Atezolizumab successfully reinvigorated JC virus immunity in a patient in Belgium with progressive multifocal leukoencephalopathy, as demonstrated by clinical, virologic, and radiologic response to treatment. However, the treatment also resulted in immune reconstitution inflammatory syndrome and life-threatening immune-related adverse events. These conditions were treated with corticosteroids, leading to treatment resistance.
Keywords: Belgium; JC virus; atezolizumab; immune reconstitution inflammatory syndrome; immunotherapy; progressive multifocal leukoencephalopathy; viruses.