Duchenne and Becker muscular dystrophy are genetic, muscle-wasting conditions caused by the complete or partial lack of a protein called dystrophin.
Dystrophin is an important component of the muscles and when it is missing or not fully functional, muscle fibres break down and are replaced by fibrous and or fatty tissue causing the muscles to weaken gradually.
Duchenne and Becker muscular dystrophy usually affect only boys. However some girls and women can also be affected as manifesting carriers.