Orbital lymphoma misdiagnosed as Graves' ophthalmopathy.

OBJECTIVE: To describe a case of bilateral orbital lymphoma mistakenly diagnosed as Graves' ophthalmopathy. METHODS: We present a case report, with laboratory data and photographic documentation, and discuss the differential diagnosis in patients with orbital masses. RESULTS: A 65-year-old man with bilateral exophthalmos and substantial weight loss was referred to the Endocrine Clinic for evaluation of possible Graves' disease. A 6-cm mass was detected in the left axilla. Biopsy of this mass revealed the histopathologic diagnosis of anaplastic B-cell lymphoma. Treatment with intrathecally administered methotrexate and orally administered dexamethasone promptly resulted in decreased proptosis. CONCLUSION: The most frequent cause of bilateral proptosis is Graves' ophthalmopathy, and when it is associated with weight loss in an elderly patient, the initial diagnostic consideration is thyrotoxic Graves' disease. This case should remind physicians that bilateral orbital lymphoma, although uncommon, may mimic Graves' ophthalmopathy.