Duchenne muscular dystrophy (DMD) is a severe type of muscular dystrophy. The symptom of muscle weakness usually begins around the age of four in boys and worsens quickly. Most are unable to walk by the age of 12. Scoliosis is also common.
The disorder is X-linked recessive. About two thirds of cases are inherited from a person's mother, while one third of cases are due to a new mutation. It is caused by a mutation in the gene for the protein dystrophin.