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, and 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. 
These include alpha-actin (ACTA1), alpha- and beta-tropomyosin (TPM3 and TPM2), 
troponin T (TNNT1), and 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. Greater understanding of muscle formation and cause of 
disease can be established through the study of the effect of mutations on the 
functional proteins. However, a major limitation in the understanding of 
congenital myopathies is the lack of correlation between the degree of 
sarcomeric disruption and disease severity. Consequently, great difficulty may 
be encountered when diagnosing patients and predicting the progression of the 
disorders. There are no existing cures for congenital myopathies, although 
improvements can be made to both the standard of living and the life expectancy 
of the patient through various therapies.