Could you explain what is duchenne muscular dystrophy?

See link below: "duchenne results in progressive loss of strength and is caused by a mutation in the gene that encodes for dystrophin. Because dystrophin is absent, the muscle cells are easily damaged. The progressive muscle weakness leads to serious medical problems, particularly issues relating to the heart and lungs." - see more at: http://www.Parentprojectmd.Org/site/pageserver?Pagename=understand_about#sthas.