Steroids, Seizures, and a Surprising Pathogen: A Case of Listeria Meningoencephalitis

Altered mental status is a challenging chief complaint with a wide differential diagnosis. Altered mentation in the setting of new-onset seizures requires consideration of myriad causes, not limited to electrolyte derangements, toxin withdrawals, central nervous system (CNS) infections, hypoxic brain injury, and inflammatory diseases. We report a 50-year-old man with a history of hypertension and asthma who presented to the emergency department (ED) for new-onset seizures with a prodrome of unusual behavior for several days, and in the ED experienced status epilepticus requiring intubation and deep sedation. He was found to have multiple metabolic derangements, including hypertriglyceridemia, elevated lactate, and diabetic ketoacidosis. Despite correction of initial laboratory derangements, the patient's mental status did not improve. A lumbar puncture performed on hospital day 3 revealed Listeria monocytogenes infection, and the patient subsequently improved slowly with antibiotics. The culprit microorganism was unexpected. It was later discovered that the patient was taking prednisolone tablets purchased overseas for his asthma because he was unable to afford his asthma maintenance inhalers. This case highlights the challenges in the diagnosis of altered mental status when immune status is unknown, the importance of obtaining collateral history for unprescribed medications, and the dangers of self-medication.