Muscular dystrophies and other genetic myopathies

Muscular dystrophies are a genetically and phenotypically heterogeneous group of progressive muscle diseases. Modern molecular genetic techniques have made it possible to clarify the genetic mutations responsible for most muscular dystrophies. Despite advances in genetics, the importance of the clinical history and physical examination has increased rather than diminished. It is only through correctly identifying the clinical features that the appropriate diagnostic investigations will be performed. Although muscular dystrophies are typically slowly progressive disorders in which muscle atrophy and weakness are the defining characteristics, diagnostic confusion with the idiopathic inflammatory myopathies (IIM) can occur, and a diagnosis of muscular dystrophy may be considered only after the failure of immunosuppressive treatment for a presumed case of IIM. This chapter reviews the various muscular dystrophies, and discusses how to differentiate between them and the IIM.