NMDAR autoimmune encephalitis and fulminant relapse of multiple sclerosis: a rare overlap syndrome.

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disease that has been rarely associated with AQP4-IgG and MOG-IgG demyelinating diseases, and even more rarely with multiple sclerosis. We present the case of a woman in her 40s with confirmed NMDAR encephalitis and coexistent fulminant relapse of multiple sclerosis treated with alemtuzumab 6 years prior, who had a favourable outcome following treatment with ocrelizumab. We proceed to systematic review of similar reported cases, finding a lower than anticipated prevalence of underlying malignancy compared with isolated NMDAR encephalitis, in this rare overlap syndrome.