To study the biochemical markers of bone turnover in children with juvenile chronic arthritis (JCA) and to compare these parameters with those in healthy children in order to evaluate the relationships between age, disease activity and biochemical variables.
Sixty-two children with JCA and 157 healthy children were studied. Serum samples were analyzed for their concentrations of minerals, osteocalcin (OC) and bone-specific alkaline phosphatase (BAP). Urine samples were examined to monitor the excretion of hydroxyproline (HYP) and deoxypyridinoline crosslinks (DPD).
OC, BAP, HYP/Cr, DPD/Cr values were decreased in healthy girls more than 12 years of age and in healthy boys more than 14 years of age compared to younger children from the same population. Lower levels of OC and BAP were observed in younger children with JCA (girls < or = 12 yrs.; boys < or = 14 yrs.) compared to healthy children of the same age. Older girls with JCA (> or = 13 yrs.) were found to have increased HYP/Cr and DPD/Cr values compared to older healthy children.
These results indicate that abnormalities of bone metabolism occur in an age-related fashion in JCA. This was demonstrated by a reduction in the markers of bone formation in younger JCA patients. Moreover, in older girls the markers of bone resorption were found to be elevated. Taken together, these findings suggest that bone formation is reduced from early childhood to mid-puberty, while resorption levels increase in children with JCA after this time.