Febrile infection-related epilepsy syndrome with claustrum sign following a human rhinovirus-positive respiratory illness in an adult: a case report.

Background: Human rhinovirus (HRV) is the predominant viral pathogen causing community-acquired upper respiratory tract infections, typically manifesting as mild coryzal symptoms. Severe neurological complications, including febrile infection-related epilepsy syndrome (FIRES), are exceptionally rare. Case presentation: We report a case of febrile infection-related epilepsy syndrome (FIRES) with bilateral claustral involvement occurring in temporal association with an HRV-positive febrile respiratory illness, identified at the General Hospital of Ningxia Medical University in April 2025. The patient presented with acute refractory status epilepticus following a prodromal febrile illness. Neuroimaging revealed bilateral claustral hyperintensities and symmetrical thalamic lesions, while continuous electroencephalographic monitoring demonstrated burst-suppression patterns with frontotemporal discharges. HRV was detected in a respiratory tract specimen by nucleic acid testing but was not detected in the cerebrospinal fluid; the relationship between HRV detection and the neurological syndrome is therefore interpreted as a temporal association rather than a proven causal one, since a single respiratory detection may represent asymptomatic carriage rather than active infection. Conclusions: This case underscores the importance of considering FIRES in patients with acute encephalopathy following a respiratory infection, even when the implicated pathogen-human rhinovirus in this case-is detected only in the respiratory tract, where it may represent either active infection or asymptomatic carriage. Early recognition through comprehensive neuroimaging and electroencephalographic monitoring, combined with multimodal immunomodulatory and antiseizure therapy, was followed by clinical and electrographic improvement and a favorable functional outcome in this patient; however, because corticosteroids, intravenous immunoglobulin, tocilizumab, a ketogenic diet, multiple antiseizure medications, and intravenous anesthetics were administered concurrently or sequentially, the contribution of any specific treatment cannot be determined, and no conclusions regarding treatment efficacy or the clinical utility of cytokine monitoring can be drawn from this single case. The hypothesized cytokine-mediated mechanisms underlying this clinico-radiological entity are discussed in a narrative review of the literature.