What are congenital myopathies?

Updated: Mar 11, 2019
  • Author: Matthew Harmelink, MD; Chief Editor: Amy Kao, MD  more...
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Answer

Congenital myopathies describes a set of genetic diseases that predominantly affect the muscles. The first report of a congenital myopathy was of a patient with central core disease (CCD) in 1956. Since that time, the classification of congenital myopathy has been evolving from a primary pathologic diagnosis to one with a genetic basis.

The typical features of congenital myopathy include early-onset muscle weakness, often associated with features of low muscle bulk and tone. While these features are typically found in neonates and infants, children or even adults can present with milder forms of congenital myopathy. In certain cases, patients can have normal strength and tone but be at risk of rhabdomyolysis and/or malignant hyperthermia. Due to the early weakness, dysmorphic features such as contractures, a high arched palate, and facial dysmorphisms can be seen.

The classification of congenital myopathies has evolved to no longer be a pure pathologic diagnosis but rather relying more on genetic data. However, the genotype-to-phenotype correlation is variable on the gene level and more accurate when described by a specific mutation. Given this, the taxonomy of congenital myopathies can be somewhat confusing. Diagnosis should be a combination of genetic, phenotypic, and, if needed to confirm, pathologic, electrodiagnostic, and serum features.

The skeletal muscle involvement can also result in secondary breathing and swallowing difficulties. However, non-skeletal muscle features can manifest based upon the specific disease. 

Additionally confounding is that, more recently, genes known to cause congenital myopathy have now also been described to cause a dystrophic process such as seen in congenital muscular dystrophies. However, the traditional pathologic subdivision of congenital myopathy does give some guidance in regards to genotype and prognostication and cannot be disregarded. As such, the congenital myopathies can be divided into 6 pathologic categories. [1, 2]

  • nemaline myopathy (subtypes: rod, core-rod, cap and zebra body myopathy);
  • core myopathy (subtypes: central core and multiminicore myopathy);
  • centronuclear myopathy (subtypes: myotubular myopathy and autosomal centronuclear myopathy);
  • congenital fiber-type disproportion myopathy;
  • myosin storage myopathy; and
  • nonspecific myopathic changes

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