IFNβ-1b may severely exacerbate Japanese optic-spinal MS in neuromyelitis optica spectrum

Background: Interferon-beta-1b (IFN beta-1b) has been used to prevent exacerbation of relapsing-remitting multiple sclerosis (RRMS) including optic-spinal multiple sclerosis (OSMS) in Japan. We encountered 2 patients with OSMS with unexpectedly severe exacerbation soon after the initiation of IFN beta-1b therapy. The experience urged us to retrospectively review the patients with RRMS who had been treated with IFN beta-1b to identify similar cases. Methods: At neurologic departments of 9 hospitals, the medical records of 56 patients with RRMS were reviewed to identify those who showed severe exacerbation soon after the initiation of IFN beta-1b therapy. Results: Of 56 patients with RRMS, we identified 7 who experienced severe exacerbation (exacerbation with increased scores of Expanded Disability Status Scale >= 7.0) within 90 days of the initiation of IFN beta-1b therapy. In all 7 patients, the exacerbations after the initiation of IFN beta-1b therapy were more severe than those experienced by the individual patients before the use of IFN beta-1b, and seemed to have occurred unexpectedly in a short time after the initiation of INF beta-1b therapy. A retrospective analysis revealed that all 7 patients had antibodies toward aquaporin 4, and the clinical features of all 7 patients after the exacerbation were consistent with those of neuromyelitis optica (NMO) spectrum. Conclusions: Our study suggests that IFN beta-1b may trigger severe exacerbation in patients with the NMO spectrum. In INF beta-1b therapy, cases in NMO spectrum should be carefully excluded. Neurology 2010;75:1423-1427