Background/Purpose: Childhood-onset systemic lupus erythematosus patients < 18 years (cSLE) are at risk for reduced bone mineral density (BMD) due to disease activity and chronic glucocorticoid exposure. Genetics play a role in SLE susceptibility. Our aim was to assess the genetic contribution to BMD among a multi-ethnic cSLE cohort.

Methods: All patients were diagnosed and followed at the SickKids and had baseline Lumbar Spine (LS) BMD scan, defined as 1 month prior, or up to one year post cSLE diagnosis. The main outcome of interest was LS (L1-L4) BMD z scores. Two weighted polygenic risk scores (PRSs)- 1) BMD PRS 2) SLE PRS were calculated based on largest GWASs to date. Both PRSs were regressed with BMD z-scores in linear models adjusted for demographics, glucocorticoid exposure, height percentile, BMI, and an indicator for lupus nephritis and/or neuropsychiatric lupus.

Results: The study included 284 patients, 82% female, 29% of European, and 28% of East Asian ancestry. The median age of cSLE diagnosis was 13.5 years [IQR 11.1, 15.3]. In multivariate model, a higher BMD PRS was significantly associated with low BMD z-score (β: -0.75; 95%CI: -1.32, -0.18; P=0.01) as was prior steroids use (β: -0.34; 95%CI: -0.63, -0.04; P=0.02). No association was found between SLE PRS and LS BMD z-scores. Height percentile and BMI were significantly associated with BMD z-score, however presence of LN and/or NPSLE was not.

Conclusion: High BMD PRS was significantly associated with lower LS BMD z-score in cSLE patients at baseline. BMD PRS may be an effective tool to stratify cSLE patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-association-between-systemic-lupus-erythematosus-sle-and-bone-mineral-density-bmd-polygenic-risk-scores-with-lumbar-spine-bmd-z-score-a-retrospective-cohort-study/