Bone mineral density in children and adolescents with systemic lupus erythematosus, juvenile dermatomyositis, and systemic vasculitis: relationship to disease duration, cumulative corticosteroid dose, calcium intake, and exercise

Abstract

Objective: To describe the frequency of abnormal bone mineralization in a population of children with juvenile systemic lupus erythematosus (JSLE), juvenile dermatomyositis (JDM), and systemic vasculitis; and to investigate the relationship of bone mineral density (BMD) to cumulative corticosteroid dose, disease duration, Tanner stage, calcium intake, and exercise in these patients.

Methods: A retrospective chart review of children attending the pediatric rheumatology clinic at British Columbia's Children's Hospital was conducted to obtain demographic data (sex, ethnicity, disease duration, cumulative corticosteroid dose, and mean daily corticosteroid dose). All patients had at least one BMD measurement by dual energy x-ray absorptiometry (DEXA) at lumbar spine, hip, and total body. BMD was expressed as g/cm2 and Z scores; an abnormal Z score was defined as </= -1.5. Daily calcium intake was calculated. Physical activity was scored using a validated 7 day physical activities questionnaire.

Results: A total of 36 patients were studied. Twenty-five patients had SLE, 7 had JDM, and 4 had systemic vasculitis. Fourteen subjects were Caucasian, 13 Asian, 6 East Indian, and 3 Canadian First Nations. An abnormal Z score at one or more sites was found in 10/25 (40%) with JSLE, and in 3/11 (27%) JDM/vasculitis patients. The mean Z scores (+/- SD) for lumbar spine were -1.02 (+/- 1.2), for hip -0.88 (+/- 1.3), and for total body -0.77 (+/- 1.5). Compared to children with normal bone densities, those with lower bone density tended to be younger (13.5 +/- 2.2 vs 15.5 +/- 1.7 yrs), received higher corticosteroid dosages at the time of the study (0.78 +/- 0.6 vs 0.35 +/- 0.2 mg/kg), and were more often prepubertal (OR for total body scores 5, 95% CI 0.7-46).

Conclusion: Decreased bone density is common in children with SLE and other systemic rheumatic diseases. Age, corticosteroid dose, and pubertal stage all appear to have some influence on bone mass in these children.