Anti-NMDAR and anti-MOG antibody double-positive encephalitis temporally associated with cytomegalovirus detection in cerebrospinal fluid: a case report

The co-occurrence of MOG and NMDAR antibodies has been reported in a limited number of cases and is termed the overlapping syndrome (MNOS). Viral coinfections have been identified in a subset of patients with MNOS. Herein, we report the first case of MNOS with concomitant cytomegalovirus (CMV) infection detected in cerebrospinal fluid, a finding that helps to further explore the relationship between viral infection and MNOS. A previously healthy 49-year-old man developed fever and behavioral abnormalities following prodromal symptoms. Metagenomic next-generation sequencing (NGS) of the CSF identified CMV DNA with high confidence (specific reads: 362; relative abundance: 85.97%). Serology was positive for CMV IgG but negative for IgM; serum CMV-DNA detected by real-time PCR was negative. Positivity for anti-NMDAR antibodies and anti-MOG antibodies in the CSF, whereas only anti-MOG antibodies were detected in the serum. The patient’s condition gradually improved after treatment with antiviral agents, corticosteroids, and intravenous immunoglobulin. The main limitations of this report include the lack of detection of CMV-DNA in CSF by real-time PCR, as well as the absence of dynamic assessment of serum/CSF CMV IgG/IgM, anti-NMDAR, and MOG antibody titers. Clinical vigilance for coexisting autoimmune encephalitis should be heightened following viral infections.