What Causes Duchenne? Our body is made of cells and each cell has a control centre which contains genes. Genes are made of DNA and genes are the instruction manual for building the proteins that make our bodies work. Duchenne is caused by a defect (mutation) in one of the genes in the body. Humans have around 20,000 genes and one of the largest is called the dystrophin or DMD gene. The role of the DMD gene is to make a protein called dystrophin. Duchenne is caused when very little or no dystrophin is made by the DMD gene because the DMD gene has a defect. Dystrophin is a protein that is found in all muscles used for movement (skeletal) and in heart (cardiac) muscle. A small amount of dystrophin is also found in nerve cells in the brain. In muscles, dystrophin is one of a group of proteins (dystrophin complex) that work together to strengthen muscle fibres. It is thought that these proteins act as a ‘shock absorber’ to protect muscle fibres from injury as muscles contract and relax. Without enough dystrophin, skeletal and cardiac muscles become damaged as they repeatedly contract and relax with use. The damaged cells weaken and die over time, causing the characteristic muscle weakness and wasting and heart problems seen in Duchenne. The dystrophin complex may also play a role in cell signaling by interacting with cells that send and receive chemical signals. Little is known about the role of dystrophin in the brain, research has shown that it may be important for cell to cell communication. Intellectual impairment may occur in some boys but it is not inevitable and if present, does not worsen as the condition progresses. The genetic defect that causes Duchenne can either be: Inherited (passed down through the family) or Caused by a new change in the DMD gene that occurs in the child This new genetic change is known as a ‘spontaneous mutation’ and is the cause in more than one third of cases of Duchenne. The genetic change occurs very early in development of the egg that has been fertilised which means that the change is found in all of the cells of the body.