DMD and Duchenne muscular dystrophy: Eteplirsen targets exon 51 in the dystrophin immature RNA (hnRNA) in DMD patients who carry a deletion between the terminus of exon 50 and the beginning of exon 52 comprising deletion of exons 45–50, 47–50, 48–50, 49–50, 50, 52 or 52–63.