In pediatric-onset UC, the HLA region accounts for nearly the entire genetic association, with HLA-DRB1*01:03 showing the strongest link, significantly exceeding its effect in adult-onset UC; additional independent associations have been identified with HLA-DRB1*13:01 and SNP rs17188113, suggesting both shared and pediatric-specific genetic drivers, particularly related to extensive colitis and female gender, highlighting the central role of antigenic stimulation in early disease development [31]. Here, HLA-DRB1 is linked to colitis.