Surplus protein myopathies

Certain muscular dystrophies are marked by absence or reduction of mutant p roteins, foremost dystrophinopathies and sarcoglycanopathies. Conversely, o ther sporadic and familial neuromuscular conditions are marked by a surplus of proteins present in a granular or filamentous form, such as desmin-rela ted myopathies, actinopathy and, perhaps, hyaline body myopathy. This emerg ing group of congenital myopathies is clinically, immunohistochemically, an d genetically diverse. Clinically, early- and late-onset diseases with vari able courses are described. Immunohistochemically, mutant gene-related and other proteins have been identified by immunohistochemistry. Mutations in t he desmin and alpha -B crystallin genes have been discovered in desminopath ies. Mutations in the actin gene, but in no other genes have been revealed in actinopathy. Surplus sarcoplasmic and/or intranuclear nemaline bodies ha ve been related to mutant tropomyosin-3, actin and nebulin genes. This emer ging concept of surplus protein myopathies will require substantial investi gation to further interpret the results of present and future studies. (C) 2001 Elsevier Science B.V. All rights reserved.