Assessment of bone status with dual-energy x-ray absorptiometry alone may be an insufficient indicator of skeletal health in juvenile arthritis patients, reported Dr. Helena Valta and colleagues.
Although bone mineral density (BMD) and height z scores for a group of glucocorticoid-treated children with juvenile idiopathic arthritis (JIA) suggested normal growth and low prevalence of osteoporosis, spinal imaging uncovered a high prevalence of asymptomatic vertebral fractures, indicating that osteoporosis remains a concern in this population, according to Dr. Valta of the University of Helsinki and colleagues.
Multiple studies have demonstrated systemic skeletal complications in children with juvenile idiopathic arthritis as a consequence of both active disease and the medications used to treat it, the authors wrote. The introduction of new antirheumatic drugs in recent years has allowed for therapeutic alterations, including glucocorticoid dose reductions that might mitigate skeletal damage.
In a study designed to determine whether current treatment regimens have led to improved overall skeletal health in children with JIA, the investigators evaluated growth and bone health in 62 children with JIA treated with glucocorticoids and multiple drug combinations. The study included 19 boys, median age 11.8 years, who fulfilled the revised criteria for JIA; they were followed since diagnosis at Helsinki University's Pediatric Rheumatology Outpatient Clinic at least 2 years prior to the study (J. Rheumatol. 2007 Feb. 15 [Epub ahead of print]).
During the course of their disease, all had been treated with systemic glucocorticoids for at least 3 months; 12 children received combination therapy with glucocorticoids and methotrexate only; and 50 children received glucocorticoids, methotrexate, and additional antirheumatic agents, including 20 children treated with tumor necrosis factor-α (TNF-α) antagonists for treatment-resistant JIA, the authors reported. Four had nonvertebral fractures resulting from low-energy injuries after their JIA diagnosis. None had previously diagnosed compression fractures.
The median duration of systemic glucocorticoid treatment was 24 months, and the median cumulative dose (calculated as prednisolone) and weight-adjusted dose were 2.2 g and 88 mg/kg, respectively. All of the children were assessed clinically by a pediatric rheumatologist and all underwent dual-energy x-ray absorptiometry (DXA) scans to assess bone mineral content and areal BMD (aBMD) of the lumbar spine, left femoral neck, total hip, and whole body. Instant vertebral assessment (IVA) images of the lateral and posteroanterior spine were obtained to detect vertebral compression fractures.
A review of anthropometry and imaging data showed that all but two of the patients were of normal stature at study assessment and only a minority had bone age-corrected aBMD z scores indicative of significant osteopenia or symptomatic osteoporosis. “The bone age-adjusted aBMD z score was below −1.0 and below −2.0 at the lumbar spine in 12 and in 3 patients, respectively, and at the hip in 13 patients and in 1 patient, respectively,” the authors reported.
However, the IVA images demonstrated abnormal vertebral morphology suggestive of compression fractures in six patients (10%). Five had anterior wedge deformity, and one had a compression deformity affecting the anterior, middle, and posterior heights of the vertebrae, according to the authors. There were no statistically significant differences in the duration of glucocorticoid treatment or weight-adjusted cumulative glucocorticoid dose in any patients with abnormal vertebral findings, versus patients who had normal vertebral morphology, they wrote.
An evaluation of bone health correlates in the entire study population showed no link between aBMD and disease characteristics, combination therapies at the time of assessment, or cumulative glucocorticoid dose.
While the findings suggest current treatments have led to improved overall skeletal health in children with JIA, the detection of vertebral compression fractures and some subnormal BMD readings in the cohort “are evidence for the significant potential risks of JIA to normal bone health,” the authors wrote. “More attention needs to be paid to preventive measures such as optimizing vitamin D and calcium intake, and encouraging weight-bearing physical activity in patients with satisfactory disease control.”
The study highlights bone health evaluation questions in this at-risk population, for which there are currently no standards. “We don't know enough about bone health in these children yet to be completely confident in simply using standard DXA studies; however, better tools are not routinely available yet, and DXA provides more information than routine x-rays,” said Dr. Thomas J.A. Lehman, chief of pediatric rheumatology at the Hospital for Special Surgery in New York. “If DXA [measures] are way off, everyone agrees on therapy,” he said, but no consensus exists on the interpretation of mild abnormalities in arthritic children.