DMPK and myotonic dystrophy type 1: Myotonic dystrophy type 1 (DM1) is caused by the expansion of a CTG trinucleotide repeat in the noncoding region of the DMPK gene [11], while facioscapulohumeral muscular dystrophy type 1 (FSHD1) is characterized by the contraction of the D4Z4 repeat array on chromosome 4q35 [12].