Rapid clinical stabilization following eculizumab therapy in severe anti-NMDAR encephalitis.

Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is a potentially severe autoimmune encephalitis that may rapidly progress to critical illness. We report a young patient with severe anti-NMDAR encephalitis complicated by seizures, psychiatric symptoms, behavioral disturbance, dyskinesia, and dysautonomia. Despite first-line immunotherapy with intravenous methylprednisolone and intravenous immunoglobulin, the patient remained severely disabled. Peripheral blood analysis showed elevated C5a and soluble C5b-9 levels, suggesting activation of the terminal complement pathway. After treatment with eculizumab, a monoclonal antibody targeting complement component C5, seizure ceased and psychiatric symptoms improved rapidly. These findings suggest that complement inhibition may facilitate rapid neurological recovery and may represent a potential therapeutic strategy for selected patients with severe anti-NMDAR encephalitis.