Bone Abstracts

Duchenne muscular dystrophy (DMD) is associated with an increased risk of bone fragility due to the adverse effects of prolonged glucocorticoid therapy and progressive muscle weakness on bone strength. The resultant osteoporosis, which predisposes to fragility fractures of both long bones and vertebrae, is a major cause for concern. We studied 70 boys with DMD mean age 10.74±3.83 years. Bone mineral density was measured by DXA scan on lumbar spine and total body and content Z-scores adjusted for age, gender and height. Diagnosis of osteoporosis was made according to International Society for Clinical Densitometry 2013 criteria. Evaluation of calcium, phosphorus, alkaline phosphatase content and calciotropic hormones was performed. 48 patients were treated with steroids (23- deflazacort; mean dose 0.34 mg/kg, 25 with prednisone; mean dose 0.3 mg/kg). Bone mineral density (BMD) was lower than normal for age in all patients, and even lower in the group of steroid-treated children. Children with normal BMD were significantly younger, compared to those with decreased BMD (9.636±3.33 vs 12.89±3.13 years, P<0.001). Past medical history of 18 patients (44%) revealed a bone fracture, 66% of them referred to the lower extremities. Osteoporosis was diagnosed in 15% od patients. Majority patients (64) were supplemented with vitamin D. Mean dose was 1895,6 IU/day (400–6000 IU). There was no significant difference in dose of supplemented vitamin D between ST−/+ groups. In 30% of studied patients serum concentration of vitamin D was below 20 ng/ml, and in 67% was below 30 ng/ml. Comparing blood results between children ST−/+ the only significant difference was in Alkaline phosphate activity (135.62±42.85 U/l vs 114.52±35.77 U/l, P=0.038), the remaining: 25OHD (23.10 ng/ml vs 25.7 ng/ml; P=0.09), PTH NS (16.8 vs 19.7 pg/ml), calcium NS (9.61 mg/dl vs 9.78 mg/dl; P=0.06), phosphorus NS (4.54 mg/dl vs 4.64 mg/dl). In conclusion, decreased bone mineral density was present in DMD patients, and were worsening during corticosteroid therapy. It is thus recommended that bone and mineral metabolism be carefully evaluated in patients with DMD, so that appropriate measures could be taken, especially now that chronic corticosteroid therapy is frequently given

Disclosure: The authors declared no competing interests.