Relapsing MOG-IgG-associated diseases coexisting with anti-NMDAR encephalitis: a case report and literature review

In recent years, an overlapping syndrome, MNOS, of MOG encephalomyelitis and NMDARE has been clinically identified. In these diseases, both MOG-Ab and NMDAR-Ab are positive. Previous studies were almost case reports and incomprehensive which focused on this kind of overlapping syndrome in adults.We reported a rare case of MNOS. In addition, we reviewed the clinical characteristics, diagnosis, and treatment of MNOS in adults by consulting relevant literature.The patient initially presented with CNS demyelination symptoms followed by recurrent encephalitis, concomitant anti-MOG, and NMDAR antibodies. His symptoms improved significantly after initiating hormonal therapy. We searched previous MNOS case reports and 17 adult MNOS cases were retrieved. The previous history of all patients was unremarkable. Most of these patients (72.2%, 13/18) first developed NMDR encephalitis-related symptoms, such as cognitive behavior abnormalities, cognitive decline, and epilepsy. Some patients (16.7%, 3/18) first developed MOG-related demyelinating symptoms, such as visual deterioration, walking instability, and dizziness. The most common site of new brain lesions was the supratentorial region. In the acute phase, MNOS patients were sensitive to hormone therapy. During the follow-up, 72.2% (13/18) of the patients relapsed, with a median interval of 12.25 months. Immunotherapy was still effective after recurrence, and no deaths were reported.(1) The clinical manifestations of MNOS are atypical, sometimes like MOG encephalomyelitis, sometimes like NMDARE, sometimes both of the characteristic clinical manifestations are present. (2) Immunotherapy is the primary treatment of patients with MNOS. (3) MNOS are prone to recurrence, and serum MOG and tumor markers should be monitored.