IgG4-related optic neuropathy (IgG4-RON) caused by optic perineuritis is a rare complication of IgG4-related disease (IgG4-RD).

Limited information is available in the literature on the clinical and radiologic risk factors associated with the optic perineuritis type of IgG4-RON.

We report a rare case of IgG4-RD with bilateral optic perineuritis, enlarged maxillary nerves with perineural spreading to infraorbital nerves, and pansinusitis; with the diagnosis confirmed by histopathologic study of sinus biopsy specimens.

Magnetic resonance imaging is a useful tool for diagnosing cranial nerve perineuritis, with the presence of the “doughnut” sign and “tram-track” sign indicative of inflamed soft tissues surrounding the cranial nerve.

The case described here is a “pure” case of optic perineuritis secondary to IgG4-RD, and a successful post-treatment visual outcome was obtained with treatment with oral corticosteroids followed by azathioprine.