Bone mineral metabolism in children with juvenile idiopathic arthritis--preliminary report.

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.