Endocrine Abstracts

Introduction: Intravenous bisphosphonates are the standard of care for treating skeletal complications in Duchenne muscular dystrophy (DMD), typically initiated following vertebral fracture. Short-term benefits in bone mineral density/content have been demonstrated in research studies including clinical trials. Current international guidelines recommend continued use until completion of linear growth; however, long-term efficacy data in DMD remain limited.

Aim: To evaluate changes in dual-energy X-ray absorptiometry (DXA) outcomes following long-term intravenous bisphosphonate therapy in boys with DMD.

Methods: This retrospective study included boys with DMD treated with intravenous zoledronate between 2014 and 2020 who remained on therapy for over two years. DXA data were collected at four time points: (a) first available scan, (b) pre-treatment baseline, (c) 20–24 months post-initiation, and (d) maximum follow-up. Continuous data are presented as mean (SD); p-values <0.05 were considered statistically significant.

Results: Fourteen boys (mean age at initiation: 10.8 years, SD 2.6) received zoledronate after vertebral fracture diagnosis. All were on corticosteroids (13/14 daily); 8/14 (57%) were ambulant at initiation, and 1/14 (7%) was on testosterone. At maximum follow-up (mean age 15.5 years, SD 2.9), 4/14 (29%) remained ambulant, and 4/14 were on testosterone. Despite expected age-related increases, total body less head (TBLH) bone area and BMC did not significantly change (P = 0.62 and P = 0.75, respectively). TBLH BMC-for-bone-area SDS remained stable across all time points (P = 0.05). In contrast, lumbar spine (LS) bone area and BMC significantly increased over time, with LS BMC-for-bone-area SDS improving from -0.05 (SD 1.1) at first scan to 0.85 (SD 2.0) at maximum follow-up (P = 0.02 vs first scan; P = 0.03 vs baseline). No atypical femoral fractures or cases of osteonecrosis of the jaw were reported.

Conclusion: Long-term zoledronate therapy was associated with improved spine bone mineral content, but not total body bone mineral content, highlighting the underlying impact of progressive myopathy. These findings underscore the need to investigate osteoanabolic therapies in DMD to better support skeletal health.