[MRI alterations in immunomodulation].

In this review article, typical imaging findings of diseases elicited by immunomodulatory drugs are presented. Progressive multifocal leucoencephalopathy (PML), a subacute infection due to reactivation of the JC virus, has a typical magnetic resonance imaging (MRI) pattern, which must be considered in the framework of immunomodulatory multiple sclerosis (MS) treatment with natalizumab, fingolimod, rituximab and fumarate and also in lymphoproliferative diseases or other forms of immunosuppression. Restoration of the immune system may result in an overlapping and overwhelming immune response in terms of an immune reconstitution inflammatory syndrome (IRIS). Further conditions with typical MRI patterns comprise methotrexate-associated leucoencephalopathy and posterior reversible encephalopathy syndrome (PRES). In immunotherapy with activation of T‑lymphocytes, attention should always be paid to the fact that the T‑lymphocytes activated by different processes not only target the diseased tissue but also normal brain tissue.