Myotonic dystrophy is a chronic, progressive disorder that affects muscle function. It is a type of muscular dystrophy, a group of genetic disorders that cause progressive weakness and loss of muscle mass. The two main types are Myotonic Dystrophy Type 1 (DM1) and Myotonic Dystrophy Type 2 (DM2). Both are characterized by myotonia (delayed relaxation of muscles after contraction) and other systemic symptoms.
