Abstract:

Although influenza has traditionally been considered a respiratory system-limited disease, severe influenza is often accompanied by multi-organ dysfunction. Extra-pulmonary influenza syndrome in children refers to systemic complications triggered by the influenza virus after it breaches the respiratory barrier, characterized by distinct pathological features. Based on pathogenesis, extrapulmonary influenza syndrome can be divided into two types: direct viral invasion (ectopic infection) and immune-mediated injury (represented primarily by acute necrotizing encephalopathy). The former involves epithelial barrier disruption, hematogenous dissemination, hemagglutinin-mediated tissue tropism, and host immune dysregulation; the latter is mainly driven by systemic inflammatory responses. Polymerase inhibitors show promise in reducing systemic viral load, and combination therapy with immunomodulation may improve clinical outcomes in high-risk pediatric patients. This review systematically summarizes the pathogenesis, clinical characteristics, and management strategies of extrapulmonary influenza syndrome in children, with a focus on distinguishing between the two pathological types—direct viral invasion and immune-mediated injury—to enhance early recognition and comprehensive management of this condition.

Key words: influenza virus, ectopic infection, extra-pulmonary influenza syndrome, viral sepsis, antiviral therapy, immunomodulation