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.