Bone mineral density in patients with juvenile idiopathic arthritis

Abstract

Introduction It is well known that juvenile idiopathic arthritis (JIA) as a chronic inflammatory disease with onset during the childhood, beside other complication, can lead to bone metabolism disturbance and osteoporosis. Objective To assess bone mineral density (BMD) in children with JIA and to identify factors playing role in bone mineral disturbance. Methods Seventy-five patients (26 male and 49 female) average disease duration 7.2 (2.4-16.8) years, and 73 age matched healthy control subjects (29 male and 44 female) participated in the study. Mean age of the groups was about 14.5 years. BMD was determined by dual x-ray absorptiometry (DEXA) of the lumbar spine (L2-L4). For further analysis we used the absolute value of BMD, expressed as g/cm2, Z score expressed as SD (relative value as standard deviation decline of normal BMD values of referent Italian population with identical age and gender), bone mineral content (BMC) as g/cm, and corrected BMD -BMDv as g/cm3. Results Z score in the group of patients was significantly lower (-1.02±1.6) in comparison to the control group (-0.09±1.4; p<0.001). BMD, BMDv and BMC were also statistically lower in patients with JIA. The lowest Z score was found in patients with systemic onset (-2.63 SD). Z score showed a statistically significant positive correlation with arthritis course (polyarticular course had lower Z score), body mass index and standard deviation score for height and weight. Statistically significant negative correlation was detected in regard to Z score and glucocorticoid (GC) treatment duration, GC cumulative dose, number of joints with limited range of motion, radiological stage and functional class. Conclusion The results showed a decreased BMD in patients with JIA in comparison to the control group. Systemic onset, polyarthritis, longer treatment with GC and higher cumulative dosage, as well as higher damage level (functional status and radiological stage) are factors playing negative role in bone metabolism in children with JIA.