Endocrine Abstracts

Background: Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy, resulting in death at a young age. Corticosteroids improve muscle function and slow disease progression. However long-term steroid therapy is a significant risk factor for osteoporosis.

Aim: To assess the effect of oral bisphosphonate (risedronate) treatment on bone mineral density in a cohort of steroid-treated children with DMD.

Method: Annual bone mineral density (DXA) scans were performed on boys with DMD treated with glucocorticoid under review at a National Muscle centre. Data prior to bisphosphanate initiation were compared with subsequent annual DXA assessments. Lumbar spine and total body bone densities were corrected for bone volume. Information about duration of steroid treatment and fractures was also collected. All patients received vitamin D supplementation.

Results: Data on 43 patients was analysed. The median duration of steroid therapy at the initiation of bisphosphanate therapy was 33 months (range: 0–87 months). The duration of bisphosphonate therapy ranged from 1 to 4 years (average 2 years). Total body adjusted density Z score increased post bisphosphonate therapy from −0.55 at baseline to 0.62 after 3 years (P=0.009) whilst lumbar spine adjusted density (LSAD) remained stable with a baseline value of 0.11 and 0.21 at year 3 (P=0.97). LSAD in those with an initial Z score <−1 increased from −1.44 to −0.49 (P<0.01). Eight patients had documented fractures following a fall whilst on bisphosphonate therapy. Three of these involved lumbar spine and these patients all had a LSAD < −1 SDS at baseline.

Conclusions: The size adjusted lumbar spine BMD of steroid treated patients with DMD on bisphosphonates remains stable and particular benefit was seen in those with an initial LSAD <−1 SDS. The relationship between fracture and baseline LSAD highlights the need to consider ways of refining bone protection in these patients with more targeted therapy.