Glial fibrillary acidic protein (GFAP) associated autoimmune meningoencephalitis in a patient receiving nivolumab.

Immune checkpoint inhibitors (ICIs) represent a major development in cancer treatment, allowing for improved survival and disease control in an expanding number of cancer types. Due to their mechanism of disrupting immunologic homeostasis, ICIs are frequently associated with adverse effects, termed immune related adverse effects (irAE). These side effects can affect any organ system, including the central and peripheral nervous systems. We present a case of a 47 year old man with stage IIIc metastatic melanoma who received 3 cycles of nivolumab (a monoclonal antibody inhibitor of programmed cell death protein 1 (PD-1)). After completing the third cycle, he presented with a meningoencephalitis clinical picture with an inflammatory cerebrospinal fluid (CSF) and normal MRI. He was found to have a positive anti-glial fibrillary acidic protein (GFAP) autoantibody in his CSF by immunofluorescent assay (IFA) and cell based assay (CBA) which confirmed a diagnosis of anti-GFAP autoimmune encephalitis. He was treated with immunotherapy and made a full recovery. In this report, we present the first reported case of anti-GFAP autoimmune encephalitis associated with ICI therapy and provide a brief review of the literature.