DMD and Duchenne muscular dystrophy: Duchenne muscular dystrophy (DMD), which is characterized by a progressive decrease of muscle function, is caused by frame-shifting deletions or nonsense mutations in the DMD gene (Koenig et al., 1989), being this last among the first genes where circRNAs were identified as RNA circles consisting of exons that were skipped by alternative splicing (Surono et al., 1999).