Progressive multifocal leukoencephalopathy or immune reconstitution inflammatory syndrome after fingolimod cessation? A case report

Abstract

Abstract Background Fingolimod is associated with an increased risk of developing progressive multifocal leukoencephalopathy (PML); however, its discontinuation may cause severe immune reconstitution inflammatory syndrome (IRIS). As both of these conditions (especially fingolimod induced PML) are rarely described in medical case reports distinguishing between PML-IRIS and MS-IRIS may be diagnostically challenging. Case presentation We report a patient with severe clinical decline (Expanded Disability Status Scale (EDSS) increasing from 3.5 to 7.5) and multiple, large, contrast-enhancing lesions on brain magnetic resonance imaging (MRI) a few months after fingolimod withdrawal. The diagnostic possibilities included IRIS due to fingolimod withdrawal versus PML-IRIS. The JC virus (JCV) antibody index was positive (2.56); however, cerebrospinal fluid (CSF) JCV real-time polymerase chain reaction (JCV-PCR) was negative and brain biopsy was not performed. After a long course of aggressive treatment (several pulsed methylprednisolone infusions, plasmapheresis, intravenous dexamethasone, oral mirtazapine) the patient gradually recovered (EDSS 2.5) and MRI lesions decreased. Conclusions This case report demonstrates the importance of monitoring patients carefully after the discontinuation of fingolimod for PML-IRIS and rebound MS with IRIS as these conditions may manifest similarly.