Brain MRI of progressive multifocal leukoencephalopathy and immune reconstitution inflammatory syndrome (PML-IRIS)

Progressive multifocal leukoencephalopathy and immune reconstitution inflammatory syndrome. This patient had received natalizumab for three years. She seroconverted to JC virus positivity and was taken off the drug. Three months later, she developed marked worsening of her white matter disease shown on axial FLAIR MRI (A, B) with multifocal, at times confluent, areas of signal abnormality with a patchy enhancement pattern that does not suggest multiple sclerosis exacerbation (C, D). Her CSF was positive for JC virus, and the images are consistent with progressive multifocal leukoencephalopathy/immune reconstitution inflammatory syndrome.