Duchenne muscular dystrophy (DMD, or just Duchenne) is a rare genetic disease and one of more than 30 forms of muscular dystrophy. It primarily affects males, but, in rare cases, can also affect females. Duchenne causes the muscles in the body to become weak and damaged over time. The genetic change that causes Duchenne—a mutation in the DMD gene—happens before birth and can be inherited, or new mutations in the gene can occur spontaneously.