RANKL/OPG Axis and Bone Mineral Density in Pediatric Inflammatory Bowel Disease

<b>Background</b>: Inflammatory bowel diseases (IBD), such as Crohn's disease (CD) and ulcerative colitis (UC), may impair bone metabolism, particularly in children. The RANKL/OPG axis, as a key regulator of bone turnover, may contribute to these disturbances. However, data in the pediatric population remain limited. <b>Methods</b>: A single-center, prospective observational study included 100 children aged 4-18 years, with a comparable number of girls and boys. Among them, 72 had IBD (27 CD, 45 UC) and 28 were healthy controls. Anthropometric, biochemical, and densitometric assessments were performed, including serum levels of RANKL and OPG, and markers of inflammation and bone turnover. <b>Results</b>: Children with CD had significantly lower height and weight percentiles compared to UC and controls. Serum RANKL and the RANKL/OPG ratio were significantly elevated in IBD patients, particularly in CD (<i>p</i> < 0.01). Total body BMD Z-scores were lower in IBD compared to controls (<i>p</i> = 0.03). Low BMD was found in 14.7% of UC and 26.3% of CD patients. In both groups, over 30% had values in the "gray zone" (-1.0 to -2.0). A positive correlation was observed between height and weight and bone density (<i>p</i> < 0.01). Higher OPG was associated with lower body weight (<i>p</i> < 0.001), while increased RANKL correlated with osteocalcin (<i>p</i> = 0.03). Patients receiving biological therapy had significantly lower BMD. <b>Conclusions</b>: Pediatric IBD is associated with significant alterations in the RANKL/OPG axis and reduced bone density. These findings support early screening and suggest RANKL/OPG as a potential biomarker of skeletal health.