Myotonic dystrophy is a very complicated condition. The symptoms and disease progression can vary widely. The effects can be quite different even among members of the same family, so it is difficult to predict just how the disorder will affect you and your family. One person may only have mild muscle pain or cataracts that develop in later years, while someone else with the condition may be born with serious breathing problems.
The most common effects of DM are muscle problems, including muscle weakness (myopathy), trouble relaxing a muscle (myotonia), and muscle wasting that gets worse over time (atrophy). However, it is misleading to think of DM as only a muscle disorder because it also affects many other body functions, including the heart, lungs, and gastrointestinal (GI) system. The disorder can also cause problems with cognitive function, personality, and vision. Not everyone with DM will have all or even most of the possible symptoms.