Abstract
Facioscapulohumeral (FSH) muscular dystrophy is the third most common dystrophy, after myotonic dystrophy and the dystrophinopathies (Duchenne and Becker), with a prevalence of approximately 1 in 20,000. It is inherited in an autosomal-dominant fashion and has been linked to microsatellite markers on chromosome 4q35. A deletion of a variable number of repetitive elements (known as D4Z4 repeats) leads to the generation of a small EcoRI restriction fragment that is recognized by the p13E-11 probe. The precise mechanism whereby this genetic abnormality results in disease is unclear, but it is thought that the deletion alters chromosomal structure and influences the expression of more centromerically located genes. Because of its slow progression and relatively benign course, FSH is the second most common dystrophy (after myotonic dystrophy) in adults.