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Extended report
Predicting longitudinal trajectory of bone mineral density in paediatric systemic lupus erythematosus patients
  1. Lily Siok Hoon Lim1,
  2. Susanne M Benseler1,
  3. Pascal N Tyrrell1,
  4. Elizabeth Harvey2,
  5. Diane Herbert2,
  6. Martin Charron3,
  7. Earl D Silverman1
  1. 1Division of Rheumatology, The Hospital for Sick Children, Toronto, Canada
  2. 2Division of Nephrology, The Hospital for Sick Children, Toronto, Canada
  3. 3Division of Diagnostic Imaging, The Hospital for Sick Children, Toronto, Canada
  1. Correspondence to Dr Earl D Silverman, The Hospital for Sick Children, Rheumatology, 555 University Ave, Suite 8253A, Toronto, Ontario, Canada, M5G 1X8; earl.silverman{at}sickkids.ca

Abstract

Objectives (1) To identify the average lumbar spine (LS) bone mineral density (BMD) trajectory in paediatric systemic lupus erythematosus (pSLE) patients, and (2) to identify predictors of BMD trajectory.

Methods 68 consecutive newly diagnosed pSLE patients prospectively followed in our lupus cohort with three annual dual energy x-ray absorptiometry (DEXA) examinations were studied. Low LS BMD was defined as z-score ≤−2.0. Baseline and longitudinal clinical features including disease activity, treatment and bone physiology markers were collected. Hierarchical linear modelling was used to model trajectory of LS BMD and identify predictors.

Results Women constituted 84% of the cohort and median age at diagnosis was 13.1 years. The mean LS BMD z-scores decreased over time (0.42 at first, −1.02 at second and −1.11 at third DEXA). Initially 9% of patients had a low BMD, which increased to 19% by 3 years after diagnosis. 35% of patients deteriorated in BMD category from the first to third DEXA. LS BMD (adjusted by height-for-age z-score) followed a general deteriorating trajectory of −0.06 z-score/year from diagnosis. Increased rate of deterioration of BMD trajectory was predicted by pubertal status at diagnosis, increased interval cumulative steroid exposure and decreased weight z-scores.

Conclusions The LS BMD of pSLE patients followed a general deteriorating trend over time and could be predicted by a combination of pubertal status at diagnosis, interval cumulative doses of steroids and weight z-scores. Interval cumulative steroid dose represents an important target that clinicians may modify to ameliorate deteriorating BMD trajectory over time.

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Footnotes

  • Ethics approval The study was approved by the institutional research ethics board of The Hospital for Sick Children, Toronto.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Competing interests None.

  • Data sharing statement There are no further unpublished data obtained for this particular study.

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