The burden of bone disease in Duchenne muscular dystrophy: age-specific prevalence of osteoporosis and low bone density

We evaluated fracture and osteoporosis prevalence in a large cohort of children with DMD undergoing routine spine imaging. Osteoporosis is common and worsens with age and glucocorticoid use. Low total body bone mineral density may herald clinically detectable osteoporosis. Our findings emphasize the need for better detection and prevention. INTRODUCTION: Osteoporosis is a major health concern in individuals with Duchenne muscular dystrophy (DMD) due to long-term glucocorticoid (GC) therapy, muscle weakness and restricted mobility. Osteoporosis results in long bone and vertebral fractures, which can lead to significant morbidity including premature loss of ambulation. We evaluated the age-related prevalence of osteoporosis and bone health indices in children and adolescents with DMD on daily GC therapy. METHODS: We conducted a retrospective review of patients with DMD seen at Cincinnati Children's Comprehensive Neuromuscular Center over 9 years. Bone health assessments included fracture history, routine annual spine radiographs and bone mineral density (BMD) by dual-energy X-ray absorptiometry. RESULTS: We included 408 patients with DMD (mean age 8.0 ± 3.5 years, range 3.0-19.3 years) who had received daily GC (mean age of GC start 6.4 ± 2.5 years, mean duration 2.7 ± 2.4 years). Osteoporosis prevalence increased progressively with age: 4.4%, 20.9%, and 58.3% at ages 5, 10 and 18 years, respectively. The prevalence of long bone and/or vertebral fractures was 16.5%, 37.4%, and 83.3%, respectively. Low total body BMD Z-scores preceded clinically detectable osteoporosis, while low lumbar spine values lagged behind. CONCLUSIONS: Osteoporosis, fractures, and low BMD were highly prevalent from a young age in children and adolescents with DMD and increased progressively with age and GC exposure. The prevalence of osteoporosis reflected the cumulative acquisition of vertebral fractures, consistent with long-term GC effect. These data highlight the urgent need to improve early detection and prevention of osteoporosis in individuals with DMD.