Duchenne muscular dystrophy

Muscular dystrophies are a group of muscle conditions. They result in progressive muscle weakness and wasting. Duchenne Muscular Dystrophy³ is one of the most common and severe forms affecting children.

A mistake (or mutation) in the gene that produces a protein called dystrophin causes DMD. The primary location of dystrophin is in the skeletal muscle and the heart. Small amounts of dystrophin are also present in the brain.

Dystrophin maintains muscle elasticity when skeletal and cardiac (heart) muscles contract and relax. It acts as a shock absorber and protects the muscles from injury.

Without dystrophin, muscle cells are not able to function in the normal way. They are not able to repair themselves and start to die (degeneration). At first, muscles are able to replace the loss of cells (regeneration). Over time, the muscles exhaust their capacity to regenerate new cells. Scar tissue and fat (fibrosis) replace the muscle. This leads to progressive loss of muscle and muscle strength.   

The function of dystrophin in the brain remains unclear. Its absence in the brain does not result in any detectable brain abnormalities on MRI. It seems to play a role in the development of the brain and in the signalling required to process complex information.

DMD is an X-linked condition (see ‘causes’ section below). This means that it usually only affects boys. Classified as a rare disease, it has an incidence of 1:3500-6000 in newborn males. Around 300,000 boys and young men are living with the condition worldwide.

³ Yiu, E. M. & Kornberg, A. J. Duchenne muscular dystrophy. (2015). doi:10.1111/jpc.12868