Congenital myopathies is a term used to describe a wide variety of inherited disorders of the muscles, nerves, or both, which are present at birth or infancy.
There are hundreds of congenital myopathies. The five most common types of congenital myopathy are nemaline myopathy, myotubular myopathy, central core myopathy, congenital fiber type disproportion, and multicore myopathy. Among these most common types, life span is usually normal in central core myopathy, congenital fiber type disproportion, and myotubular myopathy. However, exceptions often occur. Life span tends to be more variable in multicore myopathy and nemaline myopathy.
The diagnosis usually requires taking a sample of the weak muscle tissue for biopsy (in which a piece of tissue is removed for examination under a microscope). Specific treatments are not available, but physical therapy may help preserve function.
Resource: Merck Manual Home Edition