There are many types of muscular dystrophy (MD); all are caused by errors in genes (the units of inheritance that parents pass on to their children). In Duchenne muscular dystrophy (DMD) lack of the protein dystrophin causes muscles to deteriorate and break down, leading to progressive difficulty with walking and general mobility. DMD is the most frequently occurring and one of the most rapidly progressive of the childhood neuromuscular disorders. It affects approximately 1 in 3500 live male births throughout the world. Due to the way that it is inherited, DMD affects mostly boys, but occasionally girls are affected.