About Muscular Dystrophy

About Muscular Dystrophy.   Muscular dystrophies are a group of inherited neuromuscular disorders that lead to progressive muscle weakness and wasting. The most common and severe form of the disease is Duchenne’s muscular dystrophy. It afflicts one in every 3,500 boys who typically succumb to paralysis and death in their twenties from respiratory or cardiac complications. Other types of muscular dystrophies are less debilitating than Duchenne’s and can affect both males and females at various ages.

Causes

Duchenne’s muscular dystrophy (DMD) is caused by a mutation in the dystrophin gene, the largest known gene, located on the X chromosome. Dystrophin is an anchor-type protein that sits just inside the muscle cell membrane and tethers structural proteins inside the cell to the proteins that sit in the outer surface of the cell membrane. This connectivity effectively stabilizes the muscle cells, which are bundled together to form muscles.

 The most common type of mutation in the dystrophin gene is a deletion where part of the gene is missing but duplications and single point mutations can also occur. As a result, the body cannot make dystrophin, a protein vital for keeping muscle cells intact during the normal wear and tear of the day, and muscle cells are very susceptible to damage. Under normal conditions, damaged muscles try to regenerate.

But without dystrophin, the normal pattern of degeneration and regeneration is compromised. At a certain point, the pool of stem cells that make new muscle become exhausted, and more degeneration than regeneration occurs. As a result, the muscle becomes inflamed, is replaced with fibrous and fatty tissue, and simply wastes away over time.