Steroid-Induced Low Bone Mass in Boys with Duchenne's Muscular Dystrophy

Muscular dystrophy (MD) is an inherited muscle disorder with an unknown cause.  Only males are affected, and only females can pass on the MD gene.  MD involves slow but progressive degeneration of muscle fibers.  Duchenne muscular dystrophy (DMD) is the most common type  of MD.  DMD is rarely diagnosed before age 3 but progresses rapidly.  By age 8-10, affected children are no longer able to walk.  There is no known cure for MD; however, for unknown reasons corticosteroids, such as prednisone, delay the loss of muscle function.  If your child has DMD, you are probably aware of the use of deflazacort--it has been standard treatment for DMD for more than a decade. 

Although this particular steroid has fewer side effects than prednisone, it still can cause loss of bone density.  Since inactivity also causes bones to become thin and demineralized, boys with DMD are at high risk for breaking bones.  Alendronate (Fosamax) is used in adults to halt the progress of bone mass loss and to decrease their risk of fracture.  A study was done at a children's hospital in Canada to determine whether or not this medication would be safe and effective in children with DMD. 

The study had many limitations, including a small participation and the lack of a control group.  The outcome, nevertheless, showed a positive effect on bone density.  The improvement in bone density was even more evident with the youngest boys.  The medication was well tolerated. 

The authors of this study suggest that future studies be done with larger numbers of participants and in multiple rehab centers.  They also caution that while it has been established that preserving bone mineral density in adults is known to decrease fracture risk, it has not been established that this relationship is true of children and their bones.  Longer-term studies are indicated and optimal doses for children need to be established.


"Alendronate in the Treatment of Low Bone Mass in Steroid-Treated Boys with Duchenne's Muscular Dystrophy," Hawker, G MD MSc; Ridout, R MD; Harris, V RN; Chase, C BSc MRT(N); Fielding, L BSc; Biggar, D MD, Archives of Physical Medecine and Rehabilitation