Summary

The authors would like to present an unusual case of ocular adnexal, mucosa-associated lymphoid tissue lymphoma, isolated to a single extraocular muscle. A 59-year-old woman presented with a 3-month history of slowly progressive double vision, worse on elevation, for which her optometrist had given her prisms. A swollen left upper eyelid was present for 10 days. CT scan of the brain and orbits revealed a 3 cm × 1.5 cm mass arising from the region of the left superior rectus with no signs of bone erosion. Histology showed infiltration by small lymphoid cells. Stage 1AE low-grade marginal zone B cell lymphoma was diagnosed. Possible aetiologies included Chlamydia psittaci infection and the recently recognised IgG4-related sclerosing disease. After oral doxycycline 200 mg once a day failed to show improvement, localised radiotherapy 30 Gy resulted in excellent clinical and radiological resolution of this isolated lymphoma.