Progressive Multifocal Leukoencephalopathy Following Treatment With Obinutuzumab In A Patient With Non-Hodgkin Follicular Lymphoma: A Case Report

Clinical Practice Points •Progressive multifocal leukoencephalopathy (PML) is a rare but fatal demyelinating disease caused by John Cunningham polyomavirus, mainly affecting immunosuppressed patients. It sporadically complicates hematological malignancies and has been reported after monoclonal antibody treatment, predominantly rituximab. In recent years, obinutuzumab, a third-generation type II anti-CD20+ monoclonal antibody, has been widely used for chronic lymphocytic leukemia and follicular lymphoma. •We present the case of a patient with relapsing follicular lymphoma who developed PML after obinutuzumab therapy and is, to our knowledge, the first case to be thoroughly presented in the literature. •Although PML is very rare in everyday clinical practice, this report highlights the importance of suspecting PML in any lymphoma patient undergoing novel treatments and presenting focal neurologic deficits, in an effort to avoid unnecessary invasive procedures and delay in diagnosis.