Duchenne Muscular Dystrophy (DMD)

Duchenne Muscular Dystrophy (DMD) is a rare single gene disorder affecting 1 in 3,500 boys. The muscles of the affected person weaken and waste away (atrophy), usually beginning in the lower limbs and then spreading to the upper body as the disease progresses (1). This disorder is caused by recessive mutations in a gene called dystrophin. The dystrophin gene is located on the X chromosome (Xp21.2). Because the X-linked disorder is recessive it occurs mostly in males because males who inherit the mutated chromosome from their carrier mother do not have another copy of the X chromosome to negate it. Symptoms can be first noticed at a very young age when the affected individual is slower to start sitting, standing and walking independently than other children of their age (2). However usually the disease is not recognised until around 6 years of age. There is a continuous decline in muscle strength resulting in most being wheelchair bound …show more content…
The 14-kb mRNA transcribed from the gene is mainly expressed in the skeletal and cardiac muscles, but some is also expressed in the brain. Many different types of mutations can occur to give DMD, however all mutations are a loss-of-function mutation resulting in little or no gene product. The three common types of mutations in the dystrophin gene are large deletions of at least one exon, small point mutations and large duplications of at least one exon. Large deletions of exons occurs in 60-70% of cases, point mutations occur in 15-30% of cases and large duplications occur in 10% of cases (4). The vast majority of large deletions detected in DMD are found in two hotspots. The major hotspot spans exons 45–53 and if mutated it removes some of the rod domain of the dystrophin protein, while the minor hotspot spans exons 2–20 and mutation partially or completely removes the actin-binding sites of the protein as well as some of the rod