Rapid exacerbation of multiple sclerosis following the initiation of interferon-β: report of nine cases.

BACKGROUND: Interferon-β (IFN-β) is an effective drug in multiple sclerosis (MS) but it may cause acute exacerbation of MS following the initiation of treatment. This study evaluated patients with rapid exacerbation of multiple sclerosis (REMS) following the initiation of IFN-β. METHODS: We retrospectively reviewed the clinical records of 2350 patients with multiple sclerosis who started treatment with IFN-β and were registered with Isfahan MS Society (IMSS). Patients with rapid exacerbation of multiple sclerosis within 24 hours after initiation of IFN-β treatment were selected and their demographic and clinical data were extracted. RESULTS: We identified nine patients with rapid exacerbation of multiple sclerosis following the initiation of IFN-β. Their mean age at the time of treatment with IFN-β was 37.3 ± 6.28 years. Seven patients had rapid exacerbation of multiple sclerosis after initiation of IFN-β 1a and two patients after IFN-β 1b. The course of disease in all of these patients was relapsing-remitting. However, all had converted into secondary progression within the first year after occurrence of rapid exacerbation of multiple sclerosis following the initiation of IFN-β. CONCLUSIONS: This study may indicate that the effects of IFN-β are not purely anti-inflammatory and a small percentage of MS patients experience rapid exacerbation of multiple sclerosis following the initiation of IFN-β. Future studies are needed to validate our findings.