To present a case of a 52-year-old female with relapsing progressive bilateral optic neuritis over 5 years in the absence of systemic symptoms and serum and CSF markers suggestive of sarcoidosis, ultimately found to have neurosarcoidosis.

Neurosarcoidosis is seen in some patients with systemic sarcoidosis and can present as unilateral optic neuritis which is often progressive but may be relapsing. Rarely, neurosarcoidosis presents as bilateral optic neuritis which is more commonly seen in demyelinating disease. Especially in the absence of systemic symptoms, the diagnosis of neurosarcoidosis can be challenging and is often misdiagnosed as demyelinating disease.

The patient is a 52-year-old female who presented in April 2018 with painless left eye vision loss with rapid improvement on steroids. In December 2021, the patient had right eye vision loss that progressed to involve her left eye over the next year. She had multiple hospital admissions for steroids. Given relapsing symptoms, periventricular hyperintensities on MRI, and weakly positive oligoclonal bands, she was diagnosed with multiple sclerosis and started on ocrelizumab in September 2022. However, despite treatment, she had worsening vision. Repeat workup showed MRI with bilateral prechiasmatic optic nerve enhancement, and non-enhancing periventricular hyperintensities, negative serum and CSF ACE, aquaporin-4, and MOG antibodies, and absence of oligoclonal bands. She was started on plasmapheresis followed by IV methylprednisolone with limited improvement. CT chest showed enlarged hilar lymph node with biopsy consistent with sarcoidosis. She is now on oral, daily steroids and planned to start steroid sparing immunotherapy.

In cases of bilateral optic neuritis, neurosarcoidosis must be considered. Optic neuritis in neurosarcoidosis is associated with a strong initial response to steroids but is progressive and relapses in the absence of steroids. Identifying sarcoidosis early allows for initiation of steroid sparing agents and TNF-alpha inhibitors, which leads to better outcomes and slows disease progression.