Duchenne Muscular Dystrophy
Duchenne muscular dystrophy is an inherited, X-linked disease that affects about 1 in 3500 - 6000 males. DMD occurs as a result of a change in the dystrophin gene located at the X chromosome (locus Xp21.2). Changes in the gene cause an absence of or defect in the protein dystrophin. Boys have one X chromosome, from their mother and one Y chromosome, from their father. So, boys inherit DMD from their mother. Females have two X chromosomes and thus two copies of the dystrophin gene. One ‘normal’ dystrophin gene usually gives enough protein to protect her from the disease. The absent or abnormal DMD gene results in progressive muscle degeneration. In general leading to loss of independent ambulation by the age of 13 years in man. There is a variable expression of the gene abnormality. This is mainly due to the type of mutation and the effect on the production of dystrophin. Milder forms of the disease are intermediate muscular dystrophy and Becker muscular dystrophy. Loss of ambulation happens later in life.