Superior vena cava syndrome due to Graves' disease

We encountered a patient with Graves' disease showing superior vena cava (SVC) syndrome. The patient was a 72-year-old woman with diffuse nontoxic goiter (diagnosed as chronic thyroiditis); she developed Graves' disease during L-T4 administration. Radioiodine-131 therapy failed to give sufficient effect, and the intrathoracic goiter became enlarged in association with increases in thyroid stimulating antibody activities, followed by the development of SVC syndrome. The surgically excised thyroid gland was diffuse without any nodules. Microscopic findings revealed adenomatous hyperplasia. The present case, though extremely rare, seems important for the understanding of the mechanism of onset of SVC syndrome in relation to thyroid gland enlargement.