Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 11 3 2026 09 28 122 125 Seyedeh Rojina Mortazavi Student Research Committee, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Dina Sadeghi Student Research Committee, School of Medicine, Isfahan University of Medical Sciences, Isfahan,Iran. Solmaz Aziz-Ahari Department of Pediatric Neurology, Firoozabadi Clinical Research Development Unit (FACRDU), Iran University of Medical Sciences, Tehran, Iran 2026 05 14 2026 08 18 Influenza-associated encephalitis (IAE) is a rare but serious complication of influenza infection, predominantly affecting children. While most reported cases present with moderate to severe neurological symptoms, mild and self-limiting forms remain underrecognized. We report the case of a previously healthy 9-yearold boy who presented with fever, lethargy, behavioral changes, and two episodes of nocturnal complex behavior concerning for seizures during the course of an influenza-like illness. Laboratory evaluations were notable for leukopenia and elevated D-dimer levels. Neuroimaging revealed a medial right temporal arachnoid cyst, and cerebrospinal fluid (CSF) analysis showed mild pleocytosis with positive influenza A PCR. Electroencephalography was normal. The patient was managed with intravenous antibiotics, antiviral therapy, and supportive care. His symptoms resolved rapidly without neurological sequelae, and he made a complete recovery. This case highlights that influenza-associated encephalitis can present with mild, transient neuropsychiatric symptoms. It demonstrates that a positive respiratory influenza test does not preclude central nervous system involvement, underscoring the importance of cerebrospinal fluid analysis for diagnosis and to avoid unnecessary interventions.  https://crcp.tums.ac.ir/index.php/crcp/article/view/1193 https://crcp.tums.ac.ir/index.php/crcp/article/download/1193/792