Chronic relapsing inflammatory optic neuropathy (CRION) is defined as recurrent optic neuritis (ON) with relatively good response to steroids. Typical cases show optic nerve enhancement on MRI, and negative aquaporin-4 (AQP4) serology is a suggested criterion. Thus CRION phenotypes not uncommonly overlap with myelin oligodendrocyte glycoprotein (MOG) and MOG-associated disease (MOGAD). Several studies have shown a relatively high rate of positive MOG antibodies in CRION patients, begging the question of how to best investigate and treat CRION patients in the age of MOGAD.
We present an atypical case of a 61 year-old woman with CRION to illustrate the behaviour, investigations, and treatment issues in distinguishing between CRION and MOGAD.
A full outline and timeline of the patient’s history, exam features, investigations and treatment response are presented, as well as data supporting the potential link between CRION and MOGAD.
A 61 year-old woman presented in fall 2019 with a second R ON, her first episode having occurred 18 years prior with full spontaneous recovery. This was followed by another ON in the same eye one month later, and two severe bilateral ON attacks in a matter of a few months, resulting in light perception acuity only, and highly suggestive of MOGAD. Between 2019 and the present, her MRI has shown unchanging right optic nerve T2 hyperintense signal and gadolinium enhancement, with no other demyelinating features. Extensive immune investigations, including screening for SLE and Sjogren’s with an ENA panel, paraneoplastic antibody testing, and both local and Mayo Clinical Laboratories testing for AQP4 and MOG were unremarkable or negative, as was screening for malignancy and sarcoidosis. After her first bilateral ON episode, she had no meaningful response to high-dose steroid therapy with a prolonged taper, but had her subsequent, severe bilateral ON attack to OU LS occurred as she weaned off steroids, and required both high dose corticosteroids and plasma exchange to achieve OD HM and OS 20/60. Maintenance steroids and the initiation of a steroid-sparing agent have prevented further ON relapses thus far.
This case illustrates the similarities between CRION, MOGAD, but with several atypical features. Being aware of the possibility of MOGAD in addition to other entities, and ensuring a thorough workup with consideration of preventative immune therapy in steroid-responsive patients is essential.