Raumforderung im vorderen Mediastinum bei einer Patientin mit Morbus Basedow

HISTORY AND CLINICAL FINDINGS: A 24-year-old woman with osteosarcoma of the right thigh, diagnosed 12 years ago, complained at a follow-up examination of decreased exercise tolerance, increased nervous tension, heat intolerance, weight loss, hair loss and irregular stools. Examination revealed tachycardia (100/min), mild exophthalmus and a small goitre. INVESTIGATIONS: A decreased basal TSH level (0.002 mU/ml), raised peripheral thyroid hormone (fT4 6.7 ng/dl, total T3 7.8 micrograms/l) and a TSH receptor antibody titre of 33.4 U/l) were compatible with immune type Graves' disease. Radiology revealed an upper mediastinal space-occupying lesion which scintigraphically was separate from thyroid tissue. A metastasis of the osteosarcoma or thymus hyperplasia were considered the most likely cause. TREATMENT AND COURSE: The mediastinal lesion regressed under thyrostatic treatment with carbimazole (20 mg daily by mouth). But the clinical picture, localization and negative scintigraphy provided the diagnosis of transitory thymus hyperplasia in the course of Graves' disease. CONCLUSION: In immune type Graves' disease with a mediastinal space-occupying lesion, not only intrathoracic goitre but also thymus hyperplasia should be considered in the differential diagnosis.