Hyperintensities in limbic encephalitis after treatment with PD-1 inhibitor

Axial T2 FLAIR sequence MRI showing bilateral mesiotemporal hyperintensities (arrows) in a patient with a history of type 1 diabetes mellitus limbic encephalitis with underlying active non-small cell lung cancer, treated with durvalumab (PD-1 inhibitor) monthly infusions, stopped when he developed limbic encephalitis. His workup yielded positive GAD65 (serum titer: 533 nmole/L, CSF titer: 11.6 nmole/L). Although the titers are relatively high, GAD65 is rarely considered to be associated with underlying malignancy, and the use of immune checkpoint inhibitor makes irAE of a higher concern. (Contributed by Dr. Lama Abdel Wahed.)