Come support Pi Rho's philanthropy Ryan's Quest (DMD) Duchenne Muscular Dystrophy (DMD) is a devastating and progressive muscle disorder that only affects boys, causing a loss of both muscle function and independence. DMD affects approximately 1 out every 3500 boys born worldwide. It is the most common, lethal genetic disorder diagnosed during early childhood. Nearly all boys with DMD die by their late teens or early 20s from respiratory and/or cardiac complications.