# Case Report: Overlap syndrome of anti–NMDA receptor encephalitis and MOG-associated disease in a pediatric patient—literature insights

## TL;DR

A seven-year-old boy in Africa was diagnosed with a rare overlap of two neurological conditions, showing how antibody levels correlate with symptoms and treatment response.

## Contribution

This is the first documented African case of pediatric overlap syndrome involving anti-NMDAR encephalitis and MOGAD, with insights into clinical management and antibody dynamics.

## Key findings

- The patient showed clinical improvement after first-line immunotherapy with intravenous immunoglobulin and corticosteroids.
- A second episode occurred with a MOGAD-associated phenotype, but favorable outcomes followed treatment with immunosuppressants.
- Dual positivity for anti-NMDAR and anti-MOG antibodies persisted, linking antibody dynamics to clinical course.

## Abstract

Myelin oligodendrocyte glycoprotein antibody disease (MOGAD) and anti-N-methyl-D- aspartate receptor (NMDAR) encephalitis pediatric cases are especially challenging due to phenotypic variability, limited literature, and the absence of standardized treatment protocols. We present the first documented African case of pediatric MOG and NMDAR overlapping syndrome (MNOS), with a review of all pediatric MNOS cases reported thus far in the literature. A previously healthy seven-year-old boy developed rapid-onset sleep disturbances, neuropsychiatric symptoms, multiple cranial nerve palsies, and hyperkinetic movements. Serological and cerebrospinal fluid (CSF) analyses confirmed dual positivity for anti- MOG and anti- NMDAR antibodies. The patient responded favorably to first line immunotherapy with intravenous immunoglobulin and corticosteroids, showing marked clinical improvement by the six-month follow-up. A corticosteroid taper was initiated thereafter. At fourteen-month follow-up, he had a second episode with a MOGAD- associated cerebral cortical encephalitis phenotype. Antibody screening confirmed persistent dual positivity for both anti-NMDAR and anti-MOG antibodies. The clinical outcome was favorable following first-line immunotherapy combined with oral immunosuppressants. This case highlights the uniqueness of this entity, where antibody dynamics are closely tied to the clinical course.