Neuromyelitis optica spectrum disorders with antibodies to myelin oligodendrocyte glycoprotein or aquaporin-4: Clinical and paraclinical characteristics in Algerian patients

Background: Neuromyelitis optica (NMO) is a severe autoimmune inflammatory disorder of the central nervous system. NMO and its abortive forms are referred to as NMO spectrum disorders (NMOSD). NMOSD are mostly associated with antibodies to aquaporin-4 (AQP4-IgG). However, recent studies have demonstrated antibodies to myelin oligodendrocyte glycoprotein (MOG-IgG) in a subset of patients. Data on NMOSD in North Africa are sparse. Objective: To describe the frequency of MOG-IgG and AQP4-IgG among patients with optic neuritis (ON) and/or myelitis in Algeria as well as the clinical and paraclinical features associated with these antibodies. Methods: Retrospective testing of 42 patients with optic neuritis and/or myelitis treated at the teaching hospital of TiziOuzou for MOG-IgG and AQP4-IgG, and retrospective evaluation of the patients' medical records. Results: Six of 42 (14.3%) patients were positive for AQP4-IgG and 3/42 (7.1%) were positive for MOG-IgG. No patient was positive for both AQP4-IgG and MOG-IgG. All antibody-positive patients were women. MOG-IgG was associated with severe episodes of ON in all MOG-IgG-positive patients. Steroid treatment was followed by complete remission in two patients. AQP4-IgG was associated with ON and/or longitudinally extensive transverse myelitis (LETM), often with severe onset. While all six of the AQP4-IgG-positive patients met the 2015 IPND criteria for NMOSD, only one of the three MOG-IgG-positive patients did so. Interestingly, clinically silent extensive spinal cord or brain lesions were present in two of the three MOG-IgG-positive patients, and altered visual evoked potentials without clinical evidence of ON were found in three of the six AQP4-IgG-positive patients. Conclusion: MOG-IgG and AQP4-IgG are found in a substantial subset of Algerian patients with ON and/or myelitis, are present predominantly in women, and may be associated with differences in clinical presentation and, possibly, outcome. Only a subset of MOG-IgG positive patients meets the current diagnostic criteria for NMOSD.