Myotonic Muscular Dystrophy
Myotonic muscular dystrophy (DM) is a type of muscular dystrophy that affects both muscles and organs throughout the body. 'Myotonic' is the medical term for an inability to relax the muscles. The reason myotonic dystrophy is abbreviated DM is because its Greek name is dystrophia myotonica. Some individuals call the condition Steinert disease, naming it after the doctor who described it first. Myotonic muscular dystrophy comes in two types, of which DM1 is the more serious type. There's a gene on an individual's chromosome 19 researchers call DMPK, and in DM1 patients, this gene has a section with an abnormal expansion.
DM2, the second type of myotonic muscular dystrophy, was originally described in 1994 as a more mild presentation of DM1. Patients with DM2 have an abnormal expansion on the ZNF9 gene located on the third chromosome, and the expanded DNA causes abnormal functioning in many processes. Myotonic muscular dystrophy is one of the most common adult-onset muscular dystrophy types, and it's the most common among European adults, though it is rare in non-white populations.