Does interferon beta treatment exacerbate neuromyelitis optica spectrum disorder?

Objectives: Recent case reports and series have shown that patients with neuromyelitis optica (NMO) experience clinical deterioration under interferon beta (IFN-β) treatment. The objective of the present study was to evaluate whether and to what extent IFN-β exacerbates NMO spectrum disorders (NMOSD). Methods: We retrospectively reviewed the medical records of 40 patients with NMOSD who had been treated with IFN-β for more than 6 months and whose disease duration was more than 1 year at the initiation of IFN-β treatment. We evaluated their annualized relapse rates (ARR) and Expanded Disability Status Scale (EDSS) scores before and after IFN-β treatment. Results: In total, 95% of patients exhibited an ineffective or exacerbated response to IFN-β treatment and the mean ARR significantly increased after IFN-β treatment (p = 0.002). The increased ARR > 50% under IFN-β treatment was observed in 20 patients (50%). The mean EDSS score significantly increased following IFN-β treatment (p < 0.001). Conclusion: In patients with NMOSD, IFN-β treatment is not only ineffective for preventing relapses but also may even increase relapses significantly. Thus, a more careful diagnostic approach to differentiate NMO from multiple sclerosis and attention to decision of treatment is warranted for patients at high risk of NMO.