Duchenne muscular dystrophy (DMD) is brought on by a mutated dystrophin gene, which causes muscles to progressively degenerate.
DMD can appear as early as age three and only affects males. By the teen years DMD has invaded heart and respiratory muscles. The ability to walk is generally lost between ages seven and twelve. Teenagers can expect limited mobility, a need for mechanical support and eventually ventilation to provide adequate airflow.
DMD is a killer that routinely succeeds by age twenty. This disease never picks on anyone its own size.