Fatal Influenza A-Associated Acute Hemorrhagic Leukoencephalitis with Features Overlapping Acute Necrotizing Encephalopathy in a Young Woman: A Case Report

Acute hemorrhagic leukoencephalitis (AHLE) is a rare, hyperacute inflammatory disorder of the central nervous system that is usually diagnosed on clinical and radiological grounds when tissue is unavailable. We report a previously healthy, unvaccinated 19-year-old woman with a 5-day febrile respiratory illness and a nasopharyngeal real-time reverse transcription polymerase chain reaction test positive for influenza A. Within approximately 12 h of admission, she progressed from full consciousness to coma with signs of brainstem dysfunction and developed shock requiring vasopressors. Brain magnetic resonance imaging showed bilateral confluent white-matter lesions with vasogenic edema, symmetric thalamic restricted diffusion, midbrain and pontine involvement, and petechial hemorrhages within the pons on susceptibility-weighted imaging. Cerebrospinal fluid showed elevated protein and mild lymphocytic pleocytosis. Despite intravenous methylprednisolone, intravenous immunoglobulin, oseltamivir, and intensive care, she died approximately 36 h after admission. The diagnosis of AHLE was clinicoradiological because neuropathological examination was not performed, and the symmetric thalamic and brainstem involvement overlapped with influenza-associated acute necrotizing encephalopathy (ANE). This case illustrates the fulminant course that influenza A-associated hemorrhagic encephalopathy can take in young adults, the value of early multisequence imaging, and the difficulty of distinguishing AHLE from ANE without neuropathological confirmation.