Optic neuritis of MOG-IgG-associated autoimmune disorders: a case report

BACKGROUND: The diagnosis of immunoglobulin G serum antibodies to myelin oligodendrocyte glycoprotein (MOG-IgG) associated inflammatory demyelinating disorders can be confirmed by the presence of MOG-IgG, yet its general cut-off concentration had not yet to be defined. Whether it is significant that a seropositive lower titer level for MOG-IgG could cause disease is still unknown. CASE PRESENTATION: A 55-year-old Chinese woman presented with acute optic neuritis manifestations in the left eye. MRI showed a left optic nerve demyelination image and a T2 hyperintensity at C7 vertebral segment without any extra specific lesions. AQP4-IgG was tested seronegative, while the MOG-IgG was positive, titer 1:10, by indirect immunofluorescence. Considering the lower concentration, we retested serum MOG-IgG after 6 months of steroid therapy, using cell-based assay, then we still got the same result which was also barely above the negative cut-off value. So, the clinical diagnose was “possible MOG-IgG-associated encephalomyelitis”. The woman’s condition improved by steroid therapy without relapse. CONCLUSIONS: Seropositive MOG-IgG, even at a lower level, could lead to an autoimmune inflammatory demyelination. In adults, it commonly presents as ON and myelitis. Although the patient had a considerable reaction, steroid therapy could not make MOG-IgG seronegative, instead, the antibody may persist even during remission and flare-ups can recur after steroid withdrawal. Therefore, a long-term follow-up is necessary to monitor the patient’s prognosis.