Abstract: Objective To analyze the clinical characteristics and factors influencing liver function abnormalities in preschool children with infectious mononucleosis (IM). Methods A retrospective analysis was conduced on the clinical and laboratory data of 140 preschool children diagnosed with IM and treated at Fuyang People's Hospital from January 2020 to July 2023. Based on alanine aminotransferase (ALT) levels, the children were categorized into a normal liver function group(ALT <50 U/L) and an abnormal liver function group(ALT ≥50 U/L). Basic conditions, clinical symptoms, hospitalization duration, and laboratory indices were compared between the two groups. Statistically significant indices were further analyzed using covariance adjustment and binary regression analysis. Additionally, the clinical value of relevant indices was assessed using receiver operating characteristic (ROC) analysis, with pairwise comparisons of the area under the curve (AUC) to determine statistical significance. Results The incidence of liver function abnormalities in preschool children with IMwas 43.6%. There were no statistically significant differences in age, gender, season of onset, clinical symptoms, and viral load of EBV-positive children between the two groups (P>0.05). Compared to the group with normal liver function, the group with abnormal liver function had significantly higher hospitalization days[7(6,9)d], lymphocyte count[10.10(8.65,14.82)×10⁹/L] and CD8⁺ T lymphocytes[7690.00(4585.37,11164.50)/uL] (P<0.05), Conversely, the CD4⁺/CD8⁺ ratio[0.21(0.17,0.29)], neutrophil count[2.7(2.06,4.12)×10⁹/L], platelet count[199(148,228.5)×10⁹/L], and systemic immune-inflammation index (SII) [46.34(26.63, 93.78)]were significantly lower in the abnormal liver gunction group (P<0.05). Low SII was closely associated with liver function abnormalities in IM preschoolers. The diagnostic efficacy of SII for liver function abnormalities was assessed using ROC curve analysis, with a critical value of 59.13 and an AUC of 0.758, indicating high diagnostic value, superior to CD8⁺T lymphocytes and CD4⁺/CD8⁺ ratio. Conclusion Preschool children with IM and concurrent liver function abnormalities exhibit significant cellular immune dysfunction. Elevated CD8⁺ T-lymphocytes, low SII and low CD4⁺/ CD8⁺ ratio are associated with a high risk of liver abnormalities. These findings suggest that clinical attention should be focused on these immunological markers to better manage and monitor the risk of liver function abnormalitis in IM preschool children.

Key words: infectious mononucleosis, EBV, hepatic dysfunction, systemic immune-inflammation index