Duchenne is caused by a fault or mutation in the DMD gene. Genes are made from DNA (deoxyribonucleic acid). The DNA in the DMD gene holds the information necessary for our bodies to make the protein called dystrophin.

The DMD gene is made up from 79 pieces called ‘exons’. Each exon contains hundreds of letters of genetic code. To make protein, another molecule called ribonucleic acid (RNA) goes to work and carries a copy of the DNA code from the gene to another part of the cell.

The RNA, interacting with particles in the cell called ribosomes, ‘reads’ the code and makes the protein called dystrophin. Dystrophin is essential for muscle function.

There are three different types of changes or mutations in the DMD gene that can cause Duchenne:

  • Deletions of one or more whole exons – this is the most common type of mutation and is the cause of around 70% of cases of Duchenne.
  • Duplications (additions) of whole exons – this type of mutation is the cause of around 10% of cases of Duchenne.
  • Other small changes in parts of the genetic code, for example point mutations – this type of mutation is the cause of around 20% of cases of Duchenne.

Dystrophin will not be made at all or, if some dystrophin is made, it will not work well if the genetic code for making it is changed in any of these three ways. Without dystrophin, muscle cells weaken and get damaged over time as they contract and relax.