Case Report: Neurofilament light chain in the follow up of progressive multifocal leukoencephalopathy in a patient with multiple sclerosis treated with ocrelizumab Piñar Morales, Raquel Calle Calle, Raquel Carrasco García, María Dávila Arias, Cristina Villar Guimerans, María Luisa Barrero Hernández, Francisco Javier Progressive multifocal leukoencephalopathy (PML) results from the reactivation of John Cunningham virus JC virus and is a rare complication of anti-CD20 drug therapy. Neurofilament light chains increasingly serve as a marker of neuroaxonal damage in the follow-up of patients with multiple sclerosis (MS), but its role in the monitoring and detection of processes such as PML is yet to be defined. We report the case of a patient with MS who was treated with ocrelizumab and developed PML. Results: Serum neurofilament light chain (sNFL) levels were elevated at the diagnosis and progressively increased over his follow-up. Our results suggest that the monitoring of sNFL levels may be useful for the early diagnosis of PML in patients with MS. 2025-04-21T07:33:40Z 2025-04-21T07:33:40Z 2025-04-09 journal article Piñar-Morales R, Calle-Calle R, Carrasco-Garcia M, Davila-Arias C, Villar-Guimerans LM, Barrero Hernandez FJ. Case Report: Neurofilament light chain in the follow up of progressive multifocal leukoencephalopathy in a patient with multiple sclerosis treated with ocrelizumab. Frontiers in Pharmacology 16 - 2025. DOI: 10.3389/fphar.2025.1571699 https://hdl.handle.net/10481/103646 10.3389/fphar.2025.1571699 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Frontiers