Skeletal findings in the first 12 months following initiation of glucocorticoid therapy for pediatric nephrotic syndrome

Abstract

Incident vertebral fractures and lumbar spine bone mineral density (BMD) were assessed in the 12 months following glucocorticoid initiation in 65 children with nephrotic syndrome. The incidence of vertebral fractures was low at 12 months (6 %) and most patients demonstrated recovery in BMD Z-scores by this time point.

Introduction: Vertebral fracture (VF) incidence following glucocorticoid (GC) initiation has not been previously reported in pediatric nephrotic syndrome.

Methods: VF was assessed on radiographs (Genant method); lumbar spine bone mineral density (LS BMD) was evaluated by dual-energy X-ray absorptiometry.

Results: Sixty-five children were followed to 12 months post-GC initiation (median age, 5.4 years; range, 2.3-17.9). Three of 54 children with radiographs (6 %; 95 % confidence interval (CI), 2-15 %) had incident VF at 1 year. The mean LS BMD Z-score was below the healthy average at baseline (mean ± standard deviation (SD), -0.5 ± 1.1; p = 0.001) and at 3 months (-0.6 ± 1.1; p < 0.001), but not at 6 months (-0.3 ± 1.3; p = 0.066) or 12 months (-0.3 ± 1.2; p = 0.066). Mixed effect modeling showed a significant increase in LS BMD Z-scores between 3 and 12 months (0.22 SD; 95 % CI, 0.08 to 0.36; p = 0.003). A subgroup (N = 16; 25 %) had LS BMD Z-scores that were ≤-1.0 at 12 months. In these children, each additional 1,000 mg/m(2) of GC received in the first 3 months was associated with a decrease in LS BMD Z-score by 0.39 at 12 months (95 % CI, -0.71 to -0.07; p = 0.017).

Conclusions: The incidence of VF at 1 year was low and LS BMD Z-scores improved by 12 months in the majority. Twenty-five percent of children had LS BMD Z-scores ≤-1.0 at 12 months. In these children, LS BMD Z-scores were inversely associated with early GC exposure, despite similar GC exposure compared to the rest of the cohort.

Fig 1

Disposition of patients

Fig 2

Mean lumbar spine bone mineral density Z-scores (adjusted for BMI Z-score) and 95% CI at baseline, 3, 6 and 12 months post-glucocorticoid initiation. * Significant differences in mean lumbar spine bone mineral density Z-scores at 12 months compared to baseline.

Fig 3

Relationship between cumulative glucocorticoid dose from baseline to 3 months (mg/m²) for those with lumbar spine BMD Z-scores at 12 months ≤ −1.0 (N=16; circles and dashed regression line) compared to those with lumbar spine BMD Z-scores > −1.0 (N=49; triangles, solid regression line).