Introduction: There are very few reports assessing bone mineral mass and its metabolism in the course of juvenile idiopathic arthritis (JIA).
Study objective: To assess the levels of selected serum markers of bone formation (OCN) and resorption (CTx) in JIA children.
Material and methods: The study involved 52 children with JIA diagnosed according to the EULAR criteria of 1997, aged 6-18 years. All patients underwent densitometric measurements using dual-energy X-ray absorptiometry (DXA) to assess TBBMD (g/cm2), Spine BMD (g/cm2), Z-score for SBMD, TBBMC (g), and LBM (g). The following parameters were determined in blood serum: the level of osteocalcin (OCN) and C-terminal type I alpha-collagen chain telopeptide (CTx) using the Elecsys 2010 system (N-MID Osteocalcin, Beta-CrossLaps). A gender- and age-matched control group consisted of 16 healthy children.
Results: The mean concentrations of both osteocalcin (p<0.001) and CTx (p<0.005) were significantly higher in JIA patients as compared to the healthy controls (OCN 113.2+/-54.9 ng/ml vs. 70.2+/-48.3 ng/ml; CTx 1.4+/-0.5 mug/l vs. 1.2 +/-0.45 microg/l). The concentrations of the bone turnover markers were significantly reduced in children with higher degrees of joint destruction compared to those with anatomically normal joints (p<0.05). The mean concentration of CTx showed a significant negative correlation with the TB BMC/LBM Z-score (p<0.05). Reduced bone mass (Z-score for SBMD< -2.0) was found in 23.6% of the affected children.
Conclusions: The JIA patients had elevated levels of OCN and CTx compared to the healthy controls. Reduced bone turnover was observed in children with higher degrees of joint destruction.