[Three cases of thymic hyperplasia associated with hyperthyroidism].

We encountered three cases of thymic hyperplasia associated with hyperthyroidism. Case 1 was in a 35-year-old woman; a chest CT scan showed an anterior mediastinal mass and right-sided pleural effusion, which suggested the presence of a thymoma Case 2 was in a 21-year-old man who complained of palpebral ptosis and also had myasthenia gravis (Osserman type I). Case 3 was in a 47-year-old woman; a chest CT scan showed thymic hyperplasia and mediastinal lymphadenopathy. In all cases, anti-thyroid medication was given first, because of the associations with hyperthyroidism. Moreover, in cases 1 and 2 no tumor was found, and only hyperplasia was detected in the thymus, although both patients underwent extended thymectomy. Furthermore, surgery was not effective against the hyperthyroidism (anti-thyroid medication could not be withdrawn or reduced). In cases 2 and 3, thymic hyperplasia, as seen on chest CT scans, resolved as thyroid function was normalized by anti-thyroid medication. The pretracheal lymphadenopathy seen in case 3 also resolved. Thymic hyperplasia may have been a result, not a cause, of hyperthyroidism. When we encounter patients with thymic masses and hyperthyroidism, we should give anti-thyroid medication and observe the thymus for some time before resorting to surgery.