(519) West Nile Encephalitis Masquerading as Delirium in a Lung Transplant Patient: A Case Report

Introduction: West Nile virus (WNV) is the most common mosquito-borne disease in Arizona, and most symptomatic infections cause self-limited febrile illness. Caution is advised in elderly and immunocompromised patients, in whom devastating neuroinvasive disease can occur. We present a case in which WNV encephalitis was misdiagnosed as delirium.

Description: A 73-year-old man with a history of bilateral lung transplant and end-stage renal disease on peritoneal dialysis (PD) presented to the emergency department after an episode of hematemesis, severe abdominal pain, and obstipation. Initial assessment showed fever, hypotension, tachypnea, and elevated lab values. CT of the abdomen and pelvis with contrast revealed small pneumoperitoneum, possibly related to his PD catheter, and severe colonic ileus. With suspicion of bacterial peritonitis, the patient was started on broad spectrum antibiotics with improvement. However, he later developed altered mental status, paranoia, agitation, confusion and refusal of medical care. Delirium was diagnosed with toxic metabolic encephalopathy, however, despite delirium prevention strategies, his mental status worsened and he developed photophobia, hearing loss, and gait abnormalities requiring transfer to the ICU. A non-contrast CT and MRI of the brain were unremarkable, but EEG showed encephalopathic changes. Lumbar puncture revealed a clear lymphocytic pleocytosis prompting suspicion of viral encephalitis, and subsequent results were positive for WNV-specific IgM; a brain MRI with contrast showed symmetric midbrain and brainstem diffusion restriction, suggesting West Nile encephalitis. Consequently, immunosuppressive medications were held, and treatment with intravenous immunoglobulin and interferon alpha-2b improved his mental status, though photophobia and hearing loss persisted.

Discussion: Delirium in hospitalized patients, especially the elderly, can lead to fluctuating consciousness and cognitive impairment. However, in the ICU, a delirium diagnosis can presume non-infections causes and result in missed CNS infections. To avoid this, an early and thorough infectious workup, including a lumbar puncture (LP) for patients with fever and encephalopathy despite anticoagulation, can enable timely antibiotic adjustments, personalized therapy, and a better prognosis.