ABSTRACT Objective: To describe a case of bilateral orbital lym- phoma 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 exophthal- mos and substantial weight loss was referred to the Endocrine Clinic for evaluation of possible Graves’ dis- ease. 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 asso- ciated 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. (Endocr Pract. 2001;7:110-112) INTRODUCTION Proptosis is a common manifestation of the ophthal- mopathy of Graves’ disease, occurring in 20 to 30% of patients. It is defined as measured exophthalmos that exceeds by 2 mm the normal upper limit, which is 20 mm in Caucasians and 22 mm in subjects of African descent (1). Proptosis is usually associated with hyperthyroidism but precedes this diagnosis in about 20% of cases (1). The diagnosis of Graves’ ophthalmopathy is straightforward in a patient with thyrotoxicity and bilateral proptosis; problems in differential diagnosis usually arise when a patient is euthyroid and has unilateral proptosis. Other causes of proptosis include orbital mass lesions, in- filtrative diseases, pseudotumor, and carotid cavernous fistula (2). We describe a case of severe bilateral exophthalmos in a patient referred to the Endocrine Clinic for diagnosis and treatment of Graves’ disease but which ultimately proved to be non-Hodgkin’s lymphoma infiltrating both orbits. CASE REPORT A 65-year-old retired man had a 1-year history of pro- gressive bilateral proptosis and edema of the eyelids asso- ciated with loss of appetite, lack of energy, and weight loss of about 15 kg during the previous 2 months. Low- grade fever was also present during the same period, and the patient suffered short bursts of palpitations unrelated to effort. The patient had coronary artery disease and a history of myocardial infarction (MI) and post-MI angina. His current medications were atenolol, diltiazem, nitrates, and aspirin. The patient had undergone a gastric surgical pro- cedure for treatment of an ulcer 15 years previously. He had a history of cigarette smoking and alcohol consump- tion up to 10 years previously. The patient was referred to the Endocrine Clinic for evaluation of possible Graves’ disease. Physical examina- tion revealed an emaciated man who appeared chronically ill and slightly anemic. Severe bilateral proptosis and peri- orbital edema were noted, but he had no restriction of eye movements (Fig. 1). Palpation of the thyroid gland showed no enlargement or nodules. In the left axilla, a hard mobile mass about 6 cm in diameter was felt. A 2+ systolic murmur was detected at the apex. His blood pres- sure was 130/70 mm Hg, and the pulse was 84 beats/min and regular. No abdominal masses or enlarged lymph nodes were palpated. Initial laboratory evaluation showed a hypochromic microcytic anemia, decreased renal function, and normal results of liver and thyroid function studies—serum free thyroxine 0.98 ng/dL (normal, 0.8 to 1.9) and serum thyrotropin 1.6 μU/mL (normal, 0.4 to 4.0 by immuno- ORBITAL LYMPHOMA MISDIAGNOSED AS GRAVES’ OPHTHALMOPATHY Alexandru Buescu, MD, PhD, Patricia Teixeira, MD, Sabrina Coelho, MD, Ines Donangelo, MD, and Mario Vaisman, MD, PhD Submitted for publication May 12, 2000 Accepted for publication January 2, 2001 From the Universidade Federal do Rio de Janeiro, Centro de Ciéncias da Saúde, Hospital Universitário Clementino Frago Filho, Rio de Janeiro, Brazil. Address correspondence and reprint requests to Dr. Alexandru Buescu, R. Barão de Lucena 48, Rio de Janeiro, Brazil 22260-020. © 2001 AACE. 110 ENDOCRINE PRACTICE Vol. 7 No. 2 March/April 2001 Case Report Abbreviations: CT = computed tomography; MI = myocardial infarc- tion