Babies with congenital myotonic dystrophy are very weak and floppy and frequently have problems with sucking, feeding and breathing. If they survive the newborn stage, they generally overcome their breathing and feeding problems, but they are slow to develop language and motor skills and are often affected for life with difficulties in these areas. Myotonic dystrophy is caused by an error in a gene located on the long arm of chromosome 19. The basic fault is an unstable inherited mutation in a particular gene known as the myotonic dystrophy protein kinase gene. At the present time, it is not known how the genetic abnormality causes the disorder.
Myotonic dystrophy is transmitted via an autosomal dominant inheritance.
Dominant refers to the fact that the disorder is passed down by only one parent, who also has the disorder. There is no carrier status. Cataracts may develop frequently in people with myotonic dystrophy. They develop fairly slowly, but can occur in people as young as 30 years. Myotonic dystrophy may affect the heart muscle.