Improvement in progressive multifocal leukoencephalopathy after pembrolizumab-induced immune reconstruction inflammatory syndrome in a patient with follicular lymphoma.

Progressive multifocal leukoencephalopathy (PML) may develop in follicular lymphoma patients treated with bendamustine-rituximab. In this report, treatment with pembrolizumab successfully inhibited the clinical progression of PML by promoting radiologically demonstrated immune restoration inflammatory syndrome (IRIS), allowing complete clearance of the virus. These findings may further support the use of pembrolizumab in PML with special consideration for the potential occurrence of IRIS.