BACKGROUND: Interferon-?-1b (IFN?-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?-1b therapy. The experience urged us to retrospectively review the patients with RRMS who had been treated with IFN?-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?-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?-1b therapy. In all 7 patients, the exacerbations after the initiation of IFN?-1b therapy were more severe than those experienced by the individual patients before the use of IFN?-1b, and seemed to have occurred unexpectedly in a short time after the initiation of INF?-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?-1b may trigger severe exacerbation in patients with the NMO spectrum. In INF?-1b therapy, cases in NMO spectrum should be carefully excluded.
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