Clinical Reasoning: A 64-Year-Old Man With Confusion, Nausea, Seizure, and Fever.

Evaluating patients with encephalitis is common, but it can be complicated in immunocompromised patients. In this case, a 64-year-old man with a medical history of multiple myeloma and previous Lyme disease presented with acute onset of confusion, nausea, and fever; developed generalized tonic-clonic seizures; and subsequently became comatose. This case highlights the importance of thinking broadly beyond common viral and bacterial encephalitides and developing a comprehensive differential diagnosis.