Duchenne muscular dystrophy or DMD is the most common of the muscular dystrophies, affecting approximately 1 in every 3,500 newborn boys. It is caused by a fault in a gene called the dystrophin or DMD gene. A fault in this gene stops the body making a protein called dystrophin. This protein is important in muscle fibres, and its absence results in muscle weakness that gets worse over time because muscle cells break down and are gradually lost.
Because the dystrophin gene is on the X chromosome, Duchenne muscular dystrophy affects only boys. Girls have two X chromosomes, so if one of these is unaffected it can usually compensate for the faulty one, while boys have one X and one Y chromosome, so if their single copy of the dystrophin gene is faulty, they have the symptoms of DMD, while girls with one affected gene and one normal one usually won’t show symptoms but can be “carriers”. This means that the disease can be passed on in families – a mother who is a carrier has a 50:50 chance of having a son who is affected. But in up to about a third of cases, the mutation arises spontaneously in the boy.
The aim of this overview is to inform patients and parents about the different therapeutic approaches for Duchenne muscular dystrophy currently under investigation, to describe the advantages and disadvantages of each approach and to list the hurdles that have to be overcome before these approaches can be applied to patients.