Edith Cowan University, Research Online, Perth, Western Australia
Abstract
Duchene Muscular Dystrophy (DMD), and the milder allelic Becker muscular dystrophy (EMD), are X-linked recessive muscle wasting disorders characterised by mutations in the dystrophin gene. DMD occurs at a frequency of approximately 1 in 3500 male newborns and life expectancy is typically less than 30 years. Due to progressive muscle wasting, affected boys are restricted to a wheelchair by the age of 12 years. The most common cause of death is pneumonia, compounded by cardiac involvement. Mutations that disrupt the dystrophin reading frame, or prevent the synthesis of either terminus, preclude the synthesis of a fully functional dystrophin. The subsequent Joss of membrane integrity results in a severe DMD phenotype, as these weakened but still functional muscle fibres are subject to continuous cycles of damage and regeneration. Conversely, BMD mutations are generally found to be in-frame deletions where a shorter but semi-functional protein with intact amino and carboxyl tennini has been synthesised. BMD has an incidence almost ten times less than DMD. While the distribution of myopathy parallels DMD, the onset and progression of BMD is variable and generally less severe and some affected individuals are virtually asymptomatic
