Seronegative Autoimmune Encephalitis With Rapidly Progressive Parkinsonism.

Seronegative autoimmune encephalitis is an infrequent entity in older patients, and its presentation as rapidly progressive parkinsonism is rarely seen in cases of autoimmune encephalitis. We present a case report of an older patient who presented with worsening Parkinson's-like symptoms over a month. We highlight the importance of considering autoimmune encephalitis as a potential cause of rapidly progressive parkinsonism and the importance of radiological findings when the entire autoimmune panel is negative in such patients.