Muscular Dystrophy (MD) is a progressive loss of skeletal muscle (muscle wasting) affecting limb movement and respiration due to a mutation, both DMD and BMD versions are inherited as X-linked recessive so only affect boys, most common is Duchenne Muscular Dystrophy (DMD), affecting 1 in 3,000 males, second most common is Becker Muscular Dystrophy (BMD), affecting 1 in 30,000 males, DMD is evident by age 1- 6 years; disease is often fatal by age 25, BMD is milder, onset is later (age 12 or later); affected people live to >50 years.