Piñar Morales, RaquelCarrasco Garcia, MaríaGutierrez-Rojas, LuisBarrero Hernández, Francisco Javier2023-05-032023-05-032022-02-071662-680Xhttp://hdl.handle.net/10668/20191Progressive multifocal leukoencephalopathy (PML) is a rare complication of immunosuppressive treatment in MS patients. Immune reconstitution inflammatory syndrome (IRIS) appears after the withdrawal of certain drugs such as natalizumab (NTZ) or fingolimod. The development of PML-IRIS after NTZ treatment has been described, and its diagnosis is made by clinical and radiological criteria and the determination of the John Cunningham virus in CSF. We present a clinical case of a patient with MS who, after the withdrawal of fingolimod, developed PML-IRIS despite sustained lymphopenia. This is important for pharmacovigilance purposes, not only for NTZ but also for alternative drugs used in MS treatment.enAttribution-NonCommercial 4.0 Internationalhttp://creativecommons.org/licenses/by-nc/4.0/FingolimodImmune reconstitution inflammatory syndromeMagnetic resonance imagingMultiple sclerosisProgressive multifocal leukoencephalopathyresearch article35350291open access10.1159/000521944PMC8921886https://www.karger.com/Article/Pdf/521944https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8921886/pdf