Neuromyelitis optica spectrum disorders: comparison of clinical and magnetic resonance imaging characteristics of AQP4-IgG versus MOG-IgG seropositive cases in the Netherlands

BACKGROUND AND PURPOSE: Neuromyelitis optica spectrum disorders (NMOSDs) are a group of rare inflammatory demyelinating disorders of the central nervous system. The identification of specific antibodies directed to aquaporin 4 (AQP4-IgG) led to the distinction from multiple sclerosis. However, up to 25% of the clinically diagnosed NMO patients are seronegative for AQP4-IgG. A subgroup of these patients might be identified by antibodies directed to myelin oligodendrocyte glycoprotein (MOG-IgG). Our objective was to investigate whether the clinical characteristics of these patients differ.

METHODS: Using a cell-based assay, samples of 61 AQP4-IgG seronegative patients and 41 AQP4-IgG seropositive patients with clinically NMOSD were analysed for the presence of MOG-IgG. Clinical characteristics of the AQP4-IgG, MOG-IgG seropositive and double seronegative NMOSD patients were compared.

RESULTS: Twenty of the 61 AQP4-IgG seronegative patients tested MOG-IgG seropositive (33%). MOG-IgG seropositive patients were more frequently males in contrast to AQP4-IgG seropositive patients (55% vs. 15%, P < 0.01) and Caucasians (90% vs. 63%, P = 0.03). They more frequently presented with coincident optic neuritis and transverse myelitis (40% vs. 12%, P = 0.02) and had a monophasic disease course (70% vs. 29%, P < 0.01). AQP4-IgG seropositive patients were 2.4 times more likely to suffer from relapses compared with MOG-IgG seropositive patients (relative risk 2.4, 95% confidence interval 1.2-4.7). AQP4-IgG seropositive patients had higher Expanded Disability Status Scale levels at last follow-up (P < 0.01).

CONCLUSION: Antibodies directed to MOG identify a subgroup of AQP4-IgG seronegative NMO patients with generally a favourable monophasic disease course.