DMD and Duchenne muscular dystrophy: Duchenne Muscular Dystrophy (DMD) is a recessive, X-linked neuromuscular disorder caused by mutations in the dystrophin gene, which spans ∼2.4 megabases and includes 79 exons.1,2 These mutations lead to little or no dystrophin production (typically <3% of the normal quantity of dystrophin).3 Dystrophin is a protein critical in physically stabilizing the membranes of muscle cells.