Histological findings in follow-up liver biopsies up to 15 years after pediatric liver transplantation: Associations with subclinical rejection, fibrosis, and immunological markers

This prospective single-center cohort study evaluated histological findings in follow-up liver biopsies (fLBs) from 157 pediatric liver transplant recipients over the first 15 years after transplant. Between June 2018 and June 2024, 204 fLBs were performed at 2, 5, 10, and 15 years in clinically stable patients. Biopsies were scored for inflammation (Rejection Activity Index, RAI) and fibrosis (Ishak), and assessed for C4d, plasma cells, autoantibodies, and donor-specific antibodies (DSAs). Despite normal liver function tests, histological abnormalities were common: 61/204 biopsies (29.9%) showed RAI ≥2, consistent with subclinical acute cellular rejection (SACR), and 37/204 (18.1%) had fibrosis stage ≥2. The incidence of SACR peaked at 5 years (37.2%) and declined thereafter ( p =0.04). Inflammation was strongly associated with fibrosis (OR=12.6; 95% CI: 5.4-29.3; p <0.001). Patients off steroids had increased odds of SACR (OR=1.96; 95% CI: 1.04-3.7; p =0.04) and fibrosis ≥2 (OR 8.78; 95% CI: 3.99-19.34; p <0.001). C4d positivity, observed in 30 cases, was associated with a significantly higher risk of SACR (OR=6.48; 95% CI: 2.8-14.9; p <0.001). Among SACR biopsies, plasma cell-rich infiltrates (21.3%) were significantly associated with C4d positivity (OR=8.55; 95% CI: 2.1-35.2; p =0.002) and autoantibody detection (OR=7.8; 95% CI: 0.95-65.5; p =0.03). DSAs-II were associated with SACR ( p =0.03) but not with fibrosis or C4d. These findings highlight the importance of protocol biopsies for detecting silent graft injury and guiding individualized immunosuppression in pediatric liver transplant recipients.