Myotonic dystrophy (DM) is a multisystem autosomal dominant inherited disease that primarily affects the nervous system, causing myotonia and a characteristic pattern of muscular atrophy and weakness. Careful clinical description in the late 19th and early 20th centuries separated DM from a similar muscle disease, myotonia congenita, allowing it to emerge as a distinct nosologic disease entity. The electrical characteristics of myotonia were described in the early to mid 20th century. Assiduous study of the clinical features and genetics of DM, including the phenomenon of anticipation, culminated in the discovery of the genetic mutations underlying DM in the early 1990s.
Tramonte JJ, Burns TM. Myotonic Dystrophy. Arch Neurol. 2005;62(8):1316-1319. doi:10.1001/archneur.62.8.1316