Molecular Diagnosis of Myotonic Dystrophy

Abstract Myotonic dystrophy types 1 (DM1) and 2 (DM2) are autosomal dominant, microsatellite repeat expansion disorders that affect muscle function. Myotonic dystrophy type 1 is caused by CTG repeat expansion in the 3′ UTR region of the DMPK gene. Patients with DM2 have expansion of CCTG repeats in intron 1 of the CNBP gene. In this unit, we review and discuss the clinical phenotypes, genetic mutations causing the diseases, and the molecular diagnostic approaches and tools that are used to determine repeat sizes in DM1/2. In summary, the goal of this chapter is to provide the reader with a basic understanding of the clinical, genetic and diagnostic aspects of these disorders. © 2016 by John Wiley & Sons, Inc.