Congenital muscular dystrophies.

Congenital muscular dystrophies (CMDs) are a heterogeneous group of disorders characterized by muscle weakness from birth, or shortly after, and variable clinical manifestations of the eye and central nervous system. Some of these disorders are fatal in the first years of life, whereas others have a milder course, with survival into adulthood. The CMDs were initially classified by clinical features and country of origin; however, with new molecular techniques it is now possible to classify these patients better. More than 10 genes have been identified to date that cause forms of CMD. However, even with current molecular diagnostic techniques, only approximately 25-50% of patients with CMD have an identifiable genetic mutation. In addition, some phenotypic classifications have been attempted. There is significant overlap between the phenotypic and molecular classifications, making diagnosis within this heterogeneous group of disorders difficult.