Congenital myopathies are clinical and genetic heterogeneous disorders characterized by skeletal muscle weakness ranging in severity.

Three major forms have been identified:
 actin myopathy
 intranuclear rod myopathy
 nemaline myopathy.

Nemaline myopathy is the most common of these myopathies and is further subdivided into seven groups according to severity, progressiveness, and age of onset.

At present, five genes have been linked to congenital myopathies.

 alpha-actin (ACTA1)
 alpha- and beta-tropomyosin (TPM3 and TPM2)
 troponin T (TNNT1)
 nebulin (NEB).

Their protein products are all components of the thin filament of the sarcomere. The mutations identified within these genes have varying impacts on protein structure and give rise to different forms of congenital myopathies.

References

 Clarkson E, Costa CF, Machesky LM. Congenital myopathies: diseases of the actin cytoskeleton. J Pathol. 2004 Nov;204(4):407-17. PMID: #15495263#