Immune checkpoint inhibitors (ICI) are an effective FDA-approved treatment for various cancers including esophageal adenocarcinoma. However, multiple ICI related immune-related adverse effects (irAEs) have been reported. Neurological complications are rare but can lead to significant morbidity, including impaired or complete vision loss. We report a case of optic neuritis in a patient receiving pembrolizumab for metastatic esophageal adenocarcinoma.

A 53-year-old male status-post esophagectomy for esophageal adenocarcinoma with liver metastasis on pembrolizumab presented to the hospital with three days of painless paracentral vision loss in the left eye (OS). He denied dyschromatopsia. Neuro-ophthalmological evaluation showed visual acuity of 20/20 right eye (OD) and 20/150 OS with 4+ left optic disc edema and a left afferent pupillary defect. No other neurologic deficits were present. Work-up for atypical optic neuritis including myelin oligodendrocyte glycoprotein and aquaporin-4 IgG antibodies, ACE, ANCA, Lyme, Syphilis, Bartonella, CRMP-5 was negative. Lumbar puncture demonstrated normal opening pressure, lymphocytic pleocytosis with WBC 44/cm3, protein of 81 mg/dL (normal <45 mg/dL), negative cytology and flow cytometry, matching oligoclonal bands. MRI brain with and without contrast revealed left optic nerve enhancement. He was treated with IV methylprednisolone 1 gram for four days with significant improvement in his symptoms. He was discharged on an oral prednisone taper. Pembrolizumab was discontinued because of concern for irAE. At 3-month follow-up, he reported significant improvement in his vision with acuity of 20/25 in the left eye, full color vision, with normal formal perimetry.

Optic neuritis as an irAE from ICIs can present without typical symptoms of optic neuritis and is often painless without dyschromatopsia despite decreased visual acuity. Other causes of atypical optic neuritis should be excluded. In the absence of other etiologies of atypical optic neuritis, discontinuation of ICI should be considered. Early recognition of this adverse event can improve visual outcomes.