Bilateral Proptosis Secondary to Extranodal Marginal Zone Lymphoma Mimicking IgG4-Related Disease

A 62-year-old man presented to the emergency department with a 15-day history of persistent ocular pain and blurred vision. He reported chronic bilateral proptosis for the past 11 years (Fig. 1A,B). Hertel exophthalmometry measured 29 mm in both eyes. In 2016, he was diagnosed with immunoglobulin G4 (IgG4)-related disease based on a lower eyelid biopsy and had received methotrexate, prednisone, and folic acid, without clinical improvement. Orbital magnetic resonance imaging (Fig. 2A,B) revealed multiple infiltrative, expansile lesions with bilateral thickening of the optic, supraorbital, and infraorbital nerves. Repeat biopsy of the right infraorbital nerve showed atypical lymphoid proliferation and chronic inflammation, with 48% IgG4-positive plasma cells. Immunohistochemistry confirmed extranodal marginal zone lymphoma. Systemic workup was negative. The patient was referred for orbital radiotherapy.FIG. 1FIG. 2