Extensive white matter lesions after 2 years of fingolimod: Progressive multifocal leukoencephalopathy or MS relapse?

Background: Fingolimod is a widely used treatment for highly active relapsing-remitting multiple sclerosis. Objectives: To describe the case of a 27-year-old patient treated for more than 2 years by Fingolimod, who presented hemiplegia and speech disturbances associated with extensive white matter lesions on brain magnetic resonance imaging (MRI). Methods: Case study. Results: Although initial presentation questioned the possibility of progressive multifocal leukoencephalopathy, final diagnosis was multiple sclerosis (MS) relapse. Appropriate treatment resulted in clinical and radiological improvement. Conclusion: Severe MS relapses under Fingolimod have been reported, but late onset after treatment initiation and extensive subcortical topography is unusual and represents a diagnostic challenge.