The role of delayed bone age in the evaluation of stature and bone health in glucocorticoid treated patients with Duchenne muscular dystrophy.

Background: Low bone mineral density and an increased risk of appendicular and vertebral fractures are well-established consequences of Duchenne muscular dystrophy (DMD) and the risk of fractures is exacerbated by long-term glucocorticoid treatment. Monitoring of endocrine and skeletal health and timely intervention in at-risk patients is important in the management of children with DMD.

Methods: As part of the Norwegian Duchenne muscular dystrophy cohort study, we examined the skeletal maturation of 62 boys less than 18 years old, both currently glucocorticoid treated (n = 44), previously treated (n = 6) and naïve (n = 12). The relationship between bone age, height and bone mineral density (BMD) Z-scores was explored.

Results: The participants in the glucocorticoid treated group were short in stature and puberty was delayed. Bone age was significantly delayed, and the delay increased with age and duration of treatment. The difference in height between glucocorticoid treated and naïve boys was no longer significant when height was corrected for delayed skeletal maturation. Mean BMD Z-scores fell below - 2 before 12 years of age in the glucocorticoid treated group, with scores significantly correlated with age, duration of treatment and pubertal development. When BMD Z-scores were corrected for by retarded bone age, the increase in BMD Z-scores was significant for all age groups.

Conclusion: Our results suggest that skeletal maturation should be assessed in the evaluation of short stature and bone health in GC treated boys with DMD, as failing to consider delayed bone age leads to underestimation of BMD Z-scores and potentially overestimation of fracture risk.