Bone health in boys with Duchenne Muscular Dystrophy on long-term daily deflazacort therapy

Quality of life in Duchenne Muscular Dystrophy (DMD) has improved significantly with corticosteroid treatment. However, corticosteroids decrease bone mass and increase vertebral fragility fracture risk. We report on bone health in 39 boys with DMD on long-term deflazacort (0.9 mg/kg/day) therapy. Bone health was defined by lumbar (L(1)-L(4)) bone mineral density (BMD), long-bone and/or symptomatic vertebral fractures. Lumbar BMD was reported as height-adjusted Z-scores at initiation of deflazacort (T(0)) and 1-2 year intervals thereafter. Subcapital body fat percentage and ambulatory status were recorded. At T(0), 39 boys, aged 6.6 ± 1.6 years had height-adjusted BMD Z-score -0.5 ± 0.8, and 23.5 ± 5.0% body fat. Height-adjusted Z-scores remained stable with years of deflazacort until loss of ambulation and accrual of body fat. Nine long-bone fractures occurred in eight ambulating boys, two before T(0). Seven vertebral fractures occurred in six non-ambulatory boys after ≥ 5 years of deflazacort with height-adjusted Z-score -1.8 ± 0.7, and 47.8 ± 12% body fat. Bone health in DMD is influenced by disease progression, corticosteroids, BMD Z-scores and fat mass accumulation. Adjustments for short stature must be considered during BMD interpretation. Percent body fat and ambulatory status are useful bone health indicators. Routine use of height adjusted Z-scores is advocated for use in routine clinical practice.