Introduction to inherited muscular disorders

[Sommer]

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 dystrophy is the most common form of muscular dystrophy, and Duchenne dystrophy and Becker dystrophy are the second most common. Duchenne dystrophy is a more severe form; Becker dystrophy, although closely related to Duchenne, has a later onset and causes milder symptoms.
Other forms include Emery-Dreifuss dystrophy, myotonic dystrophy, limb-girdle dystrophy, oculopharyngeal muscular dystrophy, and congenital dystrophies.
Muscular dystrophies are distinguished by the selective distribution of weakness and the specific nature of the genetic abnormality involved.
Other inherited muscular disorders include congenital myopathies, myotonia congenita, and familial periodic paralysis.
Inherited metabolic disorders affecting the muscles, such as mitochondrial oxidative phosphorylation disorders and glycogen storage diseases, are discussed elsewhere. Only those disorders that have all or most of their effects on muscle are discussed in this chapter.