Duchenne muscular dystrophy (DMD) is a rare, fatal neuromuscular genetic disease that occurs in approximately one in every 3,500 – 5,000 males worldwide.
DMD is caused by a change or mutation in the gene that encodes instructions for dystrophin. These changes in the genetic code may include large deletions (about 60-70 percent), large duplications (about 10 percent) or other small changes (about 15-30 percent).
Genetic testing is required to confirm the diagnosis and identify the disease-causing mutation in the dystrophin gene.
THE ROLE OF DYSTROPHIN
Dystrophin is a protein that plays a key structural role in muscle fibre function. In healthy muscle, dystrophin interacts with other proteins at the cell membrane to stabilise and protect the cell during regular activity involving muscle contraction and relaxation.
Boys and young men with DMD produce little or no dystrophin in their muscle.
Without dystrophin, normal activity causes excessive damage to muscle cells, and they are ultimately replaced by fibrotic tissue and fat, leading to a progressive loss of function.
Note: Healthy and DMD muscle tissues analysed by immunofluorescence using an anti-dystrophin antibody.
Signs and Symptoms
Symptoms of DMD usually appear in infants and toddlers. Affected children may experience developmental delays such as difficulty in walking, climbing stairs or standing from a sitting position. Boys with DMD often walk on their toes and have large calves, as well as use the Gowers Manoeuvre to stand from the floor.
As the disease progresses, muscle weakness in the lower limbs spreads to the arms, neck and other areas. Most patients require full-time use of a wheelchair in their early teens, and then progressively lose the ability to independently perform activities of daily living such as using the toilet, bathing and feeding.
Eventually, increasing difficulty in breathing due to respiratory muscle dysfunction requires ventilation support, and cardiac dysfunction can lead to heart failure. The condition is universally fatal, and patients usually succumb to the disease in their twenties.