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

Cause - Insufficient production of dystrophin, a protein that helps keep muscle cells intact.

Onset - Adolescence or adulthood.

Symptoms - Generalized weakness and wasting first affecting the muscles of the hips, pelvic area, thighs and shoulders. Calves are often enlarged. BMD is similar to Duchenne muscular dystrophy but often much less severe. There can be significant heart involvement.

Progression - Disease progresses slowly and with variability but can affect all voluntary muscles. Most with BMD survive well into mid- to late adulthood.

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

Facts About Duchenne and Becker Muscular Dystrophies