INTRODUCTION: Duchenne muscular dystrophy (DMD) patients are vulnerable to osteoporosis and fractures. The present study examined the natural history and determinants of bone health in DMD to gain further insight into pathogenesis and guide future treatment strategies.

METHODS: Fracture pattern, ambulation status, chronic corticosteroid therapy, vitamin D (25-OHD) levels and body mass index (BMI) were retrospectively analysed in 48 DMD patients. The Kaplan-Meier method was used to obtain fracture probabilities. Cross-sectional analysis of Vitamin D was performed in 31 DMD patients and related to treatment.

RESULTS: 43% of DMD patients had ≥1 fracture. Fracture probabilities at ages 6, 9, 12 and 15 years were 4%, 9%, 31% and 60% respectively, accelerating around the time of ambulation loss (11.8 ± 2.7 years). Overweight or obese patients had greater fracture rate than those with normal BMI (61% and 11% respectively, P<0.05). Chronic corticosteroid therapy was utilised in 69%. A history of 25-OHD deficiency occurred in 84% and current deficiency was present in 35% of patients. Despite chronic 25-OHD supplementation, 8/21 (38%) of current patients were deficient.

CONCLUSIONS: The natural history of fracture in DMD confirms that osteoporosis and pathological fracture remain a major concern, with multiple risk factors. The present study highlights the importance of instituting a multidisciplinary approach optimising bone health at the time of diagnosis of DMD and prior to loss of ambulation. This includes regular vitamin D supplementation, weight-bearing exercise and dietary education. The optimum dose of vitamin D and safety and utility of prophylactic bisphophonates warrant further study.