MOG-IgG is Rare in AQP4-IgG Seronegative NMOSD in Brazil. Insights from a Single-Center Cohort

Introduction – Neuromyelitis optica spectrum disorders (NMOSD) are rare inflammatory conditions primarily associated with aquaporin-4 (AQP4) autoimmunity. Clinically, the disease mostly often manifests with optic neuritis and longitudinally extensive transverse myelitis. AQP4-IgG seronegative NMOSD encompasses MOG-IgG NMOSD and other heterogenous conditions, many of which with unknown etiopathogenesis. The frequency and features of MOG-IgG NMOSD remain unclear in Brazil. Objective - To study the frequency and characteristics of MOG-IgG NMOSD in a Brazilian cohort. Methods – MOG-IgG testing was performed on AQP4-IgG seronegative patients with NMOSD, atypical optic neuritis, or transverse myelitis of unknown cause, using the 2015 IPND criteria. Commercially available fixed CBA kits (Euroimmun, Luebeck, Germany) were employed for testing. Results – Out of 118 AQP4-IgG serum negative patients 25 exhibited NMOSD phenotype. Serum MOG-IgG was detected in 3 patients (12%), all of whom were women aged 11,26 and 34 years. Presenting symptoms included myelitis, unilateral optic neuritis, and a combination of unilateral optic neuritis, myelitis and brainstem symptoms. The duration between disease onset and the last follow-up varied from 8 to 17 years (median 11.2 years). The number of relapses reported were 1, 3, and 7, with a median interval of 1 month between the first and second attacks (range 0 - 32 months). EDSS scores at the last visit were 0, 1.5, and 2.0. One patient was receiving oral prednisone and azathioprine, while two were on azathioprine at the time of MOG-IgG testing. MOG-IgG titers were 1/10 in two patients and 1/32 in one. Conclusion – Our findings suggest that MOG-IgG rarely occurs in AQP-4-IgG seronegative NMOSD patients in Brazil as compared with other populations. However, limitations of our study include the time elapsed between the first attack and the testing, the use of immunosuppressants’, and the small cohort. Collaborative multicenter studies in Brazil are needed to further clear the issue.