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Introduction to Inherited Muscular Disorders


Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision Jul 2020| Content last modified Jul 2020
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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 Facioscapulohumeral Muscular Dystrophy 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 is the most common form of muscular dystrophy, and Duchenne dystrophy and Becker 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 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.

Muscular dystrophies are distinguished by the selective distribution of weakness and the specific nature of the genetic abnormality involved.

Congenital muscular dystrophy

Congenital muscular dystrophy describes a rare group of diseases with symptoms evident at birth or shortly thereafter. The diseases are genetically recessive and manifest with diminished muscle tone, sometimes called "floppy baby." Diagnosis is based on clinical presentation, muscle biopsy, and blood tests to evaluate muscle proteins and genetic abnormalities. No cure exists; treatment is focused on preserving and optimizing function.

Congenital muscular dystrophy is not a single disorder but instead refers to muscular dystrophy evident at birth or in infancy, occurring from any of several rare forms of muscular dystrophy. All such dystrophies are genetically recessive and result from mutations in a variety of different genes including those that encode for structural proteins of the basal membrane or the extracellular matrix of skeletal muscle fibers.

The diagnosis of congenital muscular dystrophy is suspected in any floppy neonate but must be distinguished from a congenital myopathy Congenital Myopathies Congenital myopathy is a term sometimes applied to hundreds of distinct neuromuscular disorders that may be present at birth, but it is usually reserved for a group of rare, inherited, primary... read more by muscle biopsy. Blood tests to evaluate muscle proteins, ultrasonography and magnetic resonance imaging of muscle, and genetic testing when available, are typically done to arrive at an accurate diagnosis.

No specific treatment exists for congenital muscular dystrophies. Orthopedic, cardiac, respiratory, nutritional, and social issues may be addressed by appropriate experts as the needs arise, and supportive care, including physical therapy helps preserve function.

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