Duchenne muscular dystrophy.

Abstract

Duchenne and Becker muscular dystrophy are X-linked muscle-wasting disorders that arise from mutations in the gene coding for dystrophin. The incidence of Duchenne muscular dystrophy (DMD) is approximately 1 in 3500 live male births, one-third of which are sporadic with no previous family history. In the absence of dystrophin, patients with DMD exhibit progressive muscle fiber necrosis which, despite the regenerative capacity of the muscle during the early stages, leads to the gradual deposition of fibrotic and fat tissues and the loss of ambulation around 11 years of age. Death due to respiratory failure usually occurs by the third decade (Emery, 1993). Becker muscular dystrophy (BMD), the incidence of which is approximately 10-fold less than DMD, follows a generally much milder course due to the presence of a partially functional form of dystrophin. Generally the BMD phenotype tends to be much more varied, both with regard to the age of onset and clinical presentation, and some patients never lose the ability to walk.