There are several types of muscular dystrophy.  The type of MD usually determines the severity of the disease. 

The most widespread and severe form of MD is Duchenne MD.  This type affects one out of every 3.5 thousand boys.  Like hemophilia, girls may carry the gene on which MD is located, but they usually do not exhibit any symptoms.  Duchenne MD affects the protein dystrophin, causing weakness as the muscles are broken down.  Though significantly less common, Becker MD is very similar to Duchenne MD, though it develops more slowly.  Myotonic MD is the most common adult form of MD.  People with this form of muscular dystrophy may have related heart problems and other defects associated with the disease.

"The body is your temple.  Keep it pure and clean for the soul to reside in."

-B.K.S. Iyengar, Yoga: The Path To Holistic Health