Dimethyl fumarate (DMF), a fumaric acid with antioxidant and immunomodulatory properties, is among the most commonly used oral therapies for relapsing multiple sclerosis (MS). Progressive multifocal leukoencephalopathy (PML) has been associated with several disease-modifying therapies (DMTs), including DMF in treating MS. We present detailed clinical characteristics of nine PML cases and show that the PML incidence in DMF-treated patients is 0.02 per 1000 patients. In addition to persistent severe lymphopenia, older age appears to be a potential risk for PML. However, younger patients without lymphopenia were also observed to develop PML. DMF-associated PML has occurred in patients with absolute lymphocyte counts (ALCs) above the guideline threshold, suggesting that changes in specific subsets might be more important than total ALC. Furthermore, since DMF has been found to decrease immune cell migration by decreasing the expression of adhesive molecules, the cerebrospinal fluid (CSF) immune profile may also be useful for assessing PML risk in DMF-treated patients. This review provides an up-to-date assessment of PML cases occurring in DMF-treated patients and discusses other potential considerations in light of our current understanding of DMF's mechanism of action on the immune system in the periphery and in the central nervous system (CNS).

中文翻译：

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富马酸二甲酯治疗的多发性硬化症患者进行性多灶性白质脑病

富马酸二甲酯 (DMF) 是一种具有抗氧化和免疫调节特性的富马酸，是复发性多发性硬化症 (MS) 最常用的口服疗法之一。进行性多灶性白质脑病 (PML) 与几种疾病缓解疗法 (DMT) 相关，包括治疗 MS 的 DMF。我们介绍了 9 例 PML 病例的详细临床特征，并表明 DMF 治疗患者的 PML 发病率为每 1000 名患者 0.02 例。除了持续的严重淋巴细胞减少外，年龄较大似乎是 PML 的潜在风险。然而，也观察到没有淋巴细胞减少的年轻患者发展为 PML。DMF 相关的 PML 发生在绝对淋巴细胞计数 (ALC) 高于指南阈值的患者中，这表明特定亚群的变化可能比总 ALC 更重要。此外，由于已发现 DMF 通过降低粘附分子的表达来减少免疫细胞迁移，因此脑脊液 (CSF) 免疫谱也可用于评估 DMF 治疗患者的 PML 风险。本综述提供了对 DMF 治疗患者中发生的 PML 病例的最新评估，并根据我们目前对 DMF 对外周和中枢神经系统免疫系统（CNS ）。