"Facioscapulohumeral Muscular Dystrophy.
Lemmers RJLF, van der Maarel SM.
In: Pagon RA, Bird TC, Dolan CR, Stephens K, editors. GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle; 1993-.
1999 Mar 08."
Disease characteristics. Facioscapulohumeral muscular dystrophy (FSHD) typically presents before age 20 years with weakness of the facial muscles and the stabilizers of the scapula or the dorsiflexors of the foot. Severity is highly variable. Weakness is slowly progressive and approximately 20% of affected individuals eventually require a wheelchair. Life expectancy is not shortened. Diagnosis/testing. FSHD is diagnosed by a molecular genetic test that identifies deletion of integral copies of a 3.3-kb DNA repeat motif, D4Z4, which is located in the subtelomeric region of chromosome 4q35. Normal D4Z4 alleles have 11-100 repeat units; those associated with FSHD have between one and ten repeat units. Molecular genetic testing detects approximately 95% of affected individuals and is clinically available. Management. Treatment of manifestations: low-intensity aerobic exercise; ankle/foot orthoses to improve mobility and prevent falls; surgical fixation of the scapula to the chest wall may improve range of motion of the arms over the short term; standard treatment of sensorineural hearing loss; lubricants to prevent drying of the sclera or taping the eyes shut during sleep to treat exposure keratitis. Surveillance: annual evaluation to assess strength and functional limitations. Genetic counseling. FSHD is inherited in an autosomal dominant manner. Approximately 70%-90% of individuals have inherited the disease-causing deletion from a parent, and approximately 10%-30% of affected individuals have FSHD as the result of a de novo deletion. Offspring of an affected individual have a 50% chance of inheriting the deletion. Prenatal testing for pregnancies at increased risk is possible if the D4Z4 contraction mutation has been identified in the family.