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

Cause - Mutations in the genes that produce emerin, lamin A or lamin C, proteins in the membrane that surrounds the nucleus of each muscle cell.

Onset - Usually by 10 years of age.

Symptoms - Weakness and wasting of shoulder, upper arm and calf muscles; joint stiffening; fainting (because of cardiac abnormalities).

Progression - Disease usually progresses slowly. Cardiac complications are common and sometimes require a pacemaker.

Inheritance -Can be X-linked recessive, primarily affecting males, who inherit the disease through their mothers. Another type is autosomal dominant, meaning it can be inherited through either parent; an autosomal recessive type occurs when a faulty gene is inherited from each parent.

Facts About Rare Muscular Dystrophies