Bone Abstracts

Introduction: Duchenne muscular dystrophy (DMD) is caused by mutation in the dystrophin gene on the X-chromosome, leading to progressive deterioration in muscle function from early childhood. Corticosteroid treatment prolongs the time to loss of walking ability and improves life span. The combination of muscular weakness, reduced mobility and steroids increases the risk of secondary osteoporosis.

Subjects and methods: In this prospective observational study, monthly intravenous pamidronate infusions were initiated (initial dose 10 mg/m², during 6 months increased to 30 mg/m²) to five boys with DMD, due to intensive back pain and multiple vertebral fractures. Their age was 11.6–16.4 years (median 12.7 years). They previously had steroid treatment during 3.5–10.6 years (median 5.5 years). Four of them continued the steroid treatment during the observation time. Two boys had experienced an extremity fracture with no or minor trauma. All but the youngest had growth arrest before baseline.

Results: At baseline they all recorded intensive back pain every day of the month, but at the latest recording (after 2–3 years of bisphosphonate treatment, median 2 years) pain had resolved completely in four and almost completely in one boy (VAS 1, 1 day/month). At baseline the median bone density z-scores of the whole body and spine were −3.5 and −2.2 respectively. At the latest recording the corresponding median z-scores were −3.9 and −2.9. Radiographs after 2 years showed slightly increased vertebral height in the youngest boy, but the other four had unchanged vertebral height and even slight progress of compressions of 2–3 vertebral bodies. No other fractures occurred.

Conclusions: Intravenous pamidronate is an effective treatment of back pain due to vertebral fractures in osteoporotic boys with DMD. Larger studies are needed to assess the treatment effects and optimal time of treatment start.