Clinical Features and Factors Associated With Outcome in Late Adult-Onset Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease.

BACKGROUND AND OBJECTIVES Data regarding late adult-onset myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) are scant. This study sought to assess the frequency, characteristics, and outcome of late adult-onset MOGAD and identify differences from early adult-onset MOGAD. METHODS This retrospective, observational study included Mayo Clinic patients with MOGAD per 2023 diagnostic criteria and with onset age 50 years or older. Clinical, laboratory, radiologic, treatment, and outcome data were collected and compared between patients aged 50-59 years and those aged 60 years or older. Finally, the characteristics and outcome of patients with late adult-onset MOGAD (aged 50 or older) were compared with a reference group of patients with early adult-onset (aged 18-49) MOGAD (n = 141). RESULTS There were 107 patients with late adult-onset MOGAD included, representing 25% of the MOGAD cohort (n = 436). The median age at onset was 59 years (range: 50-88), and 71 (66%) were female. Medical comorbidities were noted in 86 of 105 (83%). Optic neuritis was the most frequent onset attack (77/107, 72%), and the median Expanded Disability Status Scale (EDSS) score at nadir was 3 (range: 1-9). In 32 of 107 (30%), a potential trigger was noted, mostly infections. In 32 patients (30%), an alternative diagnosis was considered before MOGAD identification, most commonly giant cell arteritis (n = 15 [11 undergoing temporal artery biopsy]). By a median follow-up duration of 22 months (range: 0-306), 50 patients (47%) had a relapsing course, and preventive treatment was administered in 53 (50%). Medication side effects were common (41/107, 38%). No differences were observed in patients with MOGAD aged 50-59 years vs 60 years or older. Lastly, late adult-onset patients had more optic nerve involvement (p = 0.015; OR: 1.9; 95% CI 1.1-3.3), brainstem/cerebellar involvement (p = 0.008; OR: 3.4; 95% CI 1.1-3.3), and cognitive decline (p = 0.01; OR: 5.3; 95% CI 1.4-19.4) and less frequent myelitis (p < 0.001; OR: 0.4; 95% CI 0.2-0.7) vs those with early adult-onset MOGAD, but EDSS scores and frequency of a relapsing course were similar. DISCUSSION Late adult-onset MOGAD accounts for one-quarter of patients with MOGAD. Optic neuritis is the dominant phenotype in this age group with MOGAD and is under-recognized and frequently misdiagnosed. Outcomes in late adult-onset MOGAD are similar to those in early adult-onset disease.