BIOLOGY OF MUSCULAR DYSTROPHY
The genetic makeup of people with MD lacks or has an incorrect genetic programming that prevents their body from making the proteins needed for a healthy and functional muscle. MD can appear at an early age or could exhibit in the later stages in life. The severity of MD varies from mild cases that slowly worsen to extreme cases that are physically disabling. Some common forms of MD include Duchene muscular dystrophy (DMD), Becker muscular dystrophy (BMD), Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy (LGMD), Facioscapulohumeral muscular dystrophy (FSHD), Myotonic muscular dystrophy (MMD), and Congenital muscular dystrophy (CMD). Virtually all types of MD have progressive muscle weakness that forms in a proximal-to-distal orientation although some variations such as location, severity, and intensity of the weakness are observed.
The underlying cause of muscular dystrophy lies in the defect in the genetic code of the 427-kd skeletal muscle protein (Dp427) called dystrophin. The effect of this genetic defect manifests in what is commonly associated with MD which include weaknesses of the muscles and pseudohepertrophy. The X-linked forms of MD like Duchenne and Becker dystrophies have their defects located in the short arm of the x-chromosome which scientists located to be in the Xp21 region involving 2 million base pairs of the Dp427. The disorder of DMD and EDMD is sex-linked but has localized defects in the long arm of the x-chromosome at the q28 region while the LGMD has its genetic disorder located in the 13q12 locus, FSHD at 4q35 locus, and distal MD at 2q12-14 loci.
Most of the MD cases exhibits slight to moderate mental retardation and this occurs because dystrophin can also be found in the brain. Dystrophin has a large size and because of this, it allows dysfunctional or mistakes in the synthesis of proteins at multiple sites, explaining the ease with which the new mutation in DMD occurs. The...