This is accomplished in two ways. First, by reducing the transporter activity, more ATP is made available for the contractile process. This is illustrated by the following examples. Duchenne Muscular Dystrophy DMD is the most prevalent of a group of X-chromosome linked muscular dystrophies characterized by enlargement of muscles. It results in a rapid progression of muscle degeneration that occurs early in life.
Myocardial involvement is frequent.
The median age for death in DMD individuals is 17. An estimated 3500 boys are affected worldwide. Without it, the cell membrane becomes permeable, so that extracellular components enter the cell, increasing the internal pressure until the muscle cell explodes and dies. The subsequent immune response can add to the damage. It usually strikes in mid-life.