One in six newly diagnosed pediatric systemic lupus erythematosus patients were found to have low bone mineral density, a study has shown.
The single-cohort study of 80 children and adolescents with newly diagnosed SLE also found that steroid exposure was not significantly linked to decreased BMD.
The findings suggest that "the detrimental effect of systemic inflammation on BMD is more important than short term exposure to corticosteroids even at high dose," noted Dr. Siok Hoon Lily Lim and colleagues (Ann. Rheum. Dis. 2011;70:1991-4).
Dr. Lim of the department of pediatrics, division of rheumatology, at the University of Toronto, included patients in the study if they were between 5 and 18 years of age. All were seen at the Hospital for Sick Kids, also in Toronto, between December 2001 and December 2007. The patients underwent a dual-energy x-ray absorptiometry (DXA) scan within 3 months of SLE diagnosis.
Low lumbar spine (LS) BMD was defined as a z score of less than or equal to –2.0, in line with recommendations from the International Society of Clinical Densitometry and the American Academy of Pediatrics. In addition, a hip BMD of less than 80% was defined as low.
Overall, the median age at SLE diagnosis was 14.2 years (range, 5.0-17.7 years). The mean lumbar spine BMD z score for the cohort was –0.4 (range, –3.3 to 3.2); mean body mass index was 19.8 kg/m2.
The researchers found that at the time of the DXA scan, 12 patients (15%) had overall low BMD, defined as low lumbar spine BMD with or without low hip BMD.
One-third (26 patients) were also found to have "abnormal" BMD, defined as a lumbar spine BMD less than or equal to –1.0, with or without low hip BMD.
Meanwhile, in terms of steroid use, 22 patients were steroid naive at the time of the DXA scan, noted the researchers. "There was no difference in LS (P = 0.63) or hip (P = 0.89) BMD, irrespective of exposure to steroids," among the cohort.
"Steroid-exposed patients were not more likely to have low (LS/hip) BMD (P = 0.23)," the investigators added. The only factors that were significantly linked to low lumbar spine BMD were a low BMI (P less than 0.0001) and low corrected serum calcium (P = 0.0036).
For every standard deviation decrease in the BMI z score, the odds of having low BMD further increased by 65% (odds ratio, 0.35), Dr Lim and colleagues reported.
They said that the study was limited by a lack of information regarding patients’ genetic risk factors for low BMD. They were also unable to account for premorbid activity levels, including weight-bearing activity, which is thought to impact bone mass accrual, although this effect would likely be less pronounced in patients with lower-limb arthritis, they noted.
Nevertheless, "we recommend that all newly diagnosed patients with [pediatric] SLE should have a baseline BMD, especially in patients with risk factors identified in this study," including a low BMI, concluded the researchers. "Longitudinal follow-up of this cohort of patients will clarify their future outcomes."
The investigators reported having no relevant financial disclosures.