To describe  a case of NMDAR encephalitis with evolution to MOG antibody (MOG-Ab) syndrome.

NMDAR encephalitis is an autoimmune disorder associated with IgG antibodies to the GluN1 subunit of the NMDAR. When demyelinating lesions are present in patients with NMDAR encephalitis, one must consider the possibility of an ‘overlap demyelinating syndrome’.

Clinical case, diagnostics, imaging, and literature review.

A 34-year-old man presented to the hospital with seizures, severe headache and fever. CSF showed lymphocytic-predominant pleocytosis with elevated protein. No organism was identified. The patient was treated for presumed infectious meningoencephalitis with clinical improvement. Subsequent to discharge, CSF testing for NMDA-R antibody in CSF returned positive, however the relevance was unclear given his clinical improvement. After completion of antimicrobials as an outpatient, the patient developed new visual and brainstem symptoms prompting readmission. MRI demonstrated multiple new enhancing inflammatory lesions in the brain, bilateral optic nerves, and spine. He was treated with intravenous steroids and immunoglobulins with rapid resolution of visual symptoms as well as radiographic improvement. Testing for MOG Antibodies in serum was positive. Patient was retrospectively diagnosed with NMDAR encephalitis evolving into MOG-Ab syndrome. He was ultimately started on rituximab, and was able to return to full-time employment 6 months after initial presentation.

We discuss a challenging case of meningoencephalitis initially presumed to be of infectious etiology but subsequently diagnosed as NMDAR encephalitis with evolution to MOG-Ab associated ‘overlap demyelinating disease’. The neurologic symptoms resolved after treatment with IV steroids, IVIG and immunotherapy. The possibility of coexisting autoimmune conditions, including ‘overlap demyelinating syndrome’, must be considered when the patient develops new focal neurologic symptoms and inflammatory-appearing lesions in the optic nerve, brain, or spinal cord. Overlap demyelinating syndrome with NMO or MOG Antibodies has been reported in 3.3% of cases of NMDAR encephalitis.