Rapidly progressive acute necrotizing encephalopathy associated with influenza A in an elderly adult

We encountered a patient with rapidly progressive acute necrotizing encephalopathy associated with influenza A falling into coma from lucidity within 10 min. Background Among the influenza‐associated encephalopathies, acute necrotizing encephalopathy (ANE) has a particularly poor prognosis. While it usually progresses within 48 h, we encountered a rapidly evolving case with the patient falling into coma from lucidity within 10 min. Case Presentation A 71‐year‐old man was found unconscious after taking a 10‐min bath and brought to the emergency room. The head computed tomography (HCT) was normal, and he was diagnosed with heatstroke as a complication of influenza A. Despite effective therapy to correct his temperature, his consciousness did not improve, and within 24 h he progressed to multiple organ injury. Repeat HCT and subsequent magnetic resonance imaging revealed irreparably progressed ANE. Conclusion To effectively treat ANE, early recognition and diagnosis are critical. Our case suggests that ANE should be considered and added to the differential diagnosis for adult patients with rapid cognitive deterioration.