BACKGROUND Posterior reversible encephalopathy syndrome (PRES) is a neuroimaging-based syndrome and is associated with multifocal vasogenic cerebral edema. Patients with PRES frequently demonstrate headache, seizure, encephalopathy, altered mental function, visual loss and so on. We here report a patient who showed persistent neurologic deficits after PRES and was ultimately diagnosed with autoimmune encephalitis (AE). CASE SUMMARY This case exhibits a rare imaging manifestation of anti-casper 2 encephalitis which was initially well-matched with PRES and associated vasogenic edema. CONCLUSION AE should be further considered when the etiology, clinical manifestations, and course of PRES are atypical.