Definition of Facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy: A form of muscular dystrophy that typically begins before age 20 with slowly progressive weakness of the muscles of the face, shoulders, and feet. The severity of the disease is quite variable. Although most people with facioscapulohumeral muscular dystrophy (FSHD) retain the ability to walk, about 20% require a wheelchair. Life expectancy is not shortened.

The diagnosis can be confirmed by a DNA test disclosing the deletion of copies of a repeat motif called D4Z4 on chromosome 4. FSHD is inherited in an autosomal dominant manner. Offspring of an affected individual have a 50% chance of inheriting the mutant chromosome 4. About 10-30% of cases are due to a new mutation. Prenatal testing is available.