Listeria Monocytogenes Brain Abscess in Crohn's Disease Treated with Adalimumab

Listeria monocytogenes is a gram-positive bacterium that causes listeriosis. Brain abscess is a very uncommon manifestation of listeriosis and has not been reported to be associated with adalimumab (humira), one of the approved medications for treating Crohn's disease. A 45-year-old female with Crohn's disease presented with sudden onset of fever, headache, nausea, vomiting, and altered mental status for 1 day. She was on prednisone and 6-mercaptopurine. She had started taking adalimumab 17 days prior to admission. She had signs of toxicity, confusion, and nuchal rigidity, but showed neither central nervous system deficits nor focal deficits. The laboratory results revealed Gram-positive coccobacillus, positive blood and cerebrospinal fluid culture for Listeria monocytogenes, and a 5 × 5 mm ring-enhancing lesion of brain abscess on MRI. After holding off 6-mercaptopurine and adalimumab, her mental status improved on the next day. Finally, she was discharged on day 7 of hospitalization with ampicillin 2 g intravenously every 4 h for a total of 2 weeks. Two weeks later, the follow-up MRI showed a 2-mm area of residual enhancement in the left temporal lobe at the site of the previous brain abscess. Adalimumab, as a tumor necrosis factor (TNF)-alpha inhibitor, carries a risk of triggering opportunistic infection, such as listeriosis. With an altered mental status or neurological signs in patients receiving TNF-alpha antagonizing agent, physicians should suspect bacterial infection in the central nervous system and promptly initiate treatment for brain abscess if needed.