Abstract: Objective To analyze the clinical features of children with infectious mononucleosis (IM) complicated with liver damage. Methods Hospitalized children diagnosed with infectious mononucleosis in the Department of Infectious Diseases, Children′s Hospital of Xi′an Jiaotong University from January 1 to December 31, 2023 were collected as research subjects. According to the results of liver function examination, patients were divided into liver damage group (n=126) and non-liver damage group (n=105), and the clinical features and related laboratory tests were compared between the two groups. Results A total of 231 IM cases were collected, of which 126 cases (54.54%) developed liver damage, among them, 50 cases (39.68%) were male and 76 cases (60.32%) were female. There were 0 infants, 11 early childhood (8.73%), 67 pre-school-age patients (53.17%), 47 school-age patients (37.30%), and 1 pre-youth patient (0.79%).The proportion of female children in liver damage group was higher than that in male children (60.32% vs 39.68%, P=0.000).The median age of onset was 70 (47,104) months, and the incidence of IM in preschool age (53.17%) and school-age children (37.3%) , higher than that in other age groups (P=0.001). The hospital stay days in the liver injury group was longer than that in the non-liver injury group [7 (6,8)] (P<0.05).The percentage of abnormal lymphocytes[15.50(11.00,22.00)], EB virus quantification[812.50(0.00,2400.00)], immunoglobulin (IgM) [1.64 (1.29,2.20)] and the percentage of Ts cells (inhibitory T cells) [64.00 (57.00,71.00)] in the liver injury group were higher than those in the non-liver injury group [13.00 (9.00,20.00)], EB virus quantification [0.00 (0.00, 1240.00)], immunoglobulin (IgM) [1.36 (1.08,1.88)] and the proportion of Ts cells (inhibitory T cells) [59.00 (52.00, 67.00)];The proportion of Th cells (helper T cells) [13.50 (10.00,19.00)] and B cells [4.00 (3.00,6.00)] in the liver injury group were lower than those in the non-liver injury group [16.00 (12.00, 21.00)] and B cells [6.00 (4.00, 8.00)].There were statistically significant differences in the percentage of atypical lymphocytes, quantitative EB virus DNA, immunoglobulin (IgM) and lymphocyte subsets (proportion of Th cells, proportion of Ts cells and proportion of B cells) in 2 groups (P<0.05).There was no statistical significance in the number of immunoglobulin (IgA, IgG) and NK cells in 2 groups (P>0.05). Conclusion Liver damage is more frequently observed in IM children, with higher incidence in female children and early school age children. The percentage of abnormal lymphocytes, EB Epstein-Barr virus load and cellular immunity were correlated with liver damage in IM. Children with liver damage are prone to immune dysfunction.

Key words: Infectious mononucleosis, Liver damage, Percentage of abnormal lymphocytes, EB virus DNA quantification, Humoral immunity, Lymphocyte subsets