Figure 2: An extraorbital extension of orbital IgG4-related disease. This 60-year-old man presented with visual field defects in the right eye during a one-month period. On examination, his best-corrected visual acuity was 20/20 OD and 20/12.5 OS. Humphrey 30-2 threshold perimetry on his right eye showed an inferior altitudinal defect. He had 4 mm proptosis in the right eye (a). Magnetic resonance imaging of the brain and orbits with gadolinium showed infiltrative lesions in the right inferior orbit, infraorbital nerves (b), and also in the orbital apex and cavernous sinus (c). Clinical findings and imaging studies suggested compressive optic neuropathy. He had an elevated level of serum IgG4 (223 mg/dL; normal range: 4.8–105 mg/dL). Biopsy specimens showed lymphoproliferative lesions with IgG4-positive plasma cells and focal sclerosis (d). These findings were consistent with orbital IgG4-related disease with an extraorbital extension.