Myotonic dystrophy Type 1 is an autosomal dominant form of muscular dystrophy caused by a CTG repeat expansion in the untranslated 3′ region of myotonic dystrophy protein kinase (DMPK) on chromosome 19q13.1 Myotonic dystrophy Type 1 affects multiple organs, including the CNS. The gene discussed is DMPK; the disease is myotonic dystrophy type 1.