104 A case of natalizumab-related progressive multifocal leukoencephalopathy treated with pembrolizumab. Issue 6 (27th May 2022) - Robinson, Rebecca
Abstract : Introduction: Progressive multifocal leukoencephalopathy (PML) is a rare, but potentially devastating viral infection of the brain and can occur as a complication of natalizumab, a treatment for highly-active relapsing remitting multiple sclerosis (RRMS). Case: Patient A is 52-years-old, diagnosed with RRMS in 2015. She commenced disease-modifying therapy with natalizumab following four clinical relapses in one year and had a stable clinical course for the subsequent 4 years. She was JCV antibody positive (titre 3.64) but had opted to continue natalizumab therapy, despite the risk of PML. Early 2020, an MRI abnormality raised suspicion for PML. In May, she developed left hand weakness, pro- gressing to left hemiparesis. Serial MRIs showed increasing signal change however, it was difficult to differ- entiate PML from new inflammatory activity. CSF JCV PCR was negative on two occasions. She proceeded to brain biopsy, confirming PML. She was treated with pembrolizumab and has remained stable. Discussion: This case highlights the difficulty in distinguishing PML from an MS relapse, despite the use of MRI and CSF. We highlight the role of brain biopsy in making a definitive diagnosis. There is also lack of consensus on effective treatment for PML, but emerging evidence for use of pembrolizumab, a PD-1 inhibitor. rrobinson17@qub.ac.uk 77