Myotonic dystrophy, also known as Steinert's disease, is the most common form of muscle disease, affecting approximately one person in 8,000 worldwide. It is a multisystem disease, typically involving a wide range of other tissues as well as muscle. Anyone can be affected by myotonic dystrophy. It is a genetic disorder passed on to children of either either sex by one parent who has the disorder.
Myotonic dystrophy can affect people at any age.
The majority of people are diagnosed by the time they reach their early twenties. With each successive generation, the symptoms of myotonic dystrophy seem to get more severe, and the age at which they appear gets younger. This tendency is known as anticipation. The adult form generally appears between the ages of 10 and 30 years. The severity of symptoms, the rate of progression and the degree of disability vary widely from one person to the next, even among members of the same family.