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 about 0.5/1000 people with Duchenne or Becker muscular dystrophy Duchenne Muscular Dystrophy and Becker Muscular Dystrophy Duchenne muscular dystrophy and Becker muscular dystrophy are X-linked recessive disorders characterized by progressive proximal muscle weakness caused by muscle fiber degeneration. Becker dystrophy... read more . It is an autosomal dominant Autosomal Dominant Genetic disorders determined by a single gene (Mendelian disorders) are easiest to analyze and the most well understood. If expression of a trait requires only one copy of a gene (one allele)... read more disorder. In about 98% of patients, FSHMD is caused by a deletion on the long arm of chromosome 4, at the 4q35 locus. In up to 30% of patients, the mutation is de novo (sporadic) rather than inherited.
Symptoms and Signs
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 Pathophysiology Worldwide, about half a billion people (almost 8% of the world's population) have hearing loss ( 1). More than 10% of people in the US have some degree of hearing loss that compromises their... read more and retinal vascular abnormalities.
DNA mutation analysis
Diagnosis of facioscapulohumeral muscular dystrophy is indicated by characteristic clinical findings, age at onset, and family history and is confirmed by DNA testing.
There is no treatment for the weakness, but physical therapy may help maintain function ( 1 Treatment reference Facioscapulohumeral muscular dystrophy is the most prevalent type of muscular dystrophy. Most cases manifest by age 20. It is characterized by weakness of the facial muscles and shoulder girdle... read more ).
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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