Assessment of Bone Mineral Density in a cohort of Juvenile Idiopathic Arthritis patients

Introduction: Low bone mass is encountered in patients with Juvenile idiopathic arthritis (JIA) as a serious long-term complication of this pediatric condition and may be associated with fractures and its complications. The present study aimed to evaluate the frequency of low bone mineral density (BMD) and fragility fractures in patients with JIA in its polyarticular or oligo articular forms. Secondary, our aim was to identify factors associated with low bone mass. Patients and methods: This is a retrospective study conducted on 26 patients with JIA meeting the ILAR criteria for poly or oligoarticular form. Patients were divided into two groups according to their age : group1 including patients aged over 16 years-old and group 2 including patients aged under 16 years-old. Sociodemographic, clinical, biological and functional data were collected by consulting patient’s medical records. Bone mineral density was measured at three different sites: whole body, lumbar spine and hip using the dual-energy X-ray absorptiometry (DXA) equipment. Data were entered and analyzed using SPSS version 11.5 software. Results: Twenty-six JIA patients including 20 females (74.1%) and six males (22.2%) were enrolled with a mean disease duration of 20.23 years [2-54 years]. The mean age was 28.2 years [7-58 years]. The distribution of JIA subtypes among patients was as follows: 6 with oligo articular JIA and 20 with polyarticular JIA. Sixteen patients (59%) practiced regular physical activity. In our series, the frequency of low bone mineral density was 41% in children with JIA and 68 % in adults with JIA. Only two patients presented a fragility fracture in adulthood represented by a hip fracture following low-energy trauma and treated surgically in both cases. No patient received an anti-osteoporotic treatment. In-group 1, there was a significant correlation between low bone mass and weight (p=0.020), BMI (p=0.028), disease duration (p=0.045), positivity of AAN (p=0.050), disease activity (p=0.019), oral corticosteroid (p=0.034) and biologic treatment (p=0.043). In-group 2, a statistically significant correlation was found between low bone mass and age at the time of JIA diagnosis (p=0.041), weight (p=0.03), physical activity (p=0.05), disease duration (p=0.021), functional impact of the disease assessed by the HAQ score (p=0.018), oral corticosteroid therapy (p=0.014) and biological therapy (p=0.012). Conclusion: our study showed that a combination of factors contributed to compromise bone health in patients with JIA. Fragility fractures were rare and occurring mainly in adulthood. An adequate control of disease activity, proper management of treatment, adequate calcium and vitamin D intake, as well as regular physical activity, may contribute to preserve bone health in those patients.