Muscular dystrophies are inherited, progressive muscle disorders resulting from defects in one or more genes needed for normal muscle structure and function; dystrophic changes (eg, muscle fiber necrosis and regeneration) are seen on biopsy specimens.
Facioscapulohumeral muscular dystrophy (FSHMD) is the most prevalent type of muscular dystrophy and occurs in 7/1000 people vs 5/1000 people with Duchenne or Becker muscular dystrophy. It is an autosomal dominant disorder. In about 98% of patients, FSHMD is caused by a deletion on the long arm of chromosome 4, at the 4q35 locus. In about 10 to 33% of patients, the mutation is de novo (sporadic) rather than inherited.
Facioscapulohumeral muscular dystrophy is characterized by weakness of the facial muscles and shoulder girdle. Symptoms may develop in early childhood and are usually noticeable during adolescence; 95% of cases manifest by age 20. Initial symptoms are slowly progressive and may include difficulty whistling, closing the eyes, and raising the arms (due to weakness of the scapular stabilizer muscles). Patients eventually notice a change in facial expression.
The course is variable. Many patients do not become disabled and have a normal life expectancy. Other patients depend on a wheelchair in adulthood. An infantile variety, characterized by facial, shoulder, and hip-girdle weakness, is rapidly progressive, and disability is always severe. Nonmuscular symptoms frequently associated with this disorder include sensorineural hearing loss and retinal vascular abnormalities.
There is no treatment for the weakness, but physical therapy may help maintain function (1).
Monitoring for retinal vascular abnormalities is essential to prevent blindness.
1. Tawil R, Kissel JT, Heatwole C, et al: Evidence-based guideline summary: Evaluation, diagnosis, and management of facioscapulohumeral muscular dystrophy: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology and the Practice Issues Review Panel of the American Association of Neuromuscular & Electrodiagnostic Medicine. Neurology 85:357–364, 2015. doi: 10.1212/WNL.0000000000001783
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