Clinical challenge: An orbital Hickam's dictum.

A 53-year-old man with hyperthyroidism presented with asymmetric proptosis and diplopia. Thyroid-stimulating immunoglobulin was elevated, suggesting active thyroid eye disease. Imaging of the orbits revealed enlargement of the extraocular muscles, including irregular enlargement of the left lateral rectus muscle. Biopsy of the lateral rectus muscle demonstrated infiltration of the muscle with Bcl-2 positive B lymphocytes consistent with chronic lymphocytic leukemia (CLL). Evaluation for systemic lymphoproliferative disease was negative. The patient was treated with orbital radiotherapy at specific dosages for both TED and CLL. He responded well to therapy with a reduction in proptosis and diplopia and no evidence of recurrent CLL.