Autoimmune encephalitis.

Autoimmune encephalitis is emerging as an important and relatively common cause of encephalitis in the developed world. Crucially, early recognition and prompt initiation of a range of immunotherapies is likely to improve the outcomes of patients with autoimmune encephalitis, particularly for those with identifiable antibodies against neuronal cell surface proteins. There are a rapidly growing number of specific autoantibodies and associated syndromes, but many of these remain very rare. The majority of cases comprise anti-N-methyl-D-aspartate (NMDA) receptor encephalitis or anti-leucine-rich glioma-inactivated protein 1 (LGI1) encephalitis with the remaining cases a mixture of over 10 other specific antibodies or being seronegative. The core anti-NMDA encephalitis phenotype is a distinct symptom complex involving psychiatric and neurological features and anti-LGI1 encephalitis presents with cognitive changes and distinct seizure types. Diagnosis can be delayed owing to limited access to specialised laboratory testing or in cases with atypical or limited features.