden onset. The diagnosis of endocrine ophthalmopathy was made, based on the presence of a left intraorbital pseudotumor and left orbital extraocular muscle thickening, together with an asymptomatic atrophic thyroiditis. A treatment with plasmapheresis, prednisolone and azathioprine resulted in a spectacular improvement of the ophthalmoplegia and in a complete disappearance of the intraorbital mass. The association between endocrine ophthalmopathy and asymptomatic atrophic thyroiditis, though explainable by the immune disorder, has only rarely been described.Division of Endocrinology and Department of Internal Medicine, Academisch Ziekenhuis, Vrije Universiteit Brussel, Belgium.