Aggressive and Refractory Attack of AQP4-IgG-Positive Neuromyelitis Optica Spectrum Disorder Treated With Ravulizumab: A Case Report.

Neuromyelitis optica spectrum disorder (NMOSD) is a severe autoimmune astrocytopathy mediated by aquaporin-4-immunoglobulin G (AQP4-IgG) antibodies, leading to complement-mediated neural injury. While ravulizumab, a long-acting C5 inhibitor, is approved for relapse prevention in AQP4-IgG-positive NMOSD, its role in acute attacks remains unestablished. We report a 58-year-old woman with a highly relapsing course of AQP4-IgG-positive NMOSD who developed a fulminant attack with bilateral corticospinal tract involvement, resulting in asymmetrical tetraparesis. Despite high-dose intravenous methylprednisolone and plasma exchange (PLEX), neurological deterioration progressed. Ravulizumab (2,700 mg) was administered emergently following meningococcal prophylaxis. After treatment, neurological decline ceased, allowing gradual motor recovery and rehabilitation. At discharge, the patient showed improved strength and functional capacity, although significant disability persisted. This case suggests that ravulizumab may provide clinical stabilization in refractory NMOSD attacks unresponsive to conventional therapy. The temporal association between ravulizumab administration and the halt in clinical progression suggests a possible therapeutic effect; however, delayed responses to steroids and PLEX, along with the confounding use of intravenous Ig, preclude definitive attribution. While the use of complement inhibitors has been well established in relapse prevention, evidence for their use in acute NMOSD exacerbations remains limited. This report highlights the need for controlled studies to evaluate the efficacy, safety, and timing of ravulizumab in the management of acute, treatment-resistant NMOSD relapses.