Duchenne Muscular Dystrophy is a disease that causes rapidly worsening muscle weakness due to a lack of the protein dystrophin. It is inherited through an X-linked recessive gene, so it primarily affects boys. Symptoms begin in the legs and include fatigue, difficulty walking, and muscle weakness that gets worse over time and spreads to other muscles. There is no cure, and those affected often require use of a wheelchair by their early teens and don't survive past late teens or early adulthood.