Background: Neuromyelitis optica (NMO) is an autoimmune disease of the central nervous system in which aberrant antibody responses to the astrocytic water channel aquaporin 4 have been described. Experimental evidence is emerging that NMO is partly driven by the proinflammatory cytokine interleukin 6 (IL-6), which propagates the survival of disease-specific B cell subclasses, and deviates CD4+ T helper cell differentiation toward IL-17-producing T helper 17 cells. Tocilizumab is a recombinant humanized monoclonal antibody against the IL-6 receptor approved for treatment of rheumatoid arthritis.
Objectives: To study clinical and paraclinical effects of tocilizumab in a patient with NMO.
Design: Case report.
Setting: Academic neurology department.
Patient: A patient with highly active aquaporin 4–seropositive NMO who failed numerous immunosuppressive interventions, including high-dose corticosteroids, mitoxantrone, plasma exchange (PE), rituximab (anti-CD20), and alemtuzumab (anti-CD52), before receiving tocilizumab.
Main outcome measures: Clinical disability, magnetic resonance imaging, cytokines and transcription factors levels in the cerebrospinal fluid, and peripheral blood mononuclear cells.
Results: A patient who continued to accumulate neurological disability and magnetic resonance imaging activity while receiving numerous immunoactive therapies stabilized, and eventually improved clinically and on magnetic resonance metrics after treatment initiation with tocilizumab. Treatment and clinical response correlated with a significant reduction of IL-6 levels in the CSF as well as a diminished expression of signal transducer and activator of transcription 3.
Conclusions: Tocilizumab might be effective in NMO, here in a patient not responding to leukocyte depletion. Our findings further support data that implicate IL-6 as a critical molecule in the immunopathogenesis of NMO, and a critical role for T cells in the pathogenesis of this disorder.