As the DMPK mRNA is widely expressed in many tissues, this explains the variable multisystem involvement in DM1 patients, also affecting the central nervous system, the eye, the heart, the smooth muscle, and the endocrine system, with the related development of cognitive and behavioral deficits, premature cataracts, cardiac conduction abnormalities, endocrine dysfunctions, and gastrointestinal (GI) symptoms. Here, DMPK is linked to myotonic dystrophy type 1.