2026 American Academy of Neurology Abstract Website

Objective:

This study characterized the clinical spectrum of patients with discordant MOG-IgG titers and MOGAD diagnoses (high titer without MOGAD; low titer with MOGAD).

Background:

The myelin-oligodendrocyte glycoprotein antibody-associated disease (MOGAD) criteria require (A) a core clinical demyelinating event, (B) positive MOG-IgG, and (C) exclusion of better diagnoses. MOG-IgG (titer ≥1:100) requires no additional findings, while low positive titer (<1:100) requires ≥1 supporting clinical or MRI features.

Design/Methods:

Patients were tested for MOG-IgG from 2017 to 2024 at a single center. MOGAD criteria were applied. Patients were stratified by titer and disease characteristics.

Results:

164 MOG-IgG+ patients were identified: 117 (71%) female, median age 37 (range 3-80). 97% were tested by live fluorescence-activated cell sorting, the remainder by fixed cell-based assay. 102 (62%) had MOGAD.

84 patients were high titer MOG-IgG (≥1:100), 54 (64%) female, median age 34.5, range 3-80. 72 (86%) met criteria for MOGAD. 12 (14%), including 2 with titer 1:1,000, had alternative diagnoses: multiple sclerosis (MS, 4), malignancy (3), infection (1), immune checkpoint inhibitor related neurotoxicity (1), polyneuropathy (1), chronic pain (1), stroke (1). 1 patient had concurrent AQP4-IgG+ and lymphoma.

80 patients were low titer MOG-IgG ( <1:100), 63 (79%) female, median age 38.5, range 3-80. 30 (38%) met MOGAD criteria, based on clinical and/or radiological features (longitudinally extensive transverse myelitis in 8, optic neuritis in 11, and both in 4), short segment myelitis with negative OCBs, and MRI without features of MS.

Conclusions:

MOG-IgG titers should be carefully interpreted. While most high titer cases reflect true MOGAD, some have alternative diagnoses. Conversely, low titer MOG-IgG in the correct clinical context can fulfill MOGAD. Understanding what drives titer variability and off-target positivity needs further research.