What causes DM? Type 1 myotonic dystrophy (DM1) and type 2 myotonic dystrophy (DM2) are both caused by abnormally expanded stretches of DNA. The expansions occur in two different genes but appear to have similar effects on various cells, particularly the cells of the voluntary and involuntary muscles, including the heart and nervous system.

Understanding the Context

DM provides an example of mechanism of disease called ...