Definition - One of nine types of muscular dystrophy, a group of genetic, degenerative diseases primarily affecting voluntary muscles.

Cause - An absence of dystrophin, a protein that helps keep muscle cells intact.

Onset - Early childhood - about 2 to 6 years.

Symptoms - Generalized weakness and muscle wasting first affecting the musclesof the hips, pelvic area, thighs and shoulders. Calves are often enlarged.

Progression - DMD eventually affects all voluntary muscles, and the heart and breathing muscles. Survival is rare beyond the early 30s. A less severe variant is Becker muscular dystrophy.

Inheritance - X-linked recessive. DMD primarily affects boys, who inherit the disease through their mothers. Women can be carriers of DMD but usually exhibit no symptoms.

Facts About Duchenne and Becker Muscular Dystrophies