The average life expectancy of people with muscular dystrophy depends on the form of the disease. Most patients with one of the nine forms of muscular dystrophy live into adulthood, reports WebMD. However, people with Duchenne muscular dystrophy live only into their 30s, although a few live until age 50.
People with Duchenne muscular dystrophy are usually born with the disease. In past years, people with this form of muscular dystrophy died before age 20. Milder versions of Duchenne muscular dystrophy have a slower progression, according to the Muscular Dystrophy Association. This form of the disease is called Becker muscular dystrophy.