Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a dominantly inherited muscular dystrophy affecting about 1 in 20,000 individuals. The weakness is not restricted to areas named in the disease name; weakness may occur in hip girdle, ankle dorsiflexors, and occasionally oropharynx. Extramuscular manifestations of this slowly progressing myopathy may include hearing loss and retinal vasculopathy. All patients with a confirmed diagnosis of FSHD carry a chromosomal rearrangement within the subtelomeric region of chromosome 4q (4q35). This subtelomeric region is composed mainly of a polymorphic repeat structure consisting of 3.3-kb repeated elements (D4Z4). The number of repeat units varies from 10 to more than 100 in the population, and, in patients with FSHD, an allele of 1 to 10 residual units is observed because of the deletion of an integral number of these units.

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